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The practical application of two dormancy induction trials on douglas-fir and western hemlock container… Wickman, Marise 1985

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THE PRACTICAL APPLICATION OF TWO DORMANCY INDUCTION TRIALS ON DOUGLAS-FUR AND WESTERN HEMLOCK CONTAINER SEEDLINGS by Marise Wickman B . S . F . , University of B r i t i s h Columbia,  1979  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF FORESTRY  ln THE FACULTY OF GRADUATE STUDIES (Faculty of  Forestry)  We accept this thesis as to the  conforming  required standard  THE UNIVERSITY OF BRITISH COLUMBIA October,  1985  © Marise Wickman,  1985  In  presenting  degree freely  at  this  the  available  copying  of  department publication  of  in  partial  fulfilment  of  the  University  of  British  Columbia,  I  agree  for  this or  thesis  reference  thesis by  this  for  his thesis  and  study.  scholarly  or for  her  of  /g/'gs ^  T h e U n i v e r s i t y of British 1956 M a i n Mall Vancouver, Canada V6T 1Y3  gain  DE-6(3/81)  be  It  is  6 C/ 1  e  shall  that  agree  may  representatives.  financial  Columbia  further  purposes  permission.  Department  I  requirements  not  that  the  Library  an  by  understood allowed  advanced  shall  permission  granted  be  for  the that without  for head  make  it  extensive of  my  copying  or  my  written  -i i ABSTRACT  Two dormancy induction t r i a l s were conducted in a private container nursery in Saanichton, B r i t i s h Columbia.  The f i r s t  study examined the  effects of photoperiod induced dormancy on morphology, root growth and f i e l d performance of f a l l  planted western hemlock (Tsuga heterophyl_1ji (Raf.)Sarg.)  and Douglas-fir (Pseudotsuga  menzi_esv[ (Mirb.) Franco) seedlings.  Various  periods of eight hour days, ranging from two to eight weeks, were applied throughout July and August 1983.  Outplanting was done in late September.  Survival and growth were assessed one year  later.  The second project investigated the effectiveness  of short  days,  varying levels of moisture stress and a combination of both as dormancy induction techniques for Douglas-fir seedlings. four weeks of eight hour days. - 5 , -10, -15 and -25 bars.  The short day treatment was  Four levels of predawn moisture stress were:  These classes respectively corresponded to  c o n t r o l , l i g h t , medium and severe moisture stress l e v e l s .  Short days and  moisture stress were also combined whereby the four week period of short days followed the moisture stress treatments. applied in July and August 1984.  These induction treatments were  A l l seedlings were l i f t e d in January  and placed into cold storage for five weeks until root growth capacity, frost January.  March 1985.  1985  Morphology,  hardiness and dormancy intensity were assessed in  Root growth capacity and dormancy intensity were again measured in  March. In Study I, short days quickly i n i t i a t e d homogeneous budset in both species in approximately three weeks.  The average height increment after  treatment i n i t i a t i o n was 3.7 cm in Douglas-fir and 4.2 cm in western hemlock.  Short days reduced shoot dry weight and height. were unaffected. seedlings  Caliper and root dry weight  In September a surge in root growth occurred in hemlock  treated with six or eight weeks of short days.  The importance of  early budset to allow increased root growth prior to a f a l l demonstrated.  l i f t was  Root growth capacity was similar among a l l treatments  for both  species. The planting survival of western hemlock seedlings increasing weeks of short days. eight week regime had 91%. seedlings.  increased with  Control plants had 76% survival while the  Survival was similar for a l l treated  Douglas-fir  It ranged from 89% in the two week interval to 98% in the four  week regime.  One year height increment was s i g n i f i c a n t l y greater  and eight week short day treatments  for both species.  in the six  For hemlock, i t ranged  from 6.1 cm in the control plants to 10.4 cm in the six week trees. Douglas-fir height increment ranged from 6.4 cm for the control interval to 8.6 cm in the eight week regime. The six and eight week photoregimes produced the best quality hemlock seedlings for  for this study.  Four weeks of short days appeared adequate  Douglas-fir. In Study II short days e f f e c t i v e l y i n i t i a t e d and maintained budset  in Douglas-fir seedlings  in four weeks.  After six weeks from treatment  i n i t i a t i o n , a l i g h t to severe moisture stress was as effective height growth. effective.  in c o n t r o l l i n g  A natural photoperiod with no moisture stress was least  - i v-  In a comparison of a l l treatment combinations, only the control plants  under a natural  photoperiod were s i g n i f i c a n t l y larger in a l l  morphological properties. had similar effects  Short days, moisture stress or a combination of both  on reducing height, c a l i p e r , shoot dry weight and root dry  weight. Unstressed seedlings in a natural daylength had the highest of root growth capacity.  value  A l l other treatment combinations had s i g n i f i c a n t l y  lower root growth capacity.  Only the severe stress under a natural  photoperiod s i g n i f i c a n t l y reduced root growth capacity compared to any other treatment.  Short days accelerated  March dormancy intensity t e s t s .  bud burst in the January and  Frost hardiness was similar among a l l  treatments. Selection of a regime which controlled height growth while maintaining seedling quality was not clearcut. moisture stress was most effective morphological and physiological  A short photoperiod with no  in i n i t i a t i n g budset.  differences  However, few  were evident between short day  plants and l i g h t and medium stressed seedlings.  -v~ TABLE Or' CONTENTS  Thesis abstract  ii  Table of Contents  v  L i s t of Tables  viii  L i s t of Figures  xi  Acknowledgements  xiv  CHAPTER ONE Introduction  1  1.1  Thesis Objectives  7  1.2  What is Stock Quality?  8  1.2.1  Seedling Morphology  10  1.2.2  Root Growth Capacity  14  1.2.3  Frost Hardiness  20  CHAPTER TWO 2.1  Classical  Dormancy  2.2  The Complex Interaction Between Hormone Regulators and Physiological  2.3  3.0 4.0  22  Dormancy  The Environmental Role in Dormancy  24 27  2.3.1  The Phytochrome System  29  2.3.2  Environmental Signals in Dormancy Development . . . .  31  2.3.3  Environmental Factors  39  in Dormancy Release  The Effect of L i f t i n g and Storage on Seedling Survival and Growth Performance Conclusions  44 49  -vi -  CHAPTER THREE The Effect of Photoperiod Induced Dormancy on Morphology, Root Growth and Outplanting Performance of Western Hemlock and Douglas-fir Containerized Seedlings  51  3.1  Introduction  51  3.2  Study Area  53  3.3  Materials and Methods  53  3.4  3.5  3.6  3.7  3.3.1  Seedlings  53  3.3.2  The Blackout System  54  3.3.3  Treatments  54  3.3.4  Measurements  55  3.3.5  Statistical  Nursery T r i a l  Analysis  56  Results  56  3.4.1  Greenhouse Climate  56  3.4.2  Rate of Bud Formation  56  3.4.3  Morphology  58  3.4.4  Root Growth Capacity  77  3.4.5  Frost Hardiness  77  Planting T r i a l  Results  77  3.5.1  Climate  77  3.5.2  Visual Observations  79  3.5.3  Survival and Growth Performance  81  Discussion  93  3.6.1  Nursery T r i a l  93  3.6.2  Planting T r i a l  96  Conclusions  104  -vi i CHAPTER FOUR Dormancy Induction of Douglas-fir Containerized Seedlings: A Comparison Between Moisture Stress, Short Days and a Combination of Moisture Stress Followed by Short Days  108  4.1  Introduction  108  4.2  Methods  109  4.2.2  Measurements  4.2.3  Statistical  4.3  Ill Analysis  Results  Ill 112  4.3.1  Treatments  112  4.3.2  Daily Climate  116  4.3.3  Bud Formation and Incidence of Reflushing  116  4.3.4  Morphology  122  4.3.5  Root Growth Capacity (RGC)  132  4.3.6  Dormancy Intensity  135  4.3.7  Frost Hardiness  139  ...  4.4  Discussion  139  4.5  Conclusions  149  REFERENCES  153  APPENDICES  162  1  162  II  166  Ilia  168  I lib  170  IV  172  V  174  VI  196  VII  197  vii i LIST OF TABLES Table No. Table 1.1 Table 1.2  Page 1984 proposed stock specifications of s i t e types  for a variety  Ministry of Forests stock specifications container crops  12 for 1983 13  Table 1.3  Index of root growth capacity  19  Table 3.1  The average height growth in Douglas-fir and western hemlock seedlings after short day dormancy commenced until buds formed  61  Morphology measurements for western hemlock seedlings upon the completion of a l l short day dormancy induction regimes on 17 August 1983  63  Morphology measurements for Douglas-fir seedlings upon the completion of a l l short day dormancy induction regimes on August 17, 1983  63  Morphology measurements for western hemlock seedlings four weeks after the completion of a l l photoregime treatments on 19 September 1983  64  Morphology measurement for Douglas-fir seedlings four weeks after the completion of a l l photoregime treatments on 19 September 1983  64  Caliper growth in Douglas-fir seedlings after four weeks of conditioning either inside or outside the greenhouse  65  Average shoot dry weight determinations in western hemlock seedlings which received four weeks of conditioning inside or outside the greenhouse for four weeks after dormancy induction treatments were completed  71  Average shoot dry weight determinations in Douglas-fir seedlings which received four weeks of conditioning inside or outside the greenhouse for four weeks after dormancy induction treatments were completed  71  The proportion of sampled western hemlock seedlings where root dry weights conformed to the MOF c u l l and target standards on 19 September 1983  74  Table 3.2  Table 3.3  Table 3.4  Table 3.5  Table 3.6  Table 3.7  Table 3.8  Table 3.9  ix Table 3.10 The proportion of sampled Douglas-fir seedlings where root dry weights conformed to the MOF c u l l and target standards on 17 September 1983  74  Table 3.11 Root growth capacity of Douglas-fir and western hemlock seedlings upon the completion of short day dormancy induction treatments  75  Table 3.12 Daily maximum and minimum temperatures and r a i n f a l l from the l a s t day of planting on 26 September 1983 until 31 October 1983  78  Table 3.13 The incidence of top k i l l , dead or missing terminal buds and needle loss in outplanted western hemlock seedlings. Visual damage was observed in the spring following the f a l l planting  80  Table 3.14 The incidence of top k i l l , dead or missing terminal buds and needle loss in outplanted Douglas-fir seedlings. Visual damage was observed in the spring following the f a l l planting  80  Table 3.15 Survival results for western hemlock one year after planting  86  Table 3.16 Survival results for Douglas-fir one year after planting  86  Table 3.17 Morphology measurements in outplanted western hemlock. Seedlings were assessed after one growing season in October 1984  88  Table 3.18 Morphology measurements in outplanted Douglas-fir. Seedlings were assessed after one growing season in October 1984  88  Table 4.1  Table 4.2  Plant moisture s t r e s s , styroblock weight, waterloss on a weight b a s i s , and s o i l water content at the time each treatment was watered  116  Terminal bud formation in Douglas-fir seedlings maintained under five dormancy induction regimes. Assessment made sixteen days after treatment  121  -X-  Table 4.3  Table 4.4  Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9  The effect of photoperiod and moisture stress on terminal bud formation of Douglas-fir seedlings. Assessment made four weeks after project i n i t i a t i o n . . . .  121  Bud formation and incidence of reflushing in eight dormancy induction treatments applied to Douglas-fir seedlings  122  Morphology measurements of Douglas-fir seedlings at the time of the January 1985 l i f t  126  The effects of photoperiod and moisture regime on total height in Douglas-fir seedlings  130  The effect of photoperiod and moisture regime on caliper growth of Douglas-fir seedlings  13 0  The effect of photoperiod and moisture regime on shoot dry weight accumulations of Douglas-fir seedlings The effects of photoperiod and moisture regime on root dry weight of Douglas-fir seedlings  134 134  Table 4.10 The effect of moisture stress on root growth capacity of Douglas-fir seedlings under two photoperiods  136  Table 4.11 The effect of photoperiod and moisture stress on dormancy intensity of Douglas-fir seedlings. Tests were conducted during the January l i f t and after five weeks of cold storage  139  -xi LIST OF FIGURES  Figure 1.1 Figure 1.2  P e r i o d i c i t y of root growth p o t e n t i a l , root growth and shoot growth as i t relates to bud dormancy  15  Seasonal changes of root growth potential (RGP), cold hardiness ( L T 5 0 ) and water potential at zero turgor (C|J ) in Douglas-fir seedlings  16  Schematic model of hormonal interaction and the the regulation of shoot growth  28  The i n t e r r e l a t i o n s h i p between DBB, DRI and c h i l l i n g sum. The slope and positioning of the curves w i l l vary with temperature and photoperiod  41  The effect of variable weeks of short days (SD) on height growth of Douglas-fir seedlings  59  The effect of variable weeks of short days (SD) on height growth of western hemlock seedlings  60  The effect of variable weeks of short days (SDO on shoot dry weight of western hemlock seedlings  66  The effect of variable weeks of short days (SD) on root growth of western hemlock seedlings  67  The effect of variable weeks of short days (SD) on shoot dry weight of Douglas-fir seedlings  68  The effect of variable weeks of short days (SD) on root growth of Douglas-fir seedlings  69  The effects of variable weeks of short days and conditioning on shoot dry weight of Douglas-fir seedlings in late September  72  z  Figure 2.1 Figure 2.2  Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4 Figure 3.5 Figure 3.6 Figure 3.7  Figure 3.8 Figure 3.9  The September l i f t  root dry weights of hemlock  seedlings treated with variable weeks of short days. . . .  76  One year survival in outplanted western hemlock seedlings treated with variable weeks of short days. . . .  82  Figure 3.10 One year survival of Douglas-fir seedlings with variable weeks of short days  treated  83  -xi i Figure 3.11 Total height, after one year, of outplanted western hemlock seedlings treated with variable weeks of short days  84  Figure 3.12 Total height, after one year, of outplanted Douglas-fir seedlings treated with variable weeks of short days.  85  Figure 3.13 Height increment after one growing season in western hemlock seedlings treated with variable weeks of short days  89  Figure 3.14 Height increment after one growing season in Douglas-fir seedlings treated with variable weeks of short days  90  Figure 3.15 Relative height growth ( y r - 1 ) after one growing season in western hemlock seedlings treated with variable weeks of short days  91  Figure 3.15 Relative height growth ( y r - 1 ) of outplanted Douglas-fir seedlings treated with variable weeks of short days  92  Figure 4.1 Figure 4.2 Figure 4.3  Figure 4.4  Figure 4.5  Figure 4.6  The relationship between shoot water potential and s o i l water content {%)  117  The relationship between water potential and styroblock weight  118  Budset incidence in Douglas-fir seedlings after four weeks of treatment with moisture s t r e s s , short days or a combination of both  123  Incidence of flushed terminal buds in Douglas-fir seedlings after four weeks of treatment with moisture stress and short days  124  The final height of Douglas-fir seedlings treated with moisture s t r e s s , short days or a combination of both  128  The effects of moisture stress and photoperiod on the final c a l i p e r measurement of Douglas-fir seedlings in January 1985  129  -xiiiFigure 4.7  Figure 4.8  Figure 4.9  The effects of moisture stress and photoperiod on the final measurement of shoot dry weight of Douglas-fir seedlings in January 1985  132  The effects of moisture stress and photoperiod on the final root dry weight measurement of Douglas-fir seedlings in January 1985  133  The effects of moisture stress and photoperiod on root growth capacity of Douglas-fir seedlings measured in l a t e January 1985 137  Figure 4.10 The effects of moisture stress and photoperiod pretreatment on dormancy intensity of Douglas-fir seedlings in January 1985  140  Figure 4.11 The effects of moisture stress and photoperiod pretreatment on dormancy intensity of Douglas-fir seedlings in March 1985  141  -xi v-  ACKNOWLEDGEMENTS  I would l i k e to offer  a very special  constant moral support and exhuberant laboratory.  I am also grateful  thanks to Lynn Husted for her  assistance in the f i e l d and in the  to her for i n i t i a t i n g this graduate  research project with CIP Forest  Products.  I would also l i k e to thank Mike Wickman for cheerfully  measuring  and weighing l i t e r a l l y thousands of forest seedlings; Grace Briggs for processing the data and typing the manuscript; assistance in the laboratory;  Cathy Haskin for her  and the technical s t a f f of CIP Forest  Products for growing and planting the seedlings and conducting  field  assessments. I would also l i k e to express gratitude to CIP Forest Products  for  financing the research project and for supplying the technical assistance. Special  thanks to Ed McDonald of MacMillan Bloedel Ltd. for  donating a l l the hemlock seedlings. Finally,  I am grateful  for the financial  support provided to me by  the National Science and Engineering Research Council of Canada.  1  CHAPTER ONE INTRODUCTION  Reforestation is the most extensively practised s i l v i c u l t u r a l a c t i v i t y in B r i t i s h Columbia.  In spite of a depressed forest  provincial mandate for reforestation  remains strong in the face of reductions  in the provincial s i l v i c u l t u r e budget.  In the f i s c a l year of April  to March 31, 1985 over 100 m i l l i o n trees were planted. doubtful  economy, the  that the present reforestation  Although i t  continued government funding demonstrates  B r i t i s h Columbia's reforestation  forest  regions was:  Thus,  the p o l i t i c a l and, to a lesser  extent, s i l v i c u l t u r a l importance of reforestation  to the "seventies",  is  programme meets a l l industrial and  crown requirements, the programme has not been seriously c u r t a i l e d .  change in emphasis since i t s  1, 1984  in B r i t i s h Columbia.  programme has undergone a major  inception approximately four decades ago.  Prior  the planting prescription for B r i t i s h Columbia's coastal broadcast  (^^eudotsu£a_mef22i^s(Mirb.)  burn and plant bareroot Douglas-fir Franco).  Productivity was the theme.  With  easy swings of the mattock., a planter generally drove over 1000 bare root seedlings  per day into rocky s o i l s .  done with one gentle pull  Planting quality surveys were quickly  on the terminal shoot of the seedling.  Planting  survival was surveyed on thousands of hectares by a brief examination of 25 or so staked seedlings  in  a plantation.  new philosophies towards reforestation.  However, the seventies  brought in  Species prescriptions on a s i t e  specific basis slowly evolved with the increasing awareness of ecosystem c l a s s i f i c a t i o n and habitat typing.  Emphasis on planting productivity partly  2  shifted to include planting q u a l i t y . stock handling in the f i e l d .  More attention was focussed  also on  Planting checks and survival surveys  became  more intensive. Along with this s h i f t  in emphasis to planting q u a l i t y , an awareness  of the stock's physiological quality increased throughout the late seventies. Foresters  demanded  numerous conferences  better,  high quality seedlings.  on stock q u a l i t y , no agreement yet exists on what  morphological and physiological attributes tree.  However, in spite of  comprise a singular,  high quality  After the 1980 IUFRO Symposium on "Techniques for Evaluating Planting  Stock Quality", quality was defined as "fitness for purpose" of ensuring plantation establishment this rather esoteric  and growth performance (Ritchie 1984a).  d e f i n i t i o n does l i t t l e to create standards to which  nursery managers should grow t h e i r forest seedlings. reflects  However,  A high quality seedling  a complexity of physiological and morphological  properties.  S p e c i f i c a l l y defining stock quality may prove too i d e a l i s t i c a task.  Stock  quality requirements vary with species, s i t e , time of planting, environment and numerous other factors. quality continues. attributes  Yet, the search for understanding of stock  Two symposia recently convened to discuss the seedling  which seem correlated with successful  growth performance (Duryea and Landis 1984; are divided into two groups: (Duryea 1985; Ritchie 1984a).  plantation establishment and  Duryea 1985).  material attributes Material attributes  These  attributes  and performance  attributes  are d i r e c t l y measured  components which ultimately contribute to seedling performance.  Foliar  nutrient concentrations, carbohydrate levels and shoot height are only a few  3  examples of these components.  Performance attributes reflect  the  of a whole seedling that is subjected to a particular test such as growth capacity or seedling vigour.  performance root  At Oregon State University, evaluation  tests for both these attributes are either being implemented or are in a process of development. Similar research  is being done by the Ministry of Forests but a  serious gap continues to exist between research, operations. operations  and  reforestation  Part of the problem results from lack of feedback  from planting  to the nurseries.  silviculturists'  It is in  nurseries  the f i e l d  foresters',  and nursery managers' best interests to be aware of the  research about the physiological and morphological attributes of forest seedling q u a l i t y .  The track record for planting survival and plantation  growth must be improved.  Although stock handling and planting quality have  probably improved s u r v i v a l , plantation failures still  present economical and s i l v i c u l t u r a l  and poor growth performance  problems.  Although there are numerous factors involved in plantation failures:  poor s i t e preparation, planting q u a l i t y , stock handling, s i t e  q u a l i t y , summer drought, e t c . ;  poor physiological adaptation  i t s environment is frequently a common cause (Chavasse 1980; Cleary 1974;  Nelson and Lavender 1976).  In other words,  of the stock to Lavender and  the seedling  physiologically out of synchrony with i t s environment (Sandvik 1980). example of this is when stock is early l i f t e d and f a i l elevation s i t e . sufficiently  Poor survival  frequently occurs.  is An  planted on a high  The seedlings are not  hardened to withstand the early frosts common in high elevation  4  zones.  Physiological  vigour or condition of a forest seedling  determined by nursery environment and cultural practices.  is  largely  The scheduling of  nursery regimes is very important to seedling q u a l i t y ; time and method of dormancy induction, date of l i f t and duration of cold storage can influence seedling performance  Duryea and Lavender 1982;  Lavender and Cleary 1974;  and Hermann 1970; 1983,  physiology and subsequent f i e l d survival and growth  (Chavasse 1980;  et a l . 1972;  Ritchie 1984b, 1982;  1976a, 1969b).  roots during l i f t i n g ,  Hermann 1967; Hermann  Lavender and Wareing 1972; Timmis 1974;  Lavender  van den Driessche  Dormant trees are better able to withstand exposure of extended periods of cold storage and the harsh  environment of a planting s i t e .  Dormancy is not a steady state; i t  constantly developing or slowly releasing  (Campbell 1978).  and planting window is narrower than the interval budflush.  greatly  is  Hence the l i f t i n g  between budset and  In a d d i t i o n , dormancy is interrelated with two other  performance a t t r i b u t e s : root growth capacity and frost hardiness.  important Cold  hardiness or acclimation is necessary for seedlings to withstand cold storage, outdoor overwintering or the early frosts of f a l l root growth capacity,  the potential  planting.  High  a b i l i t y of seedlings to grow new roots,  may be necessary to ensure freshly planted seedlings quickly establish new roots prior to the onset of summer drought.  The interaction between l i f t i n g  date, duration of storage and state of dormancy can greatly affect the level of root growth capacity and degree of frost hardiness (Ritchie 1984a, 1984b, 1985;  Ritchie and Dunlap 1980).  determine survival and outplanting  A l l of these factors, in t u r n , can performance.  5  Although the importance of these physiological attributes to the production of high quality seedlings is undeniable, the prime objective operational  forest nurseries  remains dogmatically singular:  seedlings which meet predetermined morphological size  to produce  specifications.  Nurseries grade t h e i r seedlings on morphological c r i t e r i a such as c a l i p e r and seedling dry weights.  of  height,  Nursery culturing techniques such as  f e r t i l i z a t i o n and i r r i g a t i o n regimes are commonly prescribed to manipulate these specifications  in a forest crop.  Height and seedling balance are the  main parameters used to gauge seedling growth. target s p e c i f i c a t i o n s ,  Once seedling shoots approach  height growth is controlled in container and bareroot  crops by a r t i f i c a l l y inducing dormancy.  This can be done in several  ways:  drought s t r e s s , reduction of nitrogen supply or the application of short days.  Moisture stress is probably the most common technique employed in  container nurseries. elongation and c e l l  It quickly i n h i b i t s the growth processes of c e l l division.  The reduced water content in the planting  medium also reduces nutrient a v a i l a b i l i t y and plant nutrient uptake.  The  advantages of moisture stress include ease of implementation and low cost. Possible disadvantages are physiological damage or death i f the stress is too severe. Another method of dormancy induction is photoperiodic c o n t r o l .  The  mode of action through which short days i n i t i a t e budset is not well understood.  It may affect the balance of growth promoting and i n h i b i t i n g  hormones so that c e l l  elongation in the apical meristem is reduced.  photoperiod is shortened in greenhouse nurseries,  When the  budset is i n i t i a t e d quickly  6  and uniformly. when several  The development of frost hardiness  is enhanced in Douglas-fir  weeks of eight hour days are applied in the middle of summer.  This has important, implications to the c u l t i v a t i o n of f a l l  scheduled stock.  The disadvantages of short day dormancy induction are l o g i s t i c s  and costs.  It is also important to minimize l i g h t leaks in a darkened greenhouse and to prevent high temperatures. Although the purpose of any of these induction techniques control of height growth, the effect of the regime on physiological and outplanting performance must also be considered. scientific  is quality  There is extensive  evidence which demonstrates that dormancy is easily  initiated  through environmental manipulation; but there are few published studies which examine how specific  nursery induction regimes influence seedling morphology,  physiology and outplanting performance.  This may not be surprising  since  environmental factors such as l i g h t i n t e n s i t y , thermoperiod and photoperiod complexly interact to influence dormancy, frost hardiness physiological processes. different,  and various  other  Because every nursery or greenhouse environment is  a regime s p e c i f i c  to one nursery may produce different  results at  another nursery. The s t a f f at CIP Forest Products Nursery faced this problem in 1982 where their moisture stress dormancy induction regime produced  inconsistent  results for c o n t r o l l i n g height in t h e i r Douglas-fir and western hemlock (Tsuga heterophyl1_a (Raf.) Sarg) container stock.  They wanted to develop  another technique that quickly and homogeneously i n i t i a t e d budset. Consequently, two dormancy induction studies were conducted at the nursery over two consecutive years.  The overall intent was to p r a c t i c a l l y apply  7  proven physiological operational  principles and documented methods in order to develop an  nursery regime which effectively  controlled height growth through  budset i n i t i a t i o n and also enhanced or at least maintained seedling and plantation  performance.  The f i r s t until  the f a l l  study was implemented in the summer of 1983 and continued  of 1984.  A reduced photoperiod of 8 hour days was applied on  Douglas-fir and western hemlock seedlings at variable intervals the summer.  quality  Morphological c h a r a c t e r i s t i c s ,  frost hardiness  capacity were measured at the end of the treatment outplanted in the f a l l .  period.  throughout  and root growth Seedlings were  Survival and growth performance were assessed during  the following autumn in October 1984. Although the application of short days controlled height growth, logistics  and expenses of a "blackout" structure were problems.  Consequently  in the following summer of 1984, a second study was i n i t i a t e d in order to evaluate the comparative effects of short days and moisture s t r e s s . Treatments were again applied throughout the summer. root growth capacity,  frost hardiness  This time, morphology,  and dormancy intensity were assessed  just prior to January l i f t and again after five weeks of cold storage. Although CIP Forest  Products outplanted these seedlings in May 1985,  planting t r i a l was not included in this graduate research  1.1  Thesis  project.  Objectives  The overall objectives of this thesis are: 1. To develop an operational dormancy induction regime which effectively and homogeneously controlled height growth in Douglas-fir and western hemlock container seedlings.  the  8  2.  To develop a dormancy induction regime which also enhanced or at least maintained seedling quality and outplanting performance.  The specific objectives of Study I are: 1. To ensure a "blackout" system, or short days, was operationally effective in i n i t i a t i n g homogeneous budset. 2.  To determine the number of weeks of 8 hour days required to i n i t i a t e and maintain budset.  3.  To determine which treatment interval or short day regime enhanced frost hardiness for f a l l scheduled planting stock.  4.  To assess the effects of photoperiod treatment on f a l l survival and growth.  5.  To investigate whether the shortened photoperiod adversely affected root biomass.  6.  To evalute the effects of a r t i f i c i a l short days on seedling morphology and root growth capacity.  planting  The s p e c i f i c objectives of Study II are: 1. To compare and evaluate the effects of various levels of moisture s t r e s s , four weeks of 8 hour days and combinations of both on seedling quality such as: morphology, root growth capacity, frost hardiness and i n t e n s i t y of dormancy. 2.  1.2  To help develop a moisture stress regime that e f f e c t i v e l y i n i t i a t e d budset without reducing physiological quality and root morphology.  What is Stock Quality? CIP Forest Products was interested in short days simply as a tool  to stop shoot growth and meet specified height standards for various species and stock types.  However, included in this research project were a few basic  physiological tests which hopefully reflected more aspects of seedling quality than just morphological c h a r a c t e r i s t i c s . physiological  In this thesis  quality was assessed by testing for frost  growth capacity and dormancy i n t e n s i t y .  hardiness,  root  Although there are numerous aspects  9  of physiological  q u a l i t y , these tests were selected  because they are  frequently used in applied research and occasionally in operational production.  nursery  There is published evidence which demonstrates t h e i r usefulness  in predicting  when to l i f t and store nursery seedlings, and in providing  some indication of t h e i r fitness for outplanting (Burdett et a l . 1984; Glerum 1985, Duryea 1985;  Ritchie 1985;  Ritchie and Dunlap 1980).  The f i n a l  for any seedling crop i s , of course, how well i t survives and performs field.  test in the  An outplanting t r i a l was conducted for Study I, but time did not  permit one for Study II. for Study II r e l i e s quality.  Consequently, assessment of treatment  effectiveness  heavily on these physiological tests and on morphological  Unfortunately, no d e f i n i t i v e test exists to predict how well a crop  meets the overall reforestation in the f i e l d .  objectives of surviving and performing well  There are, however, several  which in combination indicate a  potential a b i l i t y to grow well when outplanted and thus may reflect quality seedling.  Whether this potential  a high  is actually realized is determined  by planting q u a l i t y , stock handling, time of planting and species and stock type s u i t a b i l i t y for the s i t e as well as numerous s i t e factors.  Therefore,  these conditions must be considered when evaluating these predictive tests for fine tuning nursery culture regimes.  Because of seasonal  climatic  v a r i a b i l i t y and operational  stock handling, the fine tuning of cultural  techniques  years of physiological and morphological  requires  and feedback  several  from the f i e l d .  testing  Consequently, the results from these two  research studies r e a l i s t i c a l l y w i l l  only provide general  guidelines to CIP  Forest Products Nursery on how to improve dormancy induction techniques of the Douglas-fir and western hemlock container stock.  Nursery staff must  10  continue to monitor t h e i r induction techniques through quality testing and planting performance t r i a l s effectively  in order to develop some f l e x i b l e methods which  i n i t i a t e budset, control height growth and maintain or enhance  physiological  quality.  There are two proceedings which summarize extensively the numerous aspects and evaluation techniques of stock quality (Duryea 1985; New Zealand Journal of Forestry Science 10(1).  In the following pages only those aspects  of seedling quality assessed in this research project are b r i e f l y reviewed. Dormancy w i l l  not be discussed  in this section because the next chapter  reviews the importance of dormancy to seedling q u a l i t y .  1.2.1  Seedling Morphology The grading c r i t i e r i a for operational forest  predominantly based on morphological characteristics  nurseries  are  (Ritchie 1984a).  Height, caliper and root-shoot ratio (R/S) are most commonly used as a basis for c u l l i n g seedlings within any crop.  Bud height, root weight and shoot  weight are also measured in some nurseries.  Although there are  extensive  research publications which examine the correlation between morphology and outplanting performance, Ritchie (1984a) suggests that comparisons of outplanting performance based upon morphology are largely invalidated because the physiological condition of the seedling is seldom quantified.  Definitive  conclusions about the relationship between seedling performance and morphology are only v a l i d when a l l test seedlings physiological state.  are in the same  Nonetheless, i t is generally accepted that i f  seedlings  11  are in the same physiological state, large seedlings but smaller ones survive better  (Thompson 1985).  grow better in the f i e l d  Larger trees have a higher  photosynthetic capacity for the production of biomass. however, have lower transpirational  Smaller t r e e s ,  demands because of smaller leaf  area.  Hence, their a b i l i t y to survive f i r s t year summer drought is improved (Hahn and Smith 1983; Thompson 1985).  On a s i t e specific basis, the relationship  between s i z e , survival and growth performance varies according to brush competition, moisture regime, aspect, s o i l depth and numerous other environmental factors.  For example, on a dry south slope a short compact  seedling with lower transpirational  demand is desirable but on a north, moist  slope, a t a l l seedling is required to compete with the brush. In spite of these s i t e effects, morphology are s t i l l  evident.  reviews on these trends. transpirational  area,  some general trends about seedling  Thompson (1985) and Ritchie (1984a) provide  Height, a measure of photosynthetic capacity and  is well correlated with growth performance but a trade  off exists between growth and survival  (Thompson 1985).  Thompson (1985) also  reports that a better relationship exists between c a l i p e r , growth performance and s u r v i v a l . stem diameter. important.  Seedling dry weights are correlated in a similar manner as The root-shoot r a t i o , a measure of seedling balance, is also  It influences the water balance of a seedling where increasing  the r a t i o , at a given height, improves water uptake to meet transpirational demands (McDonald and Running 1979). In B r i t i s h Columbia, the Ministry of Forests morphological specifications variety of s i t e types  (MOF) has outlined  for a number of species stock types for a  (Table 1.1)  Every year the MOF determines  12  Table 1.1  1984 Proposed stock s p e c i f i c i a t i o n  for a variety of s i t e  types.  Species Site_Type  Stock Type  Target Standards  -  "HttcmT~CaT"Tmm7  Maximum Height  TcmJ  Fdc  Xeric  1+0 PSB 313  17.0  3.2  25.0  Fdc  Mesic  2+0 BR  30.0  5.5  40.0  Fdc  Brush  2+0 BR  45. 0  6.4  60.0  FDS  Alder Rehab. 1+2 BR  60.0  12.0  80.0  Cw  Mesic  1+0 PSL 310  20. 0  2.5  27.0  Cw  Brush  1+1 PBR 310  50. 0  6. 0  65.0  SS  Severe Brush 1+2 BR  60.0  12. 0  80.0  1+0 PSB 211  17. 0  2.5  25.0  1+1 PBR 211  35.0  5.0  Hw Hw  Brush  ^ _ Table 1.2. MINISTRY OF FORESTS STOCK SPECIFIC^ IONS FOR 1983 CONTAINER CROPS Top Dry Weight - grams (Top Line) Height - Centelmeters (Top Line) Root Dry Weight - grams (Bottom Line) Root Collar Diameter - millimeters (Bottom Line)  CO  O  Species Amabalis Fir Bg Grand Fir Bn~ Noble Fir Cw~ West Red Cedar W Yellow Cedar Fdc Coastal Doug-fir Fdi Interior Doug-fir HaT Mountain hemlock W Western hemlock. Lw"~ Western Larch W Lodgepol Pine Py Yellow Pine Se, SW, S'Frame s~~ Se, Sw G'Hse Sitka Spruce  rH  1.7  2.0  T 6 ~  T3  TT  2.0 2.3 2 . 10 12.5 15 2.4 3.0 2.0 13 2.0  11  2.2  14 2.2 12.5 2.0 2.2  12.5 15 2.5 3.0 T2~ 2.2  2.2  1775" 2.5 2.5 3.0 17.5 203.5 15 3.1 3.7 2.8 2.7 15" T775" 20 2.8 2.5 2.2 15 2.5 2.0 17.5 20 3.2 3.5 TB  T7TT  is—  T775" 2 T T  TO  T5T3" T 5  2.5  T~ T~  2.4 10 1.7 1.8 12 15 2. 2.7 12.5 14 1.8 2.0 2.2  17 3.0  IF  25  w  22  25  30"  22  25  CO  CL.  .5 .3 .4 .25 .5 .3 .5 .2  SO  -  3.0  3.2  13 3.0 17 2.5 20 3.0 18 2.  W  JT  -  3.0  2.5 12.5 2.2 15 2.8 15 2.25  2T"  3.0  TT W  22  3.5 22  25  03 to m i O to in to t to to 0 3 0 0 co a. , c co CO COU co OCO o CO  O  rH  rH rH  OO  rH  rH  rH  <N  rH  CO  CO  CL.  CL.  CL  CL.  CL.  .6 .4 .55 .35 .7 .5  .3 .2 .5 .3 .45 .25 .6 .35 .5 .3 .4 .2 .8 .4 .5 .2  .9 .5 1.0 .6 .6 .3 .8 .4  .8 .4 .6 .35  30  -  2.6  11  9  CL.  Cu  3.0  T3~ -  CL. U  -  2.5  2.5  rJ  "TT  T5~~  T 5  2.25  O  CL.  10  ""5  rH rH  O  M  <S> CL.  Ba  rH  rH  i00 toO*t _i a. cu cou a. O  rH  .6 .4 .5 .3 .7 .45 .7 .5 .5 .25 .9 .5 .6 .25  .7 .4 .7 .5 .8 .5 .6 .3  .5 .3 .8 .5 .7 .4 .8 .5 .6 .5 .7 .3 1.0 .6 .8 .4  1.5 .8 1.7 .9 .8 .4 1.0 .6  1.0 .6 .9 .5  1.0 .6  1.2 .7  .8 .5 1.0 .6 1.0 .7  1.0 .6 .8 .6 .9 .6 .9 .7 .9 .4 1.2 .7 1.0 .5  1.7 .9  1.0  .65  1.6 .8  .75  310408  rH  PSL CPP  T  O  Maximum Acce]?tabl( PSB 41SB  rH  Tai[get  |  rH  Cull Staiidard  PSB 313  oo CO O oo ttoo in o to *t ccoo COO. icon C O o.co a. u co co a.  CO to m tO (N to C CO O C O C O c o to O . U o. a. a. a. 10  rH rH  Maximum Acceptable  Target  PSB 211  Cull Standard  14  morphological  standards to which a l l crown land seedlings must be grown  (Table 1.2).  These  specifications  are probably altered annually in order to  incorporate the previous year's growth curves, any new planting t r i a l and to probably reflect  1.2.2.  the r e a l i s t i c  results  goals of the current growing season.  Root Growth Capacity High root growth capacity, the potential a b i l i t y of seedlings to  grow new roots when placed into a favourable  environment, is  thought  necessary to ensure that freshly planted seedlings quickly establish new roots prior to the onset of summer drought (Ritchie 1985, Ritchie and Dunlap 1980; Sutton 1980).  Early exploitation of s o i l moisture and nutrients may  improve a seedling's chance of s u r v i v a l . glauca  In studies with white spruce  (Picea  (Moench) Voss) and lodgepole pine (Pinus_contorta Dougl. ex Loud), a  strong correlation between root growth capacity, seedling survival and height growth performance was demonstrated  (Burdett,  Simpson and Thompson 1983).  The p e r i o d i c i t y of root growth capacity is related to the stages of dormancy and growth p e r i o d i c i t y (Ritchie and Dunlap 1980). capacity and actual  Root growth  root growth are low throughout the phase of active  shoot  elongation because of the competition for current photosynthates.  Once  budset occurs in late summer, current photosynthates  for root  extension as well as for secondary radial  growth.  are available  Thus, a f a l l  surge in root  growth commonly occurs throughout September and October for many coniferous trees of the Pacific Northwest. supply for root growth.  Autumn r a i n f a l l also increases s o i l  Any successful  fall  moisture  planting program should attempt  Root Growth Root growth  Dormancy deepening  Figure 1.1  True Dormancy  Shoot Growth  Quiescence  Shoot elgation  Dormancy Induction  P e r i o d i c i t y of root growth p o t e n t i a l , root growth shoot growth as i t relates to bud dormancy (Ritchie and Dunlap 1980).  16  1  I  Nov. Dec. Jan.  Figure 1.2  I  !  L _ _  Feb. Mar. April  Seasonal changes of root growth potential (RGP), cold hardiness ( L T 5 0 ) and water potential at zero turgor (<),2) in Douglas-fir seedlings. Reproduced from Ritchie 1985.  17  to capture this period. minimal until  Root growth subsequently  spring temperatures improve.  declines and remains  Root growth commonly peaks prior  to spring bud f l u s h . Root growth capacity in Douglas-fir increases during winter as dormant buds accumulate c h i l l i n g hours (Figure 1.1).  In coastal  Douglas-fir,  RGC culminates in January when the c h i l l i n g requirement is f u l f i l l e d and Dunlap 1980).  Winter l i f t i n g of seedlings has minimum impact on  seedlings during this time.  One possible explanation is that the high peak  of RGC coincides when stress resistance culminates 1985).  (Ritchie  Frost hardiness  in a seedling  (Ritchie  and drought tolerance are both at t h e i r maximum at  approximately the same time as RGC (Figure 1.2).  Consequently, root growth  capacity may also be an i n d i r e c t measure of seedling tolerance to stress in such species as Douglas-fir tolerance  (Ritchie 1985).  Root growth capacity and stress  rapidly decline with dormancy release.  They are at minimum once  buds flush. The magnitude and development of root growth capacity varies with species, provenance and stock type (Ritchie 1985). techniques also affect physiological  its  development.  Nursery cultural  Time of l i f t i n g in relation to  dormancy and to the size of carbohydrate  duration of storage affect  potential  root growth levels  reserves, and the (Ritchie 1985; 1982).  When seedlings are outplanted numerous factors determine the magnitude of root growth capacity expression Physiological practices  (Ritchie 1985; Ritchie and Dunlap 1980).  condition at the time of planting is affected  and by subsequent stock handling.  conditions of the planting s i t e w i l l  by nursery  F i n a l l y the environmental  influence the extent of new root growth.  18  Soil temperature, moisture and degree of s o i l compaction a l l influence the expression of root growth potential  (Ritchie 1985; Ritchie and Dunlap 1980).  In spite of the varying factors which depress root growth in the f i e l d , several  studies demonstrate a high correlation between laboratory  tested root growth capacity and actual  field survival.  Burdett et a l .  (1983)  reported a correlation coefficient of 0.90 for root growth potential and f i r s t year survival of white spruce and a correlation coefficient root growth potential and height growth in lodgepole pine.  of 0.82 for  However, Sutton  (1983) reported root growth capacity and height growth in outplanted pine and spruce were poorly correlated. Some physiologists  question whether high root growth capacity  i t s e l f the direct cause of high survival and growth performance.  is  Lavender  (1985, pers. comm.) suggests that root growth capacity may reflect more basic physiological attributes  of a seedling and that root growth capacity,  does not account for seedling outplanting response. that root growth capacity predicts  Richie (1985) suggests  f i e l d performance because i t appears to be  correlated with cold hardiness and stress resistance (Figure 1.2), physiological attributes  important to seedling performance.  published evidence is presently available which confirms this Methods to test for root growth potential reviewed by Ritchie (1984a; 1985).  itself,  two  However, no hypothesis.  in forest seedlings are  They mostly involve counting the number  of new roots and measuring root length on seedlings grown in a controlled environment after  a specified time period.  The method employed in this  research project follows the methodology of Burdett (1979) where seedlings are placed into the controlled environment growth chamber for seven days (Appendix I).  The number of new roots are counted and rated into an index  19  TABLE 1.3  Index of root growth capacity  IRG  (IRG) (Burdett et al .  1983)  Description  0  no new roots  1  some new roots,  2  1-3 new roots over 1 cm long  3  4-10 hew roots over 1 cm long  4  11-30 new roots over 1 cm long  5  31-100 new roots over 1 cm long  6  101-399 new roots over 1 cm long  none greater than 1 centimeter  (cm) long  20  ranging from 0 to 7 (Table 1.3). order to f a c i l i t a t e many nurseries  operational  This quick rating system was designed in nursery testing  as routine monitoring.  This test was applied in the  as one of three tests to discern treatment quality  1.2.3  and is presently employed in  differences  on physiological  performance.  Frost  Hardiness  Frost hardiness temperatures.  refers to a seedling's a b i l i t y to withstand low  Hardy seedlings are able to tolerate extracelluar  formation and to avoid lethal Intracellular  ice usually forms when temperatures rapidly f a l l  decreases of 2° or 3°C per hour commonly occur in nature. extracellular  ice  i n t r a c e l l u l a r ice formation (Brown 1980). at a rate  greater than 10°C/min and rarely occurs naturally (Weiser 1970).  1970).  project  Gradual  Ice forms in  spaces where water has the lowest solute concentrations  (Weiser  Cell wall permeability increases in hardy tissue to allow the  diffusion  of water to these e x t r a c e l l u l a r  formation of i n t r a c e l l u l a r ice is avoided.  spaces.  Hence, the lethal  Tree buds also avoid freezing  injury by the supercooling of water to temperatures as low as - 4 0 ° C (Wallner et a l . 1981);  although temperatures of - 5 ° are most common (Glerum 1985).  Hence supercooling of water is not a major component of frost  hardiness  development. Cold acclimation occurs in at least two stages (Weiser 1970). In the f i r s t  phase, short days and warm temperatures i n i t i a t e the hardening  process through the cessation of shoot growth (Aronsson 1975; Brown 1980;  21  Timmis 1976).  Secondly, cold hardiness  is enhanced by low temperatures.  Although these environmental signals are similar to those which i n i t i a t e and enhance dormancy, dormancy and hardiness occur independently of one another (Timmis and Worrall  1975).  extremely hardy t i s s u e . temperatures  In a t h i r d stage, very low temperatures  This level of hardiness  induce  is quickly lost with warming  (Weiser 1970).  Short days may i n i t i a t e frost hormones within leaves (Weiser 1970).  hardiness  by affecting  Decreasing temperatures  affect carbohydrate metabolism, enzymology, protein synthesis plant hormones (Brown 1980).  the level of possibly as well  as  In addition to these environmental s i g n a l s ,  mineral n u t r i t i o n and moisture are also implicated as factors in cold acclimation (Aronsson 1980;  Benzian 1965;  Benzian et a l .  Christersson 1975, 1976, 1978; Timmis 1974).  1974;  Depending on moisture stress  l e v e l , moisture stress can enhance, reduce or not affect frost (Blake et a l . 1978; Glerum 1985, van den Driessche 1969). enhance frost  hardiness  in seedlings through its effect  economy (Christersson 1976, 1975). aspect of frost  hardiness.  hardiness  Potassium may  on internal water  Drought resistance is another important  It is frequently necessary for a seedling to be  able to tolerate the desiccating effects of frozen s o i l .  Seedlings  balanced n u t r i t i o n appear to acclimate to lower temperatures with unbalanced n u t r i t i o n (Aronsson 1980; The p e r i o d i c i t y of frost  than seedlings  Larsen 1978; Timmis 1974).  hardiness in Douglas-fir follows a s i m i l a r  pattern as that of root growth capacity.  The nursery practices  and cold storage are usually executed when frost  hardiness  of l i f t i n g  is high because i t  is necessary for seedlings to withstand the freezing temperatures or outdoor overwintering.  with  of storage  22  CHAPTER TWO BUD DORMANCY IN FOREST SEEDLINGS  2.1  Classical  Dormancy  Dormancy is c l a s s i c a l l y predisposed classical  defined as "any case in which a tissue  to elongate does not do so (Doorenbos 1953).  In forest t r e e s ,  dormancy usually refers to the apical meristem or bud.  phases characterize of quiescence,  dormancy (Romberger 1963).  Three major  They include an i n i t i a l  followed by rest and a subsequent return to quiescence  (Lavender and Stafford  1985).  In Douglas-fir, in physiological  budset is  i n i t i a t e d in July when terminal buds form  response to summer drought  Lavender 1981, 1985; Zaerr et a l . 1981).  (Blake et a l . 1979; Hanover 1980;  This f i r s t  phase of dormancy is  called quiescence or imposed dormancy because growth is inhibited  exogenously  by the environment (Doorenbos 1953; Lavender 1982; Romberger 1963). of favourable  A return  conditions such as early autumn rain or premature i r r i g a t i o n in  the nursery w i l l happen, several 1984).  stage  stimulate bud flush and shoot elongation. physiological  If this does not  and morphological changes occur  (Lavender  The bud continues to develop and grow with the formation of  additional  leaf primordia  (Bachelard  1980; Owens and Molder 1973a, 1973b).  Although mitotic a c t i v i t y is declining in the meristematic  apex,  cells  continue to divide in the apex region where the primordia are being formed. Within the tree stem, the cambium also remains active while radial l i g n i f i c a t i o n of tissue proceeds.  growth and  23  Quiescence occurs from mid July until late September in the Pacific Northwest (Lavender 1985).  Although moisture stress i n i t i a t e s this  the shortening photoperiod of late summer is thought necessary development into rest (Lavender 1985; Lavender and Stafford temperatures  for  1985).  enhance bud maturation (Cheung 1978; Lavender 1984,  Nelson and Lavender 1979;  phase,  Mild  1982;  Sandvik 1980).  Coniferous trees of the Pacific Northwest generally enter rest in late September (Lavender 1985). (Romberger 1963). remain mild.  It is imposed by conditions within the bud  It develops as the photoperiod shortens while temperatures  A l l mitotic a c t i v i t y ceases within the bud near the end of this  stage (Owens and Molder 1973a 1973b; greatly accumulated .  As temperatures  Lavender 1985).  Growth i n h i b i t o r s have  become lower, buds slowly accumulate  t h e i r c h i l l i n g hours which in turn eventually decreases growth i n h i b i t o r levels.  This eventually releases the bud from r e s t .  to develop (Lavender 1985).  Cold resistance begins  Buds enter quiescence again in December where  the continued accummulation of c h i l l i n g hours permits a greater growth response over a wider range of temperatures within the environment (Campbell 1978).  The major i n h i b i t i n g factor during this phase of quiescence is cold  temperature.  C h i l l i n g f u l f i l l m e n t and warmer temperatures  generally result  in active shoot growth around A p r i l . If seedlings buds w i l l  have not progressed  properly through these stages,  not flush with warming spring temperatures.  They may burst late in  the spring in response to lengthening photoperiod (Campbell 1978; van den Driessche 1976a, 1975).  However, competitive advantage to brush invasion can  be quickly lost when this occurs in a new plantation.  Stress resistance  24  rapidly declines with the cessation of quiescence and the onset of shoot elongation.  Nursery disturbance or outplanting is not  The preceding paragraphs were a general stages of dormancy as i t is c l a s s i c a l l y  defined.  advisable.  review of the physiological A second d e f i n i t i o n of  dormancy is based on the overall stress resistance of the entire  seedling  (Lavender 1985).  generally  develops  Operationally referred to as hardening o f f ,  it  in Douglas-fir in November and reaches a maximum in January or  February.  As previously stated, root growth capacity,  frost hardiness and  winter drought tolerance a l l generally peak in late January in coastal Douglas-fir  (Ritchie 1985).  The nursery practices  of l i f t i n g , storage and  planting are recommended during this phase of maximal stress resistance (Lavender 1985; Lavender and Wareing 1972). A t h i r d d e f i n i t i o n is provided by Owens and Molder (1973a) who describe  bud dormancy on the basis of mitotic a c t i v i t y .  dormant when c e l l  d i v i s i o n ceases within the apex.  from December to April  Buds are  This occurs  considered  approximately  and coincides generally with the development of stress  resistance.  2.2  The Complex Interaction Between Hormone Regulators and Physiological Dormancy.  In spite of extensive research into the biochemical regulation of plant growth, the exact role of specific  plant hormones in dormancy  development and release is not c l e a r l y understood (Bachelard 1980; Hanover  25  1980; Saunders  1978; Zaerr 1985).  Bachelard (1980) suggested that  investigations  into the hormonal control of bud dormancy have largely  focussed on whole bud extracts even though dormancy development and release involve different a c t i v i t i e s  within different  regions of the apical meristem.  He i d e n t i f i e d a need to examine the biochemistry within s p e c i f i c regions  apical  in order to further the understanding of hormonal c o n t r o l .  Research  into the role of plant hormones is also restricted by the d i f f i c u l t y in extracting and detecting hormones that are present at r e l a t i v e l y low concentrations  (Zaerr 1985).  Saunders  (1978) concluded that due to the  complexity of hormonal, environmental and genetic interactions, attempts to isolate a specific  hormone and assign i t an exact role in dormancy w i l l  prove  fruitless. There are several  publications which provide a review of the history  and status of plant growth regulator research Weber 1978; Saunders  (Bachelard 1980; Nooden and  1978; Wareing and Saunders  1971).  scope and objective of this paper to discuss them.  It is beyond the  Instead, the general  concepts of the biochemical control of bud dormancy are presented; although i t must be emphasized that no general accepted  (Saunders 1978).  hormonal theory is understood or widely  The internal regulation of active shoot growth and  bud dormancy may be mediated through a balance of growth promoting and growth i n h i b i t i n g hormones (Hanover 1980; Lavender and Hermann 197 0). is imposed when the promoter to i n h i b i t o r ratio favours 1980).  High levels of the i n h i b i t o r , abscisic  Bud dormancy  i n h i b i t o r s (Hanover  acid (ABA) or "dormin" are  frequently but not always correlated with bud dormancy in woody plants (Bachelard 1980;  Nooden and Weber 1978).  In the buds of Douglas-fir  26  seedlings,  Hermann and Lavender (1972) speculated that i n h i b i t o r  accumulations were very high since exogenous applications of indoleacetic acid (IAA) and g i b b e r e l l i n (GA) were unable to induce bud f l u s h .  However,  since ABA has not always been detected in dormant buds, Bachelard (1980) suggested that changes in ABA levels are not the only mode of action in bud dormancy. Growth promoters include auxins, g i b b e r e l l i c acids, cytokinins and ethylene.  Although auxins influence c e l l  d i v i s i o n within the shoot and  control correlative i n h i b i t i o n of a x i l l a r y buds, t h e i r role in terminal bud dormancy is not considered major (Bachelard 1980).  Gibberellins (GA) may  promote dormancy release where the ratio of GA to ABA determines the i n i t i a t i o n or release of bud dormancy;  low GA to high ABA possibly  imposes  dormancy while high GA to low ABA may release the shoot apex from growth inhibition  (Forycka et a l .  1978).  There are at least f i f t y g i b b e r e l l i c acid  compounds which exhibit some degree of s p e c i f i t y of species and physiological  function (Bachelard 1980).  controlled by gibberellins  (Zaerr 1985).  the shoot but possibly the root as w e l l .  Shoot elongation and flowering are They are not only metabolized in Cytokinins, which are synthesized  in root meristems and in the shoot, are also implicated in dormancy release, and their precise role in dormancy is not understood (Alvim, Hewett and Saunders  1976;  Staden and Brown 1978;  wareing and Saunders  1971).  For  example, when root meristems were removed from the roots of Douglas-fir seedlings,  l i t t l e effect  on bud burst and vigour was evident in seedlings  l i f t e d and cold stored after  October (Hermann and Lavender 1972).  A  27  s i m p l i s t i c model of hormone interaction is shown in Figure 2.1, but i t does not indicate how hormone levels activities  (Bachelard  interact to regulate specific  development  1980).  In spite of this complex interaction between hormones and growth, there have been recent attempts to extract hormones from seedling tissue as a means of assessing seedling  vigour and growth potential  status of dormancy (Ritchie 1984a). analyzing low concentrations  (Zaerr 1985) and the  However, the d i f f i c u l t y in detecting and  of hormones has not yet been overcome  (Zaerr  1985).  2.3  The Environmental Role in Dormancy In a natural  environment the internal regulation of dormancy and  growth is f i n e l y synchronized with the environment and the seasons.  Apical  dormancy probably evolved in temperate zone species in order to promote survive cold winter temperatures and summer drought. factors which signal  There are environmental  to the plant the timely i n i t i a t i o n of bud dormancy.  following sub-sections are a review of the environment factors which with bud dormancy and how the trees "perceive" these s t i m u l i .  The  interact  28 old leaves  •> DORMIN  young leaves  > GIBBERELLIN  stem apex  > AUXIN —  •> counteracts effect of g i b b e r e l l i n  -> internode  extension  t—> •>  mobilisation of nutrients  —CYTOKININ  root Figure 2.1  Schematic model of hormonal interaction and the regulation of shoot growth. Figure from Bachelard (1980)  29  2.3.1  The Phytochrome System The apical meristem of seedling shoots is a s i t e of perception  environmental signals (Hanover 1980; Hermann and Lavender 1972). also a perception s i t e for photoperiodism (Wareing 1956).  for  Foliage  is  Light and  photoperiod signals are mediated by phytochrome in young seedlings (Hanover 1980;  Hillman 1967; Mandoli and Briggs 1984).  spectral  l i g h t quality and the ratio of energy between the red and far red  wavelengths full  (Mandoli and Briggs 1984).  sunlight, converts  the absorption of far Pfr.  This pigment is sensitive to  Red l i g h t r a d i a t i o n , prevalent in  phytochrome into an active form which is sensitive to  red l i g h t .  Hence this active form is referred to as  In poor l i g h t or dark conditions far red l i g h t dominates.  It  produces  the inactive form (Pr) which is sensitive to the absorption of red l i g h t . Active phytochrome promotes  seed germination but suppresses shoot  elongation. Response to daylength or photoperiod is a type of phytochrome mediated response. horticultural  Most of the research on photoperiodism has focussed on  plants such as chrysanthemums.  However, since growth  p e r i o d i c i t y in young seedlings is mediated by phytochrome, an awareness of the importance of l i g h t quality and quantity on phytochrome w i l l  develop  understanding on how to regulate seedling growth and dormancy through manipulation of the nursery environment. There are several of seedlings.  studies which demonstrate photoperiodic responses  Short days induce bud formation in Douglas-fir and western  hemlock (Cheung 1973; Hermann et a l . 1972; Lavender and Hermann 197 0; Lavender and Wareing 1972;  Lavender and Cleary 1974; Matthews 1977; Nelson  30  and Lavender 1979, 1969b 1970).  1976; McCreary et a l .  When Timmis and Worrall  1978; Tanaka 1974, van den Driessche  (1975) interrupted these long night  treatments with fifteen  minutes of red l i g h t , bud maturation was delayed in  Douglas-fir  Frost hardiness also declined.  seedlings.  l i g h t was radiated  immediately after the red l i g h t , the red l i g h t effect was  not reversed but accentuated.  McCreary et a l .  (1978) also  photoperiodic response in Douglas-fir seedlings. photoperiod was extended with supplemental shoot growth of Douglas-fir A total  However, when far red  reported  When an eight hour  l i g h t exceeding  37 |iWcm"2 , the  seedlings increased and bud dormancy prevented.  photoperiod of eight hours i n i t i a t e d dormancy and enhanced cold  hardiness.  However, very low l i g h t leaks decreased hardiness.  In western  hemlock seedlings, an eight hour photoperiod also inhibited shoot growth and i n i t i a t e d budset, but supplemental  l i g h t as low as l . O i a E m - 2 delayed bud  formation (Hauessler 1981). The effect of supplemental critical  factor  in nurseries especially where northern provenances  species are grown. intensities  far red l i g h t on growth or dormancy is a and  Extension of the photoperiod with r e l a t i v e l y low l i g h t  (containing far red l i g h t )  promotes shoot extension  in northern  or high elevation species which require a long photoperiod to maintain shoot growth (Arnott 1979; elongation differs 1981).  Tinus 1981).  The l i g h t quality which promotes  from the l i g h t quality necessary for photosynthesis  Light in the photosynthetic active range occupies the  wavelengths  shoot  from 0.40 to  u t i l i z e d for photosynthate  0.70nm.  (Tinus  shorter  The energy captured in this range is  production which in turn supplies energy for many  plant metabolic and biological  processes and biomass production.  at a maximum wave- length of 0.66 \im also occupies  this range.  Red l i g h t , However, far  31  red l i g h t is beyond this  range and is at a maximum of 0.73 0 u i m .  shoot elongation when above a c r i t i c a l  2.3.2  It  promotes  level.  Environmental Signals in Dormancy Development The environmental signals which ensure that growth p e r i o d i c i t y and  dormancy are synchronized with the seasons were b r i e f l y discussed during the review on the physiological  stages of dormancy.  Lavender (1981) provides a  concise but extensive review of these environmental factors. natural  Generally, in a  environment moisture stress or short days i n h i b i t height growth and  i n i t i a t e budset (Hanover 1980,  Lavender and Cleary 1974).  Continued short  days and mild temperatures maintain budset and enhance bud maturation (Sandvik 1980). Temperatures  Short days and cold temperatures promote cold  about 5°C slowly f u l f i l l  dormancy release (Campbell  the c h i l l i n g requirement necessary for  1978, Ritchie 1982).  Once this requirement  met, warm temperatures promote bud flush in the spring. sequential  hardiness.  is  The natural  changes in photoperiod and thermoperiod that occur from l a t e  summer through to spring cause successive, harmonized physiological and anatomical progression  changes within temperate tree species.  However, this  of environmental events is frequently altered and delayed in  nursery environments, especially  in container seedling greenhouses  and Cleary 1974; Matthews 1977).  reduced in fibreglass greenhouses.  (Lavender  The moisture regime is t o t a l l y regulated in  greenhouses and partly controlled in bareroot f i e l d s .  outdoors.  natural  Temperatures  Light quality  is  can vary from the ambient  Frequently northern latitude or high elevation species are grown  in southern coastal nurseries in B r i t i s h Columbia.  For these seedlings  32  nursery photoperiod does not coincide with seedlot origin and planting s i t e destination. natural  Because the nursery environment may vary from the  environment, nurserymen should be aware of how their specific  environment influences dormancy. fall  prospective  the sequence or progression  This fact is especially  lifting  of physiological  true when stock is scheduled for  and outplanting on a high elevation s i t e .  induced s u f f i c i e n t l y  nursery  early  If dormancy is not  early through environmental manipulation, the  grown in a l u s h , low elevation greenhouse environment w i l l  seedling  not be  physiologically adapted or synchronized with the colder harsh high elevation site.  In f a c t , this disharmony between planting environment and the  physiological failures  status of the seedling  in the Pacific Northwest.  is a major cause of f a l l  plantation  The need for synchrony also applies to  nurseries which overwinter container stock outside (Glerum 1985) or which place stock into cold storage for the winter (Hermann et a l .  1972).  If the  seedlings are subjected to cold temperatures prior to entering phyiological dormancy, bud maturation is  retarded.  If cold hardiness is not  sufficiently  developed, seedling tissue becomes susceptible to damage from outdoor or cold storage temperatures. result  frosts  Poor survival and/or growth response may  in the following spring. Thus far this section has focussed on the synchrony between  seedling physiology and the environment.  How does the nurseryman ensure that  his seedlings have developed through these phases of dormancy or that his stock is physiologically adapted to its environment whether i t be in a cooler or outplanted in the f i e l d ? research  investigating  this  The following paragraphs are a review of problem.  33  Scheduling of dormancy induction determines  greatly the synchrony  between the environment and the physiological stage of dormancy.  In the  Pacific Northwest dormancy induction should commence in mid June to early July in stock scheduled for f a l l will  planting (Lavender and Cleary 1974).  This  ensure seedlings are s u f f i c i e n t l y hardened for an early l i f t and  outplanting. sufficient  For spring scheduled stock, budset must be i n i t i a t e d in  time to allow the buds to mature under the short days and mild  temperature  conditions of late September and October.  The s p e c i f i c  date to  i n i t i a t e an induction regime in container greenhouses is largely determined by seedling size where budset is i n i t i a t e d as a means of c o n t r o l l i n g height growth and the S/R r a t i o . After reviewing the l i t e r a t u r e induction regimes are available 1973;  Lavender and Cleary 1974;  Lavender 1978;  Matthews 1977; McCreary, Tanaka and Tanaka 1974; Timmus 1974; Timmis  Tinus 1981; Zaerr, Cleary and Jenkinson 1981).  moisture stress i n i t i a t e s  Although  dormancy in Douglas-fir and western hemlock  seedlings in natural environments and in bareroot f i e l d s , effective  dormancy  to the nurseryman (Blake et a l . 1979; Cheung  Nelson and Lavender 1979;  and Tanaka 1976;  i t appears several  short days are also  in promoting budset in seedlings grown in environment chambers or  greenhouses. effectively  In most of the reported studies photoperiods of 8 to 10 hours i n i t i a t e d budset in Douglas-fir and western hemlock seedlings.  Although a drastic  reduction of the photoperiod is recommended (Sandvik  1980), the effects  of reducing daily photosynthetic active radiation must be  considered.  A general  decline in root growth was reported in Douglas-fir  seedlings receiving short day treatments after October (Lavender and Wareing 1972).  The number of active  roots, as well as new roots, was reduced.  A  34  reduction in photosynthate was suggested as a possible cause. empirical t r i a l s  Local  have incurred a similar response even when short day  treatments were applied in August (Matthews 1977). Early dormancy induction with short day treatments frost  hardiness.  also influences  Compared to a natural summer photoperiod, an 8 hour  photoperiod actually enhances cold acclimation in several tree species (McCreary et a l . 1978; Timmis and Worrall  Rosvall-Ahnebrink 1981; Tanaka 1972).  (1975) reported that a six hour photoperiod decreased  hardiness in Douglas-fir compared to the eight hour regime. al.  However,  When McCreary et  (1978) applied eight weeks of 8 hour days to Douglas-fir, hardiness of  the treated seedlings  did not d i f f e r from that of the c o n t r o l , but the  a b i l i t y to quickly acclimate developed shortly after  the eight week period.  Consequently, a conditioning period following eight weeks of short days was recommended for stock scheduled for early l i f t  fir  and f a l l  planting.  Once short day treatments  are applied to actively growing Douglas-  and western hemlock seedlings,  budset occurs quickly and homogeneously.  In a controlled environment of 20°C and eight hour days, western hemlock stopped elongating in three weeks (Cheung 1973). four weeks.  Buds were evident  There was 97% bud formation by the seventh week.  was delayed by temperatures  after  This response  lower or higher than 2 0 ° C .  In most nurseries throughout the Pacific Northwest early budset most commonly i n i t i a t e d with moisture stress (Tinus 1981; Zaerr et a l . 1981).  Lammas and proleptic growth are minimized compared to regularly  watered seedlings.  Blake et a l .  (1979), however, demonstrated that the  level of stress and date of induction affected Douglas-fir seedlings.  cold acclimation in  A predawn plant moisture stress of -5 to -10 bars  is  35  enhanced cold hardiness while a level of -10 to -15 bars reduced i t . hardiness was also greater in seedlings where treatments mid July compared to treatments  Cold  were i n i t i a t e d in  started in August and September.  Thus an  interaction between moisture stress and photoperiod was demonstrated whereby a mild stress applied just prior to a naturally declining photoperiod appeared most effective  on hardiness enhancement.  induction during short days reduced hardiness l e v e l s .  Later  Van den Driessche  (1969b) also reported that moisture stress applied to Douglas-fir seedlings during shortened photoperiods of 8 or 12 hours reduced hardiness.  Hardiness development was unaffected  long day regime. greatest  Seedlings  frost  by stress applied under a  treated with short day regimes exhibited the  hardiness. An interaction between moisture stress and container density on  frost  hardiness of Douglas-fir seedlings also occurs.  Timmis and Tanaka  (1976) reported that levels were lower in stressed high density seedlings compared to stressed low density seedlings.  Unlike Blake et a l .  (1979),  seedlings which received greater stress acclimated to lower freezing temperatures. Withdrawal of nitrogen (N) f e r t i l i z e r has also proven  effective  in i n i t i a t i n g budset although the date of treatment i n i t i a t i o n strongly interacts with the N withdrawal treatment  (Timmis 1974).  In a Douglas-fir  seedling t r i a l , removal of N in the twelfth week from seedling germination required 45 days for 5 0% of the seedlings to form terminal buds.  When the  same treatment was applied in the fourteenth week, only 29 days were required for 50% of the sample population to set bud.  36  Timmis (1974) also examined the effects of different NPK f e r t i l i z e r on cold acclimation. phosphorus and potassium f e r t i l i z e r hardiness  to - 1 3 ° C .  to obtain hardiness  received no f e r t i l i z e r greatest hardiness  K and N. on c e l l  (PK) d r a s t i c a l l y  of - 2 4 ° C .  Interestingly,  (-NPK) had a similar hardiness  reduced frost allowed seedlings  the seedlings which level.  However, the  occurred in an application of NPK when K was reduced by  50% of the previous level relation-  Withdrawal of N while maintaining  Nitrogen only and NPK f e r t i l i z e r s levels  balances of  ship existed  (NPK1/2).  Timmis (1974) concluded that a direct  between cold acclimation and the balance  Potassium may affect  sap osmotic p o t e n t i a l .  initial  hardiness  between  levels through i t s  effect  However, the N P K 1 / 2 , N and -NPK treatments  s i g n i f i c a n t l y reduced root growth compared to the standard NPK f e r t i l i z e r . There was also less than 5% bud occurrence in the NPK and N P K 1 / 2 treatments. hardiness  Timmis (1974) recommended a tissue K/N ratio of 0.6 for  enhancement.  At that level the adverse effect on rooth growth  would be reduced. Cheung (1973) compared the effectiveness of a l l three major dormancy induction techniques on western hemlock containerized seedlings. Short days induced 100% terminal budset in the shortest time period.  For  the same time duration, withdrawal of N promoted 51% terminal budset and moisture stress varied between 40% to 60% depending upon time of initiation.  Only the short day treatments consistantly  treatment  produced dormant  seedlings with dark green foliage and higher N content compared to controls. attributes.  Unfortunately Cheung (1973) only examined morphological Before any treatment  is pronounced better, physiological  37  attributes  such as frost  hardiness,  root growth capacity and growth  performance should also be considered. The selection and development of an induction regime must be nursery specific  because the a l t e r a t i o n of one environmental factor such as  photoperiod or moisture regime can interact with other environmental parameters such as irradiance or temperature.  A recent study in Sweden best  demonstrates the importance of environmental interactions during a dormancy induction regime.  Unlike the Pacific Northwest, photoperiod, or short days  is an induction technique commonly employed in Sweden. seedling s t o r a b i l i t y ,  Frost  hardiness,  survival and growth have s i g n i f i c a n t l y improved in  spruce and pine with the operational application of short days (Aronsson 1975; Rosvall-Ahnebrink 1981; abies (L.)  Karst.)  Sandvik 1980).  When Norway spruce  seedlings were grown in a controlled environment chamber,  short days increased f o l i a r nitrogen content and accelerated following spring (Sandvik 1980).  below an optimum of 2 0°C delayed the induction process. during the l a t t e r  budburst in the  The rate and magnitude of these effects  were strongly dependant upon l i g h t quality and temperature.  temperatures  Day temperatures  However, low night  part of the induction phase enhanced cold  acclimation especially when irradiance levels were low.  Seedling  was reduced in low radiation levels compared to higher l e v e l s . during short day treatments where nitrogen levels  also affected  storability  Irradiance  f o l i a r nitrogen concentrations  increased with increasing irradiance.  Growth potential  of the seedlings was p o s i t i v e l y correlated with f o l i a r nitrogen. survival  (Picea  Seedling  and performance were probably further enhanced by the improved root  dry weight which was also associated with high levels of r a d i a t i o n .  Finally,  38  a provenance interaction was observed.  In summary, the effect of short days  on seedling physiology and vigour was partly influenced by short day interactions with r a d i a t i o n , temperature A thermoperiodic effect Douglas-fir seedlings.  regime and provenance.  during dormancy induction was observed in  In a nine hour photoperiod, cool day temperatures  delayed dormancy induction in coastal provenances while warm day temperatures enhanced i t  (Lavender and Overton 1972).  In contrast,  warm days and coo)  nights postponed budset i n i t i a t i o n in i n t e r i o r provenances. temperature, provenances.  Cool s o i l  independent of photoperiod, i n i t i a t e d dormancy in a l l Lavender and Overton (1972) speculated that cold s o i l  temperatures lowered seedling metabolism and reduced synthesis of cytokinins in the root t i p s .  The promotor:inhibitor balance shifted to favour growth  i nhi b i t i o n . The interactions  of photoperiod, thermoperiod and moisture regimes  were examined in western hemlock (Nelson and Lavender 1976).  A combination  of eight hour days, moderate moisture stress and warm temperatures ( 1 8 ° C day/ 12°C night) promoted the fastest rate of budset formation.  A thermoperiod of  25°C d a y / 2 0 ° C night combined with a moderate moisture stress or short days also proved effective  in i n i t i a t i n g rapid budset.  The preceding discussion of environmental factors and t h e i r i n t e r action was presented to emphasize the need to develop dormancy induction regimes that are s p e c i f i c  to a particular nursery.  Thermoperiod, photoperiod  l i g h t quality and moisture regime a l l interact to influence the developmental processes of bud dormancy.  Dormancy, in turn, is interrelated with root  growth capacity and frost hardiness.  Thus, nursery practices  dormancy may also influence these other two performance  which affect  attributes.  39  2.3.3.  Environmental Factors  in Dormancy Release:  C h i l l i n g Requirement and Bud Burst  C h i l l i n g requirement is simply the exposure period to Tow temperature  that is required to release a seedling from bud dormancy  (Nelson and Lavender 1979).  It probably evolved as a defense mechanism  against buds bursting during a period of warm winter temperatures and subsequent frost k i l l  of new growth (Ritchie 1984b).  Although the  c h i l l i n g requirement  varies between species and provenances,  approximately 2 000 hours of temperatures below 5°C from October to l a t e March satisfy the requirement for most species in the Pacific Northwest (Ritchie 1984b). requires 1982;  Under continuous cold conditions of 3 ° C , western hemlock  eight weeks of c h i l l i n g and Douglas-fir twelve weeks (Lavender  Nelson and Lavender 1979; van den Driessche 1975).  Due to  fluctuating temperatures in a natural environment this period is because warm days may reverse some of the effects of previous  longer  chilling  (Nelson and Lavender 1979). P r e c h i l l i n g conditions can affect the c h i l l i n g requirement and subsequent seedling vigour and performance.  Pretreatment with short days  and mild temperatures prior to c h i l l i n g enhanced shoot growth in western hemlock and Douglas-fir seedlings during the following spring and Stafford,  (Lavender  1985; Lavender and Wareing 1972; Nelson and Lavender 1979).  In addition, when western hemlock seedlings were preconditioned with six weeks of short days, the c h i l l i n g requirement was reduced to four weeks. Pretreatment with long days extended the c h i l l i n g requirement from six eight weeks and inhibited the rate of bud flush.  to  40  C h i l l i n g f u l f i l l m e n t is apparently affected  by cold storage.  den Driessche (1976a) reported that cold storage of Douglas-fir  bareroot  seedlings did not f u l l y s a t i s f y the c h i l l i n g requirement.  Cold stored  seedlings flushed l a t e r than naturally c h i l l e d seedlings.  However, i f  seedlings received 300 hours of natural  Van  p r e c h i l l i n g prior to storage, t h e i r  a b i l i t y to respond to cold storage temperatures was enhanced (Ritchie 1984b; van den Driessche 1975). In summary, there are three major factors which can determine the effect of c h i l l i n g on bud dormancy.  The time of c h i l l i n g and the  corresponding physiological state of the seedling are important.  As  previously stated premature c h i l l i n g in the early stages of dormancy can retard bud maturation which in turn reduces shoot growth in the following spring.  The temperature  above 5°C w i l l  of the c h i l l i n g and the fluctuation of  determine when the c h i l l i n g requirement is  temperature  fulfilled.  Campbell (1978) demonstrated that the optimum temperature to satisfy  chilling  requirement actually varies with the accumulation of c h i l l i n g hours. 2 0 days of c h i l l i n g at 4 . 4 ° C , 10°C was more effective  After  in reducing the days to  bud burst in Douglas-fir. Photoperiod during the storage or c h i l l i n g period also affects subsequent bud a c t i v i t y (Lavender et a l . 1978).  Bud a c t i v i t y in Douglas-fir  increased with exposure to long photoperiod during the c h i l l i n g phase. C h i l l i n g requirement and bud burst are strongly i n t e r r e l a t e d . this relationship is explored, a few terms will burst  be defined.  As  Days to bud  (DBB) is simply the average number of days for seedlings to break bud  (Ritchie 1984a, 1984b).  There is a negative logarithmic relationship  DBB and c h i l l i n g accumulation (Figure 2.2).  In order to l i n e a r i z e the  between  41  CHILLING SUM  Figure 2.2  The i n t e r r e l a t i o n s h i p between DBB, DRI and c h i l l i n g sum. The slope and positioning of the curves w i l l vary with temperature and photoperiod. Figure from Ritchie 1984a.  42  relationship the reciprocal of DBB is altered into a dormancy release index (DRI) where (Ritchie 1984b):  = "DOT  D R I  The figure 10 represents the number of days for a Douglas-fir seedling in a controlled environment to break bud when the c h i l l i n g requirement has been fully satisfied.  The numerator may change with seed source.  c h i l l e d seedling w i l l  Thus, a f u l l y  exhibit a DRI approaching 1, while a f u l l y dormant  seedling should have a DRI approaching  0 (Figure 2.2).  Thereby,  determination of DRI in a growth chamber environment is a means of  testing  for dormancy intensity and determining whether seedlings have accumulated sufficient  c h i l l i n g hours.  of a growth chamber.  A DRI t e s t , unfortunately,  requires time and use  Because of the interrelationship between c h i l l i n g and  DRI, recording c h i l l i n g hours may prove a more practical means of dormancy (Ritchie 1984a, 1984b, 1985), although i t s  estimating  interpretation can be  confounded by fluctuating warm and cold temperatures. As the c h i l l i n g requirement becomes f u l f i l l e d , budflush is primarily a temperature mediated response (Worrall and Mergen 1967) where further c h i l l i n g incurs a more rapid bud burst over a wider range of temperatures (Campbell 1978; van den Driessche 1975). temperature  can be accounted for by heat sums (Worrall and Mergen 1967).  is the summation of temperature  above a c r i t i c a l level such as  by the duration of the temperature. is achieved within a seedling, variation in temperature budflush.  Variation in bud flush response to It  0°C multiplied  Once the required quantity of heat sum  budflush commences.  Thus the annual spring  results in variation in the annual date of  43  The steepness of the DRI curve shown in Figure 2.2 w i l l with temperature.  Thermoperiod also affects  rate of budflush.  change  Van den  Driessche (1975) found a d a i l y regime of 1 8 . 5 ° C d a y / 7 . 5 ° C night to promote the fastest flushing rate in Douglas-fir seedlings while a regime of 13°C d a y / 1 3 ° C night produced the slowest rate.  The flushing rate in a warmer  daytime temperature of 24°C followed by a colder night temperature of 2°C was in between the f i r s t  two thermoperiods.  temperature affected  buds in two ways:  Campbell (1978) suggested that  1. Temperatures between - 2 ° C to +12°C acted as environmental information and promoted minor changes in potential bud development rate. 2. Temperatures greater than 1 2 ° C released and growth.  energy for bud burst  Photoperiod or long days play a minor role in promoting bud release.  When long day treatments  were applied to Douglas-fir in l i e u of  c h i l l i n g , less than 25% of the buds flushed (van den Driessche 1975). Although long days act as a partial and slow substitute for c h i l l i n g in trees with p a r t i a l l y f u l f i l l e d c h i l l i n g requirements, Campbell (1978) reported that an interaction between photoperiod and c h i l l i n g combined to influence budflush at lower spring  temperatures.  Soil temperature may also play a major role in affecting bud a c t i v i t y in Douglas-fir soil  (Lavender et a l . 1973).  Seedlings maintained at a  temperature of 20°C flushed two weeks e a r l i e r than at 5 ° C .  applications of g i b b e r e l l i c acid accelerated temperature  but not the warmer.  Foliar  budflush at the colder  The influence of s o i l temperature on the  export of g i b b e r e l l i c substances from the root to the shoot was implicated.  44  To summarize the preceeding section on environmental influence,  it  appears that environment, dormancy, c h i l l i n g requirement and dormancy release are i n t e r r e l a t e d .  The nurseryman must manipulate the nursery environment to  ensure his seedlings develop through the physiological stages of dormancy. The dormancy release index can provide an indication of dormancy i n t e n s i t y . Seedlings should be l i f t e d and stored when dormant, and have received approximately 300 hours of c h i l l i n g in the case of Douglas-fir to precondition them to receive further c h i l l i n g in cold storage and to enhance storeability  3.  and subsequent growth performance in the f i e l d .  The Effect of L i f t i n g and Storage on Seedling Survival and Growth Performance  In the Pacific Northwest seedlings are commonly l i f t e d in midwinter and placed into cold storage at temperatures around 0°C for several (Ritchie 1984b).  These nursery practices  can greatly affect  months  seedling  survival and growth performance in the f i e l d (Burdett and Simpson 1984). necessity  The  to l i f t during dormancy and high stress resistance creates a f a i r l y  narrow l i f t i n g window which varies with provenance, nursery, year and cultural  regime (Burdett and Simpson 1984; Ritchie 1982).  Simpson (1984) suggested that the general physiological  Burdett and  recommendation to l i f t during true  dormancy was obscure especially when dormancy refers to the  physiological state of the bud and not to the whole tree. quick tests are available  to assess the stage of dormancy.  In addition no Although mitotic  indexing provides a r e l a t i v e l y quick indication of dormancy, there are few  45  published reports which correlate mitotic index, a measure of mitotic a c t i v i t y , to date of l i f t i n g and subsequent success in seedling and planting s u r v i v a l .  storability  Ritchie (1985) recommended that selection of a  l i f t i n g date should be based on a measure of stress resistance such as tolerance rather than dormancy i n t e n s i t y .  Frost hardiness at time of  frost lift  and the a b i l i t y of seedlings to maintain high RGC during storage are strongly correlated  (Burdett and Simpson 1984). Frost hardiness  correlated.  and seedling s t o r a b i l i t y are also closely  Operationally,  selection of a l i f t i n g date generally  corresponds with the period when seedlings have attained a f a i r degree of hardiness.  A review of frost  1984 Forest Nursery Manual:  hardiness and RGC testing  is available  Production of Bareroot Seedlings  in the  (Ritchie  1984a). Several  studies have investigated the impact of l i f t i n g date and  storage duration on stock q u a l i t y .  Early f a l l  lifts  and storage adversely  affect survival and growth because the physical disturbance disrupts physiological sequence of dormancy development (Lavender 1964). l i f t i n g may also prevent seedlings from accumulating sufficient fall  (Krueger and Trappe 1967; Ritchie 1982).  Insufficient  the  Early sugars in the  food reserves  reduce the energy necessary for maintenance respiration during storage and subsequent outplanting growth (Krueger and Trappe 1967).  Sugars play an  important role in the developmental process of cold acclimation.  Primarily,  they are an energy source for the processes of a l t e r i n g the c e l l  membranes.  Increased  Ritchie  permeability is necessary to develop frost tolerance.  (1982) speculated that seedlings l i f t e d in the f a l l sugars to gain enough hardiness, theory.  may have i n s u f f i c i e n t  but no published studies support  Stress tolerance to l i f t i n g and cold storage is  this  consequently  46  reduced.  In one study, early f a l l  mortality after  l i f t e d Douglas-fir seedlings exhibited 80%  a few weeks of cold storage in temperatures  of 3°C to 5°C  (Lavender and Wareing 1972). ' When winter l i f t e d stock received the same storage treatment no mortality resulted. the roots of f a l l lifting.  Hermann (1967) also observed  that  l i f t e d stock were far more sensitive to a i r exposure during  Bud burst was delayed with increasing exposure.  accentuated this effect.  Cold storage  In a d d i t i o n , seedlings l i f t e d with low RGC are  sometimes adversely affected  by cold storage .  When  Douglas-fir seedlings  are l i f t e d and stored with high RGC, RGC is maintained and even increased beyond the normal peak period for unstored seedlings.  far  Ritchie (1982)  reported that RGC increased for six months in winter l i f t e d and stored Douglas-fir seedlings before i t subsequently declined. Long periods of storage are associated with subsequent high seedling mortality and reduced RGC (Ritchie 1982).  Reduced seedling  performance has been partly attributed to the depletion of carbohydrate reserves to maintain low levels of seedling r e s p i r a t i o n . depletion w i l l  vary because seedling carbohydrate reserves are influenced by  nursery environment, radiation l e v e l s , nursery practices fertilization  Carbohydrate  such as  regimes, time of dormancy induction, time of l i f t ,  etc.  Although the level of f o l i a r sugars in Douglas-fir was p o s i t i v e l y correlated with RGC in unstored seedlings,  Ritchie (1982) did not find a close  correlation between f o l i a r , root and stem carbohydrate (sugar) levels and root growth capacity in stored seedlings.  From these r e s u l t s , Ritchie (1982)  speculated that RGC reflected the physiological condition within the seedling.  He also observed that RGC in Douglas-fir  increased with the early  47  stages of dormancy release and decreased during the final  stages.  It was not  shown, however, that this relationship between RGC and dormancy intensity was causal.  Ritchie (1982) further speculated that carbohydrate depletion was  more related to survival than RGC. When bareroot seedlings frequently damaged.  are l i f t e d , the roots are disturbed and  However, when root tips were completely removed from  bareroot seedlings,  lifting  in December and storage had l i t t l e effect upon  seedling mortality (Lavender and Wareing 1972). the October l i f t .  High mortality occurred in  Once again the time of l i f t was a more s i g n i f i c a n t  influence on s u r v i v a l .  Early l i f t  and storage also appeared to  accentuate  any problems such as root damage, root exposure to a i r or low RGC. However, the adverse effects of cold dark storage were apparently mediated through the roots as there was l i t t l e reduction in vigour when roots were protected by warm temperature while shoots were stored at 2 ° C .  A gradual  temperature down to 2°C did not reduce seedling mortality.  reduction of the In a d d i t i o n , a  daily exposure to low i n t e n s i t i e s of radiation during storage reduced seedling mortality and improved root growth (Hermann et a l . 1972) and thereby helped to prevent the adverse effects of cold storage. short days prior to l i f t subsequent s u r v i v a l .  Pretreatment with  and storage improved seedling s t o r a b i l i t y and  This may be related to enhanced frost  hardiness which  improves seedling tolerance of cold temperature. The temperature of the cooler also influences subsequent survival.  When Douglas-fir seedlings  from - 9 ° C to 2 ° C , seedlings coastal  seedling  were stored at varying temperatures  kept at 2°C exhibited the best survival for  and i n t e r i o r provenances (van den Driessche 1976a).  growth was also reduced after  Relative shoot  storage at - 2 ° C compared to 2 ° C .  In contrast,  48  Ritchie (1984b) suggested a temperature just below 0°C was better seedlings stored greater than two months.  for  A subfreezing temperature would  reduce seedling maintenance respiration and the rate of carbohydrate depletion.  Incidence of storage molds would also decrease. Date of l i f t i n g and cold storage influences the process of dormancy  release (Ritchie 1984a; 1984b).  In one study on Douglas-fir, Ritchie (1984b)  examined how DRI changed over time in naturally c h i l l e d and cooler stored seedlings.  As natural c h i l l i n g accumulated, DRI progressed  However, DRI changed more slowly in stored seedlings. attributed to the temperature of the cooler ( - 1 ° C ) .  towards 1.  The delay was The optimum temperature  for dormancy release ranges from 4°C to 6°C (van den Driessche 1975). Ritchie (1984b) concluded that this delay in dormancy release is  desirable  when stock is scheduled for late spring planting.  therefore,  Cold storage,  can widen the planting window compared to overwintering of stock in outside beds.  By late spring overwintered stock is commonly post dormant, an  undesirable physiological state for planting.  Ritchie (1984b) also  demonstrated that cooler stored, high elevation seedlings were released from dormancy faster than low elevation stock.  This is unfortunate since high  elevation sites are frequently planted l a s t due to lingering snowpacks (Ritchie 1984b). To conclude, winter l i f t i n g and cold storage practices or at least maintain seedling quality for several reforestation  programmes.  are stored at temperatures  can improve  months into spring  RGC can improve and remain high while seedlings around 0 ° C .  Release from bud dormancy is also  delayed, an advantage in stock scheduled for planting in late spring. these advantages of cold storage are r e a l i z e d , the nursery manager must  Before  49  schedule l i f t i n g and storage practices  when seedlings are dormant, and when  stress resistance and RGC are high.  4.  Conclusions The nursery operations  of l i f t i n g and storage must be implemented  when seedlings are dormant and exhibit high stress resistance. managers should be aware of how t h e i r specific the development of physiological will  not provide this  nursery environment affects  A visual examaination of budset  information because several  biochemical and anatomical time of its  dormancy.  complex p h y s i o l o g i c a l ,  events continuously occur within the bud from the  formation to the time of flushing.  with root growth capacity,  Nursery  frost hardiness  Dormancy is also  interrelated  and growth performance.  Thus,  there is a need to test for the material and performance attributes of nursery seedlings in order to determine the overall effect of nursery regimes on dormancy and general  seedling vigour.  A number of evaluation tests  already exists and several  more are in a process of development.  capacity,  drought resistance, dormancy intensity and mineral  frost hardiness,  nutrition are only a few of the tests presently a v a i l a b l e t o manager.  Yet, one might ask:  Do these tests mean anything?  Root growth  the nursery Strong evidence  already exists that demonstrates the close correlation between frost hardiness survival  and successful  seedling storage;  and between high RGC and seedling  as well as height growth performance.  physiological  p r i n c i p l e s , a nurseryman could employ these tests to track the  effect of nursery practices these actions  With a knowledge of basic  and t h e i r scheduling on stock q u a l i t y .  are meaningless  unless feedback  However,  is provided from the f i e l d .  50  Although there is T i t t l e agreement among s c i e n t i s t s ,  foresters and  nurserymen on the d e f i n i t i o n of stock q u a l i t y , a l l acknowlege the need to improve seedling quality as a means of increasing planting survival and growth performance. first  If communication improved between these groups, the  impediment towards obtaining this objective would be removed.  A second  blockage is a general lack of monetary commitment towards improving stock quality.  Education, development and implementation of evaluation t e s t s , and  improved monitoring of new plantations a l l require government and i n d u s t r i a l funding.  Only once these funds are a v a i l a b l e , can we say there is a strong  silvicultural forest land.  commitment towards the regeneration of B r i t i s h Columbia's  51  CHAPTER THREE  STUDY ONE THE EFFECT OF PHOTOPERIOD INDUCED DORMANCY ON MORPHOLOGY, ROOT GROWTH AND OUTPLANTING PERFORMANCE OF WESTERN HEMLOCK AND DOUGLAS-FIR CONTAINERIZED SEEDLINGS 3.1 Introduction In greenhouse nurseries environmental parameters  i t is possible to regulate the  of photoperiod, moisture and temperature to  prematurely induce dormancy and enhance frost practice would prepare f a l l elevation s i t e s .  hardiness  scheduled seedlings  (Sandvik 1980).  This  for the early frosts of high  Moisture stress is already used in many operational  nurseries to i n i t i a t e early budset as a means of regulating height and seedling balance. hardiness.  However, moisture stress has variable effects on frost  Blake et a l .  (1979) found that a mild stress of -5 to -10 bars  enhanced cold acclimation in Douglas-fir seedlings  compared to regularly  watered plants but a more severe stress of -10 to -15 bars reduced hardiness levels to that of c o n t r o l .  Van den Driessche (1959b) reported that reduced  moisture supply did not hasten hardening off in Douglas-fir.  Moisture  s t r e s s , applied in an 8 or 12 hour photoperiod, actually reduced hardiness compared to frequent i r r i g a t i o n in a short photoperiod.  Dormancy was  i n i t i a t e d and hardiness enhanced by eight weeks of 8 hour days at warm temperatures  followed by a period of cooler temperatures.  studies indicate that short day treatments hardiness.  Dormling et a l .  other  i n i t i a t e budset and enhance  (1968) demonstrated this effect  The importance of warm temperatures  Several  on Norway spruce.  immediately following budset to improve  52  bud maturation was also observed. and Scots pine were successfully  Fall  planting survival of Norway spruce  improved by treating seedlings with four  weeks of 8 hour days in mid July (Rosvall-Ahnebrink 1981). demonstrated the effectiveness enhancing hardiness al.  Several  studies  of short days in i n i t i a t i n g dormancy and  in Douglas-fir (Lavender and Wareing 1972;  McCreary et  1978; Tanaka 1974, van den Driessche 1969b) and in western hemlock  (Cheung 1973, 1978; Nelson and Lavender 1976;  Haeussler 1981).  Interaction  between photoperiod and l i g h t i n t e n s i t y , l i g h t leakage and temperature have also been examined.  McCreary et a l .  (1978) and Hauessler (1981) indicated  that low intensity l i g h t leaks during the dark period delay dormancy.  Light  intensity and temperature also interact with short days to affect the rate of hardening (McCreary et a l . 1978; Sandvik 1980, van den Driessche 197 0). Generally, high irradiance, warm days and cool nights apparently  interact  with short days to hasten the hardening process while cooler temperatures  in  the following weeks enhance hardening. In spite of extensive applied research, short day treatments generally have not made a t r a n s i t i o n into operational Sweden has implemented short days as an operational nurseries employ the technique in B r i t i s h Columbia.  nurseries.  Although  cultural t o o l , only a few Due to inconsistent  results with drought s t r e s s i n g , the CIP Forest Products private nursery expressed interest  in developing short days as an operational dormancy  induction technique for western hemlock and Douglas-fir.  However, before any  costly investment was made, an operational t r i a l was established develop a short day regime which would successfully  in order to  i n i t i a t e budset and  maintain or enhance seedling q u a l i t y , especially frost  hardiness and root  53  growth capacity.  The influence of short days on survival and outplanting  performance of f a l l  3.2  scheduled stock was also  investigated.  Study Area The nursery t r i a l was conducted at the CIP Forest Products'  nursery in Saanichton, B r i t i s h Columbia. metres  It is located approximately 100  (m) above sea level on the southern t i p of Vancouver Island.  seedlings were grown and treated in a permanent fibreglass greenhouse.  private  The  structure  Irrigation and f e r t i l i z a t i o n was done by an overhead boom  system. The planting t r i a l was located in the Robertson Valley about t h i r t y miles southwest of Lake Cowichan on Vancouver Island, B r i t i s h Columbia. Fifteen plots were situated on a southeast aspect at an approximate elevation of 700 m.  The study s i t e is in the Montane Variant of the Wetter Coastal  Western Hemlock Biogeoclimatic Subzone. colluvial  veneer over igneous bedrock.  classification,  3.3  A 50X slope, the landform is a According to the CIP biophysical  s i t e productivity is poor to medium.  Materials and Methods  3.3.1.  Seedlings Western hemlock seed was operationally sown in 211 styroblock  containers in late February, 1983 at Koksilah Nursery in Duncan, B r i t i s h Columbia.  The seed was from seedlot 2248 collected from seedzone 1010 at an  elevation of 122 m.  The seedlings were transported to CIP Forest  Nursery in the middle of May, 1983.  Coastal  Products'  Douglas-fir seedlot 4371 was  sown in 313 styroblock containers on 30 March, 1983 at CIP Forest  Products  54  Nursery.  The seed came from seedzone  1020 at an elevation of 750 m.  All  seedlings received standard f e r t i l i z e r and i r r i g a t i o n regimes from the time of sowing until  the time of l i f t i n g for a f a l l  scheduled plant (Appendix  III).  3.3.2. The Blackout System A 'blackout'  system was necessary to reduce the natural photo-  period to a short day of eight hours. over a greenhouse bench section.  A large wooden frame was constructed  It was covered with black p l a s t i c .  To  reduce the buildup of high temperature the outside p l a s t i c was coated with a white latex paint to reflect afternoon.  the high intensity radiation of the late  A v e n t i l a t i o n system was also i n s t a l l e d to exhaust hot a i r .  ensure heat was not building up, temperatures hygrothermograph. 3.30 p.m.  3.3.3.  To  were monitored with a  The eight hour day started at 7:30 a.m. and finished at  Light leaks were monitored with a LIC0R photometer.  Treatments On two separate species of seedlings,  five regimes of shortened  photoperiod and two post treatment conditionings were f a c t o r i a l l y applied in a completely randomized design.  Douglas-fir and western hemlock seedlings  received variable weeks of eight hour days. 5 and 8 weeks of short days.  The five regimes were:  0, 2, 4,  The eight week treatment started on 23 June  1983 and each regime respectively commenced every following two weeks, so that a l l treatments  finished on 17 August 1983.  Each ^treatment was applied  to 500 Douglas-fir seedlings and 250 western hemlock seedlings.  After 17  August 1983, a l l regimes underwent a four week conditioning and hardening off  55  period before the f a l l  outplanting.  inside the fibreglass Seedlings September.  Half of a l l treatments were maintained  greenhouse and half were outside in f u l l  sunlight.  from a l l treatments were outplanted in the t h i r d week of  The treatments were then f a c t o r i a l l y arranged in a completely  randomized block design.  Ten Douglas-fir plots each contained ten seedlings  from each treatment while five western hemlock plots each had ten seedlings from a l l treatments. fall  A hygrothermograph was maintained on s i t e until snow  accumulated.  3.3.4  Measurements Root and shoot dry weights, height and c a l i p e r were measured at the  start of each treatment period.  Height and caliper were recorded every  subsequent week and the dry weights once every two weeks.  Ten seedlings per  treatment were sampled for each measurement. On 17 August, 1983 ten seedlings  from each treatment were tested  for root growth capacity and frost hardiness.  The procedure for root growth  capacity testing is outlined in Appendix I; i t is the standard Ministry of Forests procedure.  Sample seedlings were placed into a controlled  environment for one week.  The number of new roots were counted.  Ten trees  from a l l treatments were also placed into a freezer chest and subjected to a freezing temperature of - 5 ° C . The seedlings were then maintained in the nursery greenhouse for two weeks to be assessed for needle, bud and stem damage. The frost prior to the f a l l  hardiness test was again conducted on 19 September, just  lift.  No f a c i l i t i e s were available to assess root growth  capacity at that time. For the planting t r i a l , winter damage was assessed in May once the snow melted.  Fall  survival and growth performance were recorded in October  56  1984.  Growth measurements  included total  height, height increment and  c a l i per.  3.3.5  Statistical  Analysis  Analyses of variance (ANOVA) were conducted on a l l variables. ANOVA assumptions  The  of homoescasdicity and normal d i s t r i b u t i o n of data were  generally met (Appendix IV). the F ratio was s i g n i f i c a n t  ANOVA tables are reported in Appendix V. When in an ANOVA, treatment means were compared by  Newman-Keul's multiple range t e s t .  3.4 3.4.1  Nursery T r i a l  Results  Greenhouse Climate Daily maximum temperatures  to 3 2 ° C . was 2 6 ° C .  in the blackout system ranged from 17°C  The average daily temperature for the eight week photoregime period Temperatures exceeded 30°C on only two days.  temperatures  Nightly minimum  varied between 11°C and 18°C for an average temperature of 1 4 ° C .  These temperatures were s i m i l a r to those in the greenhouse bench where seedlings were grown under a natural photoperiod (Appendix VII).  3.4.2  Rate of Bud Formation Short days or reduced photoperiod was an effective  tool to control  height growth in Douglas-fir and western hemlock container stock.  In  Douglas-fir, soft brown buds formed and became v i s i b l e in two to three weeks from treatment i n i t i a t i o n .  The red, pointed buds characteristic of this  species were observed in three to four weeks.  Date of treatment i n i t i a t i o n  appeared to influence the rate of budset where treatments  i n i t i a t e d in late  57  June or early July produced buds on seedlings in about three weeks and treatments started in Tate July or early August produced buds on seedlings in about two weeks.  This most l i k e l y reflects the effect of the naturally  declining photoperiod on slowly i n i t i a t i n g budset, especially since 20% of the Douglas-fir control seedlings had terminal buds when the photoregimes were completed on 17 August 1983.  On this date, buds had formed on a l l  Douglas-fir seedlings in the eight and six week regimes.  The four week  regime had 95% incidence of budset while the two week short day interval had buds on 80% of the plants. Terminal buds of western hemlock seedlings apparently formed at a slower rate.  However, new buds on hemlock are d i f f i c u l t to detect.  Short  days, regardless of date of treatment i n i t i a t i o n , produced detectable terminal  buds in about four weeks.  When a l l regimes were completed on 17  August 1983 a l l seedlings in the six and eight week short day intervals exhibited terminal  buds while only 55% of the plants in the four week regime  had detectable terminal  buds.  Buds were not evident in the two week regime  or control seedlings at that time. Four weeks after the completion of the photoregimes, terminal buds had formed on a l l hemlock seedlings but controls.  There was no incidence of  a second flush in any of the treatment regimes for either the inside or outside conditioning.  In the treated Douglas-fir seedlings, the occurrence  of proleptic and lammas growth was less than 1%.  Terminal buds were evident  in v i r t u a l l y a l l treated seedlings regardless of inside or outside conditioning.  Terminal buds had i n i t i a l l y formed on 90% of a l l control  Douglas-fir seedlings by t h i s date, but 25% of these seedlings also underwent a second flush by this time.  58  3.4.3  Morphology Trends in height growth throughout the treatment period until  fall  plant are presented in Figures 3.1 and 3.2.  the  Douglas-fir height  generally l e v e l l e d off in three weeks when the photoregime was i n i t i a t e d in Tate June or early July.  Height growth stopped in about two weeks for the  four and two week regimes. early August.  These treatments were started in late July and  A similar trend was observed for the western hemlock seedlings  where the six and eight week treatments  i n i t i a t e d in late June or early  July,  respectively, stopped height growth in three weeks while the four and two week treated plants, treatments  started in late July and early August, ceased  shoot elongation in about two weeks. Since the overall purpose of operational  dormancy induction is  control of height growth, i t is important to know how much height growth is expected once treatment  is i n i t i a t e d .  This information would help guide a  nurseryman when to commence the induction process. growth after  The range of height  treatment i n i t i a t i o n is reported in Table 3.1.  The average  height growth for a l l treated Douglas-fir seedlings was 3.7 cm and for western hemlock 4.2 cm.  There was no apparent correlation between date of  treatment i n i t i a t i o n and magnitude of height growth. Due to the staggered arrangement of treatment i n i t i a t i o n dates total  height was s i g n i f i c a n t l y different  between most of the treatments  the August and September sample periods whereby early i n i t i a t e d were s i g n i f i c a n t l y shorter than later regimes and the c o n t r o l . morphological results are found in Tables 3.2,  3.3,  for  treatments All  3.4 and 3.5.  59  Figure 3.1.  The effect of variable weeks of short days (SD) on height growth of Douglas-fir seedlings.  60  Figure 3.2.  The effect of variable weeks of short days (SD) on height growth of western hemlock seedlings.  61 Table 3.1.  The average height growth in Douglas-fir and western western hemlock seedlings after short day dormancy commenced until buds formed.  PHOTOREGIME (weeks of short days)  AVERAGE HEIGHT GROWTH (cm) Douglas-fir  Western hemlock  Control Two Four Six Eight  2.5 3.9 5.4 3.2  4.7 4.4 4.1 3.7  Average  3.7  4.2  62  Caliper measurements the photoperiod treatments  in the Douglas-fir seedlings were unaffected by  (Tables 3.3 and 3.5).  However, seedlings  conditioned outside of the greenhouse had s t a t i s t i c a l l y plants conditioned inside the greenhouse  (Table 3.6).  larger calipers than This  significant  difference, an average of 0.21 mm, probably is not operationally s i g n i f i c a n t . Conditioning or photoperiod did not influence caliper growth in the western hemlock seedlings  (Table 3.2 and 3.4).  Trends in shoot and root biomass, as measured on a dry weight basis, are demonstrated in Figures 3.3,  3.4,  3.5 and 3.6.  Shoot dry weight  accumulation generally slowed down and occasionally l e v e l l e d off in treated western hemlock seedlings 1983.  u n t i l the a r t i f i c i a l  photoperiod stopped on 17 August  After this time, shoot dry weight increased in a l l treatments  were l i f t e d in the t h i r d week of September.  u n t i l they  Shoot dry weight accumulation  generally slowed down in Douglas-fir plants placed under short day regimes. With the exception of the eight week regime, shoot dry weights continued to increase until  the seedlings  were l i f t e d in September throughout a l l  photoregimes including control until  the seedlings were l i f t e d in September.  In both species root dry weight accumulated at similar rates for a l l treatments.  However, once the treatments were completed on 17 August, 1983,  western hemlock root dry weights greatly increased in the six and eight week photoregimes.  Root dry weight also increased but at a slower rate,  other treatments.  in a l l  A surge in root growth also occurred in Douglas-fir  the shortened photoperiod resumed to i t s natural length.  after  63  Table 3.2.  Morphology measurements for western hemlock seedlings upon the completion of a l l short day dormancy induction regimes on 17 August 1983.  MEASUREMENT  PHOTOREGIME (weeks) Control  Height (cm)  21.3 a  Caliper (mm) Shoot dry weight Root dry weight  (g) (g)  Two  Four  Six  Eight  23.O 3  17.4 b  17.0bc  14.3 C  2.55 a  2.37ab  2.15 b  2.45ab  2.38ab  0.84 a  0.77 a b  0.53 b  0.59 a b  0.5 C5  0.27 a  0.21 a  0.2 O3  0.18 a  0.22 a  Values within rows followed by the same l e t t e r are not s i g n i f i c a n t l y different at p = 0.05.  Table 3.3.  Morphology measurements for Douglas-fir seedlings upon the completion of a l l short day dormancy induction regimes on 17 August 1983.  MEASUREMENT  PHOTOREGIME (weeks) Control  Two  Four  22.2 a  18.7bc  16.5cd  Six  Eight  Height (cm)  20.7ab*  Caliper (mm)  2.53 a  2.51 a  2.54 a  2.76 a  2.5 O9  1.06 a  1.13 a  0.98 a  0.829  0.7 3 a  0.283  0.3 O3  0.26 a  0.29 3  0.3 4 a  Shoot dry weight Root dry weight *  (g) (g)  13.4 d  Values within rows followed by the same l e t t e r are not s i g n i f i c a n t l y different at p = 0.05.  64  Table 3.4.  Morphology measurements for western hemlock seedlings four weeks after the completion of a l l photoregime treatments on 19 September 1983.  MEASUREMENT  PHOTOREGIME (weeks) Control  Height (cm)  22.1ab*  Caliper (mm) Shoot dry weight Root dry weight *  (g) (g)  Two  Four  23.9 a  20.0bc  Eight  18.8 C  14.9 d  2.94ab  3.09 a  3.0cP  b  2.94ab  2.59 b  1.14a  1.20*  1.00 a b  1.07 a b  0.78 b  0.43 a  0.42 a  0.42 a  0.6 &  0.52 a  Values within rows followed by the same l e t t e r are not s i g n i f i c a n t l y di fferent at p = 0. 05.  Table 3.5.  Morphology measurements for Douglas-fir seedlings four weeks after the completion of a l l photoregime treatments on 19 September 1983.  MEASUREMENT  PHOTOREGIME (weeks) Control a* 22.9 a  Height (cm) Caliper (mm) Shoot dry weight Root dry weight  *  Six  (g) (g)  Two  Four  Six  Eight  22.4 a  17.5 b  16.3 b  12.9 C  3.29 a  3.44 a  3.27 a  3.38 a  3.07 a  1.76 a b  1.8 0*  1.52 a b  1.38 b  0.88C  0.61 a  0.61 a  0.66 a  0.7 4 a  0.63 a  Values within rows followed by the same l e t t e r are not s i g n i f i c a n t l y different at p = 0.05.  65  Table 3.6.  Caliper growth in Douglas-fir seedlings after four weeks of conditioning either inside or outside the greenhouse.  PHOTOREGIME (weeks)  *  CALIPER GROWTH AFTER FOUR WEEKS OF CONDITIONING Inside (mm)  Outside (mm)  Control  3.13  3.46  Two  3.48  3.40  Four  2.97  3.57  Six  3.27  3.47  Eight  3.06  3.08  Average  3.18 a *  3.40 b  Values followed by same l e t t e r are not s i g n i f i c a n t l y p = 0. 05.  different  66  Figure 3.3.  The effect of variable weeks of short days (SD) on shoot dry weight of western hemlock seedlings.  67  0.8  0.7-  0.0  J  1 0  Figure 3.4.  1 2  1 4  1 6  1 8  1 10  WEEKS FROM TREATMENT INITIATION  r 12  The effect of variable weeks of short days (SD) on root growth of western hemlock seedlings.  68  2-,  2  4  6  8  10  WEEKS FROM TREATMENT INITIATION Figure 3.5.  The effect of variable weeks of short days (SD) on shoot dry weight of Douglas-fir seedlings.  69  Figure 3.6.  The effect of variable weeks of short days (SD) on root growth of Douglas-fir seedlings.  70  Short days generally reduced shoot dry weight of western hemlock, at both the 17 August and 19 September period (Table 3.2 and 3.4).  However,  shoot dry weight also varied between some treatments because of the staggered arrangement of treatment i n i t i a t i o n dates.  The eight week regime exhibited  s i g n i f i c a l l y reduced shoot dry weight compared to that of control because height growth stopped in this interval several weeks before i t ceased in control  seedlings.  shorter.  That i s , the eight week seedlings were s i g n i f i c a n t l y  The two week seedlings were not s i g n i f i c a l l y different in shoot dry  weight from control  plants because height growth stopped within a s i m i l a r  time period; hence total days or the effect  heights were also the same.  of the early  The effect  of short  date of treatment i n i t i a t i o n on shoot dry  weight was also evident four weeks after the photoregimes were completed. The eight week regime had s i g n i f i c a n t l y less shoot dry weight than control seedlings.  A l l other treatments  did not d i f f e r s i g n i f i c a n t l y from c o n t r o l s .  The type of conditioning influenced dry weight determinations. conditioned western hemlock seedlings  Outdoor  had s i g n i f i c a n t l y higher shoot dry  weights than indoor conditioned plants (Table  3.7).  When the photoregimes were completed on 17 August 1983 shoot dry weights in Douglas-fir generally declined with increasing weeks of photoregime (Table 3.3, Figure 3.7). effects effect  either the  of the staggered treatment i n i t i a t i o n date on height growth or the of increasing intervals of short days.  significant, means.  This trend again reflects  The differences were not  however, because of the wide variation about the treatment  Four weeks after this sample period, there were s i g n i f i c a n t  differences  in shoot dry weights between treatments  (Table 3.5).  The eight  week regime, i n i t i a t e d in late June, had s i g n i f i c a n t l y less shoot biomass  71  Table 3.7.  Average shoot dry weights in western hemlock seedlings which received four weeks of conditioning conditioning inside or outside the greenhouse after dormancy induction treatments were completed.  PHOTOREGIME (weeks)  SHOOT DRY WEIGHT AFTER FOUR WEEKS OF CONDITIONING Inside  (g)  Outside  Control  1.04  1.24  Two  1.05  1.36  Four  0.85  1.16  Six  1.06  1.08  Eight  0.71  0.81  Average  0.94  1.13°  Values followed by same l e t t e r are not s i g n i f i c a n t l y p = 0.05.  Table 3.8.  different  Average shoot dry weights in Douglas-fir seedlings which received four weeks of conditioning inside or outside the greenhouse after dormancy induction treatments were completed.  PHOTOREGIME  *  (g)  SHOOT DRY WEIGHT AFTER FOUR WEEKS OF CONDITIONING  (weeks)  Inside  Control  1.53  2.00  Two  1.60  2.00  Four  1.26  1.78  Six  1.36  1.39  Eight  0.87  0.89  Average  b* 1.32°  1.61 a  (g)  Outside  Values followed by same l e t t e r are not s i g n i f i c a n t l y p = 0.05.  (g)  different  72  2.5-  2.3-  2.1-  1.9-  t-  1.7-1  o  >-  1.5-  8 CO 1.1-  Legend  0.9-  0.7-  0.5-  A  Outside CondHioning  X  Inside C o n d i t i o n i n g  2  4  6  8  PHOTOPERIOD REGIME (WKS) Figure 3.7.  The effects of variable weeks of short days and conditioning on shoot dry weight of Douglas-fir seedlings in late September. (Vertical bars indicate standard error of the mean.  73  than a l l other l a t e r i n i t i a t e d photoregimes. s i g n i f i c a n t l y less than the c o n t r o l .  The six week regime was also  Once again, outdoor conditioning  s i g n i f i c a n t l y enhanced shoot dry weight throughout a l l photoregime treatments (Table  3.8). When a l l photoregimes were just completed, short days had not  affected  root growth, as measured by root dry weight, of either species  (Table 3.2 and 3.3). differences  That i s ,  between treatments  for both species there were no s i g n i f i c a n t on 17 August 1983.  After four weeks of  conditioning, no photoperiod effects on root dry weight were evident for Douglas-fir.  However, the influence of short day treatments on western  hemlock root dry weight was evident although not s t a t i s t i c a l l y analysis of variance.  shown by  The six and eight week regimes had greater  than the two, four and control treatments  (Figure  root masses  3.8).  To interpret this data for operational purposes, every root dry weight measurement for each treatment was compared to the 1983 MOF western hemlock cull 3.9).  standard of 0.3g and the MOF target standard of 0.5g  The proportion of seedlings  (Table  exceeding the root dry weight cull  standard for a  211 styroblock container increased with the increasing weeks  of short days.  Only 65% of the control and two week treated plants met this  standard while 90% and 100% of the six and eight week seedlings guideline.  exceeded this  In a d d i t i o n , a greater proportion of sample seedlings  actually  conformed to the MOF target standard in the six and eight week photoregimes. The 1983 c u l l  and target standards for Douglas-fir in 311  styroblock containers are  0.4 and 0.6 g.  sample trees exceeded the c u l l  A high proportion of Douglas-fir  standard throughout a l l  treatments  74 Table 3.9.  The proportion of sampled western hemlock seedlings where root dry weights conformed to the MOF c u l l and target standards on 19 September 1983.  PHOTOREGIME (weeks)  % ABOVE ROOT DRY WEIGHT CULL STANDARD (0.3g)  % ABOVE ROOT DRY WEIGHT TARGET STANDARD (0.5g)  Control  65  20  Two  65  35  Four  60  35  Six  90  75  100  55  Eight  Table 3.10.  The proportion of sampled Douglas-fir seedlings where root dry weights conformed to the MOF c u l l and target standards on 17 September 1983.  PHOTOREGIME (weeks) Control Two  % ABOVE ROOT DRY WEIGHT CULL STANDARD (0.4g) 90  % ABOVE ROOT DRY WEIGHT TARGET STANDARD (0.6g) 55  100  50  Four  80  60  Six  95  75  Eight  95  70  75  Table 3.11.  Root growth capacity of Douglas-fir and western hemlock seedlings upon the completion of short day dormancy induction treatments.  ROOT GROWTH CAPACITY MEASUREMENT  PHOTOREGIME (weeks) Control  Two  Four  Six  Eight  Douglas-fir  4.6 a  3.0°  3.4bC  4.2ab  4.8 a  Western hemlock  3.7 a  3.3 a  4.2 a  3.7 a  3.7 a  * Values within a row followed by the same l e t t e r are not different  at p = 0. 05.  significantly  76  0.65-  0 Figure 3.8.  2 4 6 PHOTOPERIOD REGIME (WKS)  8  The September l i f t root dry weights of hemlock seedlings treated with variable weeks of short days. (Vertical bars indicate 1 standard error.)  77  (Table 3.10).  A s l i g h t l y increasing amount of seedlings met the target  standard with increasing weeks of short day treatment.  3.4.4  Root growth Capacity Short days did not affect  western hemlock seedlings between some treatments  the immediate root growth capacity of  (Table 3.11).  However, s i g n i f i c a n t  differences  of Douglas-fir seedlings were demonstrated.  c o n t r o l , eight and six week regimes had similar RGC values,  The  but the two and  four week regimes exhibited s i g n i f i c a n t l y reduced RGC values compared to the eight week or control regimes. recommended for operational  3.4.5  However, a l l values were above levels  stock.  Frost Hardiness The frost  unsuccessful seedlings  hardiness tests for 17 August and 19 September were  because of equipment malfunction.  The freezing chest froze the  approximately 7°C below the predetermined value.  In a d d i t i o n ,  freezing was uneven throughout the freezer cavity.  3.5  3.5.1  Planting T r i a l  Results  Climate Since the frost  hardiness tests were unsuccessful,  to record daily temperatures outplanting.  i t was important  on the planting s i t e immediately after  This could allow the inference of a natural frost  providing frosts followed immediately after the outplanting. and maximum temperatures  are reported in Table 3.12.  0°C or less on the second, f i f t h  testing  Daily minimum  Temperatures f e l l  and sixth night after the last day of  to  78  Table 3.12.  DATE  Daily maximum and minimum temperatures and r a i n f a l l from the l a s t day of planting on 26 September 1983 u n t i l 31 October 1983. DAYS FROM  RAINFALL  PLANTING  Sept.26 27 28 29 30 Oct. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35  MAXIMUM  MINIMUM  TEMPERATURE  TEMPERATURE  cm  °C  °C  2.0  14 13 14 13 12 9 13 14 12 13 13 15 14 11 9 11 16 11 4 3 7 6 8 6.5 5 10 8 6 1.5 6 6.5 5  2 2 0 1 3 0 1 -0.5 0 2 4.5 4.5 3 4.5 1 0 -3 3.5 1 -1 -2 -1 3 -1 0 -1 -1 0 1 1 2  _  -  _  1.0 4.0  5.0 _  _ _  2.1 2.0 15.0 _  18.0 38.0 _  3.0 _  _  _  _  28.0  _  79  planting. logistics  Repeated nighttime freezing occurred throughout October until prohibited further measurements at the end of the month.  was 118 cm from the completion of planting on September 26 until 3.5.3  Visual  Rainfall  October 31.  Observations  Because of the occurrence of frosts immediately after outplanting, f i e l d observations  of possible frost  damage were attempted in early November,  However, snowfall prohibited road access to the s i t e . inspection of the planting t r i a l  The f i r s t  visual  was not possible until early May once the  snowpack was gone and crew personel were available.  Thus, i t was not  possible to s p e c i f i c a l l y conclude that any visual damage was due to frost  tolerance differences  initial  among treatments.  Visual damage inspection involved subjective assessment of the needle, buds and tops without destroying any l i v e seedlings. assessed while conducting a spring survival survey. winter t o p k i l l  In western hemlock  occurred in 23% of the control seedlings  top foliage was deep red while lower foliage  Damage was  (Table 3.13).  remained green.  The  The frequency  decreased with the increasing weeks of short days the seedlings  received in  the nursery. There was no t o p k i l l eight hour days.  in hemlock seedlings  preconditioned with eight weeks of  Since the seedlings were flushing during the survey period,  missing and dead terminal buds were easily detected. photoregime treatments  The six and eight week  a l l had flushing terminal buds on the l i v e trees.  Live control plants had 21% of t h e i r terminal buds missing or dead while the two and four week regimes respectively had 4 and 3 percent terminal bud l o s s . Poor retention of one year needles was evident throughout a l l  treatments.  80  Table 3.13.  PHOTOREGIME (weeks)  The incidence of top k i l l , dead or missing terminal buds and needle loss in outplanted western hemlock seedlings. Visual damage was observed in the spring following the f a l l planting.  Topkill  DAMAGE No Terminal Bud  Needle Loss  No. Live Trees  23  21  33  76  Two  9  4  57  83  Four  4  3  49  85  Six  3  0  33  88  Eight  0  0  33  90  Control  Table 3.14.  The incidence of top k i l l , dead or missing terminal buds and needle loss in outplanted Douglas-fir seedlings. Visual damage was observed in the spring following the f a l l planting.  PHOTOREGIME (weeks)  DAMAGE {%) Topkill  No Terminal Bud  Needle Loss  No. Live Trees  17  6  5  188  Two  7  4  6  18 0  Four  3  0  10  198  Six  2  2  5  189  Eight  3  3  7  191  Control  81  The occurrence of these types of damage was not related to the inside or outside conditioning a l l treatments A similar trend in t o p k i l l seedlings  (Table 3.14).  received prior to f a l l  planting.  incidence occurred in the Douglas-fir  There were 17% dead tops in control plants, 1% in  the two week regime and 3% in the eight week treatment.  The occurrence of  missing or dead terminal buds was not as prevalent in Douglas-fir.  Even the  control seedlings  slightly  only had 8% of this type of damage.  with increased weeks of short day preconditioning. ranged from  4% to 10% throughout a l l treatments.  or inside conditioning was evident.  Poor needle retention No effect  of the one year needles in the Douglas-fir seedlings  3.5.3.  of the outside  Most of the one year foliage  treatments was a lacklustre pale red green colour.  in both species possibly reflects  It decreased  The general  in a l l  discoloration  and the poor retention  the effects of winter desiccation.  Survival and Growth Performance There was l i t t l e difference between survival assessed in the spring  and f a l l .  Very l i t t l e mortality occurred in the f i r s t  the 1984 f a l l  survival results  are  growing season.  Only  discussed.  Survival of western hemlock seedlings  generally improved with  increasing weeks of short day preconditioning (Figure 3.9).  In an analysis  of variance, however, only the eight week regime had s i g n i f i c a n t l y better survival  (91%) than the control treatment  (76%)  (Table 3.15).  This trend was  not evident for Douglas-fir where survival was high throughout a l l (Figure 3.10).  treatments  It ranged from 89% in the two week interval to 98% in  the four week regime (Table 3.16).  82  100 n  95-  PHOTOPERIOD REGIME (WKS) Figure 3 . 9 .  One year survival in outplanted western hemlock seedlinas treated with variable weeks of short days.  83  100  0  2  4  6  8  PHOTOPERIOD REGIME (WKS) Figure 3.10.  One year survival of Douglas-fir seedlings treated with variable weeks of short days.  84  Figure 3.11.  Total height, after one year, of outplanted western hemlock seedlings treated with variable weeks of short days.  85  2 4 6 PHOTOPERIOD REGIME (WKS) Figure 3.12.  8  Total height, after one year, of outplanted Douglas-fir seedlings treated with variable weeks of short days. (Vertical bars indicate standard error of the mean.)  - Table 3.15.  Survival results for western hemlock one year after planting. TREATMENT  Six weeks  76' ab 86 ab 86 ab 88  Eight weeks  91'  Control Two weeks Four weeks  *  Values followed by the same l e t t e r are not different at p = 0.05.  Table 3.16.  significantly  Survival results for Douglas-fir one year after planting. TREATMENT  SURVIVAL  Control  9 0",ab*  Two weeks  89L  Four weeks  982 ab 95 ab 94  Six weeks Eight weeks  *  SURVIVAL [%)  Values followed by the same l e t t e r are not di fferent at p = 0. 05.  {%)  significantly  87  Trends in total  height of outplanted western hemlock and  Douglas-fir seedlings are shown in Figures 3.11 and 3.12.  Total height  generally declined with increasing photoperiod because of the effect  of the  staggered arrangement of treatment i n i t i a t i o n dates on seedling height in the nursery.  However, only the two and four week regimes had s i g n i f i c a n t  differences  in total  height of the western hemlock plants  Douglas-fir, the six and eight week treatments were s t i l l  (Table 3.17).  In  s i g n i f i c a n t l y less  than the four week interval which were a l l s i g n i f i c a n t l y lower than the control and two week dormancy induction regimes Although total  (Table 3.18).  height declined with increasing treatment,  actual height increment in the f i r s t  the  season of outplanting generally  increased as the number of weeks of short day preconditioning increased (Figure 3.13 and 3.14).  In fact  height increment was 10.4 cm and 9.8 cm for  the six and eight week regimes in western hemlock.  This was s i g n i f i c a n t l y  greater than the four week, two week or control seedling height increment which were respectively 7.1, 7.0 and 6.1 cm (Table 3.17). s i g n i f i c a n t differences  In Douglas-fir,  in increment were also demonstrated between the  control treatment and the six and eight week short day regimes  (Table 3.18).  The short day treatments were not s i g n i f i c a n t l y d i f f e r e n t , although increment increased from 7.0 cm for the two week interval to 8.6 cm in the eight week regime.  By calculating r e l a t i v e height growth rate (RGHR) height increment  was corrected to allow for i n i t i a l  size differences  at the time of planting.  In western hemlock, RGHR increased with increasing short day preconditioning (Figure 3.15). actual  Statistically,  s i g n i f i c a n t differences were the same as  height increment differences  (Table 3.15).  A similar trend was found  88  Table 3 . 1 7 .  Morphology measurements i n o u t p l a n t e d western hemlock. S e e d l i n g s were a s s e s s e d a f t e r one growing season i n October 1984.  MEASUREMENTS  PHOTOREGIME  Control Height  (cm)  23.2 * a b  Height increment (cm)  6.1  Caliper  3.27  Rhgr  (yr  )  Two Weeks  Four Weeks  S i x Weeks  E i g h t Weeks  25.4  21.8  b  24.0  a b  21.8  b  b  10.4  a  9.8  a  7.0  b  a b  0.321°  a  7.1  b  3.41  2.99  a  0.350°  3.48  b  0.398°  0.585  •Values w i t h i n rows f o l l o w e d by the same l e t t e r are not d i f f e r e n t at p = 0. 05. ** R e l a t i v e h e i g h t growth  Table 3 . 1 8 .  a b  0.607  a  3  significantly  rate.  Morphology measurements i n o u t p l a n t e d D o u g l a s - f i r . S e e d l i n g s were a s s e s s e d a f t e r one growing season i n October 1984.  MEASUREMENTS  PHOTOREGIME Control  Height  3.35  a  (cm)  27.0 * a  Height increment (cm)  6.4°  Caliper  4.54  Rhgr**(yr" )  0.294  Two Weeks  Four Weeks  S i x Weeks  E i g h t Weeks  26.5  24.2  20.5  20.4  C  8.6  a  7.5  a  4.29  a  c  7.6  a b  b c  8.0  a b  4.51  a  0.347  b  a  4.34  b  0.388  C  b  •Values w i t h i n rows f o l l o w e d by the same l e t t e r are not di f f e r e n t at p = 0. 05.  4.02  a  0.511  3  a  0.523  significantly  3  ¥ ¥  1  0  Figure 3.13.  i  1  1  2 4 6 PHOTOPERIOD REGIME (WKS)  i  8  Height increment after one growing season in western hemlock seedlings treated with variable weeks of short days. (Vertical bars indicate standard error of the mean.)  0  2  4  6  8  PHOTOPERIOD REGIME (WKS) Figure 3.14.  Height increment after one growing season in Douglas-fir seedlings treated with variable weeks of short days. (Vertical bars indicate standard error of the mean.)  91  0.65  0 55  O rr rI  e>  0.45-  LU I  LLI >  0.35  0 25  2 4 6 PHOTOPERIOD REGIME (WKS) Figure  3.15.  Relative height growth (yr~ ) after one growing season in western hemlock seedlings treated with variable weeks of short days. (Vertical bars indicate standard error of the mean.)  92  0.65  0.55-  0.25 J  1  0 Figure 3.16.  1  ;  1  2 4 6 PHOTOPERIOD REGIME (WKS)  8  '  Relative height growth (yr ) of outplanted Douglas-fir seedlings treated with variable weeks of short days. (Vertical bars indicate standard error of the mean.)  93  for Douglas-fir  (Figure 3.16).  However, significant  short day treatments were established.  differences  between  RGHR of the six and eight week  regimes were s i g n i f i c a n t l y greater than those of the four and two week regimes as well as the c o n t r o l .  The four week treatment  had a s i g i f i c a n t l y  higher RGHR than the c o n t r o l . Caliper of either species was unaffected conditioning.  by short day pre-  The inside or outside conditioning which followed the short  day treatments in the nursery did not influence any of these measured growth characteristics.  3.6  Discussion  3.6.1  Nursery T r i a l Height growth in Douglas-fir and western hemlock container  seedlings was successfully application of short days.  controlled by i n i t i a t i n g early budset with the Buds formed in two to three weeks in Douglas-fir  and three to four weeks in western hemlock.  The rate of bud formation may  vary s l i g h t l y from year to year in CIP Forest Products nursery because the rate of budset in Douglas-fir apparently changed with the date of initiation.  treatment  However, buds possibly may have formed faster in l a t e r  initiated  treatments because of the inductive effect of the naturally declining photoperiod. set  Twenty percent of the plants under a natural  bud when the photoregimes were completed on 17 August.  photoperiodic effect  seems l i k e l y because date of treatment  photoperiod had This i n i t i a t i o n did  not affect bud formation in western hemlock and the control hemlock seedling  94  did not have terminal buds on 17 August.  Cheung (1973) also demonstrated  that when short days were applied to western hemlock in the 14th, 16th and 18th week from germination, formation of terminal buds was not influenced by time of a p p l i c a t i o n . Temperature, however, is a major factor which affects bud formation.  Cheung (1978) reported that under an eight hour regime bud  formation in western hemlock was slower at temperatures  above or below 2 0 ° C .  Nelson and Lavender (1976) suggested that warm temperatures  of 25°C and 20°C  in a short photoperiod induced dormancy in western hemlock at a faster rate than a cool thermoperiod.  In Douglas-fir, Lavender and Overton (1972)  reported that cool temperature  delayed dormancy in coastal  seedlings maintained under a nine hour photoperiod.  Douglas-fir  In general, i t would  appear that budset is quickly i n i t i a t e d under a short day regime with warm temperatures.  The effect  of temperature on bud formation must be considered  when drawing conclusions from this study.  Daily maximum temperatures  averaged 26°C ranging from 17°C to 3 2 ° C .  The summer of 1983 was only  moderately warm and dry for southern Vancouver Island. summer may affect  A hotter or cooler  rate of bud formation and hence, the amount of shoot  extension once treatment is  initiated.  Short days generally reduced shoot dry weight in Douglas-fir and western hemlock.  Root dry weight was unaffected  photoregimes were just completed on 17 August. in the l i t e r a t u r e .  in both species when the Similar results are reported  Short photoperiod greatly reduced shoot dry weight  accumulation in black spruce, but i t only s l i g h t l y affected (D'Aooust and Cameron 1981).  root dry weight  However, Cheung (1973) demonstrated that  short  days s i g n i f i c a n t l y reduced shoot and root dry weight accumulations in western  95  hemlock seedlings.  The root/shoot dry weight ratio increased, implying the  root system was less affected  by short photoperiod than the shoot.  freshweight of Douglas-fir seedlings  The  also declined under a short  photoperiod (Lavender and Hermann 1970).  In addition, the roots were also affected by  short days since the number of active roots decreased.  In a second study,  Lavender and Wareing (1972) also showed that the number of active declined when Douglas-fir was pretreated with short days. reports,  roots  Unlike these  root biomass and root growth were not reduced by short day  pretreatments  in this thesis study.  throughout a l l treatments  Douglas-fir root dry weight was s i m i l a r  at both sample periods.  In addition, the six and  eight week regimes had s i m i l a r root growth capacity values to that of control. Although not s t a t i s t i c a l l y  s i g n i f i c a n t , western hemlock root dry  weight actually increased in the six and eight week regimes compared to a l l other treatments  after the four week conditioning period.  proportion of seedlings  exceeding the MOF c u l l  In a d d i t i o n , the  standard for root dry weight  dramatically increased with increasing weeks of short day treatment. occurrence reflects  the f a l l  coniferous species set bud. week regimes.  This  surge in root growth which commonly occurs once Budset was complete in the four, six and eight  Hence once the daylength was extended to a natural period,  increased photosynthates were probably channelled to the roots.  In the  treatment where budset was incomplete, photosynthates were probably u t i l i z e d to a greater extent in the shoot.  Hence, root biomass was s l i g h t l y less in  the control and two week photoregimes.  This theory seems plausible because  96  the RGC test indicates that the number of active roots was not reduced in hemlock seedlings potential  pretreated with short days.  Hence, the expression of  root growth probably varied among treatments because of the varying  competition for photosynthates extending apices.  in seedlings with complete budset or active  A s i m i l a r trend was not apparent in Douglas-fir because  incidence of budset was high throughout a l l treatments.  That i s , the  majority of shoots i n a l l treatments were no longer elongating.  3.6.2  Planting T r i a l Preconditoning with short days generally improved one year survival  and outplanting performance of f a l l container stock. seedlings  planted western hemlock and Douglas-fir  The increased survival of the treated western hemlock  compared to hemlock controls most l i k e l y reflects  frost tolerance associated  with short day  preconditioning especially since  frost occurred within the f i r s t week following outplanting. visual damage to the seedlings of t o p k i l l budkill  the increased  also supports this claim.  The type of  The high incidence  in the control and two week photoregimes and the high incidence of  in the control seedlings suggest that the stems and buds were not as  tolerant of the early f a l l  frosts and winter desiccation.  That i s , the  seedlings  from these treatments were less hardened off at the time of the  fall  and outplanting.  lift  Stem tissue was probably more succulent and more  susceptible to damage by the frosts which immediately followed the outplanting.  A difference in stress resistance or frost tolerance in the  control and treated hemlock seedlings can be inferred from the survival data. The higher mortality of the control  plants suggests stress resistance or  97  possibly frost hardiness was lower than the seedlings short days.  preconditioned with  Budset occurred in the control treatment during the end of the  four weeks of conditioning period.  Thus the hardening off phase which  commonly followed budset had not yet developed by the time the seedlings were lifted.  Because these plants had only just entered into dormancy, resistance  to the desiccating effects of l i f t i n g ,  handling and planting was possibly  lower than a l l other treatments where budset occurred a minimum of four weeks prior to l i f t i n g .  Thus, besides lower frost tolerance, a reduced resistance  to the stress associated with planting may also account for the lower survival of the control treatment. It is unfortunate that the frost tolerance tests for the 19 August and 19 September sample periods were unsuccessful  because the results would  have permitted a more conclusive explanation for why survival improved and seedling damage decreased with increasing weeks of short day preconditioning o f western hemlock seedlings.  However, there is conclusive evidence reported  in the l i t e r a t u r e which shows that preconditioning with short days enhances frost  hardiness in several  coniferous species.  Frost hardiness was enhanced in Douglas-fir seedlings  under an  eight week regime of eight and ten hour days (McCreary et a l . 1978). grown under natural and extended photoperiods were less hardy. six hour short day improved frost treatment, regimes.  Plants  Although a  hardiness compared to the control  i t reduced hardiness levels compared to the eight and ten hour The importance of a conditioning period following short day  treatment was also demonstrated whereby the seedlings  preconditioned with  short days continued to develop greater levels of frost  hardiness up to four  98  weeks l a t e r .  Timmis and Worrall  eight or ten hours induced frost  (1975) also demonstrated that a short day of hardiness in Douglas-fir.  were again s l i g h t l y reduced by a six hour regime.  Hardiness levels  Tanaka (1974) reported  that cold hardiness development was accelerated by two or three weeks in Douglas-fir container seedlings  preconditioned with eight hour days.  an important finding for stock scheduled for early f a l l  This  is  lift  and outplanting.  van den Driessche (197 0) reported that frost hardiness f i r s t  increased at the  end of the fourth week of an eight hour photoregime, although the rate of hardening was affected treatment, seedlings  by the level of l i g h t i n t e n s i t y .  After eight weeks of  cultured under an eight hour regime were s i g n i f i c a n t l y  hardier than plants grown in a sixteen hour photoperiod, providing the l i g h t intensity was s u f f i c i e n t to meet photosynthesis requirements. hardiness levels of seedlings several weeks l a t e r .  However,  in long and short day photoregimes were s i m i l a r  In a second study, van den Driessche (1969b) also  demonstrated that short days enhanced hardiness in the f a l l , mid-November seedlings  but by  grown in a natural photoperiod had attained s i m i l a r  levels of cold hardiness.  Thus, for a coastal  species an operational  advantage of short day preconditioning is accelerated frost hardiness in stock scheduled for high elevation sites in the f a l l . hardiness benefits,  In addition to  frost  Lavender and Wareing (1973) demonstrated that short day  preconditioning of Douglas-fir enhanced seedling resistance to the effects root pruning, l i f t i n g and cold storage.  This documented finding may account  for the poorer survival of the hemlock control seedlings.  These plants  possibly had not yet developed resistance to the stresses of l i f t i n g and planting.  of  99  The effect  of short days on accelerated cold acclimation has been  demonstrated in other species.  After six weeks of eight hour days at 2 0 ° C ,  black and white spruce seedlings were hardy to at least - 9 ° C , the l i m i t of the frost evaluation procedure employed in the study (Columbo et a l . 1981). In a f a l l  outplanting of Norway spruce, frost  injury to the needles was  reduced from 63% to 5% with only a two week short day preconditioning period in July or August (Sandvik 1980).  Several other studies document the  positive effects of short days on frost hardiness of Norway spruce and Scots pine (Aronsson 1975;  Christersson 1978; McGuire and F l i n t  Rosvall-Ahnebrink 1981). hardiness of coastal and cool temperatures  1962;  There is not, however, much l i t e r a t u r e on the  western hemlock.  frost  Timmis (1976) reported that short days  promote cold acclimation in western hemlock as  generally does in northern coniferous species.  it  Cheung (1978) examined  hardiness of high and low elevation western hemlock seedlings  frost  under three  temperature regimes of 1 0 ° , 2 0 ° and 30°C and two photoperiods of sixteen or eight hours.  Frost hardiness was greatest under the short day regime of  1 0 ° C , but bud formation was i n h i b i t e d .  Consequently a short day regime of  20°C was recommended as a dormancy induction technique.  Other studies on  photoperiod in western hemlock have dealt p r i n c i p a l l y with dormancy, c h i l l i n g requirement and growth response,  but not frost hardiness  (Hauessler  1981;  Nelson and Lavender 1976). From this b r i e f discussion of the l i t e r a t u r e i t appears there is much evidence to support the inference that differences  in survival and  seedling stem and bud damage in the western hemlock seedlings differences  in frost  reflect  hardiness or overall stress resistance levels produced  100  by the treatments of natural  photoperiod or short days.  When Norway spruce  seedlings were preconditioned with four weeks of 8 hour days and outplanted in the f a l l , frost damage was reduced and three year survival was improved (Rosvall-Ahnebrink 1981).  Survival of f a l l  increased with short day pretreatment  planted black spruce also  (D'Aoust and Cameron 19819).  Tanaka  (1974) reported similar results when Douglas-fir container seedlings were fall  planted on high elevation s i t e s .  In a l l these outplanting studies the  improved survival was attributed to enhanced frost hardiness  promoted by  short day preconditioning. Although western hemlock survival increased with increasing weeks of short days, only the eight week photoregime had s i g n i f i c a n t l y higher survival than the c o n t r o l .  Nonetheless,  even the two week photoregime had  10% higher survival than the control or natural  photoperiod treatment.  Thus,  the importance of early budset prior to l i f t i n g and the effect of short day treatment on f a l l drastic  survival of f a l l  planted hemlock was demonstrated.  reduction in t o p k i l l or frost damage between natural  The  photoperiod and  any of the short day treatments was also shown. The trend in survival with short day treatment was not so in the Douglas-fir seedlings. week photoregimes  apparent  Survival was higher in the four, six and eight  compared to the natural  day regime, but i t was not s t a t i s t i c a l l y  photoperiod or the two week short significant.  Interestingly,  even  these treatments had a high rate of survival at 90% and 89% respectively. This high survival of these treatments probably occurred because over 20% of the control or natural  photoperiod and 80% of the two week regime had set bud  when the photoregimes were completed on 19 August 1984.  Thus, even the  101  control seedlings underwent a hardening off period before the l i f t on 19 September.  Thus, some degree of frost hardiness and stress resistance had  probably developed when the seedlings were outplanted. the control plants implies that the natural  The early budset of  photoperiod had declined below  the level c r i t i c a l for shoot elongation for this particular Douglas-fir or that the i r r i g a t i o n regime was i n s u f f i c i e n t growth.  Since hemlock shoots were s t i l l  provenance of to maintain  elongating under a natural  photoperiod, i t would suggest that the i r r i g a t i o n was frequent enough to maintain growth and that the c r i t i c a l photoperiod for the Douglas-fir  seedlot  was greater than the c r i t i c a l daylength for the hemlock seedlot. In spite of the fact that buds had formed throughout a l l of the Douglas-fir treatments, short day pretreatment differences  in survival  still  and seedling frost damage.  resulted  in some  This suggests seedlings  pretreated with more than two weeks of eight hour days had attained a s l i g h t l y higher level of frost hardiness. damage to the stem, was s t i l l There was no difference  T o p k i l l , an indication of frost  higher in the control with an incidence of 17%..  in t o p k i l l between the four, six and eight week  regimes which suggest that frost hardiness in the stem was similar for these treatments.  The s l i g h t l y higher survival  in these three photoregimes  also  implies a short day preconditioning period greater than two weeks enhanced overall frost hardiness or stress  resistance.  The hemlock seedlings generally exhibited s l i g h t l y lower survival at each treatment  level than the Douglas-fir  plants.  One possible  explanation  is that frost hardiness or stress resistance was higher in the  Douglas-fir  during l i f t i n g and planting.  Timmis (1976) suggested that  102  hemlock acclimates  slower than Douglas-fir and speculated  less desirable species for f a l l been more suitable for  planting.  that hemlock was a  Secondly, the study s i t e may have  Douglas-fir.  Pretreatment with short days s i g n i f i c a n t l y increased f i r s t growth on an absolute and r e l a t i v e basis of f a l l Douglas-fir seedlings.  year  planted western hemlock and  In western hemlock a preconditioning period of six or  eight weeks produced a s i g n i f i c a n t l y greater height growth response. In Douglas-fir,  the six and eight week treatments had s i g n i f i c a n t l y  greater  height growth compared to the control but not to the two and four week regimes.  However, r e l a t i v e  height growth was s i g n i f i c a n t l y greater in the  six and eight week photoregimes  compared to a l l other treatments.  Few of the  published studies on photoperiodism and dormancy have discussed one year height growth in a planting t r i a l .  Rosvall-Ahnebrink (1981)  demonstrated  that Scots pine seedlings and Norway spruce seedlings treated with four weeks of short days, had greater height growth during the f i r s t addition, pretreatment the f i r s t  growing season.  with short days also resulted in e a r l i e r budflush in  spring and delayed apical  growth cessation in the f a l l .  This  probably accounted for the increased shoot elongation throughout the growing season. reported  first  Under a controlled environment, Lavender and Wareing (1970)  that short day pretreatment  accelerated  seedlings compared to a long day photoregime. for western hemlock (Nelson and Lavender 1976). also accelerated  In  bud a c t i v i t y in Douglas-fir  A similar result was reported Short day preconditioning  budflush in Norway spruce seedlings maintained in an  environment chamber (Sandvik 1980).  However, Sandvik (1980) attributed  the  e a r l i e r budflush to the higher f o l i a r nitrogen reserves that accumulated in  103  the f a l l  d i r e c t l y after treatment with short days.  Cheung (1973) also  discovered that f o l i a r nitrogen increased in western hemlock seedlings treated with eight hour days compared to sixteen hours or a moisture stress regime.  In addition to greater f o l i a r nitrogen accumulation and an  alteration in growth pattern, a third explanation to possibly account for increased height growth can be inferred from Colombo et a l . (1981).  Apical  meristems were larger and contained far more needle primordia in spruce seedlings  grown under an eight hour day at 2 0 ° C .  However, these seedlings  were compared to production run stock where temperatures were controlled.  not  That i s , cooler tempeatures may also account for the smaller bud  size with fewer primordia. Since the timing of budflush and analysis of f o l i a r nitrogen was not assessed in this study i t is not possible to infer an explanation for increased height growth from the data. seedlings Study II.  However, bud a c t i v i t y was assessed in  grown under a natural photoperiod and in an eight hour regime in These results  are reviewed in the next chapter.  Nonetheless,  it  was c l e a r l y demonstrated that a short day treatment of six or eight weeks increased f i r s t year growth performance of f a l l Douglas-fir container seedlings.  planted western hemlock and  Potential for this may be found in the  selection and proper scheduling of a dormancy induction regime that enhances frost stock.  hardiness, stress tolerance and growth potential of operational  nursery  Although such a regime cannot be recommended from this study, the  potential  benefits  of short days were demonstrated.  104  3.7  Conclusions  Short photoperiod applied to Douglas-fir and western hemlock container stock quickly i n i t i a t e d homogeneous budset. demonstrated that short days was an effective  It was  successfully  operational tool to control or  stop height growth in order to meet predetermined target specifications seedlings.  for  Shoot elongation in both species generally stopped in about three  weeks when treatments were i n i t i a t e d in late June and early July and in two weeks when treatments were started averageheight  growth after  in late July or early August.  The  the short photoperiod was i n i t i a t e d was 3.7 cm in  Douglas-fir and 4.2 cm in western hemlock. to four weeks in the treatments  Douglas-fir buds formed in three  i n i t i a t e d in late June and early July and two  to three weeks in l a t e r i n i t i a t e d treatments.  The faster rate of bud  formation was attributed to dormancy induction effect  of a naturally  declining photoperiod in this particular Douglas-fir provenance. not detected on western hemlock seedlings photoregime.  until  Buds were  the fourth week of the short  It should be pointed out that the rate of apical growth  cessation and bud formation is specific to the environmental conditions of this particular study.  Incidence of second flushing in seedlings  pretreated  with short days was nonexistant in western hemlock and only 1% in Douglas-fir. Caliper was unaffected by short day pretreatment.  Shoot dry weight  was s i g n i f i c a n t l y reduced by increasing weeks of short day treatment. However, this reduction in shoot dry weight reflects treatment i n i t i a t i o n dates.  the effect  of staggered  The eight week treatment was i n i t i a t e d in late  105  June when the seedlings were shorter than when four weeks were started in late July.  Outdoor conditioning enhanced shoot dry weight accumulation in  both species. Short day pretreatments root growth capacity.  In f a c t ,  did not adversely affect  the f a l l  root dry weight or  surge in root growth in western  hemlock seedlings was accelerated in the six and eight week photoregimes. Only 65, 65 and 60%, respectively of the c o n t r o l , two week and four week short day seedlings  had root dry weights which exceeded the MOF cull  while 90% and 100% of the six and eight week treatments standard at the September l i f t .  for a f a l l  exceeded this  Once again this result possibly r e f l e c t s  importance of early budset i n i t i a t i o n to encourage f a l l lifting  standard  scheduled outplanting.  That i s ,  the  root growth p r i o r to  i t is d i f f i c u l t to  discern whether the six and eight week regimes enhanced root growth or the early i n i t i a t e d date accounted for this surge in root growth.  This trend was  not evident in the Douglas-fir experiment where even control seedlings set bud three to four weeks prior to l i f t .  had  This implies that the early  i n i t i a t i o n of budset in the hemlock seedlings  led to increased root growth in  September. Nothing can be concluded about frost  hardiness levels at the time  of photoregime completion and after a four week conditioning period because the tests were unsuccessful.  However, inferences about frost  levels produced by the different treatments planting t r i a l . shoots.  Winter t o p k i l l  hardiness  can be drawn from the f a l l  is the result of frost damage to seedling  Incidence of t o p k i l l was 23% in the hemlock control seedlings, and  9% in the two week plants.  It decreased to 0% in the eight week seedlings.  106  In addition, terminal bud k i l l  was 21% in the control compared to 4% in the  four week and 0% in the six and eight week seedlings.  Incidence of  frost  damage to western hemlock plants declined with increasing weeks of short day treatment. regimes.  However, damage frequency was similar for the six and eight week These results  imply that short day pretreatment of six or eight  weeks enhanced frost tolerance to levels greater than seedlings  grown under a  natural summer photoperiod. The preconditioning of Douglas-fir seedlings with short photoperiod also enhanced frost hardiness l e v e l s . inthe control and two week plants.  Topkill was 17% and 7% respectively  The incidence was only 2 or 3% in the  four, six and eight week treatments. Short day pretreatment also enhanced the planting survival of western hemlock seedlings. days.  Survival increased with increasing weeks of short  However, only the eight week regime was s i g n i f i c a n t l y higher.  A  treatment difference in stress resistance to the desiccating effects lifting, data.  of  handling and planting or in frost hardiness can be inferred from the  Survival of Douglas-fir seedlings  increased s l i g h t l y , but not  s i g n i f i c a n t l y when more than two weeks of short days were applied. were no s t a t i s t i c a l  differences  between most of the treatments.  based on incidence of frost damage  However,  and the s l i g h t improvement in s u r v i v a l ,  short day pretreatment greater than two weeks enhanced frost Douglas-fir  There  hardiness in the  seedlings.  Short photoperiod s i g n i f i c a n t l y improved growth performance of f a l l planted Douglas-fir and western hemlock container seedlings. species,  In both  the six and eight week regimes produced a s i g n i f i c a n t l y greater  107  height growth response than a l l other treatments.  The western hemlock  treated with six week regimes grew an average of 10.4 cm compared to 6.1 in the plants under a natural  photoperiod, an increase of 4.3 cm.  in height growth was less dramatic for Douglas-fir.  The increase  Control plants  grew 6.4  cm while the eight week seedlings grew 8.6 cm, an increase of 2.2 cm. Caliper growth was unaffected  by short day precondition.  Based on plantation growth performance, survival  rates and  incidence of frost damage, a six or eight week photoregime appeared  to  produce the best quality western hemlock seedlings for this study.  It was  also shown that a short photoperiod of this duration did not adversely  affect  root biomass or root growth capacity. Selection of the best photoregime for Douglas-fir is not so obvious since even the control seedlings set early buds.  However, based on the  outplanting r e s u l t s , i t would appear that at least four weeks of short days were necessary to grow a seedling that survived and grew better on this particular planting  site.  A few points must be considered when reviewing these conclusions. The outplanting t r i a l was conducted on only one s i t e type, that was assessed as having a poor to medium productivity. will  Growth performance and survival  vary according to p r o d u c t i v i t y , aspect, elevation, moisture regime and  various other factors.  In a d d i t i o n , the t r i a l  involves only one summer which  may or may not reflect weather conditions typical of south Vancouver Island. It would also be of interest and third growing season. operational  to examine survival and growth after the second  If CIP Forest Product employs short days as an  dormancy induction, plantations  and growth performance.  should be monitored for survival  108  CHAPTER FOUR STUDY TWO DORMANCY INDUCTION OF DOUGLAS-FIR CONTAINERIZED SEEDLINGS: A COMPARISON BETWEEN MOISTURE STRESS, SHORT DAYS AND A COMBINATION OF MOISTURE STRESS FOLLOWED BY SHORT DAYS 4.1  Introduction The 1983 operational  t r i a l demonstrated the effectiveness  of short days  in i n i t i a t i n g budset, enhancing survival in western hemlock and f i r s t growth performance in hemlock and Douglas-fir container seedlings. however, evidence that moisture stress is also an effective  year  There i s ,  tool in  controlling height and inducing dormancy in forest seedlings (Blake et a l . 1979; Cheung 1973; Lavender and Cleary 1974; McDonald and Running 1979; Timmis and Tanaka 1976; Zaerr et a l . 1981). short days quickly enhance frost 1978; Tanaka 1974;  Blake et a l .  studies indicate that  hardiness in Douglas-fir  Timmis and Worrall  Reports on the effect  Several  1975;  (McCreary et a l .  van den Driessche 1969b, 1970).  of moisture stress on frost  hardiness are c o n f l i c t i n g .  (1979) demonstrated that hardiness was enhanced at a shoot  water potential of -5 to -10 bars and reduced at a plant moisture stress of -10 to -15 bars.  Timmis and Tanaka (1976) reported that a stress of -6 bars  enhanced hardiness compared to -12 bars.  Van den Driessche (1969b) concluded  that moisture stress had no s i g n i f i c a n t effect Douglas-fir seedlings;  on frost  hardiness in  but under a short photoperiod seedlings regularly  watered acclimated faster than seedlings infrequently i r r i g a t e d . these studies frost  In a l l  hardiness tests were conducted immediately after  treatment or within 11.5 weeks of treatment. Frost hardiness  is an important attribute of seedling q u a l i t y .  enables seedlings to withstand the freezing temperatures  of outdoor  It  109  overwintering or of winter l i f t i n g and cold storage. operational hardiness  dormancy induction technique should enhance or at least  levels.  operational  Selection of an maintain  Other measureable attributes to consider in developing an  tool for c o n t r o l l i n g height growth, and i n i t i a t i n g and  maintaining budset are root growth capacity, dormancy intensity and morphological c h a r a c t e r i s t i c s  such as bud height and root dry weight.  Extensive evidence  that moisture stress and short days are both  effective  indicates  in inducing budset.  An operational  the effectiveness of both as operational and Douglas-fir.  t r i a l was conducted to assess  induction tools for western hemlock  The study was designed to evaluate and compare the  effects  of short days and moisture stress on the physiological and morphological quality of Douglas-fir container seedlings. included root growth capacity, time of an operational  parameters  dormancy intensity and frost hardiness  at the  January l i f t , and root growth capacity and dormancy  intensity after five weeks of operational  4.2  The physiological  cold storage.  Methods Four levels of moisture stress and two photoperiod regimes were  f a c t o r i a l l y applied to Douglas-fir seedlings in a completely randomized design.  The coastal  provenance seedlings were from seedlot 7276 collected  from seedzone 1020 at an elevation of 925 m. styroblock containers  They were sown in 313  on 23 March 1984 at the CIP Forest Products Nursery in  Saanichton, B r i t i s h Columbia.  They were cultured under the  nursery's  standard f e r t i l i z e r and i r r i g a t i o n regimes until treatments commenced on 19 July 1984 (Appendix III).  The four levels of moisture stress were:  control,  110  l i g h t , medium and severe which respectively corresponded to predawn pressure bomb readings of 0 to -5 bars, -10 bars, -15 bars and -25 bars.  Styroblock  weights and s o i l water content were measured concurrently in order to correlate them with pressure bomb readings.  Soil water content was  determined by bulking the planting media from the pressure bombed seedlings. Soil  samples were weighed immediately after  pressure bombing and again  approximately 24 hours of oven drying at 7 0°C.  Soil water content was  estimated as a percentage of the oven dried weight of s o i l . period was conducted over a two week period.  after  The stress  Each time seedlings  reached  t h e i r respective stress l e v e l s , they were rewatered and allowed to dry out agai n. The two levels of photoperiod were the natural daylength and four weeks of eight hour days.  The photoperiod was controlled in a greenhouse  with black p l a s t i c curtains.  outfitted  Light leaks were monitored on the treatment  benches with a LICOR photometer.  Temperatures were recorded by a  hygrothermograph. Although moisture stress and photoperiod regimes were f a c t o r i a l l y arranged, not a l l treatments were applied concurrently. moisture stress and the unstressed 19 July. treatments  The four levels of  short photoperiod treatments  commenced on  Once the two weeks of stress were completed, half of a l l these then received four weeks of eight hour days until  3 September.  When a l l treatments were f i n i s h e d , a l l seedlings were cultured under CIP Forest Products Nursery standard regimes.  The seedlings were l i f t e d in the  third week of January 1985 and placed into cold storage for five weeks.  Ill  4.2.2  Measurements Treatment effects were evaluated by assessing seedling morphology, root  growth capacity, frost  hardiness and dormancy i n t e n s i t y .  were measured weekly during the treatment period. were recorded every second week.  Shoot and root dry weights  Once the treatments were completed, a l l  measurements were done monthly until Forty-five seedlings  Height and c a l i p e r  the seedlings were l i f t e d in January.  per treatment were measured for each sample period.  Root growth capacity (RGC) was tested at the time of seedling l i f t and after  five weeks of cold storage.  The RGC tests were conducted according to  the procedures outlined by the Ministry of Forest (Appendix 1).  Twenty trees  were sampled from each treatment at each test period. Frost hardiness was assessed by subjecting seedlings  to a range of  freezing temperatures and determining the temperature at which 50% ( L T 5 0 ) of the seedlings  died or were severely damaged.  were a l l included in the assessment.  Bud, stem and needle damage  Eighty seedlings from each treatment  were shipped to a laboratory in Washington state in early January. procedures for this test are outlined in Appendix  The  II.  Dormancy intensity was simply assessed by placing twenty sample seedlings  per treatment into a growth chamber and monitoring the number of  days required for budbreak.  The environment conditions in*the chamber were  20°C during the day and night with a daylength of 16 hours.  4.2.3  Statistical  Analysis  Treatment effects were assessed in analyses of variance.  When either  or both of the two factors were s i g n i f i c a n t , treatment means were compared by  112  Newman-Keul's multiple range t e s t .  Several of the analyzed variables did not  meet the assumption of homogeneous variance, as indicated by a Bartlett Chi-square t e s t .  Transformation did not result in homoescasdicity.  Consequently, interpretations from these analyses should be made with caution.  The analyses which did not meet this basic assumption are outlined  in Appendix IV.  4.3  Tables for analyses  of variance are reported in Appendix V.  Results  4.3.1  Treatments The actual pressure bomb values for each level of moisture stress were  similar to proposed levels  (Table 4.1).  Severe, medium, l i g h t and control  moisture stress treatments corresponded to average predawn shoot water potential measurements of -23.4, -17.5, -9.5 and -4.9 bars,  respectively.  Daily pressure bomb readings and the ranges are included in Appendix VI.  The  stress period lasted sixteen days during which time each treatment reached its  respective stress level at least twice.  The block weights, water loss on  a weight basis and s o i l water content associated stress are reported in Table 4.1. staff  with each class of moisture  It is important for operational nursery  to note that an average 313 block weight of 4.5 kg produced a l i g h t  stress of -9.7 bars while only a s l i g h t decrease to 4.35 kg resulted in a medium moisture stress of -17.5 bars. incurred a severe stress of -23.4 bars.  A s i m i l a r l y small reduction to 4.05 kg The relationships between shoot  water potential and styroblock weight, and plant moisture stress and s o i l water content are shown in Figures 4.1 and 4.2.  From these graphs i t  is  evident that as s o i l water content or styroblock weights become increasingly lower, small changes in these measurements produce major changes in plant  Table 4.1  Plant moisture stress, styroblock weight, waterloss on a weight basis, and s o i l content at the time each treatment was watered.  TREATMENT  DAY OF IRRIGATION1 1-PM 5-PM 8-AM 12-AM 16-AM  Control  Average Light Stress  6-AM 11-AM 16-AM  Average Medium Stress  7-AM 13-AM  Average Severe Stress Average  8-AM 16-AM  STYROBLOCK WEIGHT (kg)  WATER LOSS (kg)  ACTUAL PMS (-bars)  PROPOSED PMS (-bars)  6.2 5.7 5.6 5.1 4.9  1.25 2.35 2.20 2.90 3. 00  4.1 5.7 5.0  5.5  2.34  4.9  4.5 4.6 4.5  3.10 3.30 3.00  9.6 9.8 9.0  4.53  3.13  9.5  4.3 4.4  3.5 3.10  18.4 16.7  35 33  4.35  3.3  17.5  15.0  4.0 4.1  3.70 3.70  23.8 23.0  4.05  3.70  23.4  Number of days from treatment i n i t i a t i o n .  water  SOIL WATER CONTENT {%) 66 60 62 58 56  -  5.0  6 0.4 41 49 41  10.0  40.3  34 32 29  25.0  30.5  114  SOIL WATER CONTENT(%) Figure 4.1  The relationship between shoot water potential and s o i l water content (%).  115  Figure 4.2. The relationship between water potential and styroblock weight.  116  moisture s t r e s s .  The curves represented in these figures  are specific to the  conditions of this study and cannot be used to estimate stress levels in Douglas-fir seedlings  4.3.2  in another growing season.  Daily Climate The weather remained hot and dry throughout the dormancy induction  period.  During the actual moisture stress period from 19 July 1984 to 3  August 1984, daily maximum temperatures average temperature of 2 9 . 5 ° C .  ranged from 2 3 ° . to 34°C for an  Nightly minimum temperatures  varied from 7 °  to 1 6 ° C , for an average temperature of 1 3 ° C . The temperature regimes in the short day greenhouse were warmer.  Daily temperatures  rose as high as  38°C.  They were frequently in the mid-thirties throughout the entire treatment period.  No l i g h t leaks were detected on the research bench in the short day  greenhouse.  4.3.3  Bud Formation and Incidence of Reflushing In the f i r s t  sixteen days of experimentation a short photoperiod was  compared to four levels of moisture stress under a natural daylength.  The  rate of bud formation varied between treatments at the end of this approximate two week period (Table 4.2).  Short days exhibited the fastest  rate of bud formation where 87% of the seedlings days. and  set terminal buds in sixteen  This was s i g n i f i c a n t l y greater than the control plants with 44% budset  the medium stress seedlings  with 51% incidence.  Although bud formation  was highest under the short day regime, i t did not d i f f e r s i g n i f i c a n t l y from the l i g h t stress at 69% and the severe stress at 80%.  With the exception of  the medium class of moisture s t r e s s , increasing levels of moisture stress  117  resulted in an increasing rate of bud formation. statistically  However, this trend was not  significant.  At the end of the moisture stress period, half of the blocks from each stress treatment were placed under a short photoperiod. after  Two weeks l a t e r or  four weeks from project i n i t i a t i o n , photoperiod and moisture stress  pretreatment s i g n i f i c a n t l y affected significant  incidence of budset.  There was also a  interaction between moisture stress preconditioning and  photoperiod (Figure 4.3).  The interaction occurred at the control or regular  i r r i g a t i o n level of moisture stress where the magnitude of the response to a natural or short daylength was different from any other level of moisture stress.  At each level  of moisture s t r e s s , incidence of budset was  s i g n i f i c a n t l y higher in the short day regime (Table 4.3).  Under a natural  photoperiod, budset incidence was s i g n i f i c a n t l y greater in seedlings  treated  with a l i g h t , medium or severe moisture stress compared to the control plants.  Although pretreatment with moisture stress increased terminal bud  formation, no s i g n i f i c a n t differences were demonstrated between these three classes.  In a short day regime, preconditioning with moisture stress did not  s t a t i s t i c a l l y affect  budset four weeks from project i n i t i a t i o n .  That i s ,  after two weeks of short days, the moisture regime applied prior to short day treatment did not influence the number of seedlings with terminal buds. When the means of a l l treatment combinations were compared, seedlings under a short day regime had s i g n i f i c a n t l y more terminal buds after  four  weeks from project i n i t i a t i o n , regardless of moisture regime (Table  4.4).  Only the short day seedlings  pretreated with medium moisture stress were  similar to the l i g h t and severe stressed plants under a natural daylength.  118 Table 4.2  Terminal bud formation in Douglas-fir seedlings maintained under five dormancy induction regimes. Assessment made sixteen days after treatment i n i t i a t i o n .  TREATMENT Natural  PROPORTION OF SEEDLINGS WITH TERMINAL BUDS {%)  Photoperiod Control  44 c  Light Stress  69ab be  Medium Stress  51  Severe Stress  8 0a  Short Photoperiod  87 a  •Values followed by the same l e t t e r p = 0.05.  Table 4.3  are not s i g n i f i c a n t l y  different  at  The effect of photoperiod and moisture stress on terminal bud formation of Douglas-fir seedlings. Assessment made four weeks after project i n i t i a t i o n . PHOTOPERIOD  MOISTURE STRESS  Natural  Short  %seedlings with terminal buds Control Light  ll.l6*1 al** 62.2ai  93.3aI1 all 88.9311  Medium  51.1aI  80.0aI1  Severe  64.4aI  91.1aI1  •Values within a column followed by the same l e t t e r are. not different at p = 0.05.  significantly  **Values within a row followed by the same Roman number are not different at p = 0. 05.  significantly  119  Table 4.4  Bud formation and incidence of reflushing in eight dormancy induction treatments applied to Douglas-fir seedlings.  WEEKS FROM TREATMENT INITIATION FOUR  SIX  TREATMENT %Budset  %Reflushed  82 a  76 b  24 b  light stress  d* 11° 62bc  24 b  iooa  oa  medium stress  51 C  2 0b  98 d  0a  severe stress  64bc  24 b  98 a  O3  4b  96 a  4a  100a  O3  Natural  Photoperiod  control  %Budset  %Reflushed  Short Photoperiod control  93 a  l i g h t stress  89 a  ll  medium stress  8 0ab  13 b  iooa  o3  severe stess  91 a  9b  100 a  o3  b  •Values within a column followed by the same l e t t e r are not s i g n i f i c a n t l y different at p = 0.05.  120  100  0J  ,  1  Control  Figure 4.3.  i  Light Medium MOISTURE REGIME  1  —  1  Severe  Budset incidence in Douglas-fir seedlings after four weeks of treatment with moisture stress, short days or a combination of both. (Vertical bars indicate standard error of the mean.)  121  Figure 4.4. Incidence of flushed terminal buds in Douglasf i r seedlings after four weeks of treatment with moisture stress and short days. (Vertical bars indicate standard error of the mean.)  122  For a l l levels of moisture s t r e s s , short photoperiod reduced the incidence of reflushing four weeks from treatment However, the only s i g n i f i c a n t  difference  control moisture stress level  (Table 4.4).  affected  i n i t i a t i o n (Figure  4.4).  between photoperiods occurred at the That i s , moisture regime only  the occurrence of reflushing under a natural  photoperiod at the  control moisture regime l e v e l . To summarize, after a four week period, a short photoperiod, regardless of the level of moisture s t r e s s , was more effective  in i n i t i a t i n g and  maintaining budset compared to seedlings under a natural Six weeks from treatment  photoperiod.  i n i t i a t i o n terminal buds had formed in 96% or  more of the seedlings in a l l treatments but the control moisture regime in a natural  daylength.  Only 76% of these plants had terminal buds.  Incidence of  reflushing was 24% in this treatment compared to negligible levels ether treatment combinations  (Table 4.4).  days or a combination of both effectively  in a l l  Therefore, moisture s t r e s s ,  short  i n i t i a t e d and maintained budset  after a six week period commencing in the third week of July and ending in the f i r s t was least  4.3.4  week of September.  A natural  photoperiod without moisture  stress  effective.  Morphology Seedlings maintained under a natural  photoperiod with a control  moisture regime were s i g n i f i c a n t l y larger in height, c a l i p e r , shoot dry weight and root dry weight than a l l other treatment combinations at the time of the January l i f t  (Table 4.5).  Because of the size differences  produced  only under these particular conditions or this treatment combination,  Table 4.5 Morphology measurements of Douglas-fir of the January 1985 l i f t .  seedlings at the time  MEASUREMENTS TREATMENT  Natural  Caliper  (cm)  (mm)  Ht/C 1  Shoot Dry  Root Dry  weight  Weight (g)  (g)  S/R2  Bud Height (mm)  Photoperiod  control light  a* 23.3 17.4  2.47  17.8 16.3  2.49 2.57  a  stress  cde  medium stress severe stress Short  Height  bC  ef  2.98  7.8 7.0 7.1  a  C  C  bc  1.74  a  0.94  C  C  2.1  b  1.7  5.3 5.5  b  1.9 1.3  5.5 5.5  b  2.5  b  2.0 1.6 1.7  5.7 5.5  0.83 0.55 0.56  6.3  1.05 1.00  C  0.56  6.9 6.7  1.25 1.09  0.49 0.54  6.3 6.6  0.95° 0.92  bC  b  a  a  a  a  Photoperiod control light  18.7 17.6 b  stress  medium stress  16.l  severe stress  16.5  2.70 2.63 2.57  b  Gde  f  def  bc  bc  2.49°  b  C  bC  0.58 0.55  b  b  •Values within a column followed by the same l e t t e r are not s i g n i f i c a n t l y different at p = 0. 05. 1  Height to caliper  2  Shoot to root  ratio.  ratio.  a  a  5.2 5.1  a  a  124  significantly statistical  interactions occurred between the factors of  photoperiod and moisture regime due to the factorial treatments.  For every interaction the different  arrangement of the  response usually occurred at  the control moisture stress level between the two types of photoperiod. Significant  differences  in total  of the treatments (Table 4.5). water regime under a natural  height were demonstrated  However, with the exception of the control  photoperiod these s t a t i s t i c a l  probably have l i t t l e operational  signficance  in a natural  differences  unless the crop height were  approaching the upper or lower l i m i t s of the cull control  between many  standard.  Except for the  daylength, mean heights only ranged from 16.1 cm for the  medium stress under a short day to 18.7 cm for the short day control a statistically  significant  but operationally small difference  There were no apparent trends in total  height (Figure 4.5).  of 2.6 cm.  When moisture  stress effects were analyzed under a short day regime, no differences found between the l i g h t , severe and medium stress l e v e l s .  regime,  were  The regularly  watered plants were s i g n i f i c a n t l y t a l l e r by 1.1 to 2.6 cm (Table 4.6). the natural  photoperiod, only the regularly watered plants  greater total  height.  4.6 cm.  had s i g n i f i c a n t l y  When the effects of photoperiod were examined at each  moisture regime, s i g n i f i c a n t (Table 4.6).  In  differences  were found at the control level  Natural photoperiod produced a t a l l e r plant by an average of  A significant  increase of 1.7 cm in a natural  photoperiod was shown  at the medium moisture stress c l a s s . Photoperiod did not s i g n i f i c a n t l y affect caliper growth at any of the moisture stress levels  (Table 4.7).  However, under a natural  photoperiod the  control water regime s i g n i f i c a n t l y increased caliper growth (Figure 4.6).  No  Control  Figure 4.5.  Light Medium MOISTURE REGIME  Severe  The f i n a l height of Douglas-fir seedlings treated with moisture s t r e s s , short days or a combination of both. (Vertical bars indicate standard error of the mean.)  126  Figure 4.6.  The effects of moisture stress and photoperiod on the f i n a l c a l i p e r measurement of Douglasf i r seedlings in January 1985. (Vertical bars indicate standard error of the mean.)  127 Table 4.6  The effects of photoperiod and moisture regime on total in Douglas-fir seedlings.  MOISTURE STRESS REGIME  Natural  fii2I9fIB152 total  Control  height  height  Short (cm)  Light  23.33*1 bl** 17.4Di  18.7aI1 hT 17.6D1  Medium  17.8bI  16.1bH  Severe  16.3bI  16.5bI  •Values within a column followed by the same l e t t e r are not different at p = 0. 05.  significantly  •Values within a row followed by the same Roman number are not different at p = 0.05.  Table 4.7  significantly  The effect of photoperiod and moisture regime on caliper growth of Douglas-fir seedlings.  MOISTURE STRESS REGIME  Natural  £M5£i.£!2P  Short  caliper (mm) Control  2.983*1 hT**  2.70aI aT  Light  2.47 D 1  2.6331  Medium  2.49bI  2.57aI  Severe  2.57bI  2.49aI  •Values within a column followed by the same l e t t e r are not di fferent at p = 0.05.  significantly  ••Values within a row followed by the same Roman number are not di fferent at p = 0. 05.  significantly  128  differences  were detected between the remaining moisture stress  Caliper was unaffected  by moisture stress in a short day regime.  Shoot dry weight was affected (Figure 4.7). occurred.  levels.  by photoperiod and moisture regime  A s i g n i f i c a n t interaction between these two factors  also  Under a natural photoperiod, regular watering s i g n i f i c a n t l y  increased shoot dry weight compared to the three levels of moisture stress (Table 4.8).  There were no differences  moistures s t r e s s .  between a l i g h t , medium or severe  Regular watering under a short photoperiod also increased  shoot dry weight compared to a severe or medium stress level but not compared to a l i g h t moisture stress regime. short day seedlings  Shoot dry weight was also s i m i l a r among  pretreated with a severe, medium or l i g h t s t r e s s .  Photoperiod s i g n i f i c a n t l y affected  shoot dry weight but the magnitude and  direction of the response varied at each pretreatment moisture regime.  At  the control and medium stress regimes, shoot dry weight increased s i g n i f i c a n t l y under a natural photoperiod; although response magnitude was greater  in the control treatment.  Shoot dry weight was greater  day regime at the l i g h t stress l e v e l .  in the short  No difference between photoperiods  occurred at the severe moisture regime. Once again i t can be argued whether these s t a t i s t i c a l operationally important.  differences  In the l i g h t to severe moisture stress regimes  are for  both photoperiods shoot dry weight only ranged from 0.92 to 1.09 g, a difference of 0.17 g.  In an operational  perspective i t would seem that only  regularly watered plants under a natural daylength had greater shoot dry weights.  Under a natural photoperiod, shoot dry weight was 1.74 g and under  a short day i t was 1.25 g.  When a l l treatment combinations were compared in  129  1.9  0.8  1  1  Control  Figure 4.7.  !  Light Medium MOISTURE REGIME  ;  1  Severe  The effects of moisture stress and photoperiod on the final measurement of shoot dry weight of Douglas-fir seedlings in January 1985. (Vertical bars indicate standard error of the mean.)  130  Figure 4.8.  The effects of moisture stress and photoperiod on the final root dry weight measurement of Douglas-fir seedlings in January 1985. (Vertical bars indicate standard error of the mean.)  131 Table 4.8  The effect of photoperiod and moisture regime on shoot dry weight accumulation of Douglas-fir seedlings.  MOISTURE STRESS REGIME  PHOTOPERIOD Natural  Short shoot dry weight  (g)  Control  1.74 *  Light  0.94bI**  1.09abH  Medium  1.05bH  0.95bI  Severe  1.00 b I  0.92 b I  a  1.25aI1  1  •Values within a column followed by the same l e t t e r are not different at p = 0.05.  significantly  •Values within a row followed by the same Roman number are not different at p = 0.05.  Table 4.9  The effects of photoperiod and moisture regime on root dry weight of Douglas-fir seedlings.  MOISTURE STRESS REGIME  significantly  PHOTOPERIOD Natural  a*I  Short root dry weight  (g)  Control  0.83  Light  0.55  bi  0.54  Medium  0.56  bi  0.58  Severe  0.56  bi  •Values within a column followed by the same l e t t e r are not different at p = 0.05.  0.49  0.55  all al al al  significantly  ••Values within a row followed by the same Roman number are not different at p = 0.05.  significantly  132  a multiple range t e s t , only the control moisture stress plants under a natural photoperiod were s i g n i f i c a n t l y greater than a l l other treatments (Table 4.5).  Although, s i g n i f i c a n t differences  were s t i l l  shown between  various other treatment combinations, i t is doubtful whether i t was of operational  significance.  Although an analysis of variance indicated that root dry weight was affected  by photoperiod and moisture stress pretreatment, these effects were  only evident at one p a r t i c u l a r treatment combination (Table 4.5, Regularly watered seedlings greater  root biomass.  did not affect  level  (Figure The final  under a natural photoperiod had s i g n i f i c a n t l y  Under a short day regime, moisture stress  root dry weight.  the control moisture regime.  4.9).  pretreatment  Short days only reduced root dry weight at  This effect  did not occur at any other moisture  4.8). morphology measurement analyzed was bud height.  photoperiod or moisture stress s i g n i f i c a n t l y affected  Neither  bud height (Table  4.5).  4.3.5  Root Growth Capacity (RGC) L i f t RGC and post storage RGC values were very similar (Table 4.10).  Since these values from both sample periods were s i m i l a r , treatment will  only be discussed  for one data set,  January l i f t  RGC.  effects  The effects of  one factor were analyzed by each level of the second factor because of a s i g n i f i c a n t interaction between photoperiod and moisture s t r e s s . Pretreatment moisture regime s i g n i f i c a n t l y affected did not.  RGC but photoperiod  Under a natural daylength, RGC generally declined with increasing  133 Table 4.10  The effect of moisture stress on root growth capacity of Douglas-fir seedlings under two photoperiods.  MOISTURE STRESS REGIME 1.  2.  ROOT GROWTH CAPACITY UNDER TWO PHOTOPERIODS Natural  Short  control  4.00a*  2.9 &  l i g h t stress  2.50°  2.45 a  medium stress  2.90°  2.95 a  severe stress  1.65 c  2.75 a  control  3.95 a  2.60 3  l i g h t stress  2.45°  2.85 a  medium stress  2.65°  2.65 a  severe stress  1.65 c  2.85 a  January L i f t  Post Storage  •Values within a column of a numbered section are not s i g n i f i c a n t l y at p = 0.05.  different  134  4.5  Figure 4.9.  The effects of moisture stress and photoperiod on root growth capacity of Douglas-fir seedlings measured in late January 1985. (Vertical bars indicate standard error of the mean.)  135  moisture stress (Figure 4.9).  The control RGC was 4.0 which was  s i g n i f i c a n t l y greater than the other moisture stress levels  (Table 4.10).  The RGC values for the l i g h t and medium levels were similar at 2.50 and 2.90, respectively. of 1.65.  RGC was s i g n i f i c a n t l y lower in the severe stress with a value  However, the effect  of pretreatment moisture stress was not evident  under a short day regime where no differences  in RGC were demonstrated  between any of the moisture stress l e v e l s .  4.3.6  Dormancy Intensity Days to bud break or dormancy intensity at the January  lift  s i g n i f i c a n t l y decreased with short day treatment at the control and medium stress moisture regimes (Table 4.11).  Short photoperiod reduced days to bud  break at the l i g h t and severe moisture stress levels but not s i g n i f i c a n t l y . Therefore, bud a c t i v i t y generally increased in seedlings short days (Figures  4.10,  pretreatment did not affect  4.11).  pretreated with  In a short photoperiod, moisture stress  dormancy i n t e n s i t y .  Under a natural photoperiod,  s i g n i f i c a n t l y more days were required to break buds of the regular watered seedlings.  No differences were demonstrated between the l i g h t , medium and  severe moisture stress  levels.  Dormancy i n t e n s i t y after  five weeks of cold storage decreased  s i g n i f i c a n t l y under a short photoperiod, irrespective of moisture stress (Table 4.11).  Moisture stress had no s i g n i f i c a n t effect  intensity under either photoperiod.  on dormancy  136  Table 4.11  The effect of photoperiod and moisture stress on dormancy intensity of Douglas-fir seedlings. Tests were conducted during the January l i f t and after five weeks of cold storage. DORMANCY INTENSITY UNDER TWO PHOTOPERIODS  MOISTURE STRESS  Natural  Short  REGIME  (days to bud break)  (days to bud break)  1.  2.  January L i f t control  21.4  l i g h t stress  18.8  medium stess  18.7  severe stress  17.2  Post Storage control  23.1  l i g h t stress  21.8  medium stress  22.7  severe stress  24.9  a* I bl*< bl bi  al al al al  15.8 17.3 17.2 16.4  14.5 17.7 18.3 14.4  all al all al  all all all all  •Values within a column of a numbered section followed by the same l e t t e r are not s i g n i f i c a n t l y different at p = 0.05. ••Values within a row of a numbered section followed by the same Roman number are not s i g n i f i c a n t l y different at p = 0.05.  137  26  Control  Figure 4.10.  Light Medium MOISTURE REGIME  Severe  T h e effects of moisture stress and photoperiod pretreatment on dormancy intensity of Douglasf i r seedlings in January 1985. (Vertical bars indicate standard error of the mean.)  138  26  24  w T3  22-  ro 20 >t CO UJ r-  Z  \  18  >-  o  z < 16 cc  /  o  /  /  D  \  \  \  Legend 14  A  Noturol Photoperiod  X  Short Days  12  Control Figure 4.11.  Light Medium MOISTURE REGIME  Severe  The effects of moisture stress and photoperiod pretreatment on dormancy intensity of Douglasf i r seedlings in March 1985. (Vertical bars indicate standard error of the mean.)  139  No s t a t i s t i c a l  comparisons between the two sample periods were made  since the test environments were d i s s i m i l a r .  The January test was done in a  20°C thermoregime while the March test was conducted under a daily temperature of 30°C and a nightly temperature of 2 5 ° C .  However, inspite of  the warmer temperatures of the March t e s t , more days were required to induce budflush in seedlings  4.3.7  under a natural daylength.  Frost Hardiness At the January l i f t  no differences  in frost hardiness were demonstrated  between any of the treatment combinations.  At a test temperature of - 2 1 ° C ,  only 0 to 2.5% of the sample seedlings died throughout a l l However, greater than 50% of a l l test seedlings were dead at - 2 4 ° C . -24°C.  Hence, the LT 5 Q  treatments.  in a l l treatment combinations  for a l l treatments was between - 2 1 ° C and  Neither moisture stress or photoperiod affected  frost hardiness  five  months after the treatments were applied.  4.4  Discussion The effects of moisture s t r e s s , short days and a combination of both  reported in this study must be interpreted with caution for several  reasons.  F i r s t , the assumption of homogeneous variance was frequently not met.  This  must be considered when treatment means were demonstrated by a multiple range test to be s i g n i f i c a n t .  Secondly, the effects of treatment combinations on  such variables as budset incidence, morphology and root growth capacity may partly reflect the influences of operational practices applied prior to project i n i t i a t i o n .  A s p e c i f i c example of this is the budset incidence  recorded after only 16 days of treatment.  Even 44% of the regularly watered  140  seedlings in a natural  photoperiod had formed terminal buds.  84% of a l l these seedlings had flushed. pretreatment  Two weeks  An examination of the operational  i r r i g a t i o n regime accounts for this occurence.  the project i n i t a t i o n , nursery staff  later  At the date of  had already commenced an overall  moisture stress regime to slowly reduce height growth throughout the f i r crop.  By mid-July the average stressed 313 block weight in greenhouse  the location of the research t r i a l , was only 4.3 kg. medium moisture stress in this research project. population was selected  from the operational  six,  This corresponded to a  Since the experiment  stock in July, a l l seedlings had  received a moisture stress regime prior to project i n i t i a t i o n .  For this  reason, the fast rate of bud formation was most l i k e l y affected  by the  pretreatment operational  i r r i g a t i o n regime.  The high rate of reflushing  evident in the control seedlings under a natural daylength occurred because once the study began frequent  i r r i g a t i o n maintained control blocks around 5.5  kg. The operational  i r r i g a t i o n regime may also explain the d i s s i m i l a r i t y in  the RGC and root dry weight results between Study I and Study II.  In Study I  four weeks of short days in a frequent i r r i g a t i o n regime did not reduce RGC or root biomass in Douglas-fir seedlings compared to that in plants under a natural daylength. The operational  Short days reduced these characteristics  in Study  II.  i r r i g a t i o n regime applied in late June and early July 1984  may have affected  these r e s u l t s .  In 1983 seedlings were frequently watered  prior to and during the dormancy induction project. A d i s s i m i l a r i t y in thermoregime also existed between the short day and natural daylength treatments.  The greenhouse where short days were applied  was at least 5°C warmer during the day.  Temperatures frequently exceeded  141  35°C.  This high thermoregime may also have affected  seedling vigour and root  growth response. Interpretation of the data was further complicated by the  significant  interactions between moisture regime pretreatment and photoperiod.  In the  morphology data, the interaction was usually between the two photoperiods at the control moisture regime.  Reasons for this occurrence are obvious.  An  eight hour day, regardless of moisture regime, and the selected levels of l i g h t , medium and severe moisture stress under a natural daylength are environmental conditions which promote dormancy induction and i n h i b i t shoot growth of coastal  Douglas-fir seedlings.  Frequent i r r i g a t i o n that v i r t u a l l y  eliminates plant moisture stress encourages  growth in the growing season.  When this was combined with a late July and early August photoperiod, conditions remained favourable  for shoot elongation.  Hence this  treatment  combination was the only one which promoted shoot growth for a longer period of time.  The interaction between photoperiod and plant moisture stress was  shown as s i g n i f i c a n t  because at the same control moisture l e v e l , growth was  inhibited by the inductive short day regime.  For a l l other moisture stress  l e v e l s , growth stopped regardless of photoperiod regime. The effect  of moisture stress or short days on reduced height growth,  root dry weight and shoot dry weight coincides with results documented in the literature.  Dry weight accumulation in the shoots of black spruce seedlings  and height increment decreased  s i g n i f i c a n t l y when photoperiod was reduced  from 15 to 8 hours (D'Aoust and Cameron 1981). effect  on root dry weight accumulation.  Daylength had less of an  The fresh weight of Douglas  seedlings declined under a nine hour day (Lavender and Wareing 1972).  fir When  142  container Douglas-fir seedlings were subjected to moisture stress of -6 and -12 bars in the 8th through the 16th week from sowing and the 12th through the 21st week, the higher stressed seedlings had lower shoot dry weights of 32% and 38% for the two treatment dates and lower root dry weights of 12% and 35% (Timmis and Tanaka 1976).  The results of this thesis study are similar  to those of Timmis and Tanaka (1976), where root dry weight declined from 0.83 g at a stress treatment of -4.9 bars to 0.55 g at a stress of -9.5 a decrease of 34%.  bar,  However, stresses of -17.5 and -23.4 bars resulted in no  further decrease in root biomass.  A similar trend was evident for shoot dry  weight. When Blake et a l .  (1979) applied plant moisture stresses of -6 to -8  bars to bareroot Douglas-fir seedlings,  the effect  of the stress on root dry  weight depended upon the date of treatment i n i t i a t i o n .  Plants stressed on  July 15 had s i g n i f i c a n t l y larger root dry weights than seedlings l a t e r in the summer.  treated  Only the plants which received treatment in September  had s i g n i f i c a n t l y reduced root dry weight. Cheung (1973) concurrently applied moisture stress or short days to western hemlock container seedling.  Total height, shoot dry weight and root  dry weight s i g n i f i c a n t l y decined under either treatment.  Shoot dry weight  was reduced to 0.359 g in a short day regime and to 0.490 g with moisture stress when treatments  were i n i t i a t e d 16 weeks from sowing.  was 0.69 0 g in seedlings under a natural daylength. in both treatments  Shoot dry weight  Root dry weight declined  compared to the control but the difference was not  significant. The effect  of the dormancy induction treatments  of this project on  shoot and root dry weight are in agreement with the above reported studies.  143  That i s , short days, a l i g h t to severe moisture s t r e s s , or a combination of both reduced shoot and root dry weight compared to a control moisture under a natural  photoperiod.  regime  However, the short day effect on shoot dry  weight accumulations diminished under increased levels of moisture  stress.  Short photoperiod did not influence root biomass in a l i g h t to severe s t r e s s . The influence of short days on root dry weight apparently coincides with those of Cheung (1973) and Timmis and Tanaka (1976). A l i g h t to medium stress under a natural growth compared to the unstressed treatment.  daylength reduced c a l i p e r This result  is in agreement  with Timmis and Tanaka (1976) who demonstrated that caliper growth was reduced by 21% and 30% in seedings stressed to -12 bars at two i n i t i a t i o n dates compared to plants  stressed to -6 bars.  Blake et a l .  showed that Douglas-fir c a l i p e r growth was unaffected and a stress treatment of -6 to -8 bars.  by time of application  Under a short day regime,  stress did not affect c a l i p e r growth in this thesis The final morphological characteristic treatment effects were demonstrated.  (1979), however,  project.  analyzed was bud height.  budset i n i t i a t i o n reduced the number of needle primordia in black  natural terminal  spruce  temperatures probably affected  bud  The delay in bud formation in the control seedlings under a  daylength occurred in the summer. buds had formed.  temperatures.  delayed  However, the delay in bud formation occurred in  September and October when cooler f a l l maturation.  No  This result seems surprising in view of  the findings reported by Colombo and Smith (1984) who reported that  container seedlings.  moisture  By September 3, 76% of the  Bud maturation proceeded under warm f a l l  The delay in budset i n i t i a t i o n was probably i n s u f f i c i e n t  influence bud height.  to  In addition to time of bud formation, seedling vigour  144  at the time of dormancy induction is also important to the resultant bud size and the number of primordia within the bud (Thompson 1985). also an indication of potential shoot growth in the f i e l d . potential  f i e l d performance of the seedlings  Bud height is If this is  so,  in this study was possibly  unaffected by the various induction treatments.  However, i t would seem  unwise to infer such a conclusion from one t e s t . Of the three physiological attributes measured, only frost was unaffected by moisture stress or short day treatments.  It is  hardiness unfortunate  a hardiness test was not conducted shortly after treatment completion. Evidence in the l i t e r a t u r e demonstrates that frost hardiness  differences  occur when Douglas-fir seedlings are treated with short days, long days or moisture stress.  When bareroot Douglas-fir seedlings were treated with eight  weeks of 8 or 10 hour days, frost hardiness was enhanced not immediately upon treatment completion, but two and four weeks after treatment (McCreary et a l . 1978).  That i s , the a b i l i t y to acclimate quickly improved after short day  pretreatment.  Tanaka (1974) reported a similar result for container  Douglas-fir seedlings.  Several other studies concur with these findings  (Aronsson 1975; Christersson 1978;  D'Aoust and Cameron 1981; McGuire and  F l i n t 1962; Rosvall-Ahnebrink 1981; van den Driessche 1970). Evidence on the influence of moisture stress on cold hardiness in coniferous species of the Pacific Northwest is c o n f l i c t i n g .  In a controlled  moisture stress of -6 and -12 bars applied in the 8th through 16th weeks from sowing and the 12th through 21st weeks, Douglas-fir container seedlings were tested for frost hardiness immediately after treatment, after  5.5 weeks of  cold treatment at 5°C in an eight hour photoperiod, and after 11.5 weeks of similar cold treatment.  Hardiness was similar between both stress levels  145  immediately after treatment.  After eleven weeks of cold treatment,  seedlings  pretreated with the milder stress were 4 to 5°C hardier than the higher stressed plants.  Blake et a l .  (1979) appied three levels of moisture s t r e s s ,  0 to -5, -5 to -10, and -10 to -15 bars, to bareroot Douglas-fir seedlings in late July.  A mild stress of -5 to -10 bars enhanced hardiness, measured in  October and December, to that of the control while the higher stress level reduced i t . When the seedlings  of this study were l i f t e d in January, no differences  in hardiness were detected between moisture stress or short day treatments. The findings of van den Driessche (1969b) provide an explanation for this occurrence.  After six weeks, an eight hour photoperiod s i g n i f i c a n t l y  increased frost  hardiness levels  sixteen hour daylength.  in Douglas-fir compared to a twelve or  Moisture stress did not affect  frost  hardiness  but  photoperiod increased hardiness more under a well watered regime compared to increasing moisture s t r e s s .  When non-hardy plants were grown in the natural  short days of autumn or under an extended photoperiod, short day seedings quickly acclimated after mid-October. hardiness until mid- November. in both groups of seedlings. differences  The long day plants had delayed  By mid-December hardiness levels were similar These findings possibly explain why no  were detected in frost hardiness between seedlings  short days, long days or moisture s t r e s s .  treated with  Differences in hardiness probably  occurred after the treatments were completed and persisted throughout the early f a l l .  However, under the naturally declining short days and decreasing  temperatures  of late autumn and early winter, seedlings  from a l l  treatments  acclimated to similar l e v e l s , irrespective of any probable early f a l l dissimilarities.  146  The RGC results seedlings  indicate that seedling vigour was similar among  from many of the treatment combinations.  moisture stress did not affect  Varying levels of  RGC under a short day regime.  was similar in a l l the short day treatments.  That i s , RGC  Although an analysis of  variance indicated that photoperiod did not influence RGC, a multiple range test on a l l treatment combinations indicated that under a control moisture regime, short days s i g n i f i c a n t l y reduced RGC compared to a natural photoperiod.  This result is in agreement with Lavender and Wareing (1972)  who showed that root a c t i v i t y declined in seedlings days.  pretreated with short  It must be emphasized that the short day effect  the other moisture  was not evident under  regimes.  Under a natural daylength, RGC declined with increasing moisture stress.  Increased moisture stress somehow affected  a b i l i t y to regenerate  new roots.  root growth and the  Root growth and i t s  regenerative  may be influenced by moisture stress through i t s effect  on the  capacity  foliage.  F i r s t l y , photosynthetic capacity decreases with plant water d e f i c i t s and Kozlowski 1979).  (Kramer  Under repeated drying cycles photosynthesis does not  always resume to predrought levels when rewatered.  Thus, one possible  explanation for reduced root growth is a reduction in the production of current photosynthates.  However, i f this occurred, root dry weight should  have further declined under the short day regime because of the reduction in hours available for photosynthesis.  Yet, no s i g n i f i c a n t differences  were  shown between a l i g h t to severe moisture stress for either photoperiod. Under a control moisture regime, short days s i g n i f i c a n t l y reduced root growth and root growth capacity.  Lavender and Hermann (197 0) reported that  the production of substances such as hormones or sugars from mature  foliage  147  were necessary for active root growth.  This, in turn, was influenced by  daylength (Lavender and Wareing 1972).  Since daylength influences  this  process of exporting growth regulating hormones, i t is interesting to note that RGC and root growth, on a dry weight basis, was similar among a l l  short  day treatments, regardless of moisture s t r e s s , and the l i g h t and medium stresses under a natural  photoperod.  Possibly both these environmental  signals influence the export of growth regulating hormones in a similar manner.  The main factor common to a l l these treatments is that dormancy was  i n i t i a t e d at the same time.  Hence, the shift  in balance of growth promoting  and i n h i b i t i n g hormones occurred at similar times. A final explanation for the differences the preexperimental  plant vigour.  capacity  that  i r r i g a t i o n regime combined with the induction treatments  of moisture stress and short days, with i t s overall  in RGC and root biomass is  high temperature  regime, reduced  This was consequently expressed in the root growth  results.  In the dormancy intensity t e s t s , short days accelerated compared to a natural  photoperiod.  This result  bud break  is in agreement with Lavender  and Wareing (1972) who demonstrated that bud a c t i v i t y increased in seedlings pretreated with short days.  Accelerated budflush was reported in other  studies (Sandvik 1980; Rosvall-Ahnebrink 1981).  A theory for this phenomenon  is that photoperiod affects  of Douglas-fir through  the growth potential  its  influence on growth regulating hormones within the bud (Lavender and Hermann 1970;  Lavender and Wareing 1972).  natural seedlings.  The dormancy intensity results under a  daylength suggest storage was a physiological stress to these Budflush is predominantly a temperature mediated response as  c h i l l i n g require- ment becomes f u l f i l l e d (Campbell 1978; van den Driessche  148  1975).  A faster rate of budflush should have occurred in the warmer March  post storage test compared to the January l i f t t e s t .  Instead, days to  budburst increased after the storage period. The selection of the optimum treatment  for c o n t r o l l i n g height growth  while maintaining quality in a Douglas-fir container crop is not possible from this study.  The control moisture stress regime under a natural  photoperiod had the best morphological characteristics  with respect to  caliper and root biomass, the highest RGC and comparable frost hardiness the time of the January l i f t . of height growth. photoperiod.  at  This regime does not permit the manipulation  The cessation of shoot growth is controlled by the natural  The timing of dormancy induction is not  necessarily  controlled. In evaluating the remaining treatment combinations, short photoperiod with frequent  i r r i g a t i o n possibly yielded a s l i g h t l y better qualty  seedling.  This conclusion is based on the s l i g h t l y higher shoot dry weight and c a l i p e r , comparable root growth capacity and frost hardiness,  and rapid and  homogeneous budset incidence with a low incidence of reflushing. spring budflush is another possible advantage.  However, a final  Accelerated conclusion  about this regime should not be made from this study because of the pretreatment  operatonal  experimentation. II,  i r r i g a t i o n regime and the high thermoregime during  In view of the different  i f proper materials  which reflect  findings between Study I and Study  radiation and ventilate the system can  not be supplied, short days have l i t t l e benefit growth and accelerated  spring budflush.  but quick control of height  When the improved height growth  performance of outplanted seedlings in Study I is considered, this  benefit  may prove worthwhile especially on sites with excessive brush competition or  149  mid-summer water d e f i c i t s .  At present, there are i n s u f f i c i e n t studies, and  growth and y i e l d tables which demonstrate the importance of rapid and increased growth performance in the f i r s t few years of a new plantation. Therefore, the benefit of increased f i r s t year height growth cannot be t r u l y evaluated in this The results  thesis. from this study suggest that there is l i t t l e benefit in  applying short days to seedlings already treated with three possible of moisture stress for 16 days. the incidence of reflushing.  levels  The only possible advantage is to minimize  However, once moisture stressed seedlings  set  buds, maintenance of a proper moisture regime should also prevent a second flush. The evidence from the morphology, frost hardiness and root growth capacity data suggest that the l i g h t and medium moisture stress regimes also effectively  i n i t i a t e d budset after a six week period and maintained seedling  quality compared to the short day regimes. is not recommended because of i t s effect  4.5  However, a severe moisture stress  on root growth capacity.  Conclusions  Short days e f f e c t i v e l y i n i t i a t e d and maintained budset in Douglas-fir seedlings  in four weeks.  After six weeks, a l i g h t to severe  moisture stress was as effective as short days in controlling height growth. Unstressed seedlings  in a natural photoperiod had the slowest rate of bud  formation and the highest incidence of llamas growth. Severe, medium, l i g h t and control moisture stress  treatments  corresponded to average predawn shoot water potential measurements of -23.4,  150  -17.5, -9.5 and -4.9 bars respectively.  The operational method of weighing  styroblock weights as an indication of moisture stress was related to plant moisture s t r e s s , but once 313 block weights approached 4.5 kg, small reductions in block weight produced major increases in plant moisture stress. Short days,  irrespective of moisture s t r e s s , and a l i g h t to severe  moisture stress under a natural  photoperiod s i g n i f i c a n t l y reduced total  height and c a l i p e r compared to the control moisture regime in a natural photoperiod.  With the exception of the l i g h t stress l e v e l , short days  reduced shoot dry weight accumulations.  In addition, control or regularly  watered seedlings had greater shoot dry weights than l i g h t to severe moisture stresses. Short days and a l i g h t to severe moisture stress  significantly  reduced root dry weight compared to a c o n t r o l , natural photoperiod treatment. Among these treatment combinations, however, no s i g n i f i c a n t  differences  occurred. In a comparison of a l l treatment combinations, only the control plants under a natural morphological significant  photoperiod were s i g n i f i c a n t l y larger in a l l  properties  differences  than seedlings from a l l other treatments. were s t i l l  Although  shown between these other treatments,  seems doubtful whether these differences  were operationally  it  significant.  That i s , short days, moisture stress or a combination of both had s i m i l a r effects on reducing the seedling morphological characteristics  of height,  c a l i p e r , shoot dry weight and root dry weight. Unstressed seedlings in a natural daylength had the highest of root growth capacity.  A l l other short day and moisture stress  value  treatments  151  reduced root growth capacity.  Most treatments  had similar l e v e l s .  Only the  severe stress under a natural photoperiod reduced root growth capacity below any  other treatment combination.  Five weeks of cold storage had no effect on  root growth capacity. Short days, irrespective of moisture s t r e s s , accelerated bud burst in January and March dormancy intensity t e s t s .  Moisture stress had no effect  on bud a c t i v i t y . Five months after the treatment period, no differences  in frost  hardiness were detected between any of the treatment combinations. seedlings were hardy to at least - 2 1 ° C .  All  In spite of any differences  in  hardiness levels that moisture stress or short days may have i n i t i a l l y produced in the early f a l l , hardiness after  neither of these factors  influenced frost  five months of autumn and winter temperatures and  photoperiods. The physiological and morphological characteristics  of a l l  seedlings may partly r e f l e c t the influence of the operational i r r i g a t i o n regime applied prior to project i n i t i a t i o n .  In late June and early J u l y ,  seedlings were operationally stressed to a 313 styroblock weight of 4.3kg. This corresponded to a medium moisture stress of -9.5 bars in this trial.  research  The high thermoregime of the short day greenhouse was another  which possibly influenced the r e s u l t s .  factor  Temperatures which frequently  exceeded 35°C may have reduced seedling vigour and growth. The control moisture stress regime under a natural photoperiod had the best morphological c h a r a c t e r i s t i c s  especially root dry weight and  c a l i p e r , the highest value of root growth capacity and comparable hardiness at the time of the January l i f t .  frost  It was the least effective  in  152  c o n t r o l l i n g height growth through early budset i n i t i a t i o n . The overall thesis objective was to develop a regime which effectively  controlled height growth while maintaining seedling q u a l i t y .  Of  the remaining treatments, short days with frequent i r r i g a t i o n to minimize moisture stress most closely met this objective.  Short days produced rapid  and homogeneous budset in the Douglas-fir seedlings.  The incidence of a  second flush was only 4%, the lowest of a l l treatment combinations. the control moisture regime in a natural seedlings with s l i g h t l y larger calipers  photoperiod, short days produced and greater shoot dry weights.  Budflush was also fastest in a short day regime. of quick budset and accelerated  Next to  However, with the exception  budflush, i t is d i f f i c u l t to conclude from  the results of Study II whether short days produced s i g n i f i c a n t l y  better  quality seedlings than l i g h t and medium moisture stress treatments.  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Res. 12:545-555.  30.  Duryea, M.L. and T.D. Landis. 1984. Forest nursery manual: Production of bareroot seedlings. C o l l . of Forestry, Oregon St. U n i v . , C o r v a l l i s , Oregon.  31.  D'Aoust, A . L . and S.I. Cameron. 1981. The effect of dormancy induction, low temperatures and moisture stress on cold hardening of containerized black spruce seedlings. Pages 153-161 Canadian Containerized Tree Seedling Symposium, (J.B. Scaratt et a l . , eds.) O-P-10.  32.  Forycka, D . , G. Gajowniczek, and A. Kacperska-Palacz. 1978. Changes in growth regulators during plants acclimation to winter conditions. Acta Hort. 81:77-84.  33.  Glerum, C. 1985. Frost hardiness of coniferous seedlings: principles and applications. Pages 107-123 in Evaluating seeding q u a l i t y : p r i n c i p l e s , procedures and predictive a b i l i t i e s of major tests (Duryea, M . L . , e d . ) . Forest Research Laboratory, Oregon State University, C o r v a l l i s .  34.  Gogoleva, G . A . , A . S . Jegurazdova, and T . G . Bulatova. 1978. Interaction between development of frost resistance and dormancy in plants. Acta Hor. 81:51-60.  156 35.  Haeussler, C. 1981. The effect of c r i t i c a l l i g h t intensity and ethrel sprays on dormancy induction in western hemlock. Research Branch, Ministry of Forests, B.C. E.P. 764.93.  36.  Hahn, P.F. and A . J . Smith. 1983. Douglas-fir planting stock performance comparison after the third growing season. Planters notes No. 33.  37.  Hanover, J.W. 1980.  38.  Hermann, R.K. 1967. Seasonal variation in s e n s i t i v i t y of Douglas-fir seedlings to exposure of roots. For. S c i . 13:140-149.  39.  Hermann, R . K . , D.P. Lavender and J.B. Zaerr. 1972. L i f t i n g and storing western conifer seedlings. For. Res. Lab., School of F o r . , Oregon State U n i v . , Res. Paper No. 17.  40.  Hillman, W.S. 1967. The physiology of phytochrome. Physiol. 18:301-324.  41.  Johnson-Flanagan, T and J.N. Owens. 1985. Root growth and root growth capacity of white spruce seedlings. Can. J. For. Res. 15(4):625-630.  42.  Kramer, P. and T . T . Kozlowski. 1979. Internal factors affecting growth, Pages 562-563 iji Physiology of woody plants (P. Kramer and T . T . Kozlowski, eds). Academic Press, New York.  43.  Krueger, K.W. and J.M. Trappe. 1067. Food reserves and season growth Douglas-fir seedlings. For. S c i . 13(2)-.192-202.  44.  Larsen, J.B. 1978. Untersuchungen uber die Bedeutung der Kalium und Stickstoffversorgung fur die Austrocknungsresestenz der Douglasie (jjseudotsuga menziesii im Winter. Flora 167 :197-207 (As cited in Aronsson~T98 0T7  45.  Lavender, D. 1964. seedlings.  Control of tree growth.  Tree  Bio. S c i . 30( 11):756-762.  Ann. Rev.  Plant  Date of l i f t i n g for survival of Douglas-fir For. Res. Lab., 0SU, C o r v a l l i s , Res. Note 49.  46  1978. Bud a c t i v i t y of Douglas-fir seedlings receiving different photoperiods in cold storage. P.245-248 in Proc: North American Forest Biology Workshop ( C A . Hoi l i s and A.E. Squillace, eds.). Univ. Flor Press, G a i n e s v i l l e .  47  1981. Environment and shoot growth of woody plants. Lab., 0SU, C o r v a l l i s . Res. Paper 45.  48  Fifth  For. Res.  , 1982. Seedling dormancy and frost hardiness, Pages 93-96 in Proc. Biology and Management of True F i r in the Pacific Nortfrwest  157 Symp. ( C D . Oliver and R.M. Kenady, e d s . ) . Coll. Inst, of For. Res.). Univ. of Wash., Seattle.  For.  Res.,  49  , 1984. Plant physiology and nursery environment: Interactions affecting seedling growth. Pages 133-142 in Forest Nursery Manual: Production of Bareroot Seedlings Jft.l. Duryea and T.D. Landis, e d s . ) . For. Res. Lab., Oregon State Univ., Corvallis.  50  , 1985. Bud dormancy. Pages 7-16 J^n Evaluating Seedling Quality: p r i n c i p l e s , procedures, and predictive a b i l i t i e s of major t e s t s . (M. L. Duryea, E d . ) . Forest Research Laboratory, Oregon State University, C o r v a l l i s .  51.  Lavender, D.P. and R.K. Hermann, 1970. Regulation of the growth potential of Douglas-fir seedlings during dormancy. New Phytol. 69:675-694.  52.  Lavender, D.P. and W.S. Overton. 1972. Thermoperiods and s o i l temperatures as they affect growth and dormancy of Douglas-fir seedlings of different geographic o r i g i n . For. Res. Lab., School of Forestry, Oregon State Univ., Res. Paper 13.  53.  Lavender, D.P. and P.F. Wareing. 1972. Effects of daylength and c h i l l i n g on the responses of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings to root damage and"~storage.~ Rew'pHytol 71:1055-1 067.  54.  Lavender et a l . 1973. Spring shoot growth in Douglas-fir may be i n i t i a t e d by gibberellins exported from the roots. Science 182:838-839.  55.  Lavender, D.P. and B.D. Cleary, 1974 Coniferous seedling production techniques to improve seedling establishment. Pages 177-180 in Proc. of North Amer. Containerized Forest Tree Seedling Symp. (R.W. Tinus, W.I. Stein and W.E. Balmer, e d s . ) . Denver, Colorado.  56.  Mandoli, D.F. and W.R. Briggs. Amer. 251(2) :90-98.  57.  Matthews, G. 1977.  58.  McCreary, D.D. Photoperiodic responses of Douglas-fir (Pseudotsuga menzi_esn [Mirb.] Franco] and Ponderosa pine (Pinus pon3Irosa)~sie3TTngs. (Abst) M. Sc. Theses. Oregon State OnTv. CorvaTTTsT Oregon.  59.  McCreary, D . D . , Y. Tanaka and D.P. Lavender. 1978. Regulation of Douglas- f i r seedling growth and hardiness by c o n t r o l l i n g photoperiod. For. Sci.(24):142-162.  1984.  Fiber optics in plants.  Sci.  M.O.F. unpublished data.  158 60.  McDonald, S.E. and S.W. Running. 1979. Monitoring i r r i g a t i o n in western forest tree nurseries. I).S.D.A., For. Serv. Gen. Tech. Rep. RM. 61.  61.  Nelson, E.A. and D.P. Lavender. 1976. Dormancy of western hemlock seedlings. Pages 108-107 in Western hemlock management, (W.A. Atkinson and R . J . Zasoski, e d s . ) . College of Forest Resources, Univ. Wash.  62.  Nelson, E.A. and D.P. Lavender, 1979. The c h i l l i n g requirement of western hemlock seedlings. For. S c i . 25(3):485-490.  63.  Nooden, L.D. and J.A. Weber. 1978 Environmental and hormonal control of dormancy in terminal buds of plants. Pages 224-268 vn Dormancy and development arrest (M.E. C u t t l e r , e d . ) . Academic Press New York.  64.  Nowak, J. and G.N. Brown. 1979. Free and bound g i b b e r e l l i n a c t i v i t i e s and Ent-kaurene synthesis during induction of cold hardiness in black locust seedlings.*. Physiol. Plant. 45:11-16.  65.  Owens, J.N. and M. Molder. 1973. A study of DNA and mitotic a c t i v i t y in the vegetative apex of Douglas-fir during the annual growth cycle. Can. J. Bot. 51:1395-1409.  66.  Owens, J.N. and M. Molder. 1973. Bud development in western hemlock. I. Annual growth cycle of vegetative buds. Can. J. Bot. 51:2223-2231.  67.  R i t c h i e , G.A. 1982. Carbohydrate reserves and root growth potential Douglas-fir seedlings before and after cold storage. Can. J. For. Res. 12:905-912.  68  in  1984a. Assessing seedling q u a l i t y . Pages 243-259 in Forest Nursery Manual: Production of Bareroot seedlings. Tfl.L. Duryea and T.D. Landis, e d s . ) . For. Res. Lab., Oregon State Univ. , C o r v a l l i s .  69  , 1984b. Effect of freezer storage on bud dormancy release in Douglas-fir seedlings, Can. J. For. Res. 14:186-190.  70  , 1985. Root growth p o t e n t i a l : p r i n c i p l e s , procedures, predictive a b i l i t y . Pages 93-106 in Evaluating seedling q u a l i t y : p r i n c i p l e s , procedures and predictive a b i l i t i e s of major tests (Duryea, M.L. e d . ) . Forest Research laboratory, Oregon State University, C o r v a l l i s .  159 71.  R i t c h i e , G.A. and J.R. Dunlap. 1980. Root growth p o t e n t i a l : Its development and expression in forest tree seedlings. N . Z . J . For. S c i . 10(1) :218-248.  72.  Romberger, J.A. 1963. Meristems, growth and development in woody plants: an analytic review of anatomical physiological and morphogenic aspects. Tech. B u l l . USDA. No. 1293.  73.  Rosvall-Ahnebrink, Gunnel. 1981. Practical application of dormancy induction techniques to greenhouse-grown conifers in Sweden. Pages 163-170 j n Canadian Containerized Tree Seedling Symposium (J.B. Scarett et a l . e d s . ) . 0-P-10.  74.  Sandvik, M. 1980. Use of controlled environment f a c i l i t i e s . Environmental control of winter stress tolerance and growth potential in seedlings of Picea abies (L.) Karst. N . Z . J . For. S c i . 10(1):97-104.  75.  Saunders, P. 1978. Phytohormones and bud dormancy. Pages 423-445 in Phytohormones and related compounds. A comprehensive t r e a t i s e . D.S. Letham, P.B. Goodwin and T . J . Higgins, e d s . ) . Elsevier North Holland BiomedicalPress, Amsterdam.  76.  Staden,  77.  Sutton, R.F. 1983. Root growth capacity: relationship with f i e l d root growth and performance in outplanted jack pine and blue spruce. Plant and Soil 71:111-122.  78.  Tanaka, Y. 1974. Increasing cold hardiness of container grown Douglas-fir seedlings. J. For. 72:349-352.  79.  Thompson, B.E. 1983. Why f a l l f e r t i l i z e ? Pages 85-01 in Proc. West. Nurserymen's Conf. West. For. Nurs. Council. MeHford, Oregon.  80  81.  J . V . and N.A.C. Brown. 1978. Changes in the endogenous cytokinins of bark and buds of Salix babyloni_ca as a result stem g i r d l i n g . P h y s i o l . Plant.""417145-T537"  of  , 1985. Seedling morphological evaluation - what you can do. Pages 59-72 in Evaluating seedling q u a l i t y : principles, procedures an3 predictive a b i l i t i e s of major tests (Duryea, M . L . , ed.). Forest Research Laboratory, Oregon State University, Corvalis. Timmis, R. 1974. Effect of nutrient stress on growth, bud set and hardiness in Douglas-fir seedlings. Pages 187-191 in Proc. of N.A. Conta. Forest Tree Seedling Symp. (R.W. Tinus,~W\I. Stein and W.G. Balmer, eds), Gt. Plains Agric. Council Publication #68.  160 82  1976. Frost hardiness of western hemlock. Pages 118-125 in Western Hemlock Management (W.A. Atkinson and R.J. ZasoskiT" eds.). Coll. For. Res., Univ. Wash.  83.  Timmis, R. and J. Worrall, 1975. Environmental control of cold acclimation in Douglas-fir during germination active growth, and rest. Can. J. For. Res. 5:464-477.  84.  Timmis, R. and Y. Tanaka. 1976. Effects of container density and plan water stress on growth and cold hardiness of Douglas-fir seedlings. For. Sci.22:167-172.  85.  Tinus, R.W. 1981. Environmental control of seedling physiology. 75-82 in Proc. Can. Containerized Tree Seedling Symp. (J.B. STaratt, C. Glerum, and C A . Plexman, e d s . ) . COJFRC-O-P-10.  86.  Tinus, R.W. and S . E . McDonald. 1979. How to grow tree seedlings in containers in greenhouses. USDA, For. Serv. Gen. Tech. Rep. Rm-6 0.  87.  van den Driessche, 1969a. Measurement of frost-hardiness in two-year old Douglas-fir seedlings. Can. J. Plant S c i . 49:159-172.  Pages  88  , 1969b. Influence of moisture supply, temperature and l i g h t on frost-hardiness changes in Douglas-fir seedlings. Can. J. Bot. 47:1765-1772.  89  , 197 0. Influence of l i g h t intensity and photoperiod on frost hardiness development in Douglas-fir seedlings. Can. J. Bot 48:2129-2134.  90  ,  91  , 1975. Flushing response of Douglas-fir buds to c h i l l i n g and to different a i r temperatures after c h i l l i n g . Res. D i v . , B.C.F.S. Res. No. 71.  92  , 1976a. Survival of coastal and i n t e r i o r Douglas-fir seedlings after storage at different temperatures, and effectiveness of cold storage in satisfying c h i l l i n g requirements. Can. J. For. Res. 7:125-131.  1972. Prediction of frost hardiness in Douglas-fir seedlings by measuring e l e c t r i c a l impedance in stems at different frequencies. Can. J. For. Res. 3:256-264.  161 93  1976. Prediction of cold hardiness in Douglas-fir seedlings by index of injury and conducitivity methods. Can. J. For. Res. 6:511-515.  94.  Wallner, S.J. et a l . 1981. Cold hardiness testing of container seedlings. Pages 21-25 in Proc. 1981 Intermountain Nurserymen's Assoc. Meeting. Nor. For. Res. Cen. CFS., NOR-X-241.  95.  Wareing, P.F. 1956. Photoperiodism in woody plants. Physiol. 7:191-214.  96.  Wareing, P.F. and P.F. Saunders. 1971. Hormones and dormancy. Rev. Plant Physiol. 22:261-288.  97.  Warrington, J. and D.A. Rook. 1980. Evaluation of techniques used in determining frost tolerance of forest planting stock. A review. N . Z . J . For. S c i . 10(1) -.116-132.  98.  Weiser, C . J . 197 0. Cold resistance and injury in woody plants. Science 169:1269-1278.  99.  Worrall, J. and F. Mergen. 1967. Environmental and genetic control of dormancy in Picea abi.es. Phys. Plant 20:733-745.  Ann. Rev. Plant Ann.  100. Young, E. and J.W. Hanover. 1978. Effects of temperature, nutrient an moisture stress on dormancy of blue spruce seedlings under continuous l i g h t . F o r . S c i . 24(4): 458-467. 101.  Zaerr, J.B. 1985. The role of biochemical measurements in evaluating vigor. Pages 137-141 in Evaluating seedling q u a l i t y : principles, procedures and predictive a b i l i t i e s of major tests (Duryea, M . L . , ed.). Forest Research Laboratory, Oregon State University, Corvallis.  102.  Zaerr, J . B . , B.D. Cleary, and J . L . Jenkinson. 1981. Scheduling i r r i g a t i o n to induce seedling dormancy. Nurseryman's Assoc. and West. For. Nurs. Assoc combined meeting, Aug. 12 -14, 1980. Boise, Idaho. USDA For. Serv., Gen. Tech.Rep., Int. For. and Range Exp. S t . , No. INT-109., p.71-79.  162 APPENDIX I  MONITORING THE ROOT GROWTH CAPACITY OF PLANTING STOCK 1.  1  Methods of Measurement Root growth capacity conducted under  (RGC) tests for assessing stock quality  are  standard conditions in the assumption that the results  obtained are indicative of relative capacity for root growth under f i e l d conditions.  The j u s t i f i c a t i o n  for this assumption  is the close  correlation usually observed between the RGC of stock measured under highly favorable survival  conditions in the laboratory and its  performance  (early  X growth) in the f i e l d .  1.1 Test Conditions To obtain results q u i c k l y , RGC tests are usually conducted under conditions thought most favorable  to root growth.  Although the optimum  conditions have not been precisely determined, rapid root growth has been observed in i n t e r i o r spruce, fir,  lodgepole  pine, i n t e r i o r and coastal  Douglas  western hemlock and western red cedar under the following  conditions:  Reproduced from N. Burdet. 1983. Controlling the root growth capacity planting stock. M.O.F. Unpublished report.  1  163 Standard RGC Test Conditions day temperature  3CPC.  night temperature  25°C.  daylength  16 hr.  l i g h t intensity  400 tiErn^S" 1  r e l a t i v e humidity  75%  1.2 Root Environment Test seedlings may be planted in a defined s o l i d medium or grown either hydroponically or with t h e i r roots enclosed in a mist chamber. Adequate root aeration is d i f f i c u l t to achieve in a hydroponic system.  Good results  have been reported with the root mist chamber  which is to be used for root growth testing in Ontario's nurseries.  The  reason cited for preferring this system over the use of a s o l i d medium is the saving in labour in planting trees and then washing the roots examination at the end of the t e s t .  for  It has also been suggested that  root growth is more rapid in a mist chamber than in a s o l i d medium. Nevertheless, until  local experience has been gained with the root mist  chamber, i t seems advisable that operational RGC testing in B.C. be conducted with stock planted in a standard s o l i d medium.  A suitable  medium is a 3:1 mix of peat and vermiculite (adjusted to pH 4.5 to  5.0  with dolomitic lime). 1.3  Measurement Root growth can be measured volumetrically, by surface area, or by the number or length of new roots.  Measurement by volume or area  increase is quantitative but subject to error due to decay and loss of  164 old roots during the t e s t .  Measuring the length of new roots formed is  a more r e l i a b l e quantitative technique, but i t is  extremely  time-consuming and therefore,  unacceptably expensive for use in routine  monitoring of stock q u a l i t y .  Counting new roots more than a certain  length, (usually 1 cm) is a less time-consuming method of estimating root growth, although i t is not precisely quantitative.  Root counting  can be greatly speeded up by recording root numbers in broad classes such as the following: Index of root growth (IRG)  New Roots  0  None  1  Some, none > 1 cm in length  2  1-3  >  1 cm  3  4-10  >  1 cm  4  11-30  >  1 cm  5  31-100  >  1 cm  6  101-399  >  1 cm  7  more than 3 00 > 1 cm  Using this scale i t is frequently unnecessary to count more than a minority of the roots since, when one class boundary is reached, 3, 10, 30 or 100, i t is often clear that the next boundary w i l l  e.g., not be  exceeded. The precision of this method of estimating root growth is not great.  The range of variation in the RGC of forest nursery stock  is,  however, enormous so that a crude scale is quite adequate as a basis for  165 segregating  stock into a number of RGC grades.  For purposes of quality  c o n t r o l , this is a l l that is required since only major differences in RGFC have appreciable effects  on f i e l d performance.  1.4 Duration of Tests Under the standard test conditions noted above, a mean IRG of more than 5 after 1 week has been observed in batches of a l l species (Table I).  tested  Thus a one week test is long enough to divide stock into a  number of RGC grades.  166 APPENDIX II  THE WHOLE SEEDLING ASSESSMENT METHOD FOR FROST HARDINESS EVALUATION BY C . J . SALLY JOHNSON, SEEDLING QUALITY SERVICES  One hundred seedlings were randomly selected from each treatment and shipped to Seedling Quality Services.  Four subsamples of 20 seedlings  respectively received four separate freezing temperatures of -21.0; -25.2 and - 2 6 . 1 ° C .  Twenty seedlings were maintained as controls.  -24.1, A l l test  seedlings were placed in a favourable environment and were subsequently assessed for frost  injury to needles, buds and the stem cambium.  each of these tissues was rated as follows:  I  DAMAGE SCALE  1.  Needles 0 - 1 0 with  0 - 0 % dead needles 10-100% dead needles  2.  Terminal Buds 0-1  with 0 = 1 ive bud 1 = dead bud  3.  Lateral Buds 0-9  with 0=0%  dead buds  9 = 100% dead lateral buds  Damage to  167 4.  Stem 0-4  with 0 = no stem dead 1 = top 1/4 stem dead 2 = top 1/2 stem dead 3 = entire stem dead 4 = stem girdled in lower 1/4 and therefore dead  II DAMAGE SCALE  Viabi^i_ty_rating  0  _  Needles  (economically a l i v e )  0.5 (half k i l l )  0-  0-  Buds  10  10  0-5  0 - 10  1.0 ( k i l l )  0-8  Stem  0-1  0-2 8  0 -1  0-  10  8-9  2-4  0-  10  0-7  3-4  9  0-2  0-10  From the damage scale assigned to the different t i s s u e s , a v i a b i l i t y rating is assigned in order to determine the LT 5 0  value.  If one of the l i s t  temperatures is not this value, i t is extrapolated from a graph where damage is plotted against temperature.  APPENDIX I l i a  CROP HISTORY OF DOUGLAS-FIR SEEDLINGS FROM STUDY I  169  CROP HISTORY RECORD SEEDLOT:  4390  SPECIES:  Fc  CONTAINER SIZE:  40 c u . i n .  CONTAINER TYPE:  SB313  DATE SOWN:  Mar. 23, 1984 GREENHOUSE HISTORY  WEEK  FERTILIZER TYPE/AMOUNT  April  17  7-40-17/100L-14.3kg  23  7-40-27/100L-14.3kg  25  7-40-27/100L-14.3kg  29  7-40-27/100L-14.3kg  PESTICIDE TYPE/AMOUNT  WATER  May 5  Watered only  10  Watered only  15  Watered only  21  Watered only  28  Bravo/Safers Soap  June 9  Soilwet/lOOc  15  Watered only  21  Bravp/Safers Soap  28  Watered only  July 11  Soilwet/lOOc  19  4-25-35/1 001-10kg  28  Watered only  30  Bravo  August 5  4-25-35/100L-1Okg  12  4-25-35/1001-10kg  20  4-25-35/1 00L-1 Okg  31  4-25-35/100L-1 Okg  Sept.  1 23  Bravo 4-25-35/100L-1Okg  27 Nov.  Watered only  Bravo/Safers Soap  7 28  Bravo Ca(N0 3 ) 2 /15.5kg  Bravo  APPENDIX 11 lb  CROP HISTORY OF DOUGLAS-FIR SEEDLINGS FROM STUDY II  171 CROP HISTORY RECORD SEEDLOT:  4371  SPECIES:  Fc  CONTAINER SIZE:  4 cu.in.  CONTAINER TYPE:  SB313  DATE SOWN:  Mar. 3 0, 1983  GREENHOUSE HISTORY WEEK  FERTILIZER TYPE/AMOUNT  PESTICIDE TYPE/AMOUNT  QUANTITY OF WATER  1.  l-52-17/33L-8.8Kg  2.  /40L  3.  2O-2O-2 0/37L-12.5Kg  4.  2 0-2 0-2 0/37L  5.  2O-2O-20/24L  1 L  6.  2 0-2 0-2 0/72L-15kg  1/2 hr  7.  20-20-20/31L  8.  20-20-20/75L  9.  20-20-20/37L  10.  2 0-2 0-2 0/88L  11.  20-20-20/91L  12.  20-2 0-2 0/66L  13.  2O-2O-20/56L  14.  20-20-20/76L  15. 16.  Kept Moist  80n/Bravo/275L 3/4 hr 8Qn/Bravo/275L  /115L  17.  2O-2O-2 0/42L-12.5kg  18.  2 0-2 0-2 0/84L  19.  2 0-2 0-2 0/135L  8Qn/Bravo/275L  2 0.  2 0-2 0-2 0/89L  8Qn/Bravo/275L  Flushed out  APPENDIX IV  HOMOGENEOUS VARIANCE CHECK OF DATA ANALYSES  STUDY  TABLE  VARIABLE  HOMOGENEOUS VARIANCE  I  3.2  height caliper shoot dry weight root dry weight  3.3  height caliper shoot dry weight root dry weight  * * * *  3.4  height caliper shoot dry weight root dry weight  * * * *  3.5  height caliper shoot dry weight root dry weight  * * * *  3.6 3.7 3.8  caliper shoot dry weight shoot dry weight  * *  3.11 3.15 3.16  RGC survival survival  *  3.17  total height caliper height increment r e l a t i v e growth rate  * * * *  3.18  total height caliper height increment relative growth rate  *  *  APPENDIX IV  HOMOGENEOUS VARIANCE CHECK OF DATA ANALYSES  STUDY II  TABLE  VARIABLE  HOMOGENEOUS VARIANCE  4.2 4.3  bud formation bud formation  4.4  4 4 6 6  4.5  height c a l i per shoot dry weight root dry weight bud height  *  4.10  January RGC March RGC  * *  4.11  January dormancy intensity March dormancy intensity  * *  week week week week  *  bud formation bud flushing bud formation flushing  174 APPENDIX V ANALYSIS OF VARIANCE TABLES  A.  CHAPTER THREE ANOVA TABLES 1.  ANOVA FOR TABLE 3.2:  i.  Height.  ANOVA Source  Photoregime Error Total  ii.  df  August Morphology Measurement on Hemlock,  ss  ms  4  977. 04  244.26  95  828.99  8.73  99  186.0  F-ratio  27.99  Probability  0. 0000  Caliper.  ANOVA Source  Photoregime Error Total  df  ss  ms  4  1.6 9  0.42  95  12.99  0.14  99  14.67  F-ratio  3 . 09  Probability  0.019  175 iii.  Shoot Dry weight.  ANOVA Source  df  Photoregime Error Total  iv.  ss  ms  4  0.95  0.24  45  1.76  0.039  49  2.71  df  ss  F-ratio  6.07  Probability  0.0005  Root dry Weight  ANOVA Source  Photoregime Error Total  4  ms  0. 083  0.0021  45  0.28  0. 0061  49  0.36  F-ratio  3.40  Probability  0. 0164  176 2.  ANOVA FOR TABLE 3.3: i.  Height.  ANOVA Source  df  Photoregime Error Total  ii.  August Morphology Measurements in Douglas-fir.  ss  ms  4  476.35  119.09  45  237.83  5.29  49  714.19  F-ratio  22.53  Probability  0. 0000  Caliper  ANOVA Source  Photoregime Error Total  df  ss  ms  4  0.46  0.12  45  3 . 99  0. 089  49  4.45  F-ratio  1.31  Probability  0.2812  177  iii.  Shoot Dry Wei ght  ANOVA Source  df  ss  Photoregime  4  Error  1.12  0.28  45  3.90  0. 087  49  5.02  Total  iv.  Photoregime  Total  F-ratio  3.21  Probability  0. 0210  Root Dry Weight.  ANOVA Source  Error  ms  df  4  ss  ms  0. 03 4  0. 008 6  45  0.41  0. 0091  49  0.44  F-ratio  0.9 5  Probability  0.4 449  178 3.  ANOVA FOR TABLE 3.4: i.  September Morphology Measurements in Hemlock,  Height  ANOVA Source  d  ss  ms  F-ratio  Probability  Photoregime  4  937.94  234.48  22.75  0. 0000  Conditioning  1  3.35  3.35  0.32  0.57 00  Photoregime *Conditioning  4  102.85  25.71  2.49  0. 0484  90  927.65  10.31  Error Total  ii.  99  1971.8  df  ss  ms  F-ratio  Caliper.  ANOVA Source Probability  Photoregime  4  2.75  0.68  3.82  0.0065  Conditioning  1  0.63  0.63  3.51  0.0642  Photoregime *Conditioning  4  0.96  0.24  1.33  0.2627  90  16.19  0.18  99  2 0.53  Error Total  179 iii.  Shoot Dry Weight  ANOVA Source  df  ss  ms  F-ratio  Probabili  Photoregime  4  2.38  0.6 0  5.51  0.0005  Conditioni ng  1  0.89  0.90  8.27  0. 005 0  Photoregime * Conditioning  4  0.32  0.08 0  0.7 4  0.5690  90  9.71  0.11  99  13.31  Error Total  iv.  Root Dry weight.  ANOVA Source  df  ss  ms  F-ratio  Probability  Photoregime  4  0.52  0.13  3.12  0. 0187  Conditioning  1  0.29  0.29  6.84  0. 0104  Photoregime *Conditioning  4  0.29  0.074  1.76  0.1437  90  3.76  0.042  99  4.87  Error Total  180 4.  ANOVA FOR TABLE 3.5: i.  September Morphology Measurements in Douglas-fir.  Height.  ANOVA v Source  df  ss  ms  F-ratio  Probability  358.86  87 .13  0. 0000  0. 054  0.8174  3. 63  0. 0086  Photoregime  4  Conditioning  1  0.22  0.22  Photoregime *Conditioning  4  59.83  14.96  90  37 0.69  4.12  Error Total  ii.  99  1435.4  1866.2  Caliper  ANOVA Source  df  ss  ms  F-ratio  Probabi1  Photoregime  4  1.57  0.39  1.62  0.1757  Conditioning  1  1.13  1.13  4.68  0. 03 3 2  Photoregime *Conditioning  4  1.41  0.35  1.46  0.2215  90  21.82  0.24  99  25.94  Error Total  181 iii.  Shoot Dry Weight.  ANOVA Source  df  ss  ms  F-ratio  Probability  Photoregime  4  11.16  2.79  15.74  0. 0000  Conditioning  1  2.12  2.12  11.95  0. 0008  Photoregime *Conditioning  4  1.19  0.3 0  1.68  0.1619  90  15.95  0.18  99  30.41  ANOVA Source  df  ss  Photoregime  4  0.24  0.059  Conditioning  1  0.38  0.38  Photoregime *Conditioning  4  0.17  0. 044  90  3.39  0.038  99  4.18  Error Total  iv.  Error Total  Root Dry Weight.  ms  F-ratio  Probabil  1.56  0.19 05  10.08  0. 0021  1.16  0.3354  182  5.  ANOVA TABLES FOR TABLE 3.11: i.  Douglas-fir.  ANOVA Source  df  Photoregime Error Total  ii.  Photoregime  Total  ss  ms  F-ratio  Probability  19.29  0. 0000  F-ratio  Probability  4  24.00  6.00  45  14.00  0.311  49  38. 00  Western Hemlock.  ANOVA Source  Error  RGC.  df  ss  ms  4  4 . 08  1.02  45  22. 00  0.49  49  22. 08  2 . 09  0.09 8 3  183 6.  ANOVA FOR TABLE 3.15:  ANOVA Source  Western Hemlock  df  Survival.  ss  ms  F-ratio  Probabi1ity  Plot  4  1.53  0.38  3.14  0. 0143  Photoregime  4  1.28  0.32  2.63  0. 03 3 7  Conditioni ng  1  0.038  0. 038  0.31  0.5786  Photoregime *Conditioning  4  0.43  0.116  0.89  0.4721  F-ratio  Probability  Error Total  7.  ANOVA FOR TABLE 3.16:  ANOVA Source  486  59.07  499  62.34  Douglas - f i r  df  0.12  Survival.  ss  ms  Plot  8  0.97  0.12  1.99  0. 0449  Photoregime  4  0.88  0.22  3.60  0. 0064  Conditioning  1  0.19  0.19  3.07  0.08 04  Photoregime *Conditioning  4  0.76  0.19  3.11  0. 0148  882  54.06  899  56.87  Error Total  0.061  184 8.  ANOVA FOR TABLE 3.17: i  Morphology of Outplanted  Hemlock,  Height.  ANOVA Source  df  ss  ms  F-ratio  Probability  Plot  4  569.80  142.45  4.15  0.0026  Photoregime  4  813.53  203.38  5.92  0. 0001  Conditioning  1  11.61  11.61  0.34  0.5613  Photoregime *Conditioning  4  229.39  57.35  1.67  0.156 0  Error Total  ii.  408  14010.  421  15603.  df  ss  34.34  Height Increment.  ANOVA Source  F-ratio  Probability  97.82  5.65  0.0002  3 03 . 83  17.56  0. 0000  Plot  4  Photoregime  4  Conditioni ng  1  27.58  27.58  1.59  0. 0275  Photoregime *Conditioning  4  54.08  13.52  0.78  0.5377  Error Total  391.28  ms  1215.3  410  7 09 4 .9  423  8773.0  17.31  185  iii.  Caliper.  ANOVA Source  df  ss  ms  F-ratio  Probabili  Plot  4  16.54  4.13  7.00  0. 0000  Photoregime  4  12.43  3.11  5.26  0. 0004  Conditioning  1  0.021  0.021  0. 035  0.8507  Photoregime *Conditioning  4  1.41  0.35  0.60  0.6664  409  241.54  422  272.64  Error Total  iv.  0.6 0  Relative Height Growth.  ANOVA Source  df  ss  ms  F-ratio  Plot  4  Photoregime  0.76  0.19  3.40  0.0095  4  6.20  1.55  27.74  0.0000  Conditioning  1  0.15  0.15  2.71  0.1007  Photoregime *Conditioning  4  0.41  0.10  1.82  0.1244  406  22.67  419  3 0.13  Error Total  0.056  Probability  9.  ANOVA FOR TABLE 3.18: i.  Morphology of Outplanted Douglas-fir.  Height.  ANOVA Source  df  ss  Plot  8  Photoregime  4  Conditioning  1  6.92  Photoregime *Conditioning  4  6 03 . 70  Error Total  ii.  453.88 6625.3  ms  56.73 1256.3 6.92 1 50.9 3  F-ratio  Probability  2.64  0. 0074  76.95  0.0000  0.32  0.57 08  7 . 01  0. 0 0 0 0  815  17542.  21.52  832  25243.  df  ss  ms  F-ratio  Probability  Height Increment.  ANOVA Source  Plot  8  201.15  25.14  1.64  0.1104  Photoregime  4  416.06  104.02  6.77  0. 0000  Conditioning  1  37.57  37.57  2.45  0.1182  Photoregime *Conditioning  4  64.43  16.11  1.05  0.3810  Error Total  816  12532.  833  13243.  15.36  187  iii.  Caliper.  ANOVA Source  df  ss  ms  F-ratio  Probabi!ity  Plot  8  104. 30  13.04  4.23  0. 0000  Photoregime  4  31. 19  7.80  2.53  0. 03 9 2  Conditioning  1  0. 24  0.24  0.079  0.7786  Photoregime *Conditioning  4  9. 33  2.33  0.76  0.5535  Error Total  iv.  817  2517. 0  834  2661. 0  3.08  Relative Height Growth.  ANOVA Source  df  ss  ms  Plot  8  0.64  0.080  Photoregime  4  6.65  1.66  Conditioni ng  1  0. 014  Photoregime *Conditioning  4  0. 087  Error Total  799  22.15  816  29.49  F-ratio  ProbabiV  2.89  0. 0035  59.95  0. 0000  0. 014  0.49  0.4842  0.022  0.78  0.5374  0. 028  188 APPENDIX V B.  CHAPTER FOUR ANOVA TABLES  1.  ANOVA FOR TABLE 4.2:  ANOVA Source  Induction Regime Error Total  2.  ANOVA FOR TABLE 4.3:  ANOVA Source  Terminal Bud Formation After 16 days.  df  ss  ms  4  5.93  1.48  220  44.40  0.20  224  50.33  F-ratio  Probability  7.34  0.00001  Terminal Bud Formation After 4 weeks.  df  ss  ms  F-ratio  Probability  Moisture stress  3  3.67  1.22  7.87  0. 00004  Photoperiod  1  15.21  15.21  97.95  0. 00000  Stress * Photoperiod  3  5.03  1.69  10.9 0  0. 00000  352  54.67  0.16  359  78.62  Error Total  189 3.  ANOVA FOR TABLE 4.4: i.  ii.  Bud Formation and Flushing After Four and Six Weeks,  For bud formation after four weeks see above ANOVA. Flushing after 4 weeks.  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  4.68  1.55  12.03  0.0000  Photoperiod  1  7.22  7.23  55.77  0. 0000  Stress * Photoperiod  3  7.43  2.48  19.12  0. 0000  352  45.60  0.13  359  64.93  Error Total  iii.  Bud Formation After Six Weeks.  ANOVA Source  df  ss  ms  F-ratio  12.03  0. 0000  19.12  0. 0000  Moisture stress  3  4.68  1.55  Photoperiod  1  7.22  7.23  Stress *  3  7.43  2.48  352  45.60  0.13  359  64.93  Error Total  Photoperiod  Probabi1ity  190 iv.  Flushing After Six Weeks.  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  1.56  0.52  11.79  0. 0000  Photoperiod  1  0.22  0.22  5.08  0.0248  Stress * Photoperiod  3  0.7 0  0.23  5.26  0.0000  Error Total  351  15.51  358  17.99  0. 044  4.  ANOVA FOR TABLE 4.5: i.  Morphology Measurements,  Height  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  1151.44  387.15  79.15  0. 0000  Photoperiod  1  186.91  186.91  38.21  0. 0000  Stress * Photoperiod  3  356.37  118.79  24.29  0. 0000  352  1721.76  4.89  359  3426.49  Error Total  ii.  Caliper  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  6.26  2.09  21.49  0. 0000  Photoperiod  1  0.10  0.10  1.07  0.3 027  Stress * Photoperiod  3  2.52  8.41  8.66  0.0000  325  34.17  9.71  Error Total  359  192  iii.  Shoot Dry Weight  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  17.07  5.69  32.90  0. 0000  Photoperiod  1  1.54  1.54  8.93  0. 0032  Stress *  3  4.80  1.60  9.26  0.0000  352  6 0.9 0  0.17  359  84.33  Photoperiod  Error Total  IV.  Root Dry Weight.  ANOVA Source  df  ss  Moisture stress  3  0.72  0.24  10.99  0. 0000  Photoperiod  1  0.63  0.63  29.04  0. 0000  Stress *  3  2.06  0.69  31.42  0.0000  325  7.68  0.022  325  11.09  Error Total  Photoperiod  ms  F-ratio  Probability  193  V.  Bud Height.  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  2.04  0.68  0.98  0.4045  Photoperiod  1  0.36  0.36  0.52  0.4798  Stress * Photoperiod  3  8.75  2.92  4.19  0. 0064  352  244.82  0.69  359  255.97  Error Total  5. ANOVA FOR TABLE 4.10. i.  RGC in January and March,  January RGC.  ANOVA Source  df  ss  ms  F-ratio  Probability  10.66  0.0000  Moisture stress  3  35.93  11.98  Photoperiod  1  0.0  0.0  0. 00  1. 0000  Stress * Photoperiod  3  24.25  8.08  7.19  0. 0001  152  17 0.8 0  1.12  159  230.97  df  ss  Error Total  ii.  March RGC.  ANOVA Source  ms  F-ratio  Probability  Moisture stress  3  21.65  7.22  8.13  0. 0000  Photoperiod  1  0.90  0.90  1.01  0.3155  Stress * Photoperiod  3  34.55  11.52  12.48  0. 0000  152  134.90  0.89  159  192.00  Error Total  195 6.  ANOVA FOR TABLE 4:11: i.  Dormancy Intensity in January and March,  January Dormancy Intensity  ANOVA Source  df  ss  ms  F-ratio  Probability  Moisture stress  3  67.36  22.45  4.64  0. 0039  Photoperiod  1  2 05 . 42  2 05 . 42  42.48  0.0000  Stress * Photoperiod  3  142.07  47.36  9.79  0.0000  150  725.28  4.84  157  1144.40  Error Total  ii.  March Dormancy Intensity  ANOVA Source  df  ss  Moisture stress  3  Photoperiod  1  Stress * Photoperiod  3  301.00  100.33  151  3651.50  24.18  158  5880.6 0  Error Total  57.83  ms  F-ratio  Probabi1 •  19.28  0.78  0.4973  187 0. 00 187 0. 0  77.33  0. 0000  4.15  0.007 4  APPENDIX VI  DAILY MONIOTRING MEASUREMENTS OF DOUGLAS-FIR MOISTURE STRESS TRIAL MOISTURE STRESS TREATMENT  SHOOT WATER POTENTIAL (bars) DAY  Average  1 3 5 6 8 10 12 15 16  5.0 4.3 4.7 3.5 4.1 3.8 5.7 4.1 5.0  4.5 3.5 4.5 3.0 3.5 3.0 3.5 3.0 4.5  1 3 5 6 8 10 11 12 16  5.4 4.9 7.5 9.6 4.0 8.5 9.8 3.0 9.0  4.5 4.5 6.5 7.5 3.5 7.0 8.5 2.5 7.0  Medium  1 3 5 6 7 8 10 12 13  4.7 5.6 7.3 9.3 18.4 4.9 4.4 10.5 16.7  3.5 4.5 5.5 7.0 15.0 4.0 3.5 7.0 12.0  Severe  1 3 5 6 7 8 10 12 14  4.5 5.8 7.0 9.9 17.9 23.8 4.0 3.9 10.8  4.0 4.5 5.0 7.5 12.5 2 0.0 3.0 3.5 9.0  Control  Light  Range  -  313 BLOCK Weight  (kg)  SOIL WATER CONTENT [%)  -  6.5 5.0 5.0 4.5 5.0 4.5 10.0 4.5 5.5  6.7 7.8 6.1 7.8 5.6 6.8 5.1 5.9 4.9  66 73 64 66 62 68 58 60 57  -  6. 0 5.5 10.0 13.5 4.5 12.0 14.0 4.0 12.0  6.9 5.8 4.8 4.5 5.9 4.6 4.5 7.0 4.5  69 62 49 41 63 41 39 71 41  -  5.5 7.0 8.5 14.0 2 0.0 6.0 5.0 13.5 23.5  7.1 5.8 4.9 4.6 4.3 7.0 5.5 4.6 4.4  70 59 61 43 35 71 57 41 33  -  5.0 7.0 8.5 15.0 23.5 26.0 5.0 5.0 15.0  6.9 5.8 4.9 4.5 4.2 4.0 6.9 5.6 4.4  68 63 65 40 38 32 68 61 43  -  _  _  197 APPENDIX VII DAILY MAXIMUM AND MINIMUM TEMPERATURES IN 1983 BLACK OUT SYSTEM AND ADJACENT GREENHOUSE CONTROL BENCH  DATE (1983) June 22 23 24 25 26 27 28 29 30 July 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  BLACKOUT SYSTEM " Mi nimum Maximum Temperature ( ° C ) Temperature ( ° C ) 14 17 18.5 18 18 15.5 15.5 15 14 14 13 14 16.5 13 16.5 11 11 15 14 14 14.5 13 13 13 13 14 14 14 14 13 13 13.5 13.5 14 14 13.5 13 13.5 15 13  22 25 23.5 23 27 25 23.5 25 25 21 29 24 28 29 24 23 23 23 17 19 21 26 27 21 26 30 28 20 21 28 31 25.5 28 29 21 22 25 29 30 29  GREENHOUSE CONTROL BENCH Maximum Temperature 21 23 22.5 21.5 26 25 22 25 21 21.5 25 24 27.5 25.5 23.5 21.5 23 21 19 18.5 20 26.5 27.5 19.5 25.5 30 28 21.5 23 27 3 0.5 23.5 26 26 20 21 23 27 31 27.5  198 APPENDIX VII DAILY MAXIMUM AND MINIMUM TEMPERATURES IN 1983 BLACK OUT SYSTEM AND ADJACENT GREENHOUSE CONTROL BENCH BLACKOUT SYSTEM '" Minimum Maximum Temperature ( ° C ) Temperature ( ° C )  DATE (1983) August  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 14 17  14 14 12 12.5 15 13.5 16 13 15 14 12 13.5 12 12.5 12 13  27 21 24 30 27 29 32 32 29 28 23 27.5 30 28 27 27 25  GREENHOUSE CONTROL BENCH Maximum Temperature 1 24.5 21 25 27.5 25 28.5 32.5 34 27 23.5 21.5 26.5 29.5 24.5 25.5 25.3 25  

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