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The relationship between foliar and soil chemistry, growth parameters, and variable height growth in… Husted, Lynn Diane 1982

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THE RELATIONSHIP BETWEEN FOLIAR AND SOIL CHEMISTRY, GROWTH PARAMETERS, AND VARIABLE HEIGHT GROWTH IN ADVANCE REGENERATION OF AMABILIS FIR by LYNN DIANE HUSTED B.Sc, The University of B r i t i s h Columbia, 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF FORESTRY We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March 1982 ® Lynn Diane Husted, 1982 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree t h a t the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of <L~^rj~>Cs££t~-<-j The University of Brit ish Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1WS i i ABSTRACT Many stands of advance amabilis f i r regeneration near Courtenay, B.C. e x h i b i t d e c l i n i n g height growth a f t e r an i n i t i a l l y good release response following logging of the overstory. The objectives of this thesis were to investigate the r e l a t i o n s h i p of n u t r i t i o n , p a r t i c u l a r l y nitrogen, to this height growth pattern on one s i t e . Foliage from trees representing the range of height growth on the s i t e was c o l l e c t e d twice monthly from May to September f or chemical a n a l y s i s . In September, samples from the major rooting zone (H horizon) of well and poorly grown tree microsites were also c o l l e c t e d f o r chemi-ca l a n a l y s i s . Measurements of non-nutritional factors (age and height at release, aboveground competition, diameter growth) were taken to assess the contribution of these variables to height growth. Microsite differences i n s i t e moisture were not measured due to lack of time and equipment. However, the f o l i a r chemistry of trees growing on w e l l -drained (mesic) and rapidly-drained (xeric) s i t e s was compared to estimate the e f f e c t of microsite d i f f e r e n c e s . Height growth was s i g n i f i c a n t l y r e l a t e d to f o l i a r chemistry, p a r t i -c u l a r l y nitrogen i n multiple regression equations. This r e l a t i o n s h i p was better i n most cases with summer rather than f a l l f o l i a r chemistry measurements. There were s i g n i f i c a n t differences i n nitrogen, carbon: nitrogen r a t i o s , magnesium and calcium between the humus of well and poorly grown tree m i c r o s i t e s . A proposed scenario f o r the decline i n height growth following i n i t i a l l y good relase growth was proposed. i i i None of the non-nutritional factors measured related s i g n i f i c a n t l y to height growth a f t e r release. Differences i n crown siz e at release and microsite water a v a i l a b i l i t y are the most l i k e l y factors accounting for differences i n the rate of height growth decline other than n u t r i t i o n . X V ACKNOWLEDGEMENTS I w i s h to e x t e n d my a p p r e c i a t i o n to D r . K i m m i n s , my g r a d u a t e s u p e r v i s o r , Crown Z e l l e r b a c h o f Canada L t d . and the B . C . M i n i s t r y o f F o r e s t s f o r p r o v i d i n g s u p p o r t f o r t h i s s t u d y . The a d v i c e of D r s . G r e g o r y and S t a u f f e r w i t h s t a t i s t i c a l a n a l y s i s i s g r a t e f u l l y a c k n o w l e d g e d . S p e c i a l thanks a r e due to K i r s t e e n L a i n g f o r h e r e n t h u s i a s t i c f i e l d a s s i s t a n c e , J o h n Harwigne and o t h e r T r e e Farm L i c e n s e No . 2 p e r s o n n e l f o r t h e i r s u p p o r t and i n t r o d u c t i o n to c o a s t a l f o r e s t r y , M i n and E v a Tse f o r t h e i r h e l p w i t h c h e m i c a l a n a l y s e s , and t o members o f my g r a d u a t e c o m m i t t e e , D r s . B a l l a r d , H a d d o c k , K i m m i n s , and K l i n k a f o r t h e i r g e n e r a l and s p e c i f i c comments on the t h e s i s . V TABLE OF CONTENTS Page ABSTRACT i i ACKNOWLEDGEMENTS i v TABLE OF CONTENTS v LIST OF TABLES v i i i LIST OF- FIGURES i x INTRODUCTION 1 LITERATURE SURVEY 8 1. Site Requirements of Amabilis F i r 8 1.1 Climatic 8 1.2 Edaphic 9 2. Factors L i m i t i n g Amabilis F i r D i s t r i b u t i o n at Low Elevations 10 3. Diagnosing Nutrient Deficiencies 12 3.1 S o i l Analysis 12 3.2 F o l i a r Analysis 13 3.2.1 Introduction 13 3.2.2 Standardized F o l i a r Sampling 15 3.2.3 Methods of Data Presentation .< 25 3.2.4 Interpreting F o l i a r Nutrient Data 26 LOCATION AND DESCRIPTION OF THE RESEARCH SITE 30 1. Location 30 2. History 30 v i Page 3. • Climate 33 4. Geology 34 5. Soils 35 6. Biogeoclimatic Classification 36 METHODS . 39 1. Field Sampling 39 2. Laboratory Analysis 42 3. Data Analysis 43 RESULTS AND DISCUSSION 44 1. Comparison of Fa l l Foliar Nutrients with Literature Values 44 1.1 Nitrogen 44 1.2 Phosphorus 46 1.3 Ca, Mg, and K 47 1.4 Nutrient Ratios 50 2. Relationship Between Foliar Chemistry and Height Growth 51 3. Seasonal Trends in Foliar N and P 64 4. Relationship Between Height Growth and Foliar N, P, N:P Measured During May to September 71 5. The Relationship Between Humus Nutrient Status and Amabilis Fir Growth 73 5.1 Nitrogen and C:N Data 73 5.2 Ca, Mg, and K Data 76 5.3 Proposed Relationship Between Variable Height Growth and Nutrition 79 v i i Page 6. • E f f e c t s of Non-Nutritional Factors on Variable Height Growth at the Study Site 82 6.1 Age and Height at Release 82 6.2 Degree of Aboveground Competition 84 6.3 Red i s t r i b u t i o n of Growth 85 6.4 Genetics 88 6.5 Root Disease 92 6.6 Micronutrient T o x i c i t y 92 6.7 Microsite Differences i n Moisture A v a i l a b i l i t y . 92 SUMMARY AND CONCLUSIONS 97 REFERENCES 100 APPENDICES 121 A. O f f - S i t e Hypothesis 121 B. Comment on Ca, Mg, and K Analysis 123 v i i i LIST OF TABLES Table Page 1 Mean nitrogen concentrations (% oven-dry weight) of amabilis f i r f o l i a g e from three crown l e v e l s . Con-fidence l i m i t s are at 95% l e v e l (from Cameron 1979). 20 2 P r o f i l e d e s c r i p t i o n of the study s i t e s o i l . 35 3 Mean depth and chemical properties of the LFH horizons of the Woodhus s o i l s e r i e s (adapted from Laing 1979). 37 4 Some f a l l f o l i a r nitrogen concentrations (% oven-dry weight) reported for true f i r species. 45 5 Some f a l l f o l i a r phosphorus concentrations (% oven-dry weight) reported for true f i r species. 48 6 Mean f a l l f o l i a r Ca, Mg, and K concentrations and contents i n well and poorly grown advance amabilis f i r regeneration. 49 7 Comparison of nutrient r a t i o s i n f a l l f o l i a g e of well and poorly grown amabilis f i r with other studies. 52 8 Stepwise regression with growing season N, P, and N:P measured i n current, 1- and 2-year-old f o l i a g e . 72 9 Comparison of mean pH, macronutrients and C:N r a t i o s i n humus c o l l e c t e d from well and poorly grown tree m i c r o s i t e s . 74 10 Chemical analysis of seedbed materials (from Minore 1972). 78 11 Comparison of growth parameters between well grown and poorly grown amabilis f i r . 83 12 Simple c o r r e l a t i o n c o e f f i c i e n t s (r) between needle weights, height and basal area increment. 87 13 Mean depth (cm), t o t a l N and P (% oven-dry weight), C:N r a t i o , and exchangeable Ca, Mg, and K (me/100 g) i n the FH horizons of 3 x e r i c and 3 mesic s i t e s . 94 14 Mean needle weight (mg per 100 needles) and nutrient concentration (% oven-dry weight) i n f a l l f o l i a g e of amabilis f i r on 3 x e r i c and 3 mesic s i t e s . 95 ix LIST OF FIGURES Figure 10 Page Steadily d e c l i n i n g (stagnating) height growth i n unmanaged stands of advance amabilis f i r regeneration. 2 E r r a t i c height growth i n advance amabilis f i r regeneration growing at 750 m a . s . l . Pointer i s below 1974 height increment which was shorter than normal for most Courtenay amabilis f i r . 3 Generalized r e l a t i o n s h i p between f o l i a r concentra-tions of a l i m i t i n g nutrient and tree growth (from Morrison 1974a). 14 4 Location of study s i t e on Vancouver Island, B r i t i s h Columbia. 5 Mean annual height growth of well and poorly grown amabilis f i r regeneration at the research s i t e (95% confidence l i m i t s are shown). 6 F o l i a r sampling p o s i t i o n on the fourth whorl. 7 Relationship between N:P r a t i o s i n one-year-old amabilis f i r f o l i a g e and release height growth. 54 8 Relationship between phosphorus content and nitrogen concentration i n current f o l i a g e of amabilis f i r . Relationship between magnesium content and nitrogen and potassium concentrations i n current f o l i a g e of amabilis f i r . Results of Crown Zellerbach's p i l o t f e r t i l i z e r t r i a l (from Crown Zellerbach 1978). 12 Mean N% i n current, 1-year-old, and 2-year-old f o l i a g e from May to September. 14 Phenology of current height growth of well and poorly grown trees i n 1978. 31 32 40 55 58 62 11 Tree-to-tree v a r i a t i o n i n May to September nitrogen concentrations of 1-year-old f o l i a g e from 10 poorly grown trees sampled early each month. 65 66 13 Mean P% i n current, 1-year-old, and 2-year-old f o l i a g e from May to September. 67 90 1 INTRODUCTION In 1976, Crown Zellerbach of Canada Lt d . foresters became concerned about poor height growth i n approximately 2,500 ha of young amabilis f i r (Abies amabilis (Dougl.) Forbes) stands located i n Tree Farm License No. 2 near Courtenay, B.C. Ten to twenty years ago these areas had been clearcut logged but not slashburned i n order to preserve the e x i s t i n g advance regeneration of amabilis f i r . Use of advance regeneration can shorten r o t a t i o n time and also reduce the cost of s i t e preparation and planting providing that release^ height growth i s s a t i s f a c t o r y . I n i t i a l l y , release height growth of the Courtenay amabilis f i r was promising, ranging from 20 to 40 cm annually. However, th i s e arly release growth was not always sustained. By 1976, height increments of many trees were s t e a d i l y d e c l i n i n g (stagnating) (Figure 1) or e r r a t i c with one or more periods of slow growth separated by periods of s a t i s -factory growth (Figure 2). The unsatisfactory height growth was found to some extent on a l l s i t e s regardless of slope, aspect or elevation (Wetten 1977), but there was no consistent pattern of height growth within stands on s i m i l a r s i t e s . The year of i n i t i a t i o n , the duration, and the degree of poor growth varied from tree to tree on many s i t e s , eliminating the p o s s i b i -l i t y of annual macroclimatic f l u c t u a t i o n s as a sole causal agent. Some trees resumed normal, height growth a f t e r 2 or 3 years of poor growth; others continued to stagnate for more than 10 years. Growth once overstory i s removed and advance regeneration i s no longer suppressed. Steadily declining (stagnating) height growth in unmanaged stands of advance amabilis f i r regeneration. 3 Figure 2. E r r a t i c height growth i n advance amabilis f i r regeneration growing at 750 m a . s . l . Pointer i s below 1974 height increment which was shorter than normal for most Courtenay amabilis f i r . 4 Crown Zellerbach foresters are j u v e n i l e spacing many of these stands. Because they are unable to predict i f height growth of currently vigorous amabilis f i r w i l l be s a t i s f a c t o r y i n the future, they tend to give preference i n spacing to smaller hemlock or Douglas-fir regeneration, thereby l o s i n g up to 10 to 20 years of the volume accumu-lated i n vigorous amabilis f i r trees. The foresters are also concerned about the future height growth of natural and planted amabilis f i r regeneration, should they decide to r e f o r e s t high elevation s i t e s with t h i s species. Since 1972, entomologists, pathologists, s o i l s c i e n t i s t s , eco-l o g i s t s , and foresters from government agencies, u n i v e r s i t i e s , and private companies have examined the problem but have not been able to determine the cause of stagnating or e r r a t i c growth. There was no evidence of insect or disease damage on trees with stagnating height 2 growth . Many f a c t o r s , including genetic make-up, root pathogens, competition, age at release, r e d i s t r i b u t i o n of growth from height to diameter increment i n response to wind s t r e s s , microsite differences i n nutrient or water a v a i l a b i l i t y and v a r i a t i o n s i n mycorrhizal associa-tions and an inappropriate climate for amabilis f i r have been suggested as possible explanations for the dramatic differences i n height growth exhibited by adjacent trees within a stand of advance amabilis f i r regeneration. Pers. comm. from Dr. A. Funk, Canadian Forest Service, V i c t o r i a , B.C., November, 1977. 'see Appendix A for a b r i e f d e s c r i p t i o n of Klinka's o f f - s i t e hypothesis. 5 Following a f i e l d t r i p to the problem area near Courtenay, Klinka^ (1977a) concluded the problem should be studied i n d e t a i l . This thesis reports on part of a subsequent study. Other parts of the study examined: (a) the height of growth patterns i n amabilis f i r regeneration over a range of elevations and moisture regimes, and (b) the c o r r e l a t i o n between release age, release height, degree of aboveground competition, and years of needle retention and height growth over a range of s i t e s . This d e s c r i p t i v e approach was f e l t to be necessary i n order to obtain an o v e r a l l view of the factors which might influence height growth over the range of s i t e s on the Tree Farm. Several observations i n the problem area suggested that a severe nitrogen d e f i c i e n c y might be a major factor causing reduced height growth a f t e r promising early height growth i n some advance amabilis f i r regeneration: (a) Trees e x h i b i t i n g stagnating height growth also exhibited the v i s u a l symptoms of nitrogen d e f i c i e n c y described for amabilis f i r seedlings by Davidson (1957): stunted needles, reduced leader growth, slender twigs and c h l o r o t i c f o l i a g e . One- and 2-year-old needles of the poorly grown trees were yellow green (5GY 6/8 on the Munsell colour s c a l e ) . The c h l o r o s i s was s l i g h t l y accentuated at the needle t i p s . The f o l i a g e of w e l l -Research Pedologist, B.C. Ministry of Forests. 6 grown trees was 5 GY 4/3 on the Munsell colour scale. -According to Davidson, t h i s i s the t y p i c a l colour of healthy amabilis f i r f o l i a g e . (b) A mid elevation stand of amabilis f i r i n Tree Farm License No. 2 was thinned i n 1974. A control area was not thinned i n the spring of 1976, a small area i n the thinned stand was experi-mentally f e r t i l i z e d by hand with urea at the rate of 224 kg nitrogen per ha. During the 1976 growing season, needle size of the f e r t i l i z e d trees almost doubled and the fol i a g e colour darkened to a deep blue-green. In 1977, both height and diameter growth of the f e r t i l i z e d trees responded well to the f e r t i l i z e r treatment. (c) Klinka (1977a) observed that trees with good height growth and colour were usually rooted at le a s t p a r t l y i n mineral s o i l or humus, whereas c h l o r o t i c , slow-growing amabilis f i r were often rooted mainly i n decaying wood. He hypothesized that micro-s i t e differences i n the nutrient supply of the rooting medium might be responsible f o r the v a r i a b i l i t y i n height growth within a s i t e . For my thesis research, I decided to study the r e l a t i o n s h i p between n u t r i t i o n and variable height growth i n an advance amabilis f i r stand located on a moderately well-drained (mesic) s i t e . The objectives of th i s thesis were: (a) to determine i f a s i g n i f i c a n t r e l a t i o n s h i p existed between var i a b l e height growth on the study s i t e and f a l l f o l i a r 7 chemistry, p a r t i c u l a r l y N or N:P r a t i o . N:P r a t i o s may be a •more s e n s i t i v e i n d i c a t o r of nitrogen d e f i c i e n c i e s than f o l i a r N alone (Hellman and Gessel 1963). (b) to determine i f nutrients i n current, 1- or 2-year-old f o l i a g e c o l l e c t e d during the growing season were better related to height growth than f a l l f o l i a g e values. This information would add to our knowledge of amabilis f i r chemistry. (c) to determine i f there were s i g n i f i c a n t differences i n the nutrient status of humus c o l l e c t e d from microsites of well and poorly grown trees. (d) to determine i f other, n o n - n u t r i t i o n a l , factors contributed s i g n i f i c a n t l y to v a r i a b l e height growth within a stand. 8 LITERATURE SURVEY The l i t e r a t u r e survey i s divided into three sections. The f i r s t provides a b r i e f summary of the c l i m a t i c and edaphic requirements of amabilis f i r . The second outlines the factors thought to l i m i t amabilis f i r growth at low elevations. The t h i r d section i s a review of the techniques f o r studying nutrient status and d e f i c i e n c i e s of trees. 1. Site Requirements of Amabilis F i r 1.1 Climatic Requirements Amabilis f i r grows best on s i t e s with abundant s o i l moisture and low evaporative s t r e s s . In B.C., Krajina (1969) reported that these requirements are met i f annual r a i n f a l l exceeds 2550 mm. This amount could be reduced to as l i t t l e as 1900 mm i f a s u b s t a n t i a l portion of the p r e c i p i t a t i o n f a l l s as snow. Packee (1976) suggested that the moisture requirements of t h i s species are met on s i t e s with a n e g l i g i b l e l a t e summer moisture d e f i c i t , r a r e l y exceeding 75 mm i f the s o i l moisture capacity of the s i t e was at l e a s t 100 mm. Cold a i r drainage and the depth and duration of snow packs are important factors i n f l u e n c i n g moisture conditions. Amabilis f i r s i t e s often have snowpacks l a s t i n g into May or June (Packee, 1976). Low summer temperatures also favor amabilis f i r growth (Krajina 1969). Fowells (1965) reported that amabilis f i r s i t e s are character-ized by moderate temperatures with only moderate d a i l y and seasonal v a r i a t i o n s . A mean July temperature of 16° or 17°C i s considered to be the upper threshold f or amabilis f i r s i t e s by Packee (1976). 9 1.2 Edaphic Requirements B.C. ecologists d i f f e r i n t h e i r opinion about the importance of s o i l f e r t i l i t y f o r the growth of amabilis f i r . Krajina (1969) stated that an abundant supply of calcium and magnesium, and some nitrogen i n the form of n i t r a t e were necessary for best amabilis f i r growth. He observed that the optimum growth of amabilis f i r i n the biogeoclimatic zones where i t grows, occurs on s i t e s with good to very good base status. Pack.ee (1976) and Schmidt (1957) concluded from t h e i r observa-tions that amabilis f i r was tolerant of a wide range of s o i l types and that i t s growth was r a r e l y affected by low nutrient a v a i l a b i l i t y . Since i t i s often found on a c i d i c s o i l s with n e g l i g i b l e n i t r i f i c a t i o n poten-t i a l , Packee (1976) concluded that low l e v e l s of n i t r a t e should not l i m i t i t s growth. Two Washington studies documented the e f f e c t s of s o i l f e r t i l i t y on amabilis f i r growth. Williams (1968) measured an average annual height increment of 11.5 cm f o r j u v e n i l e amabilis f i r established on s o i l s developed from an old mud flow, compared to 37.8 cm for those growing on ri c h e r basic s o i l s derived from lava beds. Since the slope, aspect, elevation, stocking and growing season were s i m i l a r on both s i t e s , he ascribed the difference i n height growth to s o i l f e r t i l i t y . Gessel and Orians (1967) observed poor growth of amabilis f i r regeneration on mid elevation s i t e s with adequate p r e c i p i t a t i o n and snowcover to s a t i s f y t h i s species moisture requirements. They found that the poor growth resulted from low s o i l f e r t i l i t y , i n p a r t i c u l a r a poor supply of 10 nitrogen. Growth response to nitrogen f e r t i l i z a t i o n was good on these s i t e s . ' ; Adequate s o i l moisture i s often considered the edaphic factor most c r i t i c a l to good amabilis f i r growth (Packee 1976). Amabilis f i r grows best on well drained s o i l s , with abundant but not excessive moisture during the growing season (Fowells 1965; Kotar 1972; Packee 1976). Optimum growth occurs on hygric or seepage s i t e s (Krajina 1969). 2. Factors L i m i t i n g Amabilis F i r at Low Elevations The factors c o n t r o l l i n g the s u r v i v a l and growth of amabilis f i r at low elevations are not well known, and although low moisture l e v e l s are probably a major l i m i t i n g f a c t o r , there i s l i t t l e experimental evidence to v e r i f y that low p r e c i p i t a t i o n and high evaporative demand l i m i t s i t s growth to higher elevations. However, i n laboratory experiments, Kotar (1972) found that amabilis f i r seedlings were les s tolerant of low mois-ture l e v e l s than western hemlock seedlings. He also observed that seed-l i n g m o r tality during prolonged summer drought was the most important single factor l i m i t i n g amabilis f i r d i s t r i b u t i o n at low elevation. But despite t h i s evidence i n support of the idea of an important influence of moisture, amabilis f i r d i s t r i b u t i o n has not been su c c e s s f u l l y correlated with t o t a l annual p r e c i p i t a t i o n (Schmidt 1957; Kotar 1972; Packee 1976). Three factors may contribute to t h i s lack of c o r r e l a t i o n : (a) i t i s d i f f i c u l t to quantify the r e l a t i v e contribution of snow, r a i n , fog d r i p , and seepage water i n s a t i s f y i n g the moisture requirements of amabilis f i r ; 11 (b) annual p r e c i p i t a t i o n may be a le s s important parameter than • p r e c i p i t a t i o n during periods of active growth. The duration of d r y - s o i l periods may be poorly correlated with t o t a l p r e c i -p i t a t i o n . (c) temperature and moisture interactions are d i f f i c u l t to evaluate. Cool temperatures, cold a i r drainage and deep snow-packs may compensate for low annual p r e c i p i t a t i o n . Fowells (1965), Fonda and B l i s s (1971) and Packee (1976) concluded that high temperatures l i m i t e d amabilis f i r d i s t r i b u t i o n at low eleva-tions more than low p r e c i p i t a t i o n . Amabilis f i r may not be p h y s i o l o g i -c a l l y tolerant of high evapotranspiration stress associated with high temperatures (Kotar 1972). Packee (1976) suggested that s i t e s with a mean July temperature greater than 17°C would be too warm for amabilis f i r . However, because of temperature and moisture i n t e r a c t i o n s , amabilis f i r d i s t r i b u t i o n may not correlate any better with one tempera-ture parameter than with t o t a l annual p r e c i p i t a t i o n . Competition and f i r e h i s t o r y may also r e s t r i c t amabilis f i r to high elevations. Kotar (1972) f e l t that the absence of amabilis f i r on low elevation s i t e s with adequate moisture may be due to the slow j u v e n i l e growth of amabilis f i r compared to other plant species better adapted to low elevation conditions. Schmidt (1957) suggested that warm dry sum-mers l i m i t e d amabilis f i r , not for p h y s i o l o g i c a l reasons, but rather through the high frequency of forest f i r e s . Because of i t s large seeds and slow migration p o t e n t i a l , amabilis f i r i s slow to re-invade large burned areas. Packee (1976) also mentioned that the frequency of f i r e s on the east side of Vancouver Island may have greatly reduced f i r d i s t r i b u t i o n . 12 3. Diagnosing Nutrient D e f i c i e n c i e s Four"techniques ( v i s u a l symptoms, s o i l or f o l i a r chemical analyses, and f i e l d f e r t i l i z e r t r i a l s ) have been used to diagnose nutrient d e f i c i e n c i e s . V i s u a l symptoms are useful as a preliminary guide i n cases of severe d e f i c i e n c i e s , but i n most cases they are not s p e c i f i c enough to diagnose i n d i v i d u a l nutrient d e f i c i e n c i e s (Morrison 1974a). F i e l d f e r t i l i z e r t r i a l s are the only sure way of i d e n t i f y i n g a single or multiple nutrient deficiency and quantifying tree growth response to varying l e v e l s of the d e f i c i e n t n u t r i e n t ( s ) . However, f i e l d t r i a l s can be time consuming, expensive, and subject to operational d i f f i c u l t i e s (Morrison 1974a). I w i l l discuss the remaining two techniques i n more d e t a i l . 3.1 S o i l Analysis S o i l analysis i s used to assess nutrient status mainly i n nurs-e r i e s , young plantations, and s i t e s devoid of trees. S i g n i f i c a n t r e l a t i o n s h i p s between s o i l and tree growth or f o l i a r nutrient l e v e l s have been reported (Titus and Boynton 1952; Leyton and Leaf 1957; Tamm 1964; Lowry 1970; Adams 1974; Malm et a l . 1974; I s i k 1978). However, these r e l a t i o n s h i p s usually have a large random error component because of s o i l sampling problems, inadequate ex t r a c t i o n and analysis techni-ques, and the confounding e f f e c t s of c h e l a t i o n , mycorrhizae, and s o i l moisture on nutrient a v a i l a b i l i t y (Leyton 1958; Morrison 1974a; Baule and F r i c k e r 1970; Z o t t l 1975). The use of s o i l analysis i s further l i m i t e d by the lack of published guidelines to evaluate the adequacy of 13 s o i l nutrient l e v e l s ( Z o t t l 1975), by the d i f f e r i n g a b i l i t i e s of i n d i v i d u a l tree species to extract s o i l n u t r ients, and p a r t l y by the i n t e r a c t i o n between elements i n the s o i l . Despite these l i m i t a t i o n s , s o i l analysis i n conjunction with f o l i a i a nalysis and v i s u a l symptoms i s a useful diagnostic procedure (Bould 1968) 3.2 F o l i a r Analysis 3.2.1 Introduction Tissue nutrient concentrations are related to the a v a i l a b i l i t y and uptake of plant n u t r i e n t s . F o l i a r a n a l y s i s , which has become synonymous with plant tissue analysis i n f o r e s t r y , i s the most common method of assessing tree n u t r i t i o n . Foliage i s usually sampled because i t con-tains the highest concentration of plant nutrients and i s the s i t e of photosynthesis. In a study of grand f i r , for example, Loewenstein and P i t k i n (1972) determined that 50% of the aboveground tree nitrogen was contained i n f o l i a g e produced i n the l a t e s t growing season. F o l i a r n u t r i e n t l e v e l s c o r r e l a t e well with tree growth when a single nutrient i s severely d e f i c i e n t (Leyton and Armson 1955; Madgwick 1964a; Morrison 1974a; van den Driessche 1974). Numerous greenhouse and laboratory studies have described the r e l a t i o n s h i p betwen tree seedling growth, nutrient concentration and nutrient supply. These studies have been used to estimate the optimum nutrient concentrations for growth. Figure 3 i l l u s t r a t e s the general 14 OPTIMUM LUXURY TOXIC CRITICAL o cc o DEFICIENT o z < UJ or o INCREASING FOLIAR CONCENTRATION OF LIMITING ELEMENT-Figure 3. Generalized r e l a t i o n s h i p between f o l i a r concen-t r a t i o n s of a l i m i t i n g nutrient and tree growth (from Morrison 1974a) . i 15 growth response curve that r e s u l t s when nutrient concentrations are increased from sub-to-supra-optimal l e v e l s . For a consistent and successful a p p l i c a t i o n of f o l i a r a n a l y s i s , knowledge of t h i s r e l a t i o n s h i p and the factors which a f f e c t i t i s e s s e n t i a l . The v a r i a t i o n caused by some factors can be minimized by c a r e f u l l y planned standardized sampling. Others cannot and they impose s i g n i f i c a n t problems f o r data i n t e r p r e t a t i o n . The following l i t e r a t u r e survey i s a less-than-comprehensive review of f o l i a r analysis sampling and i n t e r p r e t a t i o n . Goodall and Gregory (1947), Morrison (1974a), van den Driessche (1974a), Turner et a l . (1978) have published good reviews of f o l i a r a n a l y s i s . 3.2.2 Standardized f o l i a r sampling Errors introduced into f o l i a r analysis by non-standardized sampling are much greater than those introduced during chemical analysis (van den Driessche 1974). Variations i n nutrient concentrations caused by differences i n the time of f o l i a g e sampling, the age of the fo l i a g e or the p o s i t i o n of the f o l i a g e i n the crown must be minimized i n order to reduce the sampling error component i n f o l i a r n u t r i t i o n studies. ( i ) Time variables Seasonal changes i n nutrient concentrations are a major and contro-v e r s i a l source of v a r i a t i o n i n f o l i a r analyses. Most macronutrients tend to have a seasonal maximum i n f o l i a r concentration and content during the l a t e summer or early f a l l , followed by a gradual decline to a 16 spring minimum (Lowry 1968; Morrison 1974a). K concentrations, however, are usually highest i n l a t e spring or e a r l y summer (Morrison 1974a). "Optimum sampling time i s a compromise between s e l e c t i n g the period of maximum s e n s i t i v i t y to treatment or s i t e d i fference, the time of year with minimum between tree v a r i a b i l i t y and the need for a stable period i n which to complete a sampling program" (Mead and P r i t c h e t t 1974). Most f o l i a r sampling i s completed i n l a t e f a l l and early winter when nutrient l e v e l s are most stable (White 1954; Tamm 1955; Leyton 1958; Gessel 1962; Lowry 1968; Mead and P r i t c h e t t 1974). Waring and Youngberg (1972) and Smith et a l . (1970) warned that t h i s practise s a c r i f i c e d "valuable b i o l o g i c a l information" and recommended f o l i a r sampling during periods of rapid growth and high demand on nutrient reserves. Smith et a l . (1970) found that f o l i a r concentrations i n n u t r i e n t - s u f f i c i e n t and n u t r i e n t - d e f i c i e n t l o b l o l l y pine (Pinus taeda L.) approached uniform l e v e l s during the dormant season, obscuring differences i n nutrient status. Spring and e a r l y summer sampling may be preferable but i s much more time-consuming i f stands of d i f f e r e n t elevations, aspects or geographi-c a l regions are to be compared. Since nutrient concentrations fluctuate with the phenological stage of the tree, spring sampling must be standardized by c o l l e c t i n g f o l i a g e a c e r t a i n number of days a f t e r bud burst (Waring and Youngberg 1972), or a f t e r a c e r t a i n set number of accumulated degree days above a threshold temperature (Shaw and L i t t l e 1977). Annual c l i m a t i c f l u c t u a t i o n s , p a r t i c u l a r l y i n p r e c i p i t a t i o n , cause a small but s i g n i f i c a n t v a r i a t i o n i n nutrient concentrations ( P l i c e 17 1955, 1964; Lowry 1969). In a 9-year study of nutrient concentrations i n 12 Monterey pine trees (Pinus r a d i a t a L . ) , Humphreys et a l . (1972) found that N, S and C l l e v e l s were s i g n i f i c a n t l y correlated with the number of days per year with r a i n , K, Ca and Mn with t o t a l r a i n f a l l , and Fe, Na and A l with the amount of p r e c i p i t a t i o n per rainy day. The average amount of r a i n f a l l p r i o r to the sampling date also influence N, P and K concentrations ( M i l l e r 1966). Amabilis f i r f o l i a g e formed i n years' with a long growing season has higher nutrient concentrations than that formed i n years with a short growing season (Turner et^ a l . 1978). Diurnal v a r i a t i o n i n nutrient concentrations e x i s t but no systema-t i c pattern for t h i s v a r i a t i o n has been described. Fonda (1979) suggested that l a t e afternoon may be the best time to sample nitrogen as nitrogen content i s l e a s t v a r i a b l e then. Since some of the diurnal v a r i a t i o n reported i s re l a t e d to t r a n s p i r a t i o n a l patterns (Klashes 1972), i t may be best to sample f o l i a g e during periods of low or stable t r a n s p i r a t i o n rates. ( i i ) Age v a r i a b l e s Systematic v a r i a t i o n i n nutrient l e v e l s associated with needle age i s an important source of v a r i a t i o n . Morrison (1974a) summarized the general trends for tree species: (a) concentrations of mobile elements such as N, P and K are highest i n current or one-year-old f o l i a g e ; (b) concentrations of immobile elements, for example Ca, Mn, Fe, tend to increase i n older f o l i a g e ; (c) Mg concentrations show no systematic pattern. 18 These general trends were found to be true for amabilis f i r by Schwab (1979) who studied nutrient concentration changes from 1-year to 17-year-old f o l i a g e i n mature dominant and co-dominant trees. Nitrogen concentration decreased sharply from current to 1-year-old f o l i a g e and then declined s t e a d i l y with age. K and P concentrations declined sharply for two years and then decreased gradually. Most studies recommend sampling current f o l i a g e i n the f a l l (Leyton and Armson 1955; Leyton 1958; Lowry and Avard 1969; Z o t t l 1975) because concentrations of mobile ions are greatest i n current f o l i a g e and seem to c o r r e l a t e best with t o t a l height growth (Leyton and Armson 1955), with s i t e q u a l i t y and s i t e index (Lowry and Avard 1969), and with a v a i l -able s o i l nutrients (Lavender and Carmichael, 1966). However, older f o l i a g e sometimes correlates better with other tree growth parameters. Nitrogen l e v e l s i n 1-year-old needles may correlate best with current height increment (Leyton and Armson 1955) and s i t e index (Wehrmann 1959). Goodall ( c i t e d i n Goodall and Gregory 1947) found that K l e v e l s i n older f o l i a g e were a better i n d i c a t o r of K n u t r i t i o n i n K d e f i c i e n t trees than those i n younger needles D e f i c i e n c i e s of immobile nutrients such as Ca may also be best detected i n older f o l i a g e because t h e i r concentrations are highest i n older tissues (Goodall and Gregory 1947; Wells and Metz 1963; van den Driessche 1974; Raupuch et a l . 1972). Tree age i s a l i t t l e studied source of v a r i a t i o n i n nutrient con-centrations. In a study of 15-to-l14-year-old Norway spruce (Picea  abies (L.) K a r s t . ) , Hohne (1964) discovered that N, K and Ca concentra-tions varied with tree age. N concentrations peaked at 30 years; K at 20 to 50 years; and Ca between 50 and 90 years. In a s i m i l a r study 19 with Scots pine (Pinus s y l v e s t r i s L . ) , Hohne (1967) reported that con-centrations remained constant with tree age. Morrison (1974b) noted that the only f o l i a r nutrient concentration difference between the j u v e n i l e balsam f i r he studied and the concentrations reported f o r mature trees by Brazeau and Bernier (1973) was a s l i g h t tendency for mature trees to have higher Ca and Mg l e v e l s i n the upper crown. No one has studied nutrient v a r i a t i o n s with tree age i n amabilis f i r . Even i f such a study existed, the r e s u l t s might not be widely a p p l i c a b l e . Variations with age are not systematic even within a tree. In a study of Pinus radiata (D. Don), Humphreys e_t a l . (1972) detected no nutrient changes with age, Raupuch et a l . (1972) found a s l i g h t increase i n N with age and Askew (1973) reported a decrease i n Ca, P, Na, and Cl and an increase i n N, Mg, and F with age. ( i i i ) E f f e c t of crown p o s i t i o n In most trees, N, P and K concentrations decrease from the upper to lower crown p o s i t i o n ; Ca l e v e l s increase, and Mg l e v e l s f luctuate (Morrison 1974a). The general pattern varies with stand age, vigor, and density. Crown p o s i t i o n e f f e c t s are most important i n medium dense stands of mature or vigorous trees (Wells and Metz 1963; Morrison 1974a). Cameron (1979) compared N and P concentrations at d i f f e r e n t crown l e v e l s of poor and well-grown advance amabilis f i r regeneration i n a spaced stand. He found that crown p o s i t i o n s i g n i f i c a n t l y affected nutrient concentrations only i n vigorous trees (Table 1). 20 TABLE 1: Mean nitrogen concentrations (% oven-dry weight) of amabilis . f i r f o l i a g e from three crown l e v e l s . Confidence l i m i t s are at 95% l e v e l (from Cameron 1979) Age of f o l i a g e Crown p o s i t i o n Current 1-year-old Well grown trees upper middle lower Poorly grown trees upper middle lower 1.04 + .07 0.84 + .11 0.85 + .08 1.05 + .08 0.93 + .08 0.93 + .06 0.78 + .09 0.73 + .08 0.72 + .07 0.76 + .07 0.73 + .05 0.70 + .06 21 The amount of l i g h t reaching the lower crown i s influenced by stand density. Because dry matter production i s lower i n shaded than i n f u l l y illuminated branches, the former may have higher nutrient concentrations than illuminated branches (Gagnon 1964). If shading i s random or the same f o r a l l crown l e v e l s , nutrient concentrations are l i k e l y to be s i m i l a r throughout the crown. In a study of nutrient concentrations of mature, evenly shaded, amabilis f i r , Schwab (1979) reported that only phosphorus l e v e l s i n 2-year-old needles varied between crown l e v e l s . Since upper crown f o l i a g e i s l e a s t l i k e l y to be influenced by the degree of shading i n stands with v a r i a b l e stocking, Wells and Metz (1963) recommended i t may be the most r e l i a b l e sample p o s i t i o n . Nitrogen concentrations i n upper crown f o l i a g e tend to correlate best with tree growth (Leyton 1958). Cameron's 1979 data (Table 1) suggests t h i s i s the case with amabilis f i r . Differences i n f o l i a r nitrogen concentrations between well and poorly grown trees were greatest i n the upper crown f o l i a g e although s t a t i s t i c a l l y s i g n i f i c a n t differences between the two growth classes occurred also i n the lower crown f o l i a g e . However, for some nut r i e n t s , tree species, or stand d e n s i t i e s , nutrient concentrations i n the mid or lower crown p o s i t i o n may be equally, or more, s e n s i t i v e to the nutrient status and growth p o t e n t i a l of the tree. In a comparison of well grown and poorly grown Pinus  resinosa A i t . , Madgwick (1964b) discovered that lower crown K and P concentrations correlated best with the nutrient status of the trees. Gagnon (1964) found that nutrient concentrations i n the lower crown fo l i a g e of black spruce Picea mariana ( M i l l . ) B.S.P. correlated with 22 s i t e q u a l i t y and s i t e index as well as did upper crown samples, with the advantage of being easier to c o l l e c t . Non-standardized sampling positions within a branch can add small, but unnecessary v a r i a t i o n s to f o l i a r analyses (Dice 1970). In studies of intrabranch v a r i a t i o n i n Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Brackett (1964) and Dice (1970) reported that nutrient concen-tr a t i o n s were highest i n outer branch segments and increased with distance from the secondary and higher order branch t i p s . McClarnon (1979) found branch order and i t s distance from the cen t r a l stem had no s i g n i f i c a n t e f f e c t on N and P concentrations i n even-aged f o l i a g e of amabilis f i r . Within-branch v a r i a t i o n was much less than between-branch v a r i a t i o n . Nitrogen contents, (mg/100 oven-dry needles) of lower branch order needles were s i g n i f i c a n t l y greater, however, than those of high order branch needles of the same age. He concluded that If nutrient content determination were a part of f o l i a r a n a l y s i s , s t r a t i f y i n g by branch order would eliminate a small but unnecessary source of v a r i a t i o n . Differences i n a s s i m i l a t i o n rates between north-facing and south-facing f o l i a g e may have some e f f e c t on nutrient concentrations. Peterson (1961) and Tamm (1951) studying Kauri (Agathis a u s t r a l i s ) and b i r c h (Betula sp.) species r e s p e c t i v e l y , reported higher N and P concen-t r a t i o n i n north-facing branches compared to south-facing branches. However, the e f f e c t of aspect on nutrient concentrations i s probably minor (Tamm 1955). White (1954) and Humphrey and K e l l y (1962) concluded that aspect did not s i g n i f i c a n t l y influence f o l i a r concentrations i n three pine species. 23 Even though aspect i s probably a minor source of v a r i a t i o n ; Leyton and Armson (1955), Wells (1956) and Hoyle and Mader (1964) standardized t h e i r f o l i a r sampling to one aspect. Such systematic sampling might reduce v a r i a t i o n on open stands, but may not be the best strategy i n denser stands, where uneven shading or competition from adjacent trees i s l i k e l y a greater source of v a r i a t i o n than crown aspect. ( i v ) E f f e c t of crown class Hohne (1964), Lowry and Avard (1968), and Carter and White (1971) reported n e g l i b l e differences i n mean nutrient concentrations associated with crown c l a s s . Lower nitrogen concentrations (Lavender 1970), and s l i g h t l y lower P, K, Ca and Mg concentrations (Wright and W i l l 1958) have been recorded i n suppressed trees. Except for greater N and lower Ca concentration i n 1-year-old needles of subdominant trees, Schwab (1979) found that nutrient l e v e l s i n mature codominant and dominant amabilis f i r were s i m i l a r . Inconsistent trends with crown class probably r e f l e c t the changing balance between competition f o r l i g h t , moisture and n u t r i e n t s . Between-tree v a r i a t i o n i n f o l i a r nutrients i s greater i n suppressed trees compared to other crown classes (Lavender 1970; Schwab 1979). This means that a larger number of sample trees from the codominant or suppressed classes i s required to meet a desired degree of p r e c i s i o n . Lavender (1970) reported that 14 dominant, 24 codominant or 40 suppressed trees were required to estimate f o l i a r N within 5% of the mean. 24 (v) Provenance e f f e c t s Provenances of tree seedlings grown i n uniform environments d i f f e r i n f o l i a r nutrient concentrations (Mergen and Worrall 1965; Walker and Hatcher 1965; Steinbeck 1965, 1966; van den Driessche 1973). Part of t h i s v a r i a t i o n can be a t t r i b u t e d to the varying growth rate of d i f f e r e n t provenances under uniform environmental conditions, and part to the d i f f e r i n g a b i l i t i e s of provenances to absorb n u t r i e n t s . Van den Driessche (1973) found that mathematical nutrient-growth r e l a t i o n s h i p s d i f f e r e d between two provenances of Douglas-fir. In most f i e l d studies, genetic v a r i a b i l i t y must be included with the random error component unless the seed source of the sample trees i s known. (vi ) E f f e c t of disease The e f f e c t of various diseases on f o l i a r nutrient l e v e l s has not been thoroughly investigated. Tamm (1968) reported no e f f e c t of Fomes on nutrient concentration i n spruce. However, F e r r e l and Hubert (1957) found P and Ca f o l i a r concentrations i n western white pine (Pinus monti- cola Dougl.) were aff e c t e d by p o l e - b l i g h t . Singh and Bhure (1974) detected an increase i n most f o l i a r micronutrients and a decrease i n most macronutrients i n several tree species infected with A r m i l l a r i a  mellea (Vahl ex Fr.) Krummer root r o t . To avoid unnecessary disease-induced v a r i a t i o n , f o l i a g e sampling should be r e s t r i c t e d to healthy t r e e s . ( v i i ) E f f e c t of reproductive state Cone-bearing tree branches have lower f o l i a r nutrient l e v e l s than other branches (Brackett 1964; Turner et a l . , 1978). Therefore, unless 25 cone-bearing branches are the normal case (e.g. i n seed orchards) they should not be sampled. Since the seasonal d i s t r i b u t i o n and l e v e l s of nutrient can vary between the sexes i n dioecious trees, male and female trees should be sampled separately (Fletcher and Ochry-Meirch 1955). ( v i i i ) E f f e c t of s i l v i c u l t u r e treatment and l o c a t i o n S i l v i c u l t u r a l treatments (thinning, burning, or f e r t i l i z i n g ) and l o c a t i o n v a r i a b l e s (aspect, elevation, proximity to ocean or f a c t o r i e s ) are also l i k e l y to influence f o l i a r nutrient concentrations. Schwab (1979) noted that N, P, K and Mg f o l i a r concentrations increased with e l e v a t i o n i n amabilis f i r . 3.2.3 Methods of data presentation F o l i a r nutrients are reported as a percentage of oven-dry needle weight (concentration data), as mass per 100 oven-dry needles (content data), or as a r a t i o between 2 n u t r i e n t s . F o l i a r nutrient concentra-tions are the most common method of presentation, and therefore i t i s useful to present such data f o r comparison purposes. However, nutrient concentration data expresses a r a t i o between two variables (nutrient uptake and dry matter accumulation) which are not always governed by the same p h y s i o l o g i c a l or environmental f a c t o r s . For example, growth or dry matter accumulation may f l u c t u a t e with changes i n l i g h t i n t e n s i t y or temperature, r e s u l t i n g i n a change i n nutrient concentrations even though nutrient uptake and content remain constant. If dry matter f l u c t u a t i o n s obscure the r e l a t i o n s h i p between nutrie n t concentration and supply, nutrient content data may be a better 26 r e f l e c t i o n of nutrient a v a i l a b i l i t y and tree nutrient status. Tree growth i s often better correlated with nutrient content data than with concentration data (Mader 1964; Mader and Howarth 1968). Since maximum plant growth depends not only on an adequate supply of i n d i v i d u a l n u t r i e n t s , but also on a correct balance between nutrient ions (Shear et a l . , 1968), nutrient status i s often expressed as r a t i o s between various n u t r i e n t s . Optimum nutrient r a t i o s are thought to e x i s t for tree species independent of d i f f e r e n t environmental conditions (Leyton 1958). Based on a study of b i r c h , pine and spruce seedlings Ingestad (1967) proposed optimum proportions of f o l i a r nutrient: N = 100, P = 13, K = 65, Ca = 6, Mg = 85, (mass b a s i s ) . Lavrichenko ( c i t e d i n Morrison 1974a) devised another means of expressing optimum r a t i o s of N, P and K. The concentration of each of these elements was expressed as a percentage of the t o t a l concentration of a l l three elements. Optimum N, P, K proportions for pine using Lavrinchenko's scheme are 67:7:26. 3.2.4 Interpreting f o l i a r nutrient data Morrison (1974a) discussed the three stages i n the development of f o l i a r analysis i n t e r p r e t a t i o n . I n i t i a l l y , i n vestigators compare f o l i a r nutrient l e v e l s i n poorly grown and well grown trees, healthy and unhealthy trees to see i f differences i n growth are associated with differences i n nutrient concentrations. Simple co r r e l a t i o n s are used to r e l a t e f o l i a r nutrients to tree growth or s o i l n u t r i e n t s . However, i n t e r c o r r e l a t i o n s between nutrients and environmental factors make i t d i f f i c u l t to assess the independent contribution of a nutrient to tree growth or the t o t a l e f f e c t of several n u t r i e n t s . 27 The second stage i n In t e r p r e t a t i o n , according to Morrison, i s the development of simple and multiple l i n e a r regression models. This technique, popularized by Leyton and Armson (1955), i s designed to i s o l a t e the independent contributions of nutrients to growth, to ind i c a t e the most s i g n i f i c a n t growth-nutrient r e l a t i o n s h i p s , and to explain more of the v a r i a b i l i t y i n these re l a t i o n s h i p s by combining the e f f e c t of several factors (Hoyle and Mader 1964). Although multiple regression models can be a useful diagnostic t o o l , they have not been very successful i n pr e d i c t i n g tree growth response to f e r t i l i z e r s . "When growth i s l i m i t e d only by the a v a i l a b i l i t y of a p a r t i c u l a r n u t r i e n t , a l l other factors being optimal, the r e l a t i o n s h i p between supply, growth and the concentrations of that nutrient i n the f o l i a g e are more or less uniquely determined, i . e . a p a r t i c u l a r l e v e l of supply corresponds to a p a r t i c u l a r l e v e l of growth and concentration. However, t h i s s i t u a t i o n i s not r e a l i s t i c f or f i e l d conditions where growth to a less e r or greater extent i s influenced by a number of fact o r s " (Leyton 1958). Some of these factors can be eliminated by standardized sampling. Others, such as ion i n t e r a c t i o n , nutrient r e d i s t r i b u t i o n , and s o i l moisture or temperature cannot be r e a d i l y controlled or quantified and consequently they complicate data i n t e r p r e t a t i o n . The uptake and d i s t r i b u t i o n of i n d i v i d u a l plant nutrients i s not independent of the concentrations of other nutrients (Lundegardh 1951). NH^T and K , Ca and K , S04 and PO4 are reported to be antagonistic ion p a i r s (Baule and F r i c k e r 1970). High concentrations of one of these ions adversely a f f e c t s the uptake of the other. Growth d i l u t i o n i s 28 another form of ion i n t e r a c t i o n . If tree growth i s promoted by an increased supply of one nutrient, the concentration of other nutrients may decrease due to increased dry matter production, even though the a v a i l a b i l i t y and uptake of these other nutrients remains constant. Phosphorus concentrations often decrease a f t e r nitrogen f e r t i l i z a t i o n because of growth d i l u t i o n (Leyton 1957; Heilman and Gessel 1963; Lee 1971; Donald and Glen 1974). Timmer and Stone (1978) employed a graphical technique to study changes i n f o l i a r nutrients a f t e r f e r t i l i z a t i o n . Changes i n needle weight, concentration, and content of a f o l i a r nutrient are plotted on one graph. This technique, f i r s t used by Kraus ( c i t e d i n Timmer and Stone 1978), allows clearer i n t e r p r e t a t i o n s of growth d i l u t i o n e f f e c t s . Internal nutrient reserves are a source of nutrients which has not been thoroughly investigated for many tree species. They may supply a s i g n i f i c a n t proportion of the annual requirements for new growth, e s p e c i a l l y i n high elevation species with long needle r e t e n t i o n . Turner and Singer (1976) calculated that 54% of the annual requirements of N, 58% of P, 40% of K, 11% of Ca and Mg i n old growth amabilis f i r was supplied by i n t e r n a l reserves of nutrients stored i n older f o l i a g e . Current nutrient status i s influenced by past conditions, the i n t e r n a l nutrient reserves, and by current nutrient a v a i l a b i l i t y . Moisture and temperature are important variables which influence both nutrient a v a i l a b i l i t y and tree growth. Burr (1961) reported that s o i l temperature, a i r temperature and l i g h t i n t e n s i t y affected N concen-tr a t i o n s i n sugar cane. Lowest N and P concentrations were associated with high l i g h t i n t e n s i t y , warm a i r temperatures and low s o i l 29 temperatures, conditions which promoted shoot growth. Although there i s no simple r u l e governing the e f f e c t of s o i l moisture on f o l i a r nutrient concentrations (van den Driessche 1974), drought stress tends to increase f o l i a r nitrogen l e v e l s i n forest trees (Walker 1962; Pharis et a l . 1964; Hoyle 1969; Schomaker 1969; Broadfoot and Farmer 1969), and has a s i m i l a r e f f e c t on P and K l e v e l s (Walker 1963; Schomaker 1969). However, Brix (1972) and Leaf et a l . (1970) found no s i g n i f i c a n t d i f f e r -ences i n f o l i a r nitrogen concentrations between i r r i g a t e d and non-i r r i g a t e d trees. Black (1968) suggested that drought would tend to increase nitrogen concentrations i f dry matter production was reduced more than nutrient uptake, and vic e versa. Both nutrient concentration and nutrient content data should be c o l l e c t e d to f u l l y i n t e r p r e t the a f f e c t of s o i l moisture (Black 1968). If both moisture and nutrients are l i m i t i n g growth, the i n t e r p r e t a t i o n of f o l i a r data becomes very d i f f i c u l t . "Extreme d e f i c i e n c i e s can be detected on most s i t e s by f o l i a r nutrient l e v e l s but i n t e r p r e t a t i o n of the s i g n i f i c a n c e of v a r i a t i o n i n f o l i a r nutrient l e v e l s where stands are not s u f f e r i n g from extreme d e f i c i e n c i e s has remained l a r g e l y a mystery because of the i n t e r a c t i o n s among nutrients and environmental f a c t o r s " (Hoyle and Mader 1964). Incorporation of s i t e parameters such as s o i l moisture i n multiple regression r e l a t i o n s h i p s (Morrison 1974a) or the use of c u r v i l i n e a r regressions or multivariate s t a t i s t i c s (van den Driessche 1974a) may improve the diagnostic and p r e d i c t i v e value of f o l i a r analysis i n the future. 30 LOCATION AND DESCRIPTION OF RESEARCH SITE 1. Location The study s i t e i s situated on a f l a t to gently sloping, northeast facing area at an elevation of 550 m on Branch 101 k logging road, i n the Tsolum Block of the Tree Farm License No. 2, approximately 16 km northwest of Courtenay, Vancouver Island, B r i t i s h Columbia (Figure 4). 2. History A mature f o r e s t of Douglas-fir (200 years+), western hemlock and amabilis f i r that previously occupied the s i t e was clearcut logged i n 1969. The following year the s i t e was slashburned and planted with Douglas-fir. However, the f i r e was very patchy and amabilis f i r advance regeneration (<_ 1.5 m t a l l ) and the associated understory plants survived i n numerous areas that were not burnt. These trees had been growing extremely slowly p r i o r to c l e a r c u t t i n g , but height growth released i n 1971 and by 1973 averaged 30 cm. This good early height growth has not been sustained. Since 1974, some trees have exhibited s t e a d i l y d e c l i n i n g height increments and by 1978 current height growth ranged from 1 to 80 cm. Average annual height growth for the poorly grown trees (Figure 5) peaked i n 1975 at 26 cm, and then declined to 8 cm i n 1978. In contrast, height growth of well grown trees increased to 52 cm i n 1977 and then dropped s l i g h t l y to 48 cm i n 1978. This study s i t e was selected because: (a) there was a good range of height growth; igure 4. Location of study s i t e on Vancouver Island, B r i t i s h Columbi 60 J 1 1 I I I I L 2 3 4 5 6 7 8 9 YEARS AFTER LOGGING Figure 5. Mean annual height growth of well and poorly grown amabilis f i r regeneration at the research s i t e (95% confidence l i m i t s are shown). 33 (b) root rot or feeder root diseases were not detected by Dr. G. •Wallis ( P a c i f i c Research Centre, V i c t o r i a , B.C.) or Dr. B. van der Kamp (Faculty of Forestry, University of B r i t i s h Columbia, Vancouver, B.C.). Therefore, these factors could be eliminated as causal agents; (c) past and current leader damage by snow, wind or animals was n e g l i g i b l e ; (d) mycorrhizae were abundant on the roots of both poorly and well grown trees; (e) e l e v a t i o n , s o i l s , vegetation and i n i t i a l release growth patterns were s i m i l a r to those i n a nearby nitrogen f e r t i l i z e r t r i a l s i t e , permitting comparisons to be made between these two s i t e s . 3. Climate Because of the r a i n shadow cast by the Vancouver Island Mountains, the east coast of Vancouver Island has a d r i e r , more continental climate than that of the west coast of Vancouver Island. Only 10 per cent of the t o t a l annual p r e c i p i t a t i o n f a l l s i n the 3 summer months. A dry period i s normal i n l a t e July or early August (Keser and St. Pi e r r e 1973). P r e v a i l i n g winds are from the southeast i n winter and northwest i n summer. No c l i m a t i c data were a v a i l a b l e f o r the study s i t e . However, the Climatic D i v i s i o n of the Resource Analysis Branch, B.C. Ministry of the Environment, was able to supply c l i m a t i c estimates for the study area. These were based on records from the Comox weather s t a t i o n located at 34 sea l e v e l 20 km east of the study s i t e , a f t e r corrections f or d i f f e r -ences i n elevation, longitude, l a t i t u d e , and slope. A January mean of -0.9°C, a-July mean of 14.4°C, and a t o t a l annual p r e c i p i t a t i o n of 142 cm were predicted for the s i t e . From 1970 to 1977, d a i l y temperature and weekly r a i n f a l l data were c o l l e c t e d from May to August at a weather s t a t i o n a few km from the research s i t e by Zwickel (1977) as part of a grouse habitat study. His temperature data agreed c l o s e l y with the predicted data, but h i s average r a i n f a l l data for May to August was 29.2 cm compared to the 18.1 cm predicted. Monthly p r e c i p i t a t i o n averages recorded by Zwickel for May to August were respectively 10.1, 7.8, 6.0 and 6.3 cm. Predicted averages for the same months were r e s p e c t i v e l y 4.3, 3.3, 4.9 and 5.6 cm. This suggested that predicted c l i m a t i c data may underestimate p r e c i p i t a -t i o n e s p e c i a l l y during May and June. No information was a v a i l a b l e on snow depth or duration. However, l o c a l foresters have observed snow i n the v i c i n i t y of the study s i t e i n l a t e A p r i l . 4. Geology The study s i t e i s located on a t i l l parent material with a loose (ablation) layer deposited over a compacted (basal) t i l l which i s l a r g e l y impermeable to water and roots. The t i l l deposit i s underlain by basalt bedrock of the Karmutsen formation. 5. S o i l s S o i l s i n the study area were c l a s s i f i e d as Humo-Ferric Podzols (Canadian System of S o i l C l a s s i f i c a t i o n 1978) with a mor humus but minimal Ae development. A s o i l pedon i s described i n Table 2. 35 TABLE 2. P r o f i l e d e s c r i p t i o n of the study s i t e s o i l Ca Horizon Depth (cm) Description L 18-16 Undecomposed coni f e r needles, angiosperm leaves, and twigs; abundant f i n e roots; very strongly a c i d . F 16-13 P a r t i a l l y decomposed needles, leaves, twigs; abundant yellow and white mycelium; abundant f i n e roots; strongly a c i d . H 13-0 Reddish-black (10 R 2.5/1 m), dark reddish brown (5 YR 2.9 12 d); varying amounts of decaying wood; s l i g h t l y matted; yellow mycelium; abundant f i n e and medium, p l e n t i f u l coarse roots; clear smooth boundary; 10-50 cm thic k ; extremely a c i d . Ae 0-2 Dark reddish gray (5 YR 4/2m), l i g h t brownish gray (10 YR 612 d); sandy loam; blocky; s l i g h t l y s t i c k y ; f r i a b l e ; very few f i n e roots; 50% gravel; c l e a r smooth boundary; extremely a c i d . B f j 2-15 Dark reddish brown (5 YR 3/4 m), yellowish red (5 YR 4/6 m); loam; weak to moderate, medium sub-angular blocky; s l i g h t l y s t i c k y ; f r i a b l e ; few f i n e , p l e n t i f u l medium, p l e n t i f u l coarse roots; 60% gravel; d i f f u s e i r r e g u l a r boundary; extremely a c i d . B f 2 15-50 Dark red (2.5 YR 3/6 m), reddish brown (2.5 YR 5/4 d); loam; moderate, coarse sub-angular blocky; s l i g h t l y s t i c k y , f r i a b l e ; very few f i n e , few medium, very few coarse roots, 60% gravel; c l e a r i r r e g u l a r boundary; very strongly a c i d . 50+ Reddish yellow (7.5 YR 6/b d); massive; s t i c k y , very f i r m . 36 The s o i l s of the study s i t e were mapped as Woodhus g r a v e l l y loamy sands by Ferguson and Pegues (1976). Woodhus s o i l s are described by these authors as moderately stony, moderately well to well drained, and moderately well-suited to intensive f o r e s t management of Douglas-fir, western hemlock and amabilis f i r . They are found from 500 to 850 m on poorly drained gentle slopes. A thick mor humus tends to accumulate on the surface. Ferguson and Pegues (1976) recommended slashburning these s o i l s to improve pla n t a t i o n s u r v i v a l and growth. The chemical and physical properties of some s o i l s i n the Woodhus s o i l map unit were described by Laing (1979) with emphasis on the for e s t f l o o r horizons, which are the major rooting zone for the advance amabilis f i r regeneration (Table 3). 6. Biogeoclimatic C l a s s i f i c a t i o n Klinka (1977a) c l a s s i f i e d the problem area as part of the wet sub-zone of the Coastal Western Hemlock Biogeoclimatic Zone (CWHb). The presence of amabilis f i r regeneration i s a major vegetative characteris-t i c separating the wet and dry subzones of the Coastal Western Hemlock Biogeoclimatic Zone. C l i n t o n i a u n i f l o r a , Rubus pedatus and Rhytidiopsis robusta, common CWHb plant species, are present i n the herb and moss la y e r . Vaccinium alaskaense, which i s t y p i c a l of mesic to subhygric s i t e s i n the CWHb subzone (Krajina and Kojima, 1976) i s the most common shrub species. The occurrence of some natural regeneration of two higher elevation tree species, yellow cedar (Champaecyparis nootkaten- s i s D. Don Spach) and mountain hemlock (Tsuga mertensiana Bong, Carr), suggested that the study s i t e was affected by cold a i r drainage. Cold TABLE 3. Mean depth and chemical properties of the LFH horizons of Woodhus s o i l series (adapted from Laing 1979) (n = 6; standard deviation in. brackets) Horizon Depth pH Organic Total C:N Total (cm) ( i n H 20) matter % N % r a t i o " P % L 2.8 (2.2) 5.1 (0.2) 78.3 (9.6) 1.32 (0.44) 38.6 (17.5) 0.11 (0.03) F 2.8 (1.5) 4.7 (0.3) 76.3 (4.0) 1.70 (0.20) 26.4 ( 2.5) 0.14 (0.02) H 16.2 (9.6) 3.7 (0.3) 83.5 (1.6) 0.90 (0.10) 46.8 (11.8) 0.07 (0.01) Cation Exchange (me/100 g S o i l )  Total capacity Ca Mg Na K L 98.9 (9.0) 30.0 (13.6) 4.8 (1.4) 0.02 (0.01) 2.12 (0.60) F 166.4 (104.2) 28.3 (11.3) 4.7 (1.6) 0.12 (0.04) 2.76 (1.3) H 146.1 (98.7) 21.0 (7.2) 4.2 (1.9) 0.22 (0.07) 1.76 (1.70) 38 a i r drainage might be compensating for the lower p r e c i p i t a t i o n on the s i t e but perhaps not enough to support uniformly good growth of amabilis f i r (see Appendix A). In 1979, the problem area was r e c l a s s i f i e d (Klinka ejt a l . , 1979) with the lower portion (below 760 m) separated from the upper portion (approx 760 m - 1000 m) as submontane and montane va r i a n t s , respective-l y , of the CWHb subzone. The study s i t e l i e s between the mesic and sub-hygric classes (4 and 5, respectively) on the edaphic g r i d f o r the CWHb subzone (Klinka 1977b). 3 9 METHODS 1. Field Sampling Ten well grown and ten poorly grown trees with steadily declining height growth were chosen to represent the range of tree height growth on the study s i t e . A l l these trees had released well after logging (Figure 5 ) . Vigorous, well grown trees were characterized by consis-tently good height growth since release, spire-shaped crowns, normal needle length, and dark green foliage. Poorly grown trees were charac-terized by steadily declining height growth after the i n i t i a l period of good release growth, reduced needle length, chlorotic yellow-green foliage, and flat-rounded crowns. The twenty trees were paired with another twenty trees on the basis of similar size, height growth pattern, foliage colour, and degree of aboveground competition. This second set were used for the growing season f o l i a r sampling. Since the members of each pair were similar i n external characteristics, i t was hoped that their f o l i a r chemistry would not be significantly different, and that alternate sampling of the trees in each pair would provide information on seasonal variation without removing excessive foliage from individual trees. This sampling scheme resulted i n data analysis problems which are described in the next chapter. Foliage from a l l " f o r t y trees was collected on the last sampling date i n September. Random samples of current, 1- and 2-year-old foliage on tertiary and higher order branches from the fourth whorl from the top of the tree Figure 6. F o l i a r sampling p o s i t i o n on the fourth whorl. 41 (Figure 6) were c o l l e c t e d twice monthly from May to September from one member of each p a i r . Foliage from a l l 40 trees was c o l l e c t e d on the l a s t sampling date at the end of September. Samples were co l l e c t e d i n the afternoon. Weather conditions were b r i e f l y recorded at the time of sampling. The f o l i a g e samples were e i t h e r stored i n a r e f r i g e r a t o r for 2 weeks at approximately 4°C or transported immediately to the lab for oven drying. The e f f e c t of r e f r i g e r a t o r storage on f o l i a r N and P concentrations was tested by c o l l e c t i n g current and 1-year-old f o l i a g e from two t e r t i a r y branches on the fourth whorl sampling p o s i t i o n of twenty amabilis f i r outside the study area. One branch from each was oven dried immediately, the other was stored i n a r e f r i g e r a t o r f o r two weeks before drying. R e f r i g e r a t i o n had no s i g n i f i c a n t e f f e c t (p <.05) on either f o l i a r N or P. The data for the two treatments were compared by paired t - t e s t s . At the end of September, 10 of the vigorous and 10 of the poor trees were randomly selected for destructive sampling to obtain the following information: ( i ) height increments to the nearest cm from 1970 to 1978^; ( i i ) r a d i a l increments to the nearest 0.1 mm at breast height from 1976 to 1978; ( i i i ) height and age at release; ( i v ) needle retention i n years on the lower crown branches; The 1970-1978 height growth i s c a l l e d release height growth i n t h i s study. The 1978 increment i s current height growth. 42 (v) estimate of aboveground competition (obtained by counting the number of tree stems (except for seedlings) within 2 m of the sample t r e e . ( v i ) three samples of humus (H horizon of f o r e s t f l o o r ) were c o l l e c t e d with a core sampler from beneath each tree and bulked f o r chemical a n a l y s i s . One of the three samples was co l l e c t e d adjacent to the sample tree stem, the other two were c o l l e c t e d from the north and south edges of the tree canopy. A study of microsite differences i n water a v a i l a b i l i t y was not possible because of lack of time and appropriate equipment. However, i n order to gain some in s i g h t into the e f f e c t of moisture regime on f o l i a r nutrient concentrations i n the study are, 10 well grown trees were randomly selected f o r f a l l f o l i a r analysis at 3 x e r i c and 3 mesic s i t e s close to and at the same elevation as the study s i t e . 2. Laboratory Analysis Foliage samples were oven-dried f o r 24 hours at 70°C, and then the needles were stripped from the twigs and weighed. This was done because fr e s h needles, ( e s p e c i a l l y s o f t , current growth) c o l l e c t e d during the summer were too d i f f i c u l t to remove cleanly from twigs. The needles were not ground p r i o r to chemical a n a l y s i s . The weight of each needle sample averaged 2.0 g, and losses during grinding might have resulted i n i n s u f f i c i e n t sample f o r an a l y s i s . Salonius et a l . (1978) reported that 43 measured concentrations of N, P, and K did not vary s i g n i f i c a n t l y between'ground and unground samples. Total f o l i a r N and P were measured c o l o r i m e t r i c a l l y on a Technicon I n d u s t r i a l Analyzer (Anonymous 1974) following a semimicro - Kjeldahl d i g e s t i o n (Bremner 1965). Total f o l i a r Ca, Mg, and K were determined oi HC1 extracts of dry ashed samples ( A l l e n et a l . 1974) using atomic absorption spectrophotometry with a Varian-Techtron AA5 machine^. An air-acetylene flame was used for the K and Mg a n a l y s i s . A nitrous oxide-acetylene flame was used for Ca. Humus samples were a i r - d r i e d and ground. Total N and P were analyzed as described f or the f o l i a r samples. pH was measured i n a 1:5 s o i l to water suspension. Total carbon was determined by the Walkley-Black method ( A l l i s o n 1965). Exchangeable cations were extracted with NH^OAc (adjusted to pH 7.0). The exchangeable cations were analyzed by atomic absorption spectrophotometry. 3. Data Analysis Nutrient concentrations (% oven-dry weight), contents (mg/100 needles) and r a t i o s were calculated for the f a l l f o l i a r data. N and P concentrations and N:P r a t i o s were calculated f o r the growing season samples. The r e l a t i o n s h i p s between height growth and nutrient data were analyzed by stepwise regression analysis using MIDAS^ programs. Refer to Appendix B f o r comment on t h i s chemical analysis method. Michigan Interactive Data Analysis System. 44 RESULTS AND DISCUSSION The r e s u l t s are presented and discussed i n s i x sections. The f i r s t s e c t ion i s a comparison between f a l l f o l i a r nutrient data and values reported i n the l i t e r a t u r e f o r true f i r s . The second describes the rel a t i o n s h i p s between these data and height growth. Seasonal trends i n f o l i a r N and P are presented i n section three and the r e l a t i o n s h i p between height growth and these N, P and N:P data are presented i n sect i o n four. The r e l a t i o n s h i p s between humus nutrient data and amabilis f i r release growth are described i n section f i v e . F i n a l l y , i n section s i x , the e f f e c t s of non-nutritional factors on variable height growth are discussed. 1. Comparison of F a l l F o l i a r Data with L i t e r a t u r e Values 1.1 Nitrogen Nitrogen concentrations i n current and 1-year-old f a l l f o l i a g e were .71% and .74% re s p e c t i v e l y for well grown trees and .55% and .58% res p e c t i v e l y f o r poorly grown trees. These concentrations were lower than most values reported i n the l i t e r a t u r e for true f i r species (Table 4). Nitrogen concentrations i n poorly grown trees were the lowest reported i n any study of true f i r f o l i a r n u t r i t i o n , i n d i c a t i n g that these trees were severely d e f i c i e n t i n nitrogen. I n t e r e s t i n g l y , i n a l l the studies except those of Courtenay amabilis f i r stands (Cameron 1979; Briggs 1979; and t h i s study), current f o l i a r nitrogen concentrations were higher than those of 1-year-old f o l i a g e . In many conifer species, 45 TABLE 4. Some f a l l f o l i a r nitrogen concentrations (% oven-dry weight). Reported f or true f i r species Current f o l i a g e 1-year-old f o l i a g e Amabilis f i r (Abies amabilis) This Study well grown trees .71 .74 poorly grown trees .55 .58 Schwab (1979) dominant, mature trees 1.20 - 1.30 1.05 - 1.15 Gallagher (1964) ju v e n i l e trees with poor growth .92 - 1.22 .81 - .94 Beaton et a l . (1965) 8-year-old trees .99 .91 Cameron (1979) 30-year-old, thinned well grown trees 1.05 1.04 30-year-old, thinned poorly grown .78 .76 Briggs (1979) thinned .89 .93 thinned and f e r t i l i z e d 1.11 1.14 Subalpine f i r (Abies lasiocarpa) Beaton et a l . (1965) 3-6 year-old trees 1.64, 1.85, 1.05 1.59, .91 Grand f i r (Abies grandis) Loewenstein and P i t k i n (1971) f e r t i l i z e d 1.29 not f e r t i l i z e d 1.18 Balsam f i r (Abies balsamea) Morrison (1974b) j u v e n i l e trees 1.09 - 1.15 1.02 - 1.07 Brazeau and Bernier (1973) mature trees 1.34 1.23 46 f a l l f o l i a r N concentrations l e s s than 1.0 to 1.1% i n d i c a t e a nutrient d e f i c i e n c y (Leaf 1973). The difference i n nitrogen n u t r i t i o n between poorly and well grown trees was accentuated when nitrogen contents (mg nitrogen/100 oven-dry needles) were compared. Nitrogen content f o r current, 1-year-old and 2-year-old f o l i a g e of poorly grown trees averaged r e s p e c t i v e l y 1.39, 2.54 and 2.77 mg nitrogen per 100 needles. Comparable values f o r well grown trees were 2.60, 5.35, and 5.65 mg nitrogen per 100 needles. There are only a few other reports of nitrogen content data f o r true f i r s . Brazeau and Bernier (1973) found current and 1-year-old needles of balsam f i r contained 3.42 and 5.44 mg N/100 oven-dry needles r e s p e c t i v e l y . Briggs (1979) compared nitrogen contents i n amabilis f i r f e r t i l i z e d with nitrogen at the Crown Zellerbach p i l o t t r i a l and u n f e r t i l i z e d t r e e s . Nitrogen contents were 7.5 and 14.8 mg/100 needles for current and 1-year-old f o l i a g e , r e s p e c t i v e l y , of trees f e r t i l i z e d 2 years previously; 4.2 and 6.5 mg/100 needles i n current and 1-year-old f o l i a g e , r e s p e c t i v e l y , of u n f e r t i l i z e d trees. The nitrogen content data for well grown trees i n t h i s study are s i m i l a r to those of Brazeau and Bernier (1973). However, nitrogen content of poorly grown trees i s much l e s s than reported i n the other studies of true f i r s . 1.2 Phosphorus Phosphorus concentrations i n both well and poorly grown trees were s i m i l a r to those reported i n the l i t e r a t u r e for true f i r species 47 (Table 5). Mean current f o l i a r P concentrations, .18% f o r both well and poorly grown tr e e s , are within the range considered adequate for many con i f e r species (Leaf 1973; Morrison 1974a). Phosphorus contents were .61 and .94 mg per 100 needles respective-l y f o r current and 1-year-old f o l i a g e of well grown trees. Comparable values f o r poorly grown trees were .45 and .69 mg P per 100 needles. These values are s i m i l a r to those reported by Brazeau and Bernier (1973) for mature balsam f i r (.49 and .58 mg P per 100 current and 1-year-old needles, respectively) but lower than the values reported by Briggs (1979), of 1.0 and 1.4 mg P per 100 needles for current and 1-year-old f o l i a g e , r e s p e c t i v e l y , of f e r t i l i z e d trees, and .90 and 1.0 mg per 100 needles, r e s p e c t i v e l y , for current and 1-year-old f o l i a g e of unfer-t i l i z e d t r e e s . 1.3 Ca, Mg and K Mean cation concentration and content data were calculated f o r the f a l l f o l i a g e (Table 6). Calcium concentrations i n both well and poorly grown trees were above .12%, the l e v e l which i s considered adequate f o r many coni f e r species (Leaf 1973; Morrison 1974a). They were s i m i l a r to concentrations reported by Beaton eit al_. (1965) (.30 and .41% respec-t i v e l y f o r current and 1-year-old f o l i a g e of ju v e n i l e amabilis f i r ) , but higher than those reported by Schwab (1979) f o r mature amabilis f i r (.20-.25% for current f o l i a g e ) . Magnesium concentrations f o r both well and poorly grown trees were below the l e v e l s considered adequate f o r many tree species (Leaf 1973; Morrison 1974a). Leaf (1973) stated that magnesium concentrations were 48 TABLE 5. Some f a l l f o l i a r phosphorus concentrations (% oven-dry weight), Reported f or true f i r species Current f o l i a g e 1-year-old f o l i a g e Amabilis f i r (Abies amabilis) This Study well grown trees poorly grown trees ,18 ,18 .14 .16 Beaton et a l . (1965) j u v e n i l e trees ,16 .12 Schwab (1979) mature amabilis trees .20 .12 Cameron (1979) well grown, thinned amabilis f i r .17 - .19 poorly grown, thinned amabilis f i r .18 - .19 .14 - .17 ,15 - .18 Briggs (1979) f e r t i l i z e d not f e r t i l i z e d .16 .14 .31 .11 Subalpine f i r (Abies lasiocarpa) Beaton et_ a l . (1965) j u v e n i l e trees .18 - .26 .15 - .25 49 TABLE 6. Mean f a l l f o l i a r Ca, Mg, and K concentrations and contents i n well and poorly grown advance amabilis f i r regeneration (n = 20; standard deviations i n brackets) Well grown trees Poorly grown trees Cation Concentrations (% Oven-Dry Weight) Current f o l i a g e Ca .34 (.06) .26 (.06) ** Mg .066 (.084) .058 (.063) ** K 1.06 (.15) 1.08 (.24) NS 1-year-old f o l i a g e Ca .46 (.092) .42 (.09) NS Mg .051 (.014) .059 (.088) * K .88 (.15) .92 (.23) NS Cation Contents (mg/100 Needles) Current f o l i a g e Ca 123.58 (67.44) 66.73 (29.45) ** Mg 23.62 (10.68) 14.60 (3.93) ** 1-year-old f o l i a g e Ca Mg K 372.51 318.66 33.52 617.41 (149.31) (120.34) (10.63) (259.64) 264.84 (63.42) 180.96 25.59 390.23 (41.53) (6.81) (102.14) ** ** ** ** * S i g n i f i c a n t difference at p <.05 between well and poorly grown tree means. ** S i g n i f i c a n t difference at p <.01 between well and poorly grown tree means. 50 usually s i m i l a r to P concentrations. Young amabilis f i r i n the Beaton et a l . (1965) study had .08 and .07% magnesium re s p e c t i v e l y i n current and 1-year-old f o l i a g e . Current magnesium concentrations i n mature amabilis f i r studied by Schwab (1979) ranged from .096 to .110%. Mean potassium concentrations were within the range considered high for many conifer species (Leaf 1973; Morrison 1974a) and were higher than the values of .57-.65% reported by Schwab (1979) f o r current f o l i a g e of amabilis f i r . However, they were s i m i l a r to the K concentra-tions for current and 1-year-old f o l i a g e , 1.2 and 1.1%, respectively, reported by Beaton et a l . (1965) for ju v e n i l e amabilis f i r . The higher values of K i n ju v e n i l e amabilis f i r may r e f l e c t the rapid c y c l i n g of K found by Yarie (1975) i n Vaccinium spp., common shrubs on amabilis f i r s i t e s . 1.4 Nutrient Ratios N:P r a t i o s f o r current and 1-year-old f o l i a g e were 3.9 and 5.3, re s p e c t i v e l y , f o r well grown trees and 3.1 and 3.6, re s p e c t i v e l y , for poorly grown trees. N:P r a t i o s f o r both types of advance regeneration are below the range 6.7 to 12.5 considered optimum for many coniferous species (Ingestad 1967), the N:P r a t i o s calculated from Beaton et a l ' s (1965) data f o r ju v e n i l e amabilis f i r (6.2 and 7.5 resp e c t i v e l y for current and 1-year-old f o l i a g e ) and those calculated from Schwab's (1979) data f o r current f o l i a g e of mature amabilis f i r (4.8 to 7.2). 51 Ca:Mg, K:Mg, N:K, and K:Ca r a t i o s were calculated from the f a l l f oliage-data and compared to r a t i o s from Beaton et_ al_. (1965), Schwab (1979), and Ingestad (1967) (Table 7). The r e s u l t s of t h i s study were close s t to r a t i o s reported by Beaton et a l . (1965) for j u v e n i l e amabilis f i r . Ingestad's r a t i o s seemed to have l i m i t e d value for comparison. Current f o l i a r nutrient r a t i o s calculated from Beaton j 2 t a l . ' s (1965) study of Vancouver Island Douglas-fir were 2.7, 5.2, 1.8, and 1.92, r e s p e c t i v e l y , for the Ca:Mg, K:Mg, N:K, and K:Ca r a t i o s . These r a t i o s are s i m i l a r to those reported by Schwab (1979) f o r mature amabilis f i r and may be c l o s e r to the r a t i o s that are optimum for conifer trees growing i n coastal B.C. f o r e s t s . The comparison of mean f a l l f o l i a r nutrient and nutrient r a t i o data from t h i s study with l i t e r a t u r e values indicates that a severe nitrogen deficiency and a possible magnesium deficiency are related to the v a r i a b l e height growth of the amabilis f i r trees. 2. Relationships Between F a l l F o l i a r Chemistry and Height Growth The r e l a t i o n s h i p s between f a l l f o l i a r chemistry and height growth were analyzed by a MIDAS stepwise multiple regression program using a l e v e l of s i g n i f i c a n c e of .05. Sixty-four per cent of the v a r i a t i o n i n release height growth was explained by four v a r i a b l e s : the N:P r a t i o i n 2-year-old f o l i a g e , Mg% i n 1-year-old and current f o l i a g e , and P% i n current f o l i a g e . The standard error for t h i s regression was 52.2 cm. Seventy-five per cent of the v a r i a t i o n i n current height growth was explained by 4 v a r i a b l e s : N:P r a t i o i n 2-year-old f o l i a g e , Mg% i n 52 TABLE 7. Comparison of nutrient r a t i o s i n f a l l f o l i a g e of well and poorly grown amabilis f i r regeneration with other studies Well Poorly Mature Juvenile Ingestad grown grown amabilis amabilis r a t i o s 3 trees trees f i r 1 f i r 2 Current f o l i a g e Ca:Mg 5.2 4.4 2.1 3.8 .70 K:Mg 16.4 18.8 6.4 15.0 7.6 N:K .69 .55 2.0 .83 1.54 K:Ca 3.2 4.4 3.2 4.0 10.8 1-year-old f o l i a g e Ca:Mg 9.7 7.3 2.7 5.9 K:Mg 18.8 16.1 6.5 15.7 N:K .87 .68 1.8 .76 K:Ca 2.0 2.3 1.9 2.7 Calculated from Schwab's (1979) data. Calculated from Beaton e_t a l . ' s (1965) data. Calculated from Ingestad (1967) proportions (on mass b a s i s ) . 53 1-year-old and current f o l i a g e , and Ca% i n current f o l i a g e . The standard error of t h i s regression was 12.1 cm. N:P r a t i o s were the most s i g n i f i c a n t independent variables explaining 51 and 46% of the v a r i a t i o n i n current and release height growth, r e s p e c t i v e l y . Although the r e l a t i o n s h i p between N:P r a t i o s and release height growth appears c u r v i l i n e a r when plotted (Figure 7), the c o e f f i c i e n t of determination and standard error did not improve with a polynomial regression of the form y = bo + b^x^ + }>2^^. N:P r a t i o s below 7.5 seemed to be sub-optimal for height growth. Nitrogen concentrations alone explained 44 and 45% of the current and release height growth, r e s p e c t i v e l y . N:P r a t i o s seem to be a s l i g h t l y more s e n s i t i v e i n d i c a t o r of nitrogen status than N concentra-tions alone. Phosphorus concentrations were lower i n well grown trees but phosphorus contents (mg P per 100 needles) rose with increasing nitrogen concentrations (Figure 8). Therefore, the N:P i n t e r a c t i o n seems to be accounted for by growth d i l u t i o n of P content (as nitrogen concentrations increase) i n well grown trees and by P accumulation r e l a t i v e to growth (as nitrogen concentrations become d e f i c i e n t ) i n poorly grown trees. Barker et a l . (1965) reported that an increase i n the nitrogen status of seedlings accelerated seedling r e s p i r a t i o n and consequently the use of ATP, creating a demand for phosphorus. Nitrogen concentrations i n 2-year-old f a l l f o l i a g e were more p o s i t i v e l y related to release height growth than current or 1-year-old f o l i a r N. Current height growth was most s i g n i f i c a n t l y related to nitrogen concentrations i n current f o l i a g e . In contrast, Leyton (1958) found that current height growth i n nitrogen-deficient trees was best Sub-optimal Ratios Optimal ! Ratios E u o or x UJ CO < _J Ui oc 426 j 350 1 ! ° o o J o j 274 o j O o 1 j o o oo j o o o j O O 1 197 o o i o } o o ! O o o ! 1- -121 o O o 1 o o J 8 o o o j o J o ! 45 o 1 • • • • • I I I I 2.3 3.5 4.7 5.9 7.2 8.3 N/P RATIO Figure 7. Relationship between N:P r a t i o s i n one-year-old amabilis f i r f o l i a g e and release height growth. 55 105.8 87.8 R e €> C O o 69 8 U i O U co r> tr o x Q. CO O 51.8 33.8 15.8 o o o o o o oo o o o o o o o o o o o o L O O O o o _ l l _ .68360 .56580 .80140 NITROGEN (% oven-dry weight) .91920 1.0370 Figure 8. Relationship between phosphorus content and nitrogen concentration i n current f o l i a g e of amabilis f i r . 56 r e l a t e d to the nitrogen status of needles formed the previous year. Total height i n his studies was best correlated with nitrogen l e v e l s i n current f o l i a g e . In tree species with high needle retention, N% In older f o l i a g e may better r e f l e c t the t o t a l tree N reserve and therefore correlate better with tree growth than current or 1-year-old f o l i a g e . Additional f o l i a r -tree growth studies are needed to determine the best sampling age for determining the nitrogen status of amabilis f i r . Magnesium concentrations were the second most s i g n i f i c a n t v ariable i n the regression equations. Current and 1-year-old f o l i a r Mg explained an a d d i t i o n a l 21% and 15% of the v a r i a t i o n i n current and release height growth, r e s p e c t i v e l y . The regression c o e f f i c i e n t f o r 1-year-old f o l i a r Mg was negative, whereas, the c o e f f i c i e n t f or current Mg was p o s i t i v e i n the multiple regressions. This difference i n sign was not an a r t i f a c t of the a n a l y s i s . In simple regressions, current f o l i a r Mg% was p o s i t i v e l y , and 1-year-old f o l i a r Mg% was negatively related to height growth. Since Mg contents (mg per 100 needles) were higher i n both f o l i a g e age classes of well grown trees compared to poorly grown trees, the negative r e l a t i o n s h i p between f o l i a r Mg i n 1-year-old needles and height growth may due to accumulation i n 1-year-old f o l i a g e of slower growing t r e e s . Mg concentrations do not vary systematically with needle age (Schwab 1979) or with increasing nitrogen supply (Ingestad 1979). U n t i l more i s known about tree physiology and ion i n t e r a c t i o n s , i n t e r - , p r e t a t i o n of f o l i a r Mg data w i l l remain d i f f i c u l t . In experimental f i e l d t r i a l s t e s t i n g the e f f e c t of nitrogen and potassium f e r t i l i z e r s on advance amabilis f i r growth, Gallagher (1964) 57 noted that height growth decreased and needle chlorosis increased when the trees were f e r t i l i z e d only with potassium. High K concentrations alone did not seem to be injurious to tree growth since potassium concentrations were .87%, 1.07% and .88% respectively for control, nitrogen-fertilized trees, and potassium-fertilized trees. Trees f e r t i -lized with both nitrogen and potassium responded as well to f e r t i l i z a -tions as nitrogen-fertilized trees. Gallagher (1964) hypothesized that potassium may interfere with calcium uptake (which he did not measure) in nitrogen-deficient trees f e r t i l i z e d with potassium. It is possible i t also interfered with Mg uptake. In this study, Mg content (mg/100 needles) was positively related to N concentrations but negatively related to K concentrations (Figure 9), suggesting a negative effect of K concentrations on Mg uptake. In a greenhouse study, Drake and Scarseth (1939) found that high levels of K caused chlorosis on a variety of agricultural crops. At the same time, Mg uptake, and to a lesser extent Ca uptake, was reduced. Current calcium levels were positively correlated with current height growth even though mean values for both well and poorly grown trees were within the adequate range reported for many conifers. Foliar calcium levels optimum for height growth in juvenile amabilis f i r may be higher than those of other conifer species or those of mature amabilis f i r . The positive correlation between f o l i a r calcium and height growth might also be due to interactions between calcium levels in the rooting zone and nitrogen mineralization or micronutrient ava i l a b i l i t y . In f i e l d and experimental t r i a l s with red f i r seedlings, Powers (1980a) reported that poor growth and chlorosis of f i r seedlings on many 58 440 .70 £ 366 .47 c O O E 292.24 r I-UJ I-z o o 218.02 CO Ul CD < 2 ui cr oc i h MI II 2 I i i l _ 143.79 h I I I h i i i i i 69 .56 | - I I I . 4 4 8 0 0 I 2 2 2 I I 2 2 2 2 I 2 2 2 2 1- CURRENT NITROGEN 2 - CURRENT POTASSIUM 2 2 2 2 2 2 2 2 2 2 2 2 2 2 _i i_ . 88080 1.3136 . 6 6 4 4 0 1.0972 NUTRIENT CONCENTRATIONS ( % oven-dry weight) 1.5300 Figure 9. Relationship between magnesium content and nitrogen and potassium concentrations i n current f o l i a g e of amabilis f i r . 59 s i t e s were associated with high concentrations of f o l i a r manganese (>300 ppm) and low concentrations of calcium (<.3%). Powers suggested that the concentrations of manganese i n l i t t e r from mature stands, as reported by Vallee (1967), might adversely a f f e c t f i r seedlings. Mature red f i r f o l i a g e contained higher l e v e l s of Mn (averaging 1174 ppm Mn), which suggested to Powers that Mn tolerance increased as the tree aged. In a f i e l d t r i a l which tested a v a r i e t y of f e r t i l i z e r s , Powers** found that a l l treatments which added nitrogen increased red f i r seedling height growth s i g n i f i c a n t l y . The only other nutrient which seemed to p o s i t i v e l y increase growth was calcium. Adding lime or promoting seedling growth with nitrogen seemed to ameliorate manganese t o x i c i t y . Although i t was possible to r e l a t e needle weights and height growth i n a s t a t i s t i c a l l y s i g n i f i c a n t manner to nitrogen concentrations, a causal r e l a t i o n s h i p between height growth and nitrogen or other nutrients cannot be assumed, regardless of the degree of mathematical c o r r e l a t i o n . Growth i s a function of many f a c t o r s , not a l l of which were measured i n t h i s study. One of these unknown factors might cause growth and nitrogen concentrations to increase or decrease simultaneous-l y , r e s u l t i n g i n a s t a t i s t i c a l l y s i g n i f i c a n t , p o s i t i v e but i n d i r e c t mathematical r e l a t i o n s h i p . Only a f e r t i l i z e r t r i a l w i l l provide conclu-sive proof that nitrogen i s l i m i t i n g growth. The time needed to estab-l i s h and evaluate a f i e l d t r i a l was beyond the scope of t h i s t h e s i s . Unpublished data on f i l e at P a c i f i c Southwest Forest and Range Experiment Station, Redding, C a l i f o r n i a . 60 However, two f e r t i l i z e r t r i a l s had e a r l i e r been established i n stands of amabilis f i r e x h i b i t i n g d e c l i n i n g height growth. In both t r i a l s , nitrogen f e r t i l i z e r improved height growth. The f i r s t of these f e r t i l i z e r t r i a l s was established by Gallagher (1964) on Blue Mountain (Washington State, U.S.A.) i n amabilis f i r regeneration which was e x h i b i t i n g poor growth. Annual p r e c i p i t a t i o n (2500 mm) was adequate f o r good amabilis f i r growth. Gallagher applied nitrogen and potassium f e r t i l i z e r s , alone and combined. Height growth was s i g n i f i c a n t l y increased by a l l f e r t i l i z e r s containing nitrogen. Nitrogen l e v e l s i n current f o l i a g e of control trees were between .92 and 1.22%; much higher than those reported i n t h i s study. The maximum f o l i a r nitrogen l e v e l recorded i n the n i t r o g e n - f e r t i l i z e d trees was 1.34%. A l i n e a r regression analysis (n = 8) by Gallagher (1964) described a p o s i t i v e r e l a t i o n s h i p between f o l i a r nitrogen concentrations i n current and 1-year-old f o l i a g e and current height growth (r = .80 and .79, r e s p e c t i v e l y ) . He concluded that f o l i a r nitrogen concentrations were a good i n d i c a t o r of tree growth p o t e n t i a l . The second f e r t i l i z e r t r i a l was a p i l o t t r i a l established by Crown Zellerbach at a l o c a t i o n close to my study areas on a s i t e which was si m i l a r i n elevation, aspect, slope, and stand h i s t o r y except that the old growth had been clearcut approximately 10 years e a r l i e r . The trees i n the f e r t i l i z e r t r i a l had released well f o r 3 to 7 years and then height growth had s t e a d i l y declined f o r 10 years or more. This stand was spaced i n 1974. A small control area was l e f t untreated. In 1976, part of the spaced area was hand f e r t i l i z e d with urea at the rate of 224 61 kg N/ha. One plot was established i n each of the treatment (spaced, spaced + f e r t i l i z e d ) and control areas of the stand. Height growth increased dramatically when the trees were f e r t i l i z e d with nitrogen (Figure 10). The height data for th i s t r i a l were analyzed by covariance with the combined 1976-1977 height growth used as the response v a r i a b l e . Since 1975 height increment was s i g n i f i c a n t l y corre-l a t e d (r = .47; p <.01) with the 1976-1977 height growth, 1975 height growth was used as the covariate. The adjusted means (49.7, 39.3, and 63.9 cm, respectively) f o r the co n t r o l , spaced 1974, and spaced 1974 + f e r t i l i z e d 1976 plots were compared by t - t e s t s . There was no s i g n i f i -cant difference between means of control and spaced-only p l o t s . Mean 1976-1977 height of the f e r t i l i z e d trees was s i g n i f i c a n t l y greater (p <.01) than that of eit h e r the control or spaced trees. Mean height i n the spaced and f e r t i l i z e d plot was 63% greater than the mean height of the spaced trees and 29% greater than that of control trees (Figure 10). These data, which were c o l l e c t e d on a s i m i l a r s i t e to the present study s i t e , suggest that nitrogen deficiency i s l i k e l y a major factor i n the stagnation of the poorly grown trees a f t e r an i n i t i a l good release period. Cameron (1979) analyzed N and P concentrations i n the spaced area of t h i s p i l o t t r i a l and Briggs (1979) compared f o l i a r N and P concentra-tions and contents i n the f e r t i l i z e d trees with trees that were only spaced (Table 4). Since f o l i a r nitrogen concentrations reported by them were s i m i l a r or higher than those reported i n th i s study for the poorly grown t r e e s i one would expect the study s i t e trees to respond well to f e r t i l i z a t i o n . 60 _ 50 E O or or ui o < < UJ 40-H 30-H a 2°-H io -H 28.7 25.4 1975 1976 1977 SPACED 1974 FERTILIZED 1976 1975 1976 1977 SPACED 1974 1975 1976 1976 CONTROL Figure 10. Results of Crown Zellerbach's p i l o t f e r t i l i z e r t r i a l (from Crown Zellerbach 1978). NJ 63 F a l l f o l i a r nutrient concentrations explained at most 75% of the v a r i a t i o n i n height growth at my research s i t e . This r e l a t i o n s h i p might have been improved by d i f f e r e n t sampling procedures: 1. Leyton (1958) reported that the best mathematical r e l a t i o n s h i p s between height growth and f o l i a r nitrogen concentrations were obtained by sampling f o l i a g e from the leader or top branch whorl. 2. New shoot production i n amabilis f i r i s dependent to some extent on i n t e r n a l reserves of n u t r i e n t s . Turner et a l . (1976) estimated that 54% of the nitrogen required f o r new growth i n mature amabilis f i r was translocated f rom older t i s s u e . The remainder was supplied by current root uptake. Although f o l i a r nitrogen l e v e l s i n top whorl f o l i a g e i s a good in d i c a t o r of the nutrient status of a tree, i t may not be l i n e a r l y related to the t o t a l nitrogen reserves i n a tree with many years of needle re t e n t i o n . M i l l e r e^ t _al. (1976) reported a second order poly-nomial r e l a t i o n s h i p between top whorl nitrogen concentrations and the t o t a l N reserves of Corsican pine. Therefore, N% i n upper crown f o l i a g e may not adequately r e f l e c t the si z e of the i n t e r n a l nitrogen reserve which i n addition to root uptake determines the p o t e n t i a l for new shoot production. Height growth may be more c l o s e l y r e l a t e d to f o l i a r nitrogen content than nitrogen concentrations since the former parameter would l i k e l y r e f l e c t the si z e of i n t e r n a l nitrogen reserves more accurately. However, the use of nutrient content data as an independent v a r i a b l e i n c o r r e l a t i o n or regression 64 analyses with a growth parameter as the dependent variable i s questionable although s t a t i s t i c a l l y v a l i d because the content data includes a measure of growth (the weight of 100 needles) and i s therefore not s t r i c t l y independent of other growth parameters (Tamm 1964). In t h i s study, height and needle weights are highly, p o s i t i v e l y correlated, preventing the use of nitrogen content data i n c o r r e l a t i o n analyses. 3. F o l i a r nitrogen l e v e l s measured during the growing season may be more p o s i t i v e l y related to height growth than dormant season l e v e l s . This p o s s i b i l i t y i s examined i n the next chapter. 3. Seasonal Trends i n F o l i a r N and P Analysis of these data are complicated by a s i g n i f i c a n t i n t e r a c t i o n between the sampling date and f o l i a r N and P concentrations for i n d i v i -dual trees. For example, the f o l i a r N values i n 1-year-old needles of 10 poorly grown trees are graphed i n Figure 11. Not a l l trees show the same trend i n f o l i a r N during the growing season. F o l i a r N and P concentrations of paired trees were not s i g n i f i c a n t -l y d i f f e r e n t at the f a l l sampling date (paired t - t e s t s , p <.05). How-ever, t h i s may not have been the case at a l l sampling dates during the growing season because of tree-to-tree v a r i a t i o n i n patterns of f o l i a r N and P changes from May to September. Therefore, two sets of N and P values are plotted i n Figures 12 and 13. The f i r s t set (k or •) represents data from f i r s t sampling date i n each month; the second set (A or 0) represents data from the second sampling date i n each month. to z o JUNE JULY AUG. SEPT. Figure 11. Tree-to-tree v a r i a t i o n i n May to September nitrogen concentrations of 1-year-old f o l i a g e from 10 poorly grown trees sampled early each month. as 2.0 CO < Ct r-Z Ul o z o o w •o O Ul o o ct I-< Ul 1I 1.6 1.4 1.2 CURRENT FOLIAGE Well grown trees sampled early in the month. Well grown trees sampled late in the month. Poorly grown trees sampled early in the month. Poorly grown trees sampled late in the month 1.0 -YEAR-OLD FOLIAGE 2-YEAR-OLD FOLIAGE •eh - i 1 1 • • MAY JUNE JULY AUG. SEPT. MAY JUNE JULY AUG. SEPT MAY JUNE JULY AUG. SEPT. Figure 12. Mean N% in current, 1-year-old, and 2-year-old f o l i a g e from May to September. CTN . 4 0 .36 .4 CO o or ui o z o u © 5 CO or o x a. co o .34 -.32 -.30 .26 .26 .24 .22 .20 .18 .16 .14 .12 .10 CURRENT FOLIAGE A Well grown trees sampled early in the month. A Well grown trees sampled late in the month. % Poorly grown trees sampled early in the month. O Poorly grown trees sampled late in the month. I-YEAR-OLD FOLIAGE 2-YEAR-OLD FOLIAGE MAY JUNE JULY AUG SEPT. MAY JUNE JULY AUG. SEPT. MAY JUNE JULY AUG. SEPT. Figure 13. Mean P% i n current, 1-year-old, and 2-year-old f o l i a g e from May to September. 68 A l i n e was interpolated through a l l the data points. Changes i n f o l i a r concentrations during the growing season were tested for s i g n i f i c a n c e by paired t - t e s t s only f o r the same trees sampled i n d i f f e r e n t months. Mean nitrogen concentration i n current f o l i a g e dropped r a p i d l y from about 2.0% to between .6% and .8% from June to August as the new fo l i a g e expanded. There was l i t t l e seasonal v a r i a t i o n i n nitrogen concentra-tions of 1 and 2-year-old f o l i a g e . Mean N concentrations i n 1 and 2-year-old f o l i a g e from poorly grown trees ranged from .52% to .62%. Mean N concentrations ranged from .68 to .90% i n 1-year-old f o l i a g e and from .71% to .92% i n 2-year-old f o l i a g e of well grown trees. Seasonal v a r i a t i o n s i n the nitrogen concentrations of 1 and 2-year-old needles were s i m i l a r . Nitrogen concentrations dropped during May and June; rose during J u l y and August; and then decreased again i n l a t e August to September (Figure 8). The i n i t i a l decrease coincided with the most ac t i v e period of new f o l i a g e production and shoot growth; the mid-summer peak, with hot, dry weather; and the l a t e summer decline with moister, cooler weather. The l a t e summer decline may r e f l e c t movement of nitrogen into newly formed buds. The decrease i n f o l i a r N during May and June was s t a t i s t i c a l l y s i g n i f i c a n t (p <.05) for both age classes of f o l i a g e from poorly grown trees and for 1-year-old f o l i a g e from well grown trees. The increase i n l a t e July and August was s t a t i s t i c a l l y s i g n i f i c a n t f o r a l l groups. The c o e f f i c i e n t of v a r i a t i o n f o r f o l i a r N concentrations at any one sampling data ranged from 7 to 17% for poorly grown trees and from 14 to 21% for well grown trees. 69 A more dramatic decline i n nitrogen l e v e l s i n 1-year-old f o l i a g e had been expected during May and June due to translocation of nutrients from old needles to new f o l i a g e biomass. Krueger (1967), Waring and Youngberg (1972) reported sharp decreases i n nitrogen concentrations of 1-year-old needles during t h i s active period of growth. There are two possible reasons for the r e l a t i v e l y stable f o l i a r nitrogen concentrations i n 1-year-old f o l i a g e during the period of active shoot growth. F i r s t , the l e v e l s of nitrogen were so low that much of the nitrogen was probably immobile ( s t r u c t u r a l l y bound) and not av a i l a b l e f or transport to new t i s s u e s . Gessel (1962) f e l t that when f o l i a r nitrogen l e v e l s dropped to .6% i n Douglas f i r most of the nitrogen would be s t r u c t u r a l l y bound. The lowest l e v e l s recorded by Schwab (1979) f o r 15 to 17-year-old amabilis f i r needles ranged from .6 to .7%. Secondly, the Douglas-fir seedlings i n Krueger's study and the low elevation Douglas-fir i n Waring and Youngberg's study probably had fewer years of needle retention than amabilis f i r . Perhaps, i n tree species with higher needle retention, t r a n s l o c a t i o n i s le s s dramatic i n 1-year-old needles because nutrients are being withdrawn from a greater number of needle ages. In Eastern Canada, Gordon (1975) reported low seasonal v a r i a t i o n i n nitrogen concentrations of 1-year-old f o l i a g e c o l l e c t e d from three species of spruce, a l l of which had needle retention of 6 to 7 years, with some retainin g needles up to 14 years. He found that there was a gradual removal of nutrients from a l l needle age c l a s s e s . In poorly grown trees, nitrogen concentrations were lowest at two c r i t i c a l periods during the growing season; at bud break and during bud 70 i n i t i a t i o n i n l a t e summer. When modelling growth response to nitrogen f e r t i l i z e r , Fagerstrom and Lohm (1973) found i t useful to separate f o l i a r nitrogen i n t o two pools; one consisting of mobile or p o t e n t i a l l y mobile nitrogen and the other s t r u c t u r a l l y bound nitrogen. They pro-posed that the l e v e l of mobile nitrogen at the time of bud formation sets an upper l i m i t to the production of new f o l i a g e the following year i n n i t r o g e n - d e f i c i e n t determinate tree species. Whether t h i s maximum po t e n t i a l growth was r e a l i z e d depended upon the l e v e l s of mobile n i t r o -gen a v a i l a b l e at the time of budburst and needle elongation. The lowest nitrogen concentration measured i n th i s study was .42%. At t h i s concentration, most of the nitrogen i s probably s t r u c t u r a l l y bound. The mean nitrogen concentration i n poorly grown, 1-year-old f o l i a g e at the time of bud break, was only .57% compared to .75% i n well grown trees. If .42% i s subtracted from both means, and the remainder considered an estimate of the pool of mobile nitrogen, t h i s pool i n well grown trees based on concentration alone was 2.2 times larger than that of poor trees. A s i m i l a r c a l c u l a t i o n f o r the l a t e July to early August period also showed a 2.4 f o l d greater mobile N pool i n well grown trees. Phosphorus concentrations during the growing season exhibited d i f f e r e n t trends i n 1-year-old f o l i a g e of poor and well grown trees (Figure 13). The greatest difference occurred i n the August samples. Phosphorus concentrations rose s i g n i f i c a n t l y i n f o l i a g e from poor trees but remained constant i n that of well grown trees. This might be explained by continuing P uptake during the summer which was d i l u t e d by continuous needle growth i n well grown trees but not i n poorly grown trees. Height growth terminated e a r l i e r i n poorly grown trees than well 71 grown tr e e s . Seasonal changes i n 2-year-old f o l i a g e were les s than i n 1-year-old f o l i a g e . Current P concentrations dropped r a p i d l y during the growing season and followed a s i m i l a r pattern i n both well and poorly grown trees. 4. The Relationship Between Height Growth and F o l i a r N, P, N:P  Measured during May to September These r e l a t i o n s h i p s were analyzed by stepwise multiple l i n e a r regression. Because of the design of the sampling, two sets of analyses were conducted: one with the 20 trees sampled i n the f i r s t half of each month and the second with the 20 trees sampled i n the l a s t half of each month (Table 8). The f i r s t variables selected i n both analyses were N:P r a t i o s . In 3 out of 4 cases, the August N:P r a t i o ( i n 1- or 2-year-old f o l i a g e ) was chosen. This N:P r a t i o explained 15 to 20% more of the v a r i a t i o n i n height growth than f a l l N:P r a t i o s . Because the data were s p l i t f o r analyses i t was not possible to pinpoint the best sampling date. However, July and August values were chosen over May, June and September values by the stepwise regression program. In 3 out of 4 cases, the i n c l u s i o n of more than one N:P r a t i o increased the R 2 value (percentage of height growth explained). These data suggest that f o l i a r sampling during the growing season may improve the r e l a t i o n s h i p between f o l i a r nutrients and growth. Seasonal v a r i a t i o n i n 1 and 2-year-old f o l i a g e was low e s p e c i a l l y i n 72 Table 8. Stepwise regression with growing season N, P and N:P data measured on current, 1- and 2-year-old f o l i a g e Dependent variable Step R2* SE** Regressor v a r i a b l e s * * * Twenty Trees Sampled i n F i r s t Half of Each Month Current height 1 .65 14.2 N:P August (1-year-old f o l i a g e ) 2 .65 12.4 N:P July (current f o l i a g e ) 3 .72 11.4 N:P Augus t (current f o l i a g e ) 4 .83 9.4 N July (2-year-old f o l i a g e ) 5 .87 8.4 N:P Augus t (2-year-old f o l i a g e ) 6 .91 7.1 N August (2-year-old f o l i a g e ) Release height 1 .62 42.8 N:P Augus t (2-year-old f o l i a g e ) 2 .74 38.7 N:P Augus t (current f o l i a g e ) 3 .83 30.2 N:P July (current f o l i a g e ) 4 .91 23.7 N:P June (1-year-old f o l i a g e ) Twenty Trees Sampled i n Second I Half of Each Month Current height 1 .71 16.2 N:P June (1-year-old f o l i a g e ) 2 .84 11.3 N:P August (2-year-old f o l i a g e ) 3 .89 9.7 N July (current f o l i a g e ) Release height 1 .62 62.2 N:P August (2-year-old f o l i a g e ) * C o e f f i c i e n t of determination. ** Standard e r r o r . ***A11 s i g n i f i c a n t at p <.05. 73 poorly grown trees. Therefore, i t may be possible to sample these 2 age classes' of f o l i a g e over a period of at l e a s t 2 weeks without introducing s i g n i f i c a n t seasonal v a r i a t i o n . Current f o l i a g e values do change r a p i d l y and s i g n i f i c a n t v a r i a t i o n could be introduced by sampling over a period of a week from May to the end of J u l y . The data are l i m i t e d to one year and to one s i t e . Seasonal v a r i a -t i o n may be greater i n other years or s i t e s . Therefore, more studies are needed before recommending a change i n the standard p r a c t i c e . 5. The Relationship Between Humus Nutrient Status and Amabilis F i r  Growth 5.1 Nitrogen and C:N Data Chemical analysis of humus from beneath well and poorly grown trees supported the hypothesis that nitrogen d e f i c i e n c y was an important determinant of d e c l i n i n g tree height growth. At the research s i t e , 80 to 100% of the amabilis f i r f i n e feeder roots appeared to be located mainly i n a thick, f e l t y mat of humus with varying proportions of decaying wood. Mean t o t a l nitrogen concentrations i n the humus of well grown and poorly grown tree microsites were .94 and .83% r e s p e c t i v e l y . C:N r a t i o s were 53.7 and 65.6 for well and poorly grown tree microsites r e s p e c t i v e l y (Table 9). Total humus nitrogen % was s i g n i f i c a n t l y higher (p <.05) and the C:N r a t i o was s i g n i f i c a n t l y lower (p <.05) for well grown tree m i c r o s i t e s . pH and % t o t a l P were s i m i l a r beneath both classes of trees. 74 Table 9. Comparison of mean pH, macronutrients and C:N r a t i o s i n humus co l l e c t e d from well and poorly grown tree m i c r o s i t e s . (n = 10; standard deviations i n brackets) Total Total pH C:N N P (% oven-dry weight) Exchangeable cations (me/100 g) Ca Mg K Well grown 3.97 53.7 .94 .101 33.4 2.85 2.73 tree microsites (.20) (9.24) (.13) (.013) (17.6) (1.07) (1.37) Poorly grown tree microsites 3.95 65.6 .83 .101 (.14) (11.2) (.14) (.016) 25.7 2.21 3.03 (10.9) (.68) (1.52) NS ** ** NS NS Si g n i f i c a n t difference i n means at p = .10 * S i g n i f i c a n t difference i n means at p = .05 Mean % t o t a l humus nitrogen under both well and poorly grown trees was lower than the range, 1.02 to 1.77%, reported by Klinka and Lowe (1976) f o r humus on mesic s i t e s i n the CWHb subzone; and at the low end of the ranges reported by Quesnel and Lavkulich (1980) for humus co l l e c t e d from x e r i c (very r a p i d l y drained), mesic (moderately well drained) and hygric (poorly drained) s i t e s i n the CWHb subzone of northern Vancouver Island. In t h e i r study, t o t a l N varied from .643 to 1.014% (x = .83) on x e r i c s i t e s , .817 to 1.288% (x = 1.02) on • mesic s i t e s , and 1.067 to 1.848% (x = 1.42) on hygric s i t e s . Mean C:N r a t i o s were higher than those reported by both studies. Klinka and Lowe (1976) found humus C:N r a t i o s ranged from 30.1 to 52.9. Mean humus C:N r a t i o s were 58.3, 47.5, and 29.5 respe c t i v e l y for x e r i c , mesic, and hygric s i t e s i n Quesnel and Lavkulich's study. High C:N ra t i o s are associated with low nitrogen m i n e r a l i z a t i o n r a t e s . A r a t i o of 25 i s considered optimum for decomposition (Bollen 1969). Even though the t o t a l N c a p i t a l of thick humus layers with high C:N r a t i o s i s large, nitrogen a v a i l a b i l i t y i s l i k e l y to be low leading to competition between decomposers and trees for the ava i l a b l e N. Immobilization of e s s e n t i a l nutrients by decomposers may exceed m i n e r a l i z a t i o n rates i n mor humus. In a study of nitrogen a v a i l a b i l i t y i n a mature amabilis f i r stand, G r i e r ^ found that s i g n i f i c a n t decreases i n t o t a l mineralizable nitrogen occurred i n trenched plots immediately a f t e r l i t t e r f a l l . This decrease was attr i b u t e d to the high Pers. comm. from Dr. C. G r i e r , U n i v e r s i t y of Washington, January, 1981. 76 C:N r a t i o of amabilis needle l i t t e r and uptake of mineralizable N by decomposers. No s i g n i f i c a n t l i n e a r r e l a t i o n s h i p s (at p <.05) between humus N% or C:N r a t i o and current f o l i a r nitrogen per cent were apparent i n a c o r r e l a t i o n analysis of the data. However, the simple c o r r e l a t i o n c o e f f i c i e n t between C:N r a t i o and f o l i a r N was higher (r = .40) than that between humus N and f o l i a r N (r = .28). Evers (1967) found that carbon/nutrient r a t i o s , i n p a r t i c u l a r C:N and C:P, i n the top 4 cm of s o i l ( i n his study, mainly F and H horizons) were better related to tree growth than any other chemical analyses. If a better measure of nitrogen a v a i l a b i l i t y had been obtained either by sampling more s o i l horizons or by using an anaerobic incuba-t i o n f or mineralizable nitrogen (Powers 1980b), the re l a t i o n s h i p between humus and f o l i a r N might have been s i g n i f i c a n t . 5.2 Ca, Mg, and K Data The f o l i a r concentration study suggested that magnesium (Mg) and calcium (Ca) n u t r i t i o n may be below optimum for height growth. Exchangeable Ca and Mg l e v e l s i n humus under well grown trees were s i g n i f i c a n t l y greater (p <.10) than those i n humus under poorly grown trees. Exchangeable K and Ca le v e l s f o r a l l microsites were within the upper range of values reported by Williams and Dyrness (1967) for fo r e s t f l o o r s (LFH) i n the Mt. Baker and Mt. Rainier E c o l o g i c a l Provinces i n Washington and by Quesnel and Lavkulich (1980) for humus (H) c o l l e c t e d 77 from r a p i d l y drained, well drained, and poorly drained s o i l s i n the west subzone-of the Coastal Western Hemlock Biogeoclimatic Zone. Exchangeable Mg data were at the low range of values reported i n these two studies. Williams and Dyrness (1967) found exchangeable Mg ranged from 3.3 to 7.0 me/100 g (x = 4.8). Exchangeable Mg l e v e l s ranged from 4.58 to 13.36 me/100 g (x = 8.33), 8.60 to 22.33 (x-= 12.35), and 1.68 to 14.07 (x = 6.79) me/100 g, r e s p e c t i v e l y for ( r a p i d l y , w e l l , and poorly drained) s i t e s i n Quesnel and Lavkulich's study. The most important factor i n f l u e n c i n g nutrient status of the rooting medium on the study s i t e was the quantity of r o t t i n g wood i n c o r -porated into the humus. However, the type of r o t t i n g wood may have also been important. Minore (1972) compared nutrient l e v e l s of hemlock duff and r o t t i n g wood of three tree species (Table 10) i n the f i e l d for a seedbed study. Hemlock duff had a much higher nutrient content than any type of r o t t i n g wood. Rotting wood of Douglas-fir and western hemlock d i f f e r e d i n t o t a l c ation content. Minore did not state whether these differences were s i g n i f i c a n t . However, his data suggest that some microsite v a r i a t i o n i n cation status of the rooting medium may be due to the type of r o t t i n g wood (Douglas-fir or western hemlock) on a s i t e . Although f o l i a r Ca and Mg explained a s i g n i f i c a n t portion of v a r i a -t i o n i n height growth, there were no s i g n i f i c a n t r e l a t i o n s h i p s between exchangeable Ca or Mg i n the humus samples and f o l i a r Ca and Mg or height growth. Exchangeable cations were extracted by NH^OAc at pH 7.0. A better r e l a t i o n s h i p between f o l i a r cations and humus cations might have resulted from extracting the humus cations with NaOAc at Table 10. Chemical analysis of seedbed materials (from Minore 1972) Seedbed T o t a l 1 N P K T o t a l 3 Ca T o t a l 6 Mg T o t a l 2 3 Extractable 3 Total 3 Exchangeable % ppm Hemlock duff 1.096 1,230 325 635 614 1,750 2,325 Douglas-fir wood .104 72 45 210 210 700 275 Sitka spruce wood .135 129 45 245 215 940 530 Hemlock wood .98 72 50 140 108 1,220 550 Kje l d a h l . Colorimetric, a f t e r p e r c h l o r i c acid oxidation. Sodium bicarbonate extraction. Flame emission a f t e r p e r c h l o r i c acid oxidation. Ammonium acetate ext r a c t i o n . Atomic absorption a f t e r p e r c h l o r i c acid oxidation. 79 pH 4.8. Klinka et a l . (1980) reported that the quantities of cations extracted by t h i s l a t t e r method correlated better with forest produc-t i v i t y . They also reported that cation quantities extracted from the whole s o i l p r o f i l e (mineral s o i l + LFH) correlated better with tree growth than those from the LFH alone. whether the difference i n exchangeable Ca or Mg between microsites i s b i o l o g i c a l l y as well as s t a t i s t i c a l l y s i g n i f i c a n t i s d i f f i c u l t to determine because adequate l e v e l s of s o i l nutrients for d i f f e r e n t tree species have not been established. 5.3 Proposed Relationship Between Variable Height Growth and N u t r i t i o n Accumulations of humus can lead to s i t e degradation i n cool, tem-perate forests with mor humus development (Roberge e_t a l . , 1968; M i l l e r et j i l . , 1976). As a f o r e s t stand matures, an increasing proportion of the s i t e nutrient supply i s immobilized i n tree t i s s u e and slowly decom-posing organic material. Decomposition may be slow due to low tempera-tures, low nitrogen or phosphorus a v a i l a b i l i t y or to the formation of stable polyphenol-protein complexes which r e s i s t degradation (Benoit et a l . , 1968). Individual nutrients are released from fresh conifer l i t t e r at various rates. Water-soluble cations are released r a p i d l y compared to or g a n i c a l l y bound n u t r i e n t s . De Catanzaro (1979) found that nutrients were released from conifer l i t t e r i n the following order: Ca>Mg>K>P>N. Therefore, N and P are the nutrients most l i k e l y to become l i m i t i n g when decomposition i s slow. P a v a i l a b i l i t y to trees i s enhanced by 80 mycorrhizae but N a v a i l a b i l i t y i s more c l o s e l y associated with the decomposition rate. Advance regeneration becomes established i n the accumulation of organic matter developed by the preceding old growth f o r e s t . If the s i t e has developed a thick layer of slowly decomposing humus, growth of the advance regeneration may be l i m i t e d by low l e v e l s of mineralizable nitrogen i n the rooting zone. There i s evidence that nitrogen a v a i l a b i l i t y i s temporarily increased when mor humus s i t e s are clearcut and the forest f l o o r d i s -turbed due to both increased surface temperatures and moisture (Likens et a l . 1970; Dominsky 1971) and decreased competition between plant roots and decomposers (Gadgil and Gadgil 1975). Lutz and Chandler (1946) stated that c l e a r c u t t i n g often improved nutrient conditions i n mor humus because decomposition i s increased, a c i d i t y i s reduced and n i t r i f i c a t i o n i s promoted. In a study of c l e a r c u t t i n g e f f e c t s on nutrient a v a i l a b i l i t y and decomposition rates, Page (1974) discovered that the thickness of the LFH layer on mor humus decreased 1.3 to 3.8 cm a f t e r c l e a r c u t t i n g on gle y s o l s , brunisols, and podzols i n Eastern Canada; pH increased .5 of a unit; and C:N ra t i o s decreased as much as 1.5 units at the 2.5 cm depth on the fo r e s t f l o o r . These changes lasted for variable periods and were greater on podzols than brunis o l s . A f t e r c l e a r c u t t i n g of old growth amabilis fir-western hemlock f o r e s t s , there i s a 30 to 35% decrease i n the fo r e s t f l o o r of mesic s i t e s f o r at l e a s t 8 to 10 y e a r s 1 0 . Pers. comm. from Wayne Martin, Graduate Student, University of B r i t i s h Columbia, January, 1982. 81 A temporary increase i n decomposition and nitrogen a v a i l a b i l i t y i s most l i k e l y the reason for the i n i t i a l l y good response exhibited by a l l advance regeneration on the research s i t e . The following i s a proposed scenario for the release growth of advance regeneration established on a thick f o r e s t f l o o r accumulation of varying composition: ( i ) advance regeneration accumulates a pool of mobile nitrogen i n a l l needle ages over and above that required for immediate growth during the temporary period of increased nitrogen a v a i l a b i l i t y a f t e r c l e a r c u t t i n g ; ( i i ) the amount of nitrogen accumulated i s proportional to the si z e of the root and crown system of advance regeneration at or s h o r t l y a f t e r the time of logging; ( i i i ) t h i s pool of mobile nitrogen, l i k e a chemical nitrogen f e r t i l i z e r a p p l i c a t i o n , sustains growth on s i t e s where low decomposition p r e v a i l s ; ( i v ) once a l l t h i s pool of a d d i t i o n a l nitrogen has been u t i l i z e d f o r new growth, height growth begins to decline i f the advance regeneration i s rooted mainly i n slowly decomposing humus; (v) advance regeneration established on microsites with greater supplies of a v a i l a b l e nitrogen continue to grow i n height f o r a longer period of time. M i l l e r et a l . (1976) studied i n t e r n a l nitrogen c y c l i n g and growth of Corsican pine on an N d e f i c i e n t s i t e . They expanded Fagerstrom and Lohm's (1977) concept of separate f o l i a r nitrogen pools by separating the mobile pool into two l e v e l s : the f i r s t , c o nsisting of recent root 82 or f o l i a r uptake; and the second, of p o t e n t i a l l y mobile i n t e r n a l reserves accumulated during previous seasons. When tree n u t r i t i o n becomes sub- optimal, and l e v e l 1 nutrients are i n s u f f i c i e n t to support growth, M i l l e r et^ al. (1976) found the l e v e l 2 nutrients were gradually mobilized, often at the expense of e f f i c i e n t or continued functioning of the older tree t i s s u e . This withdrawal eventually led to a decline i n tree growth. 6. Examination of Alternate Hypotheses to Explain Variable Height  Growth F o l i a r nutrient concentrations did not account for a l l the v a r i a b i l i t y i n height growth within a s i t e . Therefore, a l t e r n a t i v e hypotheses were examined to determine i f any explained a s i g n i f i c a n t portion of height growth d i f f e r e n c e s . Mean and standard deviations of parameters studied are summarized i n Table 11. 6.1 Age and Height at Release Within the range of ages and heights at release measured there was no s i g n i f i c a n t r e l a t i o n s h i p between height or age at release and release height growth. These r e s u l t s agree with those of Herring and Etheridge (1976). Ferguson and Adams (1979) reported that age of release influenced the degree of release response i n grand f i r . Younger trees responded more quickly than older trees (greater than 30 years at the time of release) because older trees were more l i k e l y to be infected with Echinodontium tinctorium. TABLE 11. Comparison of growth parameters between well grown and poorly grown amabilis f i r (n = 20; standard deviations i n brackets) Well grown trees Poorly grown trees Mean height at the time of logging .64 (.41) m .55 (.25) m Mean t o t a l height 9 years a f t e r logging 3.43 (.84) m 2.01 (.37) m Mean current (1978) height increment 47.8 (14.8) cm 8.3 (5.6) cm Mean 1978 secondary branch increment i n t h i r d whorl 1 8.3 (2.0) cm 4.5 (1.1) cm Mean 1977-78 diameter increment 2 earlywood 5.46 (1.53) mm 2.69 (.62) mm latewood 2.42 (.70) mm 1.17 (.32) mm Mean age at the time of logging 52.5 (30.6) yrs 45.0 (23.7) yrs Mean wt. of 100 oven-dry 1-year-old needles sampled i n the f a l l 699.4 (268.3) mg 433.8 (111.9) mg Mean wt. of 100 oven-dry current needles sampled i n the f a l l 358.1 (167.0) mg 252.4 (64.7) mg Estimate of 1-year-old f o l i a r biomass from the t h i r d whorl sampling p o s i t i o n 3035.1 (1621.7) mg 1116.8 (757.3) mg Mean needle leng th3 1-year-old 19.8 (5.2) mm 16.5 (2.1) mm current 16.3 (4.5) mm 12.1 (1.6) mm ^The sampling p o s i t i o n i s shown i n Figure 5. ^Measured at breast height. ^Needles from mid shoot positions were measured i n the f a l l . 84 Herring and Etheridge (1976) reported a very low incidence of Echinodontium tinctorium i n advance amabilis f i r stands although the incidence did increase with the proportion of stems older than 60 years at the time of release. 6.2 Degree of Aboveground Competition Release and current height growth were not s i g n i f i c a n t l y related to the competition stress index (number of competing stems within 2 m of the sample t r e e ) . Stocking de n s i t i e s expressed as trees per ha ranged from 800 to 8,000 trees per ha. In several other studies, competition has not re l a t e d s i g n i f i c a n t l y to height growth. In a study of subalpine f i r stands with stocking de n s i t i e s ranging from 1,700 to 3,000 trees per hectare, Ivanco (1976) found no s t a t i s t i -c a l l y s i g n i f i c a n t e f f e c t of stocking density on height growth. Ba s k e r v i l l e (1966) reached the same conclusion i n stands of balsam f i r stocked with 1,750 to 7,500 trees per hectare. In Gallagher's (1964) study of advance amabilis f i r regeneration the density of stock varied from 7,400 to 22,200 trees per ha, but appeared to have l i t t l e e f f e c t on tree height. Hunt 1 1 a t t r i b u t e d some of the e r r a t i c height growth at Courtenay to tree competition but emphasized that both open and densely grown trees exhibited poor or e r r a t i c height growth. Pers. comm. from Dr. A. Hunt, Canadian Forest Service, V i c t o r i a , B.C. 85 Herring and Etheridge (1976) reported that release growth i n advance'amabilis f i r regeneration tended to increase with increasing competition on 3 of the 10 coastal B.C. s i t e s which they studied. Differences i n competition stress accounted for at most 14% of the v a r i a t i o n i n height growth. Diameter growth was more strongly corre-lated with competition s t r e s s . Since competition stress influences growth of amabilis f i r on some s i t e s , stocking density should be considered when studying the r e l a t i o n s h i p between growth and nutrient data. 6.3 R e d i s t r i b u t i o n of Growth Schmidt 1 observed that some trees with poor height increment exhibited normal diameter increment i n the same year. This observation indicated that r e d i s t r i b u t i o n of growth from height to diameter i n c r e -ment might be occurring at c e r t a i n periods i n the development of the advance regeneration and could be responsible f o r periods of poor height growth. It i s known that a f t e r logging, root and diameter growth accelerates before height growth i n advance regeneration. There i s a one to two-year delay i n height growth release a t t r i b u t e d to root expan-sion , f o l i a r adaption to f u l l sunlight and stem buttressing. In t h i s study, height and diameter increment were p o s i t i v e l y c o r r e -lated (r = .66, .90, and .90, r e s p e c t i v e l y for 1976, 1977, and 1978). There was no evidence of a r e d i s t r i b u t i o n of growth between height and Pers. comm. from Mr. R. Schmidt, B.C. Ministry of Forests. Letter following a f i e l d t r i p to Tree Farm License No. 2, November, 1976. 86 diameter. Schmidt's observation may have been i n r e l a t i o n to trees with leaders snapped off by s q u i r r e l s . Some of these trees were slow to recover normal height growth but diameter growth was not affected by loss of the leader. Needle weights were also p o s i t i v e l y correlated with height and diameter growth (Table 12). Mean lengths and weights of well grown trees needles were s t a t i s t i c a l l y (p <.01) s i g n i f i c a n t l y higher than those of poorly grown trees. Lengths of midshoot needles averaged 16.3 and 19.8 mm, r e s p e c t i v e l y , f or current and 1-year-old f o l i a g e of well grown trees; but only 12.1 and 16.5 mm res p e c t i v e l y for poorly grown trees. Mean oven-dry weights for 100 current and 100 1-year-old needles were 358.1 and 699.4 mg r e s p e c t i v e l y for well grown trees, and 252.4 and 433.8 mg r e s p e c t i v e l y f or poorly grown trees. Reduced needle length and weight i n poorly grown trees strongly suggested that f o l i a g e production was much lower than i n well grown trees. In a study of balsam f i r , Morris (1955) found that average needle length and the needle biomass of a shoot were correlated (r = .9). In a study of advance amabilis f i r regeneration, Briggs (1979) also reported a highly s i g n i f i c a n t c o r r e l a t i o n ( r = .8) between needle length and needle biomass per shoot. Unfortunately, Morris (1951) reported that average needle length was less strongly correlated (r = .71) with t o t a l annual f o l i a g e biomass because of the variable number of shoots produced i n any one year. An estimate of r e l a t i v e f o l i a r biomass production was obtained by oven-drying and weighing a l l the f o l i a g e from the fourth whorl sampling 87 Table.12. Simple c o r r e l a t i o n c o e f f i c i e n t s (r) between needle weight, height, and basal area increment Oven-dry weight 1 of 100 1-year-old needles Oven-dry weight of 100 current needles Estimate of f o l i a r biomass i n fourth whorl sampling p o s i t i o n 1978 height increment .81 2 .71 .89 3 Release height .73 .63 .89 1977 basal area increment .53 NS .68 1978 basal area increment .64 .52 .82 Needles weighed i n the f a l l . A l l c o r r e l a t i o n c o e f f i c i e n t s are s i g n i f i c a n t at p = .05. Height growth from time of logging to 1978. 88 p o s i t i o n at the end of September (Table 12). This estimate indicated that f o l i a g e production i n the upper crown was 3 times greater i n well grown trees compared to poorly grown trees. The f o l i a r biomass estimate correlated better with height and diameter increments than the weight of 100 oven-dry needles (Table 12). The p o s i t i v e c o r r e l a t i o n s between needle weight, f o l i a r biomass estimate, height, and diameter increment suggest that whatever factor i s l i m i t i n g height growth a f f e c t s a l l aboveground tree growth. The strong c o r r e l a t i o n s between needle weight and height growth prohibits use of nutrient content data (mg nutrient per oven-dry mass of 100 needles) as an independent va r i a b l e i n regressions with growth parameters as dependent v a r i a b l e s . 6.4 Genetics Two observations suggested that ecotypic differences might possibly e x i s t between good and poor trees. F i r s t l y , Hunt 1^ noted that the current f a l l f o l i a g e of poor trees was paler than that of well grown trees, suggesting that the poor trees had flushed l a t e r . Secondly, p r i o r to the study, Kimmins 1^ had observed needle retention of 12 years i n trees at 400 to 600 m, which he f e l t might be unusually high f o r t h i s e l e v a t i o n . Amabilis f i r needle retention near Vancouver and Squamish, B.C. increases with elevation from as l i t t l e as 6 to 8 years at low elevations (about 400 m) to as high as 24 to 30 years i n some Pers. comm. Dr. A. Hunt, Canadian Forestry Service, V i c t o r i a , B.C. Pers. comm. Dr. J.P. Kimmins, Faculty of Forestry, U.B.C. 89 high elevation s i t e s (about 1800 m). If needle retention i s a geneti-c a l l y influenced character ( t h i s has not yet been established) Kimmins suggested that high needle retention at lower elevations i n the study area could r e f l e c t the presence of high elevation ecotypes i n the low to mid elevation stands. Differences i n c h i l l i n g requirements, r e s p i r a -t i o n , or a s s i m i l a t i o n rates between the ecotypes might cause between tree v a r i a b i l i t y i n height growth. Differences i n genetic make-up may also introduce v a r i a b i l i t y i n nutrient-height growth r e l a t i o n s h i p as reported by van der Driessche (1973) f o r Douglas-fir trees of d i f f e r e n t seed sources. The needle retention for both w e l l and poorly grown trees on the research s i t e ranged from 9 to 11 years with no s i g n i f i c a n t difference between tree growth and years of needle retention. Schwab (1979) reported 12 year needle retention for amabilis f i r growing between 400 and 700 m i n several coastal B.C. l o c a t i o n s . Therefore, needle reten-t i o n of study trees was not unusual. The phenology of 1978 height growth was recorded to determine i f a major portion of the height v a r i a t i o n could be explained by differences i n the time of height growth i n i t i a t i o n and termination (Figure 14). Emergence of needles from the bud scales was used as an i n d i c a t i o n of f l u s h i n g . Buds i n a l l crown positions of the well grown trees had flushed by May 25th and height growth was evident by May 31st. In poorly grown trees, f l u s h i n g was not widespread i n a l l crown positions u n t i l June 3rd and height growth was not general u n t i l June 7th. How-ever, i n comparison to the dramatic differences i n the rate of shoot elongation, the eight day difference i n height growth i n i t i a t i o n between 20 h TERMINATION OF HEIGHT GROWTH I P-' WELL GROWN TREES POORLY GROWN TREES MAY 25 JUNE7 JUNE 22 JULY II JULY 27 SEPT 22 Figure 14. Phenology of current height growth of well and poorly grown trees i n 1978. 91 well and poorly grown trees was a minor contribution to height growth v a r i a t i o n * This eight day difference may have been caused by d i f f e r -ences i n genetic make-up. It seemed more l i k e l y , however, that needle and shoot elongation out of the bud scales was weaker i n poor trees (giving the apperance of l a t e r flushing) due to a nutrient d e f i c i e n c y . Nitrogen f e r t i l i z e d trees i n the Crown Zellerbach p i l o t f e r t i l i z e r t r i a l flushed and began height growth before u n f e r t i l i z e d , thinned trees or control trees. The pale f o l i a g e i n poorly grown trees observed by Hunt may be inadequate n u t r i t i o n f or normal chl o r o p h y l l production or shoot extension. W o r r a l l 1 ^ found no differences i n the c h i l l i n g require-ments of amabilis f i r ecotypes. Although a mixture of ecotypes might e x i s t i n low elevation stands, t h e i r existence would be d i f f i c u l t to prove, von Rudloff and Hunt (1977) did not detect any a l t i t u d i n a l differences i n f o l i a r chemistry of amabilis f i r . Parker et^ a]L. (1979) found that periderm thickness was the only morphological c h a r a c t e r i s t i c which varied with a l t i t u d e i n mature amabilis f i r . Since needle retention i s probably affected by tree age, environment and n u t r i t i o n , as well as genetics, with our present state of knowledge, i t cannot be used as strong evidence for the existence of ecotypes. Pers. comm. Dr. Worrall, Faculty of Forestry, U.B.C. 92 6.5 Root Disease No obvious symptoms of feeder root diseases were evident on trees at the research s i t e 1 * * , some amabilis f i r i n the Courtenay stands were infe c t e d with A r m i l l a r i a mellea. These i n f e c t i o n s seemed to be secondary i n f e c t i o n s which were not responsible for the i n i t i a l slowdown i n tree growth. However, there was no conclusive information a v a i l a b l e to determine i f the i n f e c t i o n s were secondary or primary i n f e c t i o n s . Funk 1^ warned that stagnating amabilis f i r would be susceptible to secondary fungal i n f e c t i o n s . This seemed to be the case i n several stagnating stands i n the v i c i n i t y of the study area. 6.6 Micronutrient T o x i c i t y Concentrations of Fe and Mn i n acid s o i l s may reach l e v e l s toxic to tree growth. Since other tree species on the study s i t e grew normally, Mn and Fe t o x i c i t y was not considered a l i k e l y cause of variable height growth i n amabilis f i r . In future studies of amabilis f i r Mn and Fe n u t r i t i o n would be worthy of i n v e s t i g a t i o n i n l i g h t of Powers' (1980a) fi n d i n g s . 6.7 M i c r o s i t e Differences i n Moisture A v a i l a b i l i t y On s i t e s with suboptimum p r e c i p i t a t i o n f or good amabilis f i r growth, Klinka (1977a) hypothesized that regeneration may e s t a b l i s h more Pers. comm. from Dr. G. Wa l l i s , Canadian Forestry Service, V i c t o r i a , B.C. a f t e r a v i s i t to the research s i t e , May 1978. Pers. comm. from Dr. A. Hunt, Canadian Forest Service, V i c t o r i a , November 1977. 93 s u c c e s s f u l l y on microsites with a high proportion of decaying wood i n the rooting zone rather than on mineral s o i l or shallow humus micro-s i t e s . The decaying wood microsites would tend to have s u f f i c i e n t moisture for growth but low nutrient a v a i l a b i l i t y . Moisture stress would a f f e c t growth and/or nutrient a v a i l a b i l i t y on other microsites. There was i n s u f f i c i e n t time and equipment to monitor differences i n water a v a i l a b i l i t y at well grown and poorly grown tree microsites during the growing season. As an a l t e r n a t i v e , f o l i a r and FH chemistry were measured at three mesic (well drained) and three x e r i c ( r a p i d l y drained) s i t e s s i m i l a r i n elevation and aspect to the study area. The s i t e s had been logged approximately 15 years ago. Two forest f l o o r samples were c o l l e c t e d at each s i t e and separated in t o the F and H components f o r chemical a n a l y s i s . Mean values for the xe r i c and mesic s i t e s are summarized i n Table 13. S i g n i f i c a n t d i f f e r -ences between mesic and x e r i c s i t e FH chemistry were found f o r the C:N ra t i o s i n both h o r i zons and t o t a l N% i n F horizons ( t — t e s t s ; p *\.10). Mean C:N r a t i o s i n x e r i c F and H horizons, 55.2 and 80.8, res p e c t i v e l y , were almost double those of mesic s i t e s . Mean t o t a l N% for both F and H horizons were lower on the x e r i c s i t e s . There were no s i g n i f i c a n t differences i n t o t a l P or exchangeable cations between mesic and x e r i c s i t e s . Current and 1-year-old f a l l f o l i a g e was sampled from 10 amabilis f i r at each s i t e (Table 14). There were no s i g n i f i c a n t differences between the f o l i a r P, Ca, Mg or K concentrations of x e r i c and mesic s i t e amabilis f i r . However, mean N concentrations were s i g n i f i c a n t l y higher (p <.05) i n mesic s i t e trees. Nitrogen concentrations were respectively 94 Table 13. Mean depth (cm), t o t a l N and P (% oven-dry weight), C:N r a t i o , and exchangeable Ca, Mg, and K (me/100 g) i n the FH horizons of •3 x e r i c and 3 mesic s i t e s (n = 6; standard deviations i n brackets) x e r i c s i t e s Mesic s i t e s F H F H Depth 3.8 (3.7) 9.0 (8.6) 2.8 (1.5) 16.2 (9.6) To t a l N 1.13 (0.51) 0.72 (0.28) 1.70 (0.20) 0.90 (0.10) Tot a l P 0.12 (0.06) 0.08 (0.04) 0.14 (0.02) 0.07 (0.01) C:N 55.2 (38.4) 80.8 (54.3) 26.4 (2.5) 46.8 (11.8) Ca 26.5 (11.8) 17.3 (7.9) 28.3 (11.3) 21.0 (7.2) Mg 3.7 (1.2) 3.7 (0.8) 4.7 (1.6) 4.2 (1.9) K 3.0 (2.2) 1.8 (1.3) 2.7 (1.8) 1.8 (1.70) 95 Table 14. Mean needle weight (mg per 100 needles) and nutrient concen-t r a t i o n (% oven-dry weight) i n f a l l f o l i a g e of amabilis f i r on • 3 x e r i c and 3 mesic s i t e s (n = 6; standard deviations i n brackets) Mesic s i t e trees Xeric s i t e trees Current 1-year-old Current 1-year-old f o l i a g e f o l i a g e f o l i a g e f o l i a g e 1.14 (.28) .84 (.10) .86 (.10) .13 (.02) .18 (.03) .14 (.02) .64 (.12) .31 (.07) .57 (.08) .08 (.01) .08 (.01) .08 (.02) .56 (.09) .61 (.15) .54 (.12) Mean needle weight 802.00* 998.00 761 976 Trees that exhibited best height growth f or the s i t e s . Mean of 30 t r e e s . No sample v a r i a t i o n was calcu l a t e d . N .982(.15) P .17 (.02) Ca .35 (.07) Mg .08 (.01) K .67 (.15) 96 1.32 and 1.19 times greater i n 1-year-old and current f o l i a g e of mesic s i t e t rees. Mean needle weights of mesic s i t e trees, however, were only 1.03 and 1.05 times greater. These data suggest that nitrogen a v a i l a b i -l i t y or uptake was reduced proportionately more than dry matter produc-t i o n on the x e r i c s i t e . The s i g n i f i c a n t l y higher C:N r a t i o s i n the FH horizons of the 3 x e r i c s i t e s suggests that low nitrogen a v a i l a b i l i t y i s a major f a c t o r l i m i t i n g nitrogen uptake. The x e r i c s i t e s had a higher proportion of decaying wood i n the FH horizons. These r e s u l t s provide some support for Klinka's (1977a) hypothesis. However, much more d e t a i l e d study i s required to f u l l y assess the impact of moisture stress i n growth and nitrogen n u t r i t i o n of amabilis f i r . Of a l l the n o n - n u t r i t i o n a l factors examined, microsite differences i n water a v a i l a b i l i t y seem to have the greatest p o t e n t i a l to influence f o l i a r nitrogen-tree growth r e l a t i o n s h i p s . 97 SUMMARY AND CONCLUSIONS F o l i a r N and Mg concentrations i n both well and poorly grown amabilis f i r regeneration were below l e v e l s considered adequate for many conif e r species. Nutrient r a t i o s were comparable to those calculated for c oastal Douglas-fir and amabilis f i r by Beaton eit a l . 1965 and Schwab 1979 but not to Ingestad's proportions. Height growth was s i g n i f i c a n t l y related to f a l l f o l i a r chemistry i n multiple regression equations. Sixty-four per cent of the v a r i a t i o n i n release height growth was accounted for by 4 f a l l f o l i a r values: N:P r a t i o i n 2-year-old f o l i a g e , Mg% i n current and 1-year-old f o l i a g e , and P% i n current f o l i a g e . Seventy- f i v e per cent of the current height growth was explained by the N:P r a t i o i n 2-year-old f o l i a g e , Mg% i n 1- year-old f o l i a g e , and Ca% i n current f o l i a g e . Nitrogen concentrations alone explained 44 and 45% of the current and release height growth v a r i a b i l i t y , r e s p e c t i v e l y . N:P r a t i o s seemed to be a more s e n s i t i v e i n d i c a t o r of nitrogen status than N concentrations alone because of growth d i l u t i o n of P content i n well grown trees and P accumulation r e l a t i v e to growth i n poorly grown trees. Nitrogen concentrations i n 2- year-old f o l i a g e correlated more p o s i t i v e l y with release height growth than current or 1-year-old f o l i a r N. Current height growth was most s i g n i f i c a n t l y related to nitrogen concentrations i n current f o l i a g e . Although mean values of f o l i a r calcium f o r both well and poorly grown trees were within the range considered adequate for many c o n i f e r s , f o l i a r calcium was p o s i t i v e l y correlated with current height growth. Calcium a v a i l a b i l i t y may influence nitrogen m i n e r a l i z a t i o n rates or 98 micronutrient l e v e l s which i n turn a f f e c t tree growth, or adequate l e v e l s of Ca for juv e n i l e amabilis f i r may be higher than those of mature amabilis f i r . Future studies of f o l i a r n u t r i t i o n i n amabilis f i r should include Fe and Mn and future f e r t i l i z e r t r i a l s i n amabilis f i r stands should include Mg and Ca, i n addition to N, i f f o l i a r l e v e l s of Mg and Ca are low. It was hypothesized that the high concentrations of K i n the poorly grown trees may be caused by an antagonistic e f f e c t of K on Mg and/or Ca uptake. The r e l a t i o n s h i p between f o l i a r chemistry and height growth may be improved by sampling during the growing season. Seasonal changes i n f o l i a r nutrient concentrations of 1- and 2-year-old f o l i a g e were not as great as expected. Regressions with July and August f o l i a r N:P values explained more v a r i a t i o n i n height growth than f a l l f o l i a r N:P values. A study of these r e l a t i o n s h i p s over several years i s needed before the standard p r a c t i c e i s changed. Nitrogen concentrations were s i g n i f i c a n t l y lower and C:N r a t i o s higher i n humus c o l l e c t e d from poorly grown tree microsites. Because of high immobilization p o t e n t i a l of these (high C:N r a t i o ) humus layers , experimental f e r t i l i z e r t r i a l s should test r e l a t i v e effectiveness of urea versus a more soluble f e r t i l i z e r such as ammonium n i t r a t e on these s i t e s . I t was hypothesized that microsite differences i n nutrient a v a i l a b i l i t y lead to s i g n i f i c a n t differences i n post-release height growth within a s i t e . Release growth gradually declines on microsites with low nutrient a v a i l a b i l i t y . The rate of decline i s l i k e l y related to the size of i n t e r n a l tree nutrient reserves and the nutrient c a p i t a l of the rooting zone. 99 Height and age at release and competition did not explain a s i g n i -f i c a n t proportion of height growth v a r i a t i o n . Study of the e f f e c t of genetic v a r i a t i o n and microsite differences i n moisture a v a i l a b i l i t y were beyond the scope of t h i s t h e s i s . 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Ph.D. Thesis, Faculty of Forestry, Univ. of British Columbia, Vancouver, B.C. Ziegler, H. 1961. Wasserumsatz and Stoffbewegungun Fortschr. d. Bot. 23: 191-205. Zottl, H.W. 1975. Diagnosis of nutritional disturbances in forest stands. In Forest Fertilization, F i f t h IUFR0 Conference. Zinke, P.J. 1963. Tree analysis to determine nutrient status. Pages 30-44. In Proc. Fourth Cal. Forest & Soil F e r t i l i t y Conf. Soil Improvement Comm., Calif. Fert. Assoc., Redding, California. Zwickel, F.C. 1977. Local variations in the time of breeding of female blue grouse. The Condor. 79: 185-191. 121 APPENDIX A Off-site Hypothesis A joint f i e l d trip to the problem amabilis f i r stands in Tree Farm License No. 2 was made by Dr. Kimmins1^ and Dr. Klinka 1^ i n April 1977. After this f i e l d t r i p , Klinka (1977a) hypothesized that amabilis f i r was off-site as a commercial tree species in the lower elevations (below 750 m) of the wet subzone of the Coastal Western Hemlock Zone (CWHb). This off-site hypothesis was generally accepted by many industry, government, and university foresters as the most likely explanation of variation in height growth along elevation or moisture gradients. The major portion of the probelm area li e s between 460 and 1000 m in the CWHb subzone (Klinka 1977a). Forest sites in this subzone should receive enough precipitation to support good amabilis f i r growth (Krajina 1969). However, when Klinka compared mean precipitation data for the CWHb subzone (Krajina 1969) and predicted climatic data 2 0 for 760 m a.s.l. in the study area (the mean elevation of the problem amabilis f i r stands), he found that the predicted annual precipitation of 1535 mm was much lower than the 1900 mm reported by Krajina (1969) for the drier parts of the CWHb subzone. Faculty of Forestry, University of British Columbia. 'Research Pedologist, B.C. Ministry of Forests. 'The predicted climatic data was provided by Mr. R. Chilton, B.C. Ministry of Environment, Victoria, B.C. 12 2 Cold air drainage or higher than average snowfall might ameliorate the lower slope climate somewhat for amabilis f i r by lowering tempera-tures, increasing humidity, and shortening the growing season, thereby, increasing the effectiveness of the available water supply. 123 APPENDIX B Comment on Ca, Mg, and K Analysis Because of time limitations, Ca, Mg, and K concentrations were measured only for the last ( f a l l ) sampling date. Caro's acid digest as described by Lindner and Harley (1942) has replaced dry-ashing i n many labs for routine f o l i a r analysis of N, P, Ca, Mg, and K. This wet digestion technique i s not only less time-consuming but also tends to give less variable results for Ca, Mg, and K compared to dry ashing 2 1. Using a Caro's acid digest would have probably allowed seasonal analysis of Ca, Mg, and K. However, dry ashing was the standard technique i n the forest ecology lab at the time of the study. Equipment for Caro's acid digestion was not available. Pers. comm. from Dr. P. Pang, Canadian Forest Service, Victoria, B.C. and Mrs. B. Hermann, Pacific Soils Analysis Ltd., Vancouver, B.C., November, 1981. 

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