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Tomentosus root rot of white spruce in central British Columbia 1984

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TOMENTOSUS ROOT ROT OF WHITE SPRUCE IN CENTRAL BRITISH COLUMBIA by HADRIAN MERLER B.Sc, The University Of B r i t i s h Columbia, 1982 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department Of Forestry We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May 1984 © Hadrian Merler, 1984 In presenting t h i s thesis in p a r t i a l fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t 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 or her representatives. It i s understood that copying or publication of this thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Forestry The University of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: 24 August 1984 i i Abstract Root disease in 50-70 year-old f u l l y stocked white spruce stands in central B r i t i s h Columbia was investigated in two fashions. The f i r s t method was done by root excavation; to establish the identi t y of the causal organism, to investigate the etiology , and assess the damage caused by the disease. The second method involved, a survey of six 1.2 ha stands in order to estimate the incidence of the disease. Polyporus tomentosus Fr. was the only pathogen involved. Infection of spruce trees resulted when roots contacted previously existing inoculum. Although tree species other than spruce were in contact with infected roots, only spruce was infected by the root rot. No consistent crown symptoms were apparent. A complex with the root weevil Hylobius warreni Wood was evident. Results from the survey estimated that 28.4% of the area investigated was occupied by diseased trees. Of these 22.6% had butt rot, and for whole stands, 1% of the standing trees were windthrown in one season as a result of disease. Diseased trees suffered a 20% reduction of basal area increment. It was not possible to measure the mortality caused by the fungus. i i i Table of Contents Abstract i i L i s t of Tables iv L i s t of Figures v Acknowledgement v i Chapter I INTRODUCTION 1 Chapter II A REVIEW OF THE LITERATURE 3 Chapter III METHODS 11 1. SELECTION OF EXPERIMENTAL AREAS 11 2. PLOT SELECTION 13 3. EXPERIMENTAL PROCEDURES 14 4. INCIDENCE SURVEY 16 Chapter IV RESULTS AND DISCUSSION .18 1. IDENTIFICATION OF PATHOGENS 18 2. CROWN SYMPTOM DEVELOPMENT 19 3. INFECTION AND SPREAD 22 4. SUSCEPTIBILITY OF CONIFER SPECIES 27 5. IMPACT OF TOMENTOSUS ROOT ROT 31 5. 1 Survey 31 5.2 Estimation Of Losses 32 5.2. 1 Butt Rot 32 5.2.2 Increment Loss 34 5.2.3 Mortality And Windthrow 40 6. ECOLOGICAL CLASSIFICATION 43 Chapter V CONCLUSIONS 46 LITERATURE CITED 48 APPENDIX A - ECOLOGICAL SITE CLASSIFICATION AND VEGETATION LISTINGS 52 APPENDIX B - STEM MAPS OF THE TEN STUDY PLOTS 57 iv APPENDIX C - RELATIONSHIP BETWEEN TREE SIZE AND BASAL AREA INCREMENT 68 V L i s t of Tables 1. Frequency of i s o l a t i o n of P. tomentosus as a percent of a l l fungal i s o l a t i o n s in Canadian decay studies 5 2. Average disease rating (scale: 1-6) of seedlings inoculated with Polyporus tomentosus and the variety c i r c i n a t u s (from Whitney and Bohaychuk 1976) 6 3. Average age, area, stocking, and volume of spruce found in the plot study 14 4. Incidence of tomentosus root disease for a l l l i v i n g tree species examined 29 5. Incidence of Polyporus tomentosus root rot in white spruce within the Prince George survey area (Figure 1). 31 6. Number of white spruce by age class in a l l plots, showing various disease symptoms 33 7. Equations of the regression l i n e s for the logarithm of basal area versus the logarithm of diameter squared times height and resulting test for common slope 36 8. Analysis of covariance table based on the natural logarithm of basal area increment, using the natural logarithm of D.B.H. squared x Height as covariate (confidence = 0.95) 36 9. Natural logarithms of 5 year basal area increment for healthy and diseased trees 37 10. Total number of spruce trees investigated, with the percentage infected and percentage dead 40 11. Percent of the t o t a l number of spruce trees by age class 42 12. Percent of t o t a l spruce trees by diameter class 43 v i L i s t of Figures 1. Location of the study plots ( • ) (Table 3) and the incidence survey stands ( ° ) (Table 5 ) 12 2. A blown down spruce at the center of plot B4. 13 3. F r u i t i n g structure of Polyporus tomentosus emerging from a 4 cm diameter stump of a destroyed white spruce. ...19 4. F r u i t i n g structure of Polyporus tomentosus at the base, of a white spruce 19 5. Exposed roots of white spruce. Note the t y p i c a l white pocket appearance of a decayed root at the center. ...19 6. A windthrown white spruce due to complete structural and functional f a i l u r e of the roots. Red-stain appears in the f i r s t notch in the log 22 7. Root grafting of spruce roots, and red stain from Polyporus tomentosus 23 8. Exposed root c o l l a r of white spruce. Stem occurs at l e f t , an adult weevil i s at the center of the root, and a pupal chamber l i e s at bottom l e f t (arrows) 26 9. Mean basal area increment over time for healthy white spruce, and trees infected with Polyporus tomentosus. 38 10. S o i l p i t from Jerry Creek with well drained sandy loams. The s o i l p r o f i l e had a thin organic layer, with an eluviated Ae zone, and an enriched Bf layer 43 v i i Acknowledgement I would l i k e to thank Associate Professor Dr. B.J. van der Kamp for both his guidance and contributions to this study. Without his help t h i s work would not have been completed. I would l i k e to thank Dr. D.J. Morrison, whose suggestions drew my interest to t h i s study, and to Dr. R. Whitney whose research in Polyporus tomentosus inspires, and whose personal attentions encouraged. I would also l i k e to thank the staff of the B r i t i s h Columbia Ministry of Forests for their cooperation in aiding me in the f i e l d work. In addition I would l i k e to thank my wife, Marilyn, whose endurance I always marvel at. This project was funded by a contract with the Canadian Forestry. Service (Environment Canada) under the Program for Research by U n i v e r s i t i e s in Forestry (PRUF). Most of the material discussed in this thesis is also presented in the f i n a l report to the Canadian Forestry Service e n t i t l e d "Root disease of spruce in central B r i t i s h Columbia" which was submitted to the C.F.S. in March 1984 as required by the PRUF contract. 1 I. INTRODUCTION It is well known that the mature spruce (Picea glauca (Moench) Voss, P. engelmani i Parry, and their hybrids) stands of central B r i t i s h Columbia are affected by a number of butt and root decays. Among the common pathogens involved are Polyporus tomentosus Fr., Armiliar ia mellea (Fr.) Kumm., Polyporus schweinitzi i Fr., Polyporus sulphureus B u l l , ex Fr., and Flammula a l n i c o l a Fr.. In addition to butt rot, these fungi may also k i l l standing mature spruce, or lead to windthrow of l i v i n g trees. There i s l i t t l e doubt that endemic populations of spruce bark beetle (Dendroctonus rufipennis Kirby) survive largely on trees weakened or windthrown as a result of these diseases. In mature spruce forests these pathogens lead to a steady decline in volume and value. L i t t l e i s known about these diseases in immature stands. Studies in Saskatchewan, Ontario and Quebec (Whitney 1962, Whitney 1977a, Gosselin 1944) have shown that immature spruce stands can also be affected. There i s only fragmentary information on these diseases in immature stands in central B r i t i s h Columbia. There is a tendency of forest managers to hold the be l i e f that spruce stands w i l l remain free of root and butt rots u n t i l after rotation age. This may be due to the i n a b i l i t y to recognize root disease damage that does not result in obvious group dying. Infections in immature stands are t y p i c a l l y overlooked. There are some reports of extensive infection by P. tomentosus at an early age. 2 The matter is of some importance. The last decades have seen the i n i t i a t i o n of a large planting program in spruce. The stands so created w i l l be rather d i f f e r e n t than most natural stands. Natural stands have usually arisen following a major disturbance by f i r e or insects. In such cases the s i t e i s commonly occupied by mixed stands with a substantial component of aspen, willow and various shrub species. Eventually spruce outgrows and outlives these species. The resulting spruce stands t y p i c a l l y show considerable v a r i a t i o n in age, and few of them are pure. Natural spruce regeneration therefore involves a regeneration lag during which the s i t e i s largely occupied by hardwoods. This i s of some importance to root disease because the lag means that the spruce root pathogens w i l l die out, at least in the smaller roots, before spruce roots of the new generation can come in contact with them. Spruce stands created by planting shortly after logging w i l l occupy a s i t e much more quickly. One may expect therefore more root rot problems, and also that such problems w i l l show up e a r l i e r . The objectives of the present study are to determine the identity and frequency of root pathogens of immature spruce stands, to elucidate the mode of infection and spread, to describe disease symptoms, to estimate the effect of disease on growth and y i e l d , to design and conduct a survey to estimate the incidence of root disease, and to forecast future losses to the standing crop. 3 II. A REVIEW OF THE LITERATURE Most of the information on host-parasite interaction of Polyporus tomentosus on spruce i s gained from studies done by Whitney (1960,1961,1962,1964/ 1972, 1977b) in Saskatchewan and northwestern Ontario. Other studies (Denyer and Riley 1953, Gosselin 1944, Lachance 1978, Solovieff 1927) deal with losses of tree biomass and wood value both in the natural forest, and in plantations. The pathogen does not necessarily behave in the same way in d i f f e r e n t parts of the boreal forest. Both the etiology and disease impacts vary from place to place. The binomial Polyporus tomentosus Fr. s i g n i f i e s the polypore fungus with straight setae. This corresponds with nomenclature proposed by Haddow (1941) in which P. tomentosus var. c i r c i n a t u s Fr. represents the fungus with curved setae. Gosselin (1944) pointed out, however, that P. tomentosus var. c i r c i n a t u s has a duplex hymenium, and that both straight and hooked setae can occur on the same f r u c t i f i c a t i o n . This was observed by Whitney (1960) as well. Polyporus tomentosus was the only fungus found during t h i s study. None of the f r u i t i n g bodies examined contained hooked setae. The fungus has been i d e n t i f i e d from centers of tree death, primarily due to windthrow, at various locations around the northern hemisphere. The fungus was implicated in studies from western Russia (Solovieff 1927), West Poland (Domanski and Dzieciolowski 1955), North Carolina (Hepting and Downs 1944), northern Idaho (Hubert 1929), and across the Canadian Boreal forest (Whitney 1977b). 4 Twenty-one species and two v a r i e t i e s of conifers are reported as host trees to t h i s pathogen in Canada (Whitney 1978a). It causes root rot in at least 31 commercial tree species (Whitney 1977a). Table 1 summarizes the r e l a t i v e frequency with which P. tomentosus has been i s o l a t e d r e l a t i v e to other decay organisms, from various Canadian conifers in studies dealing with stem decay. Si g n i f i c a n t losses were found only in white and black spruce and possibly in lodgepole pine. A study done by Whitney (1962) in Saskatchewan showed that 19.7% of a l l the spruce trees examined carried some P. tomentosus in f e c t i o n . Host s p e c i f i c i t i y and pathogenicity of both Polyporus tomentosus and P. tomentosus var. c i r c i n a t u s was evaluated for eleven species of conifer seedlings (Whitney and Bohaychuk 1976). Isolates of both fungal v a r i e t i e s were collected from sporophores on spruce near Candle Lake, Saskatchewan. Polyporus tomentosus caused s i g n i f i c a n t l y higher disease ratings than Polyporus tomentosus var. c i r c i n a t u s . The highest disease rating was obtained on ponderosa pine, followed by lodgepole pine, white spruce, and eight other conifer species (Table 2). The test was conducted using freshly germinated seeds. Germinants were rated on a six point scale, the value "one" being the least infected and "six" being the most heavily infected. E a r l i e r tests on three of these species, black spruce, white spruce, and tamarack (Whitney 1964) showed that semi-mature black spruce i s more heavily attacked than the other two conifers. 5 Table 1 - Frequency of i s o l a t i o n of P. tomentosus as a percent of a l l fungal i s o l a t i o n s in Canadian decay studies. Spec ies Locat ion % of Total Infect ions Reference Abies amabi1is B r i t i s h (Dougl.) Forb. Columbia Abies balsamea Eastern (L.) M i l l . Picea glauca (Moench) Voss Picea mariana Canada Ontar io Alberta Ontar io (Mill.) B.S.P. Ontario Pinus contorta Dougl. var. Alberta l a t i f o l i a Engelm. Pinus strobus L. Ontario Pseudotsuga menziesii (Mirb.) Franco B.C. Tsuga heterophylla (Raf) Sarg B.C. B.C. 1.0% Buckland et al^_ 1949 0.5% Basham et a l . 1953 1.7% Whitney 1978b 85.0% Denyer and Riley 1953 16.2% Whitney 1978b 17.9% Whitney 1978b 14.0% Denyer and Riley 1953 1.3% White 1953 0.3% Thomas and Thomas 1954 1.4% Buckland et a l . 1949 0.8% Foster and Foster 1951 6 Table 2 - Average disease rating (scale: 1-6) of seedlings inoculated with Polyporus tomentosus and the variety c i r c i n a t u s (from Whitney and Bohaychuk 1976) Tree Species P. tomentosus P. tomentosus var. c i r c i n a t u s A l l : Ponderosa pine 4.4 3.2 3.8 Lodgepole pine 4. 1 3.1 3.6 White spruce 3.8 2.8 3.3 Black spruce 3.9 2.2 3.0 Tamarack 3.2 2.6 2.9 Norway spruce 3.0 2.6 2.8 Scots pine 3.6 2.0 2.8 Blue spruce 3. 1 2.0 2.6 Douglas-f i r 2.7 2.4 2.6 Red spruce 2.4 1 .7 2. 1 Eastern white pine 2.5 2.0 2.1 AVERAGE 3.3 2.4 2.9 The fungus in culture reaches maximum growth at pH 4.5 and does not grow at a l l at a pH greater than 7.0. Whitney (1960) observed that the pH of diseased tissue was considerably lower than that of healthy tissue. Studies by Whitney (1962) showed that the fungus was able to a l t e r i t s environment by decreasing the pH of infected tissue. This means that fungal growth in the roots i s not limited by pH. Fungal survival in the s o i l , 7 however, would be affected by pH. Van Groenewoud (1956) observed that the pH of the s o i l in areas severely affected by the root rot were as low as 4.5, while wherever the pH of the top s o i l was seven or higher, the disease did not occur in any damaging amounts. Using both a r t i f i c i a l and natural media, Whitney (i960) showed that P. tomentosus prefered a rather low temperature for growth. It grew best from 17 to 22 degrees Celcius, but grew well at lower temperatures, and had some growth at 0 degrees Celcius. Penetration of Polyporus tomentosus into healthy tree roots from basidiospores has not been observed. The spread of the fungus is primarily by tree to tree contact. Basidiospore infection has only been demonstrated in deep wounds (5 cm deep) of root wood. Inoculations of P. tomentosus into the roots of white spruce were only successful in instances where a wound of some sort was made on the host (Whitney 1962). Inoculation of fresh stumps was not successful (Whitney 1966). Studies by Whitney (1962,1965) showed that the mycelium does not necessarily invade through root t i p s i n i t i a l l y . The exact point of entry into the host by the pathogen has not been determined. Death of the host tissue begins at the epidermal and c o r t i c a l c e l l s of the root. H i s t o l o g i c a l examinations of infected roots showed that the cortex c e l l s are invaded both int e r - and i n t r a c e l l u l a r l y . The pericycle and the primary xylem are also infected, but to a lesser degree. Badly diseased but s t i l l l i v i n g seedlings seldom had hyphae inside the endodermis. 8 When the cortex tissue was f u l l y invaded, the ultimate death of the root ensued. The fungus advances in a tree primarily through the heartwood, but can advance in and k i l l l i v i n g bark p a r t i c u l a r l y in white and black spruce. Whitney (1962) stated, " t h i s i s rare for heartrot fungi, which o r d i n a r i l y are not considered to be truly p a r a s i t i c . " The root decay process occurs f i r s t through small branch roots. It spreads in the secondary xylem causing a reddish brown stain, followed by a white pocket formation in the later stages. Lignin i s decomposed by the fungus, leaving spots of ce l l u l o s e at intervals, resulting in the white pocket appearance. In advanced stages of attack, large roots are girdled following invasion of sapwood and bark. Eventually the root c o l l a r i s girdled, at which time the tree dies (Whitney 1962). Yellowish white flakes of mycelium form beneath the outer bark scales and the fungus transmits to healthy roots upon contact (Whitney 1962). A statement made by Whitney (1962) that, "Extensive root decay develops before the above-ground symptoms become apparent" goes largely unheeded by many foresters who tend spruce stands. Instead, recognition of the root disease i s based on more c l a s s i c root rot centers and stand openings. Absence of symptom expression was also described by Whitney (1965) who noted that large parts of the root system were k i l l e d on apparently healthy seedlings. In stands with high incidence of the disease, symptoms would possibly become more evident. Symptoms include excessive branch mortality from the lower part of the crown, 9 shortened height and l a t e r a l increments r e l a t i v e to healthy trees, and general thinning of the crown (Whitney 1977b). On severely infected trees, the needles were observed as being shorter, and having a yellow-green color. The branches bearing these needles were curled at their ends. Resinosus may result from basal bole cankers or sunken areas on the lower part of the tree (Whitney 1962). The estimation of disease impact by remeasurement of diseased plots has only been attempted by Whitney and van Groenewoud (1964) and Lachance (1978). Whitney and van Groenewoud (1964) returned to two natural stands of white spruce after a ten year period. The stands were i n i t i a l l y 38 and 51 years old. In the younger stand, the growth of healthy trees offset the volume losses attributed to mortality. However, in the case of the older stand, basal area had decreased by 24%, healthy trees decreased in numbers by 30%, and dead trees increased by 16%. The average annual rate of growth of P. tomentosus in a r t i f i c i a l l y infected roots was 3.8 cm. The rate in trees examined varied from 0.2 to 15.2 cm per year. Whitney and van Groenwoud (1964) also examined the r a d i a l increment of dead trees. It was shown that the increment did not decrease u n t i l 5-15 years prior to death of the trees. Based on fungal growth rates, however, the trees had to have been infected for 20-30 years before the trees death (Whitney 1962). In a study of plantation spruce in Quebec, Lachance (1978) reported a 27.3% ten year volume loss where Polyporus tomentosus 10 was responsible for two-thirds of the losses, both in frequency and volume. Tunneling by weevil larvae in the roots of examined spruce has been associated with the incidence of root stain and decay (Whitney 1961). The insect has been i d e n t i f i e d as Hylobius warreni Wood. Whitney (1961) stated that, "entry of fungi does not always appear to be d i r e c t l y through the wound (caused by the weevil) but is often through a more d i s t a l part of the root. " Warren's root c o l l a r weevil i s most damaging to Pinus banksiana Lamb., lodgepole pine, and white spruce. It has never been observed on Abies balsamea (L) M i l l . . The l a r v a l stage l a s t s for two years feeding on bark and cambium of the host tree. The f l i g h t l e s s adult can l i v e for four years (Cerezke 1973). Severe damage occurs in trees which are about forty years old. The greatest weevil a c t i v i t y occurs in moist to wet duff conditions, however certain l o c a l factors of stand composition and climate may produce moist conditions suitable to the requirements of these insects, even on sandy well drained s o i l s (Warren 1956). 11 I I I . METHODS Investigation of the disease followed two approaches. The f i r s t was to observe the action of the fungus and the effects on the host in some d e t a i l . Areas of severe disease were selected in order to e f f i c i e n t l y study pathogen ident i t y , disease development and spread, and the effects of infection on growth and y i e l d . The second approach involved a survey of randomly selected spruce stands. This survey provided a measure of incidence in stands which were selected on the basis of cover type. 1. SELECTION OF EXPERIMENTAL AREAS Several objectives were met in selecting representative spruce stands. The stands had to be immature (50-70 years old), even-aged, predominatly spruce, and f u l l y stocked. This enabled observations of the disease in i t s early stages. Such stands are also representative of current restocked spruce forests. Major amounts of white spruce are found in the eastern d i s t r i c t of the Prince George Forest Region. Candidate stands were a l l found within the Sub-Boreal Spruce " J " subzone (SBS J ) . In t h i s study, a l l investigations took place within areas contained in the SBS J/01, the Mesic Oak Fern association, and the SBS J/06, the Submesic Queen's Cup subassociation. Three stands were selected as matching the above c r i t e r i a , one at the Bowron River, one in the Jerry Creek drainage, and one in the Hixon Forest D i s t r i c t (Figure 1). Selection of the Jerry Creek stand was aided by consulting f i r e h i s t o r i e s from 12 the past seventy years. A l l three stands showed evidence of fast regeneration of spruce following f i r e . "Nukto Laie " \Swemp )L. \ Figure 1 - Location of the study plots ( • ) (Table 3) and the incidence survey stands ( ° ) (Table 5 ). 1 3 2 . P L O T S E L E C T I O N T h e o r i g i n a l i n t e n t w a s t o e s t a b l i s h t e n p l o t s , e a c h e n c o m p a s s i n g a s i n g l e d i s t i n c t d i s e a s e c e n t e r a n d e x t e n d i n g t o s u r r o u n d i n g h e a l t h y t r e e s . T h i s p r o v e d n o t t o b e p o s s i b l e b e c a u s e t h e d i s e a s e w a s n o t o r g a n i z e d i n d i s t i n c t r e c o g n i z a b l e c e n t e r s . I n s t e a d e a c h p l o t w a s c e n t e r e d o n a n o b v i o u s l y d i s e a s e d t r e e s u c h a s a r e c e n t i n f e c t e d w i n d t h r o w ( f i g u r e 2 ) , a t r e e w i t h s e v e r e c r o w n s y m p t o m s o r a s t a n d o p e n i n g c a u s e d b y r o o t d i s e a s e . E a c h p l o t w a s t h e n e x t e n d e d t o e n c o m p a s s a b o u t 0 . 0 1 h a ( a b o u t 3 0 t r e e s ) a n d a l l t r e e s o n t h e p l o t w e r e e x a m i n e d a s d e s c r i b e d b e l o w . P l o t s 1 - 6 w e r e l o c a t e d a t t h e B o w r o n R i v e r , p l o t s 7 - 9 w e r e l o c a t e d a t J e r r y C r e e k , a n d p l o t t e n a t H i x o n . F i g u r e 2 - A b l o w n d o w n s p r u c e a t t h e c e n t e r o f p l o t B 4 . 14 Table 3 shows the area, stocking, and volume of each of the ten pl o t s . The volume was based on Ministry of Forest volume equations for in t e r i o r spruce (B.C. M.O.F. 1976). Table 3 - Average age, area, stocking, and volume of spruce found in the plot study PLOT CODE Age Area (sq. m) Stocking (stems per ha.) Volume (cub m per ha.) B1 52 1 1 0 1610 240 B2 57 1 60 1820 238 B3 56 180 1 500 260 B4 53 290 1315 260 DC 1 62 80 2500 368 DC 2 58 1 20 1605 260 DC 3 54 240 1595 200 HIXON 56 250 1 1 60 1 70 J1 55 1 30 760 1 45 J2 64 280 640 1 06 3. EXPERIMENTAL PROCEDURES The location of a l l standing trees, l i v i n g or dead, within the plot was mapped, using a plane table. Wind-thrown trees were also mapped. A vegetative description was prepared and a s o i l p i t dug in order to place the three stands within the ecological c l a s s i f i c a t i o n scheme developed by Krajina (1969). For each tree the following were recorded: species; height; 1 5 diameter at breast height (1.3 m); age as determined from an increment core at 0.3m; and crown c l a s s . The roots of each tree on the plot were exposed by hand to examine how the fungus infected and spread through host tissue. Root exposure also allowed investigation of possible contact or grafts with other trees. Fungal presence in tree xylem was noted by a red-brown stain, followed in later stages of decay by a yellow or white pocket rot. A probe was made using an increment borer and an axe to look for these c h a r a c t e r i s t i c s . Three locations on each tree were examined; the exposed roots a meter from the root c o l l a r , the root c o l l a r , and breast height. A three number scale re l a t i n g the presence of decay symptoms was made for each point examined on the tree; one for no disease, two for stain, and three for rot. This resulted in a three number code for each tree giving a r e l a t i v e measure of disease. This code accompanied observations made on any other tree symptoms. Each standing dead and windthrown tree was thoroughly dissected to look for Polyporus tomentosus. From each of the ten plots at least ten samples of stained and decayed root or bole material was gathered in order to culture the causal organism. Cultures were also taken from unstained wood samples. Isolations were made using a s t e r i l e technique on 2% malt agar and t e t r a c y c l i n e p e t r i plates. Later in the summer, fungal f r u i t i n g bodies were coll e c t e d to aid in i d e n t i f i c a t i o n of the pathogens present. An increment core was taken from each tree at breast 16 height. The core was accepted only i f i t included the p i t h . Each core was stored in a p l a s t i c straw and retained for later measurements. Radial increment was measured in groups of five years, s t a r t i n g from the. 1982 latewood (1983 ring growth was not yet complete) back to the pith using an Addo-x tree ring counter. Wood moisture was standardized by soaking the core in water for an hour prior to measurement. Covariate analysis was used to test for s i g n i f i c a n t differences in ra d i a l increment between the disease intensity classes. Diameter squared times height was the covariate. 4. INCIDENCE SURVEY A survey of the incidence of root disease was conducted in six immature spruce stands. Candidate stands were located on the Forest D i s t r i c t forest cover maps. Accepting stands in which to do the survey was based on several c r i t e r i a . The stands had to be r e l a t i v e l y even-aged (50-70 year old or age class two), f u l l y stocked, and predominantly spruce. Stands intermixed with d i s t i n c t clumps of hardwood species were rejected since t h i s would indicate a disruption of susceptible tissue. Each candidate stand was v i s i t e d to see i f the above c r i t e r i a were met. The basic survey design followed that developed by Blooomberg (1980) for Phellinus weiri i (Murr.) Gilbertson. A baseline of 200m was established within each stand. Two grids of three regularly spaced transect l i n e s were then established, and the t o t a l length of transect l i n e f a l l i n g within infected areas was determined. The actual infected area was i d e n t i f i e d by taking increment core borings of roots of 1 7 trees situated within a given distance of the transect. This distance varied from 0.5 to 1.5 meters either side of the transect l i n e . This distance changed r e l a t i v e to stand density in that stands with greater than 1500 stems per hectare had one meter wide transect l i n e s , stands with 1000 to 1500 stems per hectare had two meter wide transect l i n e s , and stands with less than 1000 stems per hectare had three meter wide transect l i n e s . Presence of red stain or decay in the increment core was taken to indicate the presence of Polyporus tomentosus. This was also v e r i f i e d by the culturing of ten trees per survey area. The boundary between healthy and diseased areas along the transect l i n e was defined as the point midway between the projection of adjacent healthy and diseased trees. 18 IV. RESULTS AND DISCUSSION 1. IDENTIFICATION OF PATHOGENS A t o t a l of 190 attempts to iso l a t e root disease pathogens were made, including at least ten from each of the research plots. One hundred and forty of these yielded. Polyporus tomentosus cultures. The remainder were largely contaminated, but ten yielded Pleurocolla compressa (E&E) Diehl, a non- pathogenic fungus known to inhabit wood after other decay fungi. Isolation attempts were made from both red stained incipient decay and advanced decay. Polyporus tomentosus was the only root pathogen iso l a t e d . I d e n t i f i c a t i o n was based on Nobles' key (Nobles 1948), of c u l t u r a l c h a r a c t e r i s t i c s and confirmed by Dr. Whitney. 1 In addition, t y p i c a l P. tomentosus sporophores were observed on several of the plots in August. Many of them were produced on disturbed and exposed infected roots. Such sporophores were commonly s t i p i t a t e rather than shelved (Figures 3 and 4). The identity of these f r u i t i n g bodies was also confirmed as being P. tomentosus by Dr. J. Hopkins. 2 Polyporus tomentosus was the only root p a r a s i t i z i n g fungus found during th i s study. A l l the f r u i t i n g bodies had straight setae only. 1 Dr. R.D. Whitney of the Canadian Forestry Service, Sault Ste. Marie, Ontario, v i s i t e d the study s i t e s during the summer of 1983. 2 Dr. Hopkins of the P a c i f i c Forest Research Center, V i c t o r i a , i d e n t i f i e d a f r u i t i n g body c o l l e c t e d on s i t e . 1 9 Polyporus tomentosus was not isolated from unstained normal wood. I n i t i a l l y , invasion by P. tomentosus produces a l i g h t red stain. As decay progresses, the affected wood turns l i g h t yellow-brown. Shortly thereafter, t y p i c a l small pockets appear, f i l l e d with white material, a mixture of hyphae and the remains of the decayed wood (Figure 5). It is concluded that Polyporus tomentosus i s the dominant root pathogen of immature spruce. The other known root and butt rot fungi of spruce may not become common u n t i l a l a t e r age. A l t e r n a t i v e l y , other fungi may be r e s t r i c t e d to ecological conditions not encountered in this study. 2. CROWN SYMPTOM DEVELOPMENT Diseased trees did not show consistent crown symptoms that could be related to the extent of infection in roots and boles. Some trees were apparently k i l l e d by P. tomentosus, but most of these were smaller than the average tree and found in the understory. The actual cause of death in such cases was probably a combination of natural suppression and root disease. Among trees with crowns in the main canopy, a few diseased individuals showed t y p i c a l root rot crown symptoms of reduced height growth, chlorosis, and decrease in needle longevity. However others with equally severe or worse deterioration of the root system exhibited no obvious crown symptoms. On the whole, diseased trees with obvious crown symptoms were much less common than diseased trees with normal crowns. No attempts were made to quantify these observations, partly because of the d i f f i c u l t y of rating crown,symptoms objectively. 2 0 F i g u r e 3 - F r u i t i n g s t r u c t u r e o f P o l y p o r u s t o m e n t o s u s e m e r g i n g f r o m a 4 c m d i a m e t e r s t u m p o f a d e s t r o y e d w h i t e s p r u c e . F i g u r e 4 - F r u i t i n g s t r u c t u r e o f P o l y p o r u s t o m e n t o s u s a t t h e b a s e o f a w h i t e s p r u c e . 2 1 F i g u r e 5 - E x p o s e d r o o t s o f w h i t e s p r u c e . N o t e t h e t y p i c a l w h i t e p o c k e t a p p e a r a n c e o f a d e c a y e d r o o t a t t h e c e n t e r . I t s e e m s t h a t m o s t i n f e c t e d t r e e s p a s s t h r o u g h a l o n g p e r i o d d u r i n g w h i c h t h e p a t h o g e n i s a c t i v e i n t h e r o o t s y s t e m w h i l e t h e c r o w n r e m a i n s r e l a t i v e l y u n a f f e c t e d . I t f o l l o w s t h a t t h e r a t e o f m o r t a l i t y , i . e . t h e r a t e a t w h i c h s t a n d i n g t r e e s d i e , i s l o w c o m p a r e d t o t h e t o t a l n u m b e r o f i n f e c t e d t r e e s . I n a d d i t i o n , i n f e c t e d t r e e s a r e r e m o v e d f r o m t h e s t a n d b y w i n d t h r o w , o f t e n b e f o r e a n y c r o w n s y m p t o m s h a v e d e v e l o p e d ( F i g u r e 6). T r e e s w e r e o b s e r v e d w i t h e x t e n s i v e , a d v a n c e d d e c a y i n t h e r o o t s y s t e m a f f e c t i n g a l l m a j o r s t r u c t u r a l r o o t s , b u t 22 without apparent crown symptoms. Such trees are prime candidates for windthrow. It i s also clear that crown symptoms give an unreliable indication of the extent of disease in a stand. Hence surveys of the incidence of P. tomentosus require examination of the major roots for the stain and decay. At best, detection of the disease by crown symptomology would result in a conservative measure of the actual area occupied by P. tomentosus 3. INFECTION AND SPREAD On each of the ten plots, several root systems were completely excavated in order to determine the manner of infection and spread. The following pathway i s proposed. I n i t i a l infection occurs via contact between infected and healthy root systems (Figure 7). In most cases such contacts involve small roots (<2 cm diameter). I n i t i a l l y the pathogen grows ectotrophically on the surface of small roots. Penetration of bark and cambium occurs soon aft e r , and as the mycelium on the root surface grows proximally, i t continually i n i t i a t e s new points of invasion of bark and wood. The s i t e s of penetration show as small patches (<1 cm diameter) of dead brown bark. These patches grow and amalgamate u n t i l the root i s girdled and k i l l e d . As the mycelium advances proximally the root increases in s i z e . At some point, the mycelium can apparently no longer penetrate healthy bark. Instead i t advances in the xylem, t y p i c a l l y at or near the center of the root, while the outer several xylem rings remain free of disease. At the point at which t h i s switch occurs the 2 3 F i g u r e 6 - A w i n d t h r o w n w h i t e s p r u c e d u e t o c o m p l e t e s t r u c t u r a l a n d f u n c t i o n a l f a i l u r e o f t h e r o o t s . R e d - s t a i n a p p e a r s i n t h e f i r s t n o t c h i n t h e l o g . r o o t i s a b o u t 5 c m i n d i a m e t e r . T h i s m a y a l s o b e t h e p o i n t a t w h i c h t h e p r i m a r y p e r i d e r m i s r e p l a c e d b y a s e c o n d a r y p e r i d e r m . I t i s n o t c l e a r w h e t h e r t h e p a t h o g e n c a n a l s o m a i n t a i n e c t o t r o p h i c g r o w t h o n l a r g e r r o o t s a n d a l o n g t h e b a s e o f t h e t r e e i n t h e a b s e n c e o f t h e a b i l i t y t o p e n e t r a t e a n d d e r i v e e n e r g y f r o m l i v i n g h o s t t i s s u e s . T h e r e a r e r a r e o c c u r r e n c e s o f s m a l l (1 c m d i a m e t e r ) n e c r o t i c p a t c h e s i n t o t h e c a m b i u m , n e a r t h e r o o t c o l l a r . P o l y p o r u s t o m e n t o s u s w a s i s o l a t e d f r o m s u c h a r e a s , b u t s u c h p a t c h e s d o n o t a p p e a r t o s p r e a d o r e n l a r g e . 2 4 F i g u r e 7 - R o o t g r a f t i n g o f s p r u c e r o o t s , a n d r e d s t a i n f r o m P o l y p o r u s t o m e n t o s u s . T h e h o s t c o m m o n l y r e s p o n d s t o a t t a c k b y p r o d u c i n g a d v e n t i t i o u s r o o t s f r o m t h e d i s t a l s u r v i v i n g e n d o f l a r g e d i s e a s e d r o o t s . S u c h a d v e n t i t i o u s r o o t s a r e s u s c e p t i b l e t o i n v a s i o n b y t h e p a r a s i t e a n d a r e r a p i d l y k i l l e d , b u t t h e h o s t c o n t i n u e s t o r e p l a c e t h e m . I t m a y b e t h a t t h e r e d u c t i o n i n i n c r e m e n t o f d i s e a s e d t r e e s , a s d e m o n s t r a t e d b e l o w , a r i s e s b e c a u s e t h e h o s t t r e e i s f o r c e d t o s p e n d a l a r g e p a r t o f i t s e n e r g y t o p r o d u c e n e w r o o t s r a t h e r t h a n i n b o l e w o o d . I t i s n o t k n o w n w h e t h e r t h e p a t h o g e n c a n a l s o s p r e a d t h r o u g h s o i l , a n d i f s o , h o w f a r . W h i t n e y ( 1 9 6 2 ) c o u l d n o t b a i t P . t o m e n t o s u s u s i n g t h e W a r c u p n o r s c r e e n e d i m m e r s i o n p l a t e 25 techniques. However, the absence of decay f l o r a may be due to the l i m i t a t i o n s of the i s o l a t i n g technique i t s e l f . On one of the plots, a f a i r y ring of P. tomentosus f r u i t i n g bodies was observed. This could only result from a continuous ring of l i v i n g hyphae. The fungus could be growing through the s o i l (in this case, the organic horizon) able to attack roots at random locations, and s t i l l acquire energy to form f r u i t i n g structures. This is in contrast with a root disease such as Phellinus w e i r i i which i s r e s t r i c t e d to ectotrophic growth on roots in the mineral s o i l and t o t a l l y r e l i e s on root contact of the host for spread. It may also be that in the case of the f a i r y ring, the fungus is l i v i n g on a dense mat of fine spruce roots in the organic horizion rather than in the s o i l . These roots then would be quickly produced and consumed, representing a f a i r energy expenditure by the host. Once the parasite has entered a major root in the fashion described above, i t continues to grow, eventually developing into a column of decay that extends from the root into the base of the bole. Decay and stain caused by the fungus was observed up to fiv e meters above ground l e v e l . It appears that the fungus is able to grow i n t e r n a l l y into the xylem of uninfected roots of diseased trees, and when i t reaches a point where root diameter has decreased to a few centimeters, i t reemerges and i n i t i a t e s ectotrophic growth. At the point of emergence the fungus appears as small white pustules erupting from under the root bark. Every tree attacked by P. tomentosus was also affected by 26 the root c o l l a r weevil, (Hylobius warreni) (Figure 8). Attacks on the roots and the c o l l a r of the spruce host were a l l current, with signs of previous infestations. The weevil also occurred on healthy trees, but at a lower frequency. Twenty of the 125 healthy spruce trees had weevils present. Either the fungus was taking the opportunity to attack stressed roots due to weevil a c t i v i t y , or the weevil sensed stressed roots due to the fungal disease. Weevil g a l l e r i e s were largely r e s t r i c t e d to the outer bark. In almost a l l cases, the cambium d i r e c t l y underneath such g a l l e r i e s remained a l i v e . Even in instances where th i s was not the case, there were several rings of uninfected xylem tissue separating the column of P. tomentosus decay and any stain in xylem associated with the weevil wound. It i s concluded that the root c o l l a r weevil is a secondary agent that may further weaken the host, but that weevil g a l l e r i e s are not the normal s i t e of i n f e c t i o n . The spruce host normally responds to weevil attack by the production of large amounts of resin, so that the g a l l e r i e s were normally protected by and buried within large masses of resin soaked root bark and s o i l . However, as noted by Haddow (1941), in severe infections, attack through the cambial c e l l s of the roots by the pathogen also causes a copius release of resin. This may be s u f f i c i e n t in a l t e r i n g an otherwise dry si t e to the requirements of the weevil. The resin may also act as an attractant. 2 7 4 . S U S C E P T I B I L I T Y O F C O N I F E R S P E C I E S T a b l e 4 s h o w s t h e a m o u n t o f i n f e c t i o n b y s p e c i e s o b s e r v e d i n t h e t e n p l o t s . O n l y s p r u c e w a s i n f e c t e d . I n s e v e r a l i n s t a n c e s s t e m s a n d r o o t s o f t h e o t h e r s p e c i e s w e r e i n d i r e c t c o n t a c t w i t h i n f e c t e d s p r u c e r o o t s , b u t n o s i g n s o f i n f e c t i o n F i g u r e 8 - E x p o s e d r o o t c o l l a r o f w h i t e s p r u c e . S t e m o c c u r s a t l e f t , a n a d u l t w e e v i l i s a t t h e c e n t e r o f t h e r o o t , a n d a p u p a l c h a m b e r l i e s a t b o t t o m l e f t ( a r r o w s ) . w e r e o b s e r v e d . A l l t h e c o n i f e r s p e c i e s e n c o u n t e r e d i n t h e s e p l o t s h a v e b e e n r e p o r t e d a s h o s t s o f P . t o m e n t o s u s i n B r i t i s h C o l u m b i a ( L o w e 1 9 6 9 ) . W h i t n e y a n d B o h a y c h u k ( 1 9 7 6 ) o n t h e b a s i s o f a t e s t o f s e e d l i n g s , l i s t e d l o d g e p o l e p i n e a m o n g t h e m o s t s u s c e p t i b l e s p e c i e s . 28 The proportion of infected conifers on the ten plots was 170 divided by 346, or 0.491. The probability that the 51 non- spruce l i v i n g conifers escaped infection by chance would be 51 -15 P = (1 - 0.491) = 1.103 escape The hypothesis that a l l conifers were equally infected can be rejected. Different species have d i f f e r e n t rooting habits, and as a result i t may be that root contacts between species are less common than within species. Hence.if P. tomentosus were i n i t i a l l y established on spruce, the probability of further spruce infection would be greater than infection of the other species. If the l i k e l i h o o d of transfer from spruce to non-spruce were very much smaller than that from spruce to spruce, and i f the non-spruce conifers were well separated from each other, i t i s conceivable that the 51 non-spruce conifers escaped i n f e c t i o n . It can be calculated how small the probability of spread from spruce to non-spruce would have to be. The proportion of infected non-spruce trees in the population would have to be so small that the probability of selecting 51 non- spruce conifers at random, and finding them a l l uninfected, would be no smaller than 0.05. Hence the proportion (P) would have to be such that 51 (1-P) < 0.05 P < 0.057 This compares with the proportion of spruce infected of 170 divided by 295, or 0.58. If the paucity of root contacts were the cause of lack of infection of non-spruce conifers, the 29 frequency of such contacts would have to be less than 10% of the average number between spruce trees. It is therefore unlikely that lack of root contact i s responsible for the lack of infectio n of non-spruce conifers. Table 4 - Incidence of tomentosus root disease for a l l l i v i n g tree species examined. Number of Trees Spec ies Healthy Infected Abies lasiocarpa 28 0 Pseudotsuga menziesii 18 0 Pinus contorta 5 0 Populus tremuloides 2 0 Picea qlauca 1 25 1 70 It may be of course that in addition, species other than spruce are also much less susceptible than spruce. This explanation runs counter to the results of Whitney and Bohaychuk (1976), and also to observations of heavy infection on lodgepole pine in the Quesnel Lakes areas as reported by Morrison and Wilford. 3 Another explanation might be that P. tomentosus consists of several races, each adapted to a particular tree species or 3 Dr. D.J. Morrison, P a c i f i c Forest Research Center, and E. Wilford, B.C. M.O.F., in a communication with Dr. B.J. van der Kamp, U.B.C.. 30 group of species. This phenomenon has been observed for other root diseases such as A r m i l i a r i a mellea, " and Fomes annosus (Korhonen, 1978). If this were the case, damage caused by P. tomentosus on a s i t e may be avoided by a switch of conifer spec ies. Appendix B shows stem maps indicating the position of healthy, diseased and dead trees in the ten plots by species. None of the ten plots showed d i s t i n c t disease centers with evidence of progression of symptom development from the periphery to the center. Instead diseased trees exhibiting various stages of disease development and healthy trees were randomly mixed within the plots. Given t h i s s i t u a t i o n , i t was not possible to estimate the rate of spread of disease centers. A set of inoculation experiments conducted by Whitney (1962) indicates that P. tomentosus grows at 3.8 cm per year. Ectotrophic growth may be this slow, but once established in the tree, i t seems that growth through secondary xylem is much faster. The fungus could travel through the root system and contact other trees at a greater rate than ectotrophically growing fungi. It should not be concluded that infection by Polyporus tomentosus i s t r u l y random among trees in immature spruce stands. Rather, substantial sections of a stand may be t o t a l l y free of disease. However, within the diseased parts of the stand, healthy and diseased trees appear to be randomly mixed. " Dr. D.J. Morrison in a communication with the author, March, 1983. 31 5. IMPACT OF TOMENTOSUS ROOT ROT 5.1 Survey The results of the survey for incidence are reported in Table 5. Three of the six stands surveyed were also used to establish the ten research plots described above. However, the survey lines did not actually transect any of these plots. Figure 1 shows the location of the six stands. If we assume that each of the six stands surveyed represents an equal area of immature spruce forest, (essentially c l a s s i f y i n g the population into six equal s t r a t a ) , the overall area infected i s 28.4 + 13.7 percent. Table 5 - Incidence of Polyporus tomentosus root rot in white spruce within the Prince George survey area (Figure 1). Location Transect Number Percent of Area 95% conf. Width Length of Trees Infected . Interval (m) (m) examined Highway 16 1 390 1 43 6.9 6.1 Jerry Creek 2 360 128 16.8 8.2 Tabor Mtn. 2 336 1 53 . 17.6 8.6 Hixon 2 360 1 45 37.7 16.3 Aleza Lake 3 300 1 1 3 42.2 10.4 Beaver Road 1 417 1 26 49.0 24. 1 32 5.2 Estimation Of Losses The survey described above estimates the percent of the t o t a l stand area now occupied by diseased trees. The impact of P. tomentosus in these stands, w i l l in the f i n a l analysis, consist of a decrease in value at the time of harvest. This w i l l be due to a decrease in volume, and a lumber recovery loss from logs with butt rot. In this study the estimation of impact is limited to a consideration of reduction of volume. Volume losses occur in at least four ways, namely increment loss, butt rot, mortality of standing timber and windthrow. The data c o l l e c t e d allow an estimation of the current increment and butt rot losses, but cannot project losses due to the disease, up to rotation age. Whitney (i960) noted that the disease was more severe in older stands. Older infected trees themselves contained more decay. However, the r a t i o of healthy to diseased trees was equal in a l l age classes from 40 to 120 years. One may expect then, that younger stands may be able to mask a certain level of infection better than do older stands. 5.2.1 Butt Rot The extent of P. tomentosus stain and decay was measured for each infected tree. The results are presented in Table 6. Forty-five percent of the diseased trees showed P. tomentosus stain and or decay at breast height; in 34 percent the stain or decay had progressed to the root c o l l a r but not to breast height, while in the remaining 21 percent of infected trees stain and decay was r e s t r i c t e d to roots. Expressed as percent of a l l l i v i n g spruce trees encountered in the survey (using the 33 figure of 28.4 as the percent of spruce trees infected) these values become 12.9, 9.7, and 5.8 respectively. One may conclude that in the stands described in this study at least 22.6 percent of the trees show butt rot now. One would expect this figure to increase, on a stand basis, by rotation age. The ra t i o of healthy to diseased trees in the stand is unchanged but i s expressed in greater proportions in butt rot. Many of the trees in which the pathogen i s now r e s t r i c t e d to the roots w i l l develop butt rot by rotation age. Table 6 - Number of white spruce by age class in a l l plots, showing various disease symptoms. Age Class Healthy Exhibiting stain or decay by Polyporus tomentosus in roots only at the root c o l l a r at : 30-35 2 - - - 36-40 2 - - - 41-45 2 3 4 7 46-50 10 4 1 0 8 51-55 38 1 2 1 7 22 56-60 38 1 3 1 9 25 61-65 23 3 7 13 >65 10 - 1 2 TOTALS 125 35 58 77 34 It is noteworthy that the extent of decay was not dependent on tree age. Table 6 shows a similar age d i s t r i b u t i o n for a l l three disease classes. The measurements necessary to estimate the actual volume of decay were not c o l l e c t e d . At present this volume would probably be less than one percent of the t o t a l volume of spruce. This figure would increase with time, but even i f i t quadrupled by rotation age, i t would s t i l l be small. It should be realized however, that the major loss here is associated with decreased lumber recovery from logs with butt rot. Current tables for decay, waste and breakage (B.C. M.O.F. 1976) estimate the decay loss in immature spruce not bearing indicators of decay as 0%. For the 121 to 250 year age class, decay of such trees is estimated at 1.8 to 3.1 percent for diameter classes 10 to 50 cm respectively. These figures are somewhat lower than our r e s u l t s . The difference may be due to the type of spruce stand selected for the current study. 5.2.2 Increment Loss An increment core taken at breast height was co l l e c t e d from each tree in the ten p l o t s . Radial increment was measured in f i v e year periods from the 1982 ring to the p i t h . These measurements were transformed into basal area increment, using the radius measured by the increment core to estimate tree diameter. The average fiv e year basal area increment for the years 1977-1982 was 1708.2 square millimeters for healthy and 1087.3 square millimeters for diseased trees. The difference 35 was not s t a t i s t i c a l l y s i g n i f i c a n t , being masked by variation not attributable to disease. One major source of var i a t i o n was tree si z e . Large trees grow faster than small trees, and both the healthy and diseased tree classes exhibited a wide range of tree sizes (Table 11). A covariance analysis was conducted using diameter at breast height squared times the height as the covariate. In order to obtain a useful relationship between basal area increment and the covariate, i t was necessary to transform the data to natural logarithms. Appendix C shows the relationship between these variables in both natural and logarithmic form. The equations for the regression lines are given in Table 7. The equations give the relat i o n s h i p between the logarithm of basal area increment versus the logarithm of the diameter squared times height for healthy and diseased trees respectively. According to the analysis of covariance, using the computer package "Genlin" (Greig and Bjerring 1980), the regression l i n e s had a common slope, but not a common y- intercept. The analysis of covariance was then performed, and the results are shown in Table 8. Plot was considered random, and the status was considered fixed. 36 Table 7 - Equations of the regression l i n e s for the logarithm of basal area versus the logarithm of diameter squared times height and resulting test for common slope. Tree status Regression equations Healthy y = -1.120 + 0.9988 x Diseased y = -0.2238 + 0.8582 x Test Hypothesis of common slope C.L.=0.95 F= 2.21 DF1= 1 DF2= 291 Probability= 0.137 Table 8 - Analysis of covariance table based on the natural logarithm of basal area increment, using the natural logarithm of D.B.H. squared x Height as covariate (confidence = 0.95). Source df SS MS F-ratio Probability Plot 9- 10. .22 1 . , 1 3 1 . .675 0. ,095 Status 1 2. .47 2. ,47 6, .240 0. ,034** Plot x Status 9 3. .56 0. .39 0, .584 0. .809 Covariate 1 252. .18 252. .18 371 , .940 0. .000** Residual 274 185, .78 0, .68 TOTAL 294 471 . 50 37 There was 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 difference between the natural logarithm of basal area increment of diseased and healthy trees. Also note that the covariate was highly s i g n i f i c a n t . This is to be expected, as large trees grow s i g n i f i c a n t l y faster than small trees. It i s tempting to conclude that P. tomentosus is primarily a disease of smaller, stressed trees while large vigorous trees escape. However, the range of tree sizes in the diseased and healthy class overlap greatly (Tables 11 and 12). There i s no s i g n i f i c a n t difference between healthy and infected trees for either age or diameter. This i s based on a test of d i s t r i b u t i o n using the Chi-square technique with both sets of tables. Table 9 - Natural logarithms of 5 year basal area increment for healthy and diseased trees. Healthy Diseased n 1 25 1 70 Observed mean 6.749 6.405 Predicted mean 6.662 6.470 Observed standard deviation 1 .262 1 .253 Standard error of the mean 0.07 5 0.064 The calculations shown below p a r t i t i o n the difference between basal area increment of healthy and diseased trees into two parts, namely that due to differences in tree size, and that due to disease. 38 By taking the naturals of the logarithmic values of the predicted means (Table 9), the difference between healthy and infected trees i s ; 782 - 645 = 137 The difference of the naturals of the observed means i s ; 853 - 605 = 248 The predicted mean accounts for variation due to tree size which i s ; 137 = 55.2% 248 Applying these figures to the differences in untransformed basal area increment c i t e d above, i t i s concluded that the increment loss due to disease is about 1708.2 - 1087.3 x .55 = 20% 1708.2 The data were also analyzed using four disease classes, namely (1) healthy, (2) decay r e s t r i c t e d to roots, (3) decay and stain at root c o l l a r but not at breast height, and (4) decay and stain at breast height. However th i s approach resulted in a very unbalanced design, and none of the differences in basal area increment between disease classes were s i g n i f i c a n t . Figure 9 shows the pattern of basal area increment over time for trees currently c l a s s i f i e d as diseased and healthy. The dependent variable is represented by calendar years, or the number of rings from the 1982 latewood. It follows that each class averages the basal area increment for trees of d i f f e r e n t ages (see Table 11 for age d i s t r i b u t i o n ) . Trees currently healthy 39 ^ Mean Basal Area Increment of J Healthy versus Infected Trees £ 2200-1 3 XT Number of Rings from Cambium Figure 9 - Mean basal area increment over time for healthy white spruce, and trees infected with Polyporus tomentosus. show a consistently greater basal area increment over time than diseased trees. This may be attributed to the fact that healthy trees are on average somewhat larger than diseased trees. The difference in basal area increment between healthy and infected trees for the period of 1977-1982 i s a consequence of infection by p. tomentosus. In other words, increment losses have only just become detectable in the stands examined. Whitney (1962) stated that the rad i a l increment of dead trees decreased at 5-15 years p r i o r to death of the tree, but infe c t i o n , based on fungal 40 growth rates, must have been established 20 to 30 years prior to a measurable decline. As the infection i n t e n s i f i e s , one might expect the loss to become more severe as the tree's energy becomes allocated more towards the production of adventitious roots. The GENLIN test was also performed for increment rings numbered six to ten and eleven to f i f t e e n . Only the most recent group of 5 year annual growth rings showed signi f i c a n c e . In other words, the basal area increment of healthy trees could only be shown to be s i g n i f i c a n t l y d i f f e r e n t from that of infected trees for the last five years. This may in part be due to uncertainty about disease status of trees f i v e or more years ago. 5.2.3 Mortality And Windthrow Mortality in the ten study plots was largely r e s t r i c t e d to small, understory trees. One hundred and f i f t y seven dead standing trees were observed, and of these death was attributed to P. tomentosus in 82 cases. It was not possible to estimate an annual rate of volume loss due to mortality since i t was not determined how long the dead standing trees had been dead. Table 10 shows the percent of spruce trees infected. There i s no s i g n i f i c a n t difference between proportion infected for l i v i n g or dead trees. This shows that small diseased trees are no more l i k e l y to die than healthy small trees, and mortality may be attributed to causes such as crown suppression. Table 10 - Total number of spruce trees investigated, with the percentage infected and percentage dead. 41 Non-infected Infected % Infected Living 125 170 57% Dead 75 82 52% % Dead 37% 33% Six large green windthrown trees were observed in the study plots. The cause of windthrow was c l e a r l y deterioration of the root system by P. tomentosus. The t o t a l volume of these trees was considerably greater than that of the dead standing trees. Two percent of the stems examined had been windthrown. If such a rate of loss were maintained over the remainder of the rotation, considerable volume losses to the stand would r e s u l t . The remaining stand would also be much less wind-firm with the openings created. 42 Table 11 - Percent of the t o t a l number of spruce trees by age class Age Healthy Diseased 30-35 1.6 0 36-40 1.6 0 41-45 1.6 8.2 46-50 8.0 12.9 51-55 30.4 30.0 56-60 30.4 33.5 61-65 18.4 13.5 >65 8.0 1.9 100 100 N 125 170 43 Table 12 - Percent of t o t a l spruce trees by diameter class Diameter (cm) Healthy Diseased 6-14 47.2 50.0 1 5-22 36.8 44.2 23-30 12.8 5.3 >31 3.2 0.6 1 00 1 00 N 1 25 1 70 If exposure to inoculum is the determining event of infect i o n one would expect large trees to contact inoculum more frequently than smaller trees. However, as seen in Table 12, with a sample size of 295 trees, healthy trees greater than 23 cm diameter are twice as abundant as diseased trees. We cannot assert that trees of a l l sizes are equally susceptible, and in this study i t appears that large trees escaped infection more often than small trees. However the difference was not s t a t i s t i c a l l y signi f icant. 6. ECOLOGICAL CLASSIFICATION A l i s t of plants observed on the study plots i s presented in appendix A. Based on these species' l i s t s , the s i t e was f i t t e d to an ecological unit. Figure 10 shows a t y p i c a l s o i l found during t h i s study. It should be noted that t h i s study was not designed to elucidate site/disease relationships, however 4 4 F i g u r e 1 0 - S o i l p i t f r o m J e r r y C r e e k w i t h w e l l d r a i n e d s a n d y l o a m s . T h e s o i l p r o f i l e h a d a t h i n o r g a n i c l a y e r , w i t h a n e l u v i a t e d A e z o n e , a n d a n e n r i c h e d B f l a y e r . t h e e c o l o g i c a l u n i t s c o u l d p r o v i d e i n d i c a t o r s o f r e l a t i v e i n t e n s i t i e s o f P . t o m e n t o s u s . O t h e r b e n e f i t s a r e g a i n e d f r o m s u c h c l a s s i f i c a t i o n s . B a s e d o n t h e s e e c o l o g i c a l c l a s s i f i c a t i o n s , t h e B r i t i s h C o l u m b i a M i n i s t r y o f F o r e s t s w a s a b l e t o p r e p a r e a g u i d e o f s i v i c u l t u r a l i n t e r p r e t a t i o n s a n d t i m b e r i n t e r p r e t a t i o n s . O f t h e f i v e s i t e s , i n t e r e s t i n g l y e n o u g h , t h r e e a r e c l a s s i f i e d a s t h e S B S j / 0 1 . 1 , o n e a s t h e S B S j / 0 1 . 2 , a n d o n e a s t h e S B S j / 0 6 . T h e s i t e p r e p a r a t i o n s u g g e s t i o n s f o r t h e f i r s t s u b a s s o c i a t i o n ( j / 0 1 . 1 ) a r e t o m i x t h e 45 humus layer with the mineral layer after a broadcast burn and to regenerate the s i t e with lodgepole pine and spruce. The s i t e would then be managed for sawlogs on an 80 year rotation. This practice would e s s e n t i a l l y eliminate any P. tomentosus l i v i n g in small root pieces. Larger stumps not t o t a l l y consumed in the broadcast burn would pose threats i f heavily infected, but the longevity of such inoculum has yet to be determined. The result would be better spruce growth, and as observed a good pine crop as well. For the second subassociation (j/01.2) the recommendations for s i l v i c u l t u r e are to prepare the s i t e for spruce by broadcast burning and to manage the stand for 80 year old sawlogs. This technique i s c l e a r l y a mistake in areas with any P. tomentosus. A broadcast burn would do l i t t l e to remove any threat of continuing root disease, and the resulting stand would soon become infected. The f i n a l subassociation (J/06) should not have had spruce growing on i t at a l l , according to the s i l v i c u l t u r e guide. Instead the guide recommends the planting of species such as Douglas-fir, or lodgepole pine. The few stems of such species on the J/06 s i t e were growing much better than the spruce. If our preliminary observations on host s p e c i f i c i t y are correct, such a species change would also avoid Polyporus tomentosus root rot. 46 V. CONCLUSIONS Polyporus tomentosus is a common root disease in central i n t e r i o r immature spruce stands. Diseased trees occupied 28.4 .+ 13 percent of the t o t a l area in the six randomly selected stands. Infection takes place via root contact between healthy and diseased trees. The fungus advances ectotrophically on small roots, k i l l i n g them rapidly, but in large roots the pathogen is r e s t r i c t e d to the inner xylem. Polyporus tomentosus attack i s not organized in d i s t i n c t root rot centres in which a l l trees are affected. Rather, in diseased parts of a stand apparently healthy and diseased trees occur together. Obvious crown symptoms are uncommon for the age of trees examined and the extent of disease present. There is no clear r e l a t i o n s h i p between the extent of infection in the root system and the severity of crown symptoms. Only spruce is diseased. Subalpine f i r , lodgepole pine, Douglas-fir, and trembling aspen, even though often in contact with diseased spruce roots, remain uninfected. Losses result from increment reduction, butt decay and windthrow. Mortality does not appear to be a factor in stands of the age and type examined. Losses in current increment of diseased trees at a,ge 55 i s measured to be 20%. Butt decay occurs in 22.6% of a l l spruce trees. Six of the 175 diseased plot trees, or 3.4% were windthrown in one season. For whole stands t h i s y i e l d s 28.4 x 0.034 = 0.96 47 or a further annual loss of 1% of a l l the stems. The use of ecological c l a s s i f i c a t i o n may increase the ease with which stands containing P. tomentosus can be found. S i l v i c u l t u r a l prescriptions must take the presence of P. tomentosus into account. Regeneration of spruce on P. tomentosus infected s i t e s without treatment to control the disease w i l l result in severe losses. 48 LITERATURE CITED Basham, J.T., P.V. Mook and A.G. Davidson. 1953. New Information concerning Balsam F i r Decays in Eastern North America. Can. J. Bot. 31;334-360• Bloomberg, W.J. 1980b. A ground survey method for estimating loss caused by Phellinus weiri i root rot II. Survey procedures and data analysis. Can. For. Serv., Pac. For. Res. Cent., Inf. Rep. BC-R-3. 24pp. B r i t i s h Columbia Ministry of Forests. 1976. Metric diameter class for decay, waste, and breakage factors 1976, A l l . forest inventory zones. For. Env. Division, B.C.F.S. Dept. of For. Buckland, D.C., R.E. Foster and V.J. Nordin. 1949. Studies in Forest Pathology. VII. Decay in Western Hemlock and F i r in the Franklin River Area, B r i t i s h Columbia. Can. J. Res., C. 27:312-331. Cerezke, H.F. 1973. Survival of the weevil, Hylobius warreni Wood, in lodgepole pine stumps. Can. J. For. Res. 3^367- 372. Christensen, CM. 1940. Observation on Polyporus c i r c i n a t u s . Phytopath. 30:957-963. Denyer, W.B.G. and C.G. Riley. 1953. Decay in white spruce at the Kananaskis Forest Experiment Station. For. Chron. 29:235-247. Domanski, S. and W. Dzieciolowski. 1955. Zgnilizny odziomkowe soany zwyczajnej i ich warunki rozwojowe. Czesc II . Wplyw warunkow glebowych w lexnictiwie Dobrygoac (nadlesnictwo Rychtal). (Butt rot of Scots Pine and the conditions of i t s development. II Influence of s o i l conditions in Dobrygosc forest region (forests of Rychtal, West Poland)). Acta Soc. Bot. Polon. 2^:65-93. (Eng. Trans.). E i s , S., D. C r a i g d a l l i e and C. Simmons. 1982. Growth of lodgepole pine and white spruce in the central i n t e r i o r of B r i t i s h Columbia. Can. J. For. Res. 12:567-575. Etheridge, D.E. 1956. Decay in subalpine spruce on the Rocky Mountain Forest Reserve in Alberta. Can. J. Bot. 34:805- 816. Foster, R.E. and A.T. Foster. 1951. Studies in Forest Pathology. VIII Decay of Western Hemlock on the Queen Charlotte Islands, B r i t i s h Columbia. Can. J. Bot. 29:479- 49 521 . Gosselin, R. 1944. Studies on Polystictus c i r c i n a t u s and i t s rel a t i o n to butt-rot of spruce. Dept. Lands and Forests, Que. For. Serv. B u l l . No. 10(N.S.). Reprint from; Farlowia J_ :525-568. Greig, M. and J. Bjerring. 1980. UBC GENLIN: A general least squares analysis of variance program. Computing Centre, University of B r i t i s h Columbia. 55 pp. Haddow, W.R. 1941. On the history and diagnosis of Polyporus tomentosus F r i e s , Polyporus c i r c i n a t u s F r i e s , and Polyporus dual is Peck. Trans. B r i t . Mycol. Soc. 25;179-190. Hepting, G.H. and A.A. Downs. 1944. Root and butt rot on planted white pine at Biltmore North Carolina. J. For. 42 :119-123 . Hubert, E.E. 1929. A root and butt rot of conifers caused by Polyporus c ire inatus Fr. Phytopath. 19;745-747. Korhonen, K. 1978. I n t e r s t e r i l i t y groups of Heterobasidion annosum . Seloste: Juurikaavan risteytymissuhteet. Commun. Inst. For. Fenn. 94(6): 1-25. Krajina, V.J. 1969. Ecology of forest trees in B r i t i s h Columbia. Ecology Western N. Amer. 2:1-146. Lachance, D. 1976. Etude de carie dans une plantation d'epinettes blanches f e r t i l i s e e s . Can. Centre Rech. For. Laurentides, Ste. Foy, Que. Rapp. Inf. LAU-X- 18. 24 pp. Lachance, D. 1978. The effect of decay on growth rate in a white spruce plantation. For. Chron. 54(1):20-23. Lowe, D.P. 1969. Check l i s t and host index of bacteria, fungi, and mistletoes of B r i t i s h Columbia. Can. Env., Can. For. Serv., Pac. For. Res. Cent. BC-X-32. Nobles, M.K. 1948. Studies in forest pathology. VI. I d e n t i f i c a t i o n of cultures of wood-rotting fungi. Can. J. Research C. 26 :281-431. Solovieff, F.A. 1927. A rot of spruce caused by Polystictus triqueter Fr.. Materials for Mycol. & Phytopath. Leningrad. _1_:295-300. Cited i n ; Rev. Appl. Mycol. 1928. 7:351 . Thomas, G.P. and R.W. Thomas. 1954. Studies in Forest Pathology. XIV Decay of Douglas-fir in the Coastal region of B r i t i s h Columbia. Can. J . Bot. 32:630-653. 50 Van Groenewoud, H. 1956. A root disease complex in Saskatchewan white spruce. For. Chron. 32:11-13. Warren, G.L. 1956. Root injury to conifers in Canada by species of Hylobius and Hypomolyx (Coleoptera: Curculionidae) '. For. Chron. 32:7-10. White, L.T. 1953. Studies in Forest Pathology. X. Decay of White pine in the Timagami Lake and Ottawa Valley Areas. Can. J. Bot. 31:175-200. Whitney, R.D. 1960. Stand-opening disease and the pathogenicity of Polyporus tomentosus Fr. on white spruce ( Picea qlauca (Moench) Voss.T! Ph.D. Thesis, Queen's University., Kingston, Ontario. 98 pp. Whitney, R.D. 1961. Root wounds and associated root rots of white spruce. For. Chron. 37:401-411. Whitney, R.D. 1962. Polyporus tomentosus Fr. as a major factor in stand-opening disease of white spruce. Can. J. Bot. 4_0 : 1631-1658. Whitney, R.D. 1963. A r t i f i c i a l infection of small spruce roots with Polyporus tomentosus . Phytopath. 53:441-443. Whitney, R.D. 1964. Inoculation of eight Saskatchewan trees with Polyporus tomentosus . Can. Dep. For., Bimonthly Prog. Rep. 20(5):3. Whitney, R.D. 1965. Mycorrhiza-infection t r i a l s with Polyporus tomentosus and P. tomentosus var. c i rc inatus on white spruce and red pine. For. S c i . 11:265-270. Whitney, R.D. 1966. Germination and Inoculation tests with basidiospores of Polyporus tomentosus . Can. J. Bot. 44 :1333-1343. Whitney, R.D. 1972. Root rot in white spruce planted in areas formerly heavily attacked by Polyporus tomentosus in Saskatchewan. Can. Dep. Fish. For., Bimonthly Res. Notes. 28 (4):24. Whitney, R.D. 1977a. Polyporus tomentosus root rot of conifers. Dept. Fish. Environ., Can. For. Serv., Sault Ste. Marie, Ont., For. Tech. Rep. 18. 12 pp. Whitney, R.D. 1977b. Polyporus tomentosus root rot on conifers. Forestry Technical Report, Can. For. Ser. (1977). No. 18, 10 pp. {En,27 ref.,3 pi.} Great Lakes For. Res. Cent., Sault Ste. Marie, Ont. 51 Whitney, R.D. 1977c. Variation of Polyporus tomentosus Fr. in c u l t u r a l c h a r a c t e r i s t i c s and pathogenicity on conifer seedlings. Can. J. Bot. 55: 1389-1398. Whitney, R.D. 1978a. Polyporus tomentosus root and butt rot of trees in Canada. Statement Paper for 5th International Conference (Kassel,Germany) August 1978 on Problems of Root and Butt Rot in Conifers, pp. 283-297. Whitney, R.D. 1978b. Root rot of spruce and balsam f i r in northwestern Ontario. I I . Causal fungi and s i t e relationships. Can. For. Serv., Sault Ste. Marie, Ont. Rep. O-X-284. 42 pp. Whitney, R.D. and H. Van Groenwoud. 1964. The rate of advance of stand-opening disease over a ten-year period in white spruce at Candle Lake Saskatchewan. For. Chron. 40 -.308-312. Whitney, R.D. and W.P. Bohaychuk. 1976. Growth of Polyporus tomentosus cultures derived from basidiospores, sporohore tissue, and decayed wood. Can. J. Bot. 54(22):2597-2602. Wood, C.S., G.A. Van Sickle and T.L. Shore. 1984. Forest insect and disease conditions, B r i t i s h Columbia & Yukon, 1983. Can. Env., Can. For. Serv., P.F.R.C. BC-X-246. Pp. 27. 52 APPENDIX A - ECOLOGICAL SITE CLASSIFICATION AND VEGETATION LISTINGS The following s i t e s plots have been c l a s s i f i e d in the biogeoclimatic unit of the Sub-Boreal Spruce J. Information from each plot includes a s i t e description, a vegetation l i s t i n g , some of these based on the B r i t i s h Columbia Ministry of Forests abbreviations, and the accepted subzonal d i v i s i o n . A l l sites are further gradations of the SBSj/01, or the Mesic Oak Fern. Site j_ : Beaver Forest Road, kilometer 44. Taken from plot B1. This s i t e has been c l a s s i f i e d as the SBSj/01.2, a Mesic Oak Fern, Thimbleberry subassociation. The s i t e is f l a t , s l i g h t l y undulating, with no aspect. It is a f l u v i a l terrace, with s o i l s that are t y p i c a l l y Humo-ferric podzols. The s i t e i s submesic- submesotrophic. A2 75% Piceene, Abielan A3 20% Abielas, Piceene B1 10% Abielas B2 05% Abielas C 15% Aralnud, Corncan D 97% Pleusch, P t i l c r i , Rhyttri Species l i s t : Abies lasiocarpa Picea exg Pseudotsuga menziesi i Rubus pa r v i f l o r u s A r a l i a nudicaulis Cornus canadensis Lonicera involucrata Pleurozium schreberi Ptilium c r i s t a - c a s t r e n s i s Maianthemum canadense O r t h i l i a secunda Rhytidiadelphus triquetrus Lycopodium annotinum Chimaphila umbellata Gymnocarpium dryopteris Ribes lacustre M i t e l l a nuda Rubus pubescens Viburnum edule Rosa a c i c u l a r i s Lycopodium obscurum 53 Site Two : Jerry Creek, 500 road. Taken from plot J567. This s i t e is located in the Jerry Creek valley, at the toe of a 20m slope. The s i t e i s t y p i c a l of the SBSj1/01.1, the Mesic Oak Fern Black Huckleberry subassociation. The s o i l s are t y p i c a l of a leached brunisol developed from g l a c i a l - f l u v i a l material. The s o i l p i t had charcoal, and had no seepage at 25cm depth. The s o i l was t y p i c a l l y a medium-textured,sandy loam with coarse fragments of 40.-50%, and some larger cobbles to 20cm diameter. The humus form i s a mor. The s i t e i s mesic-submesotrophic. A2 35% Piceene, Abielas A3 15% Piceene B1 8% Abielas B2 5% Rubupar, Vaccmem, Loniinv C 90% Gymndry, Rubuped, Corncan, Aralnud D 99% Pleusch, P t i l c r i Species l i s t : Picea exq. A r a l i a nudicaulis Gymnocarpium dryopteris CIintonia u n i f l o r a Smilacina racemosa Ribes lacustre Streptopus roseus Abies lasiocarpa Cornus canadensis Rubus pedatus Lycopodium annotinum Viburnum edule Orthi1ia secunda Pleurozium schreberi Ptilium c r i s t a - c a s t r e n s i s Rhytidiadelphus triquetrus T i a r e l l a t r i f o l i a t a Vaccinium membranaceum Lonicera involucrata Heracleum sphondylium Veratrum v i r i d e Oryzopsis a s p e r i f o l i a Rubus pa r v i f l o r u s Spiraea b e t u l i f o l i a 54 Site three : Highway 16, 20 kilometers east of Prince George. Taken from survey stand. This s i t e has s i l t y clay lacustrine l u v i s o l s o i l s with a moder humus. It is a f l a t area characterized by periods of high water. The s i t e is t y p i c a l of the SBSj1/01.1, the Mesic Oak Fern, Black Huckleberry subassociation. A1 5% Piceene A2 15% Piceene A3 20% Piceene, Abielas B1 03% Abielas, Piceene, Corncan, Rubupub B2 02% Sorbsco, Vibuedu C 10% Corncan, Rubupub D 99% P t i l c r i , Pleusch Species l i s t : Spirbet Loni inv Vibuedu Vaccmem Petapal Achimil Pleusch P t i l c r i Rosaac i Poputre Piceene Actarub Corncan Astecon Rubupub Goodpbl Fragvir A s t e c i l Linnbor Sorbsco G a l i t r f 55 Site four : Hixon 3800 road, Kilometer 12. Taken from Hixon study p l o t . This s i t e is t y p i c a l of the SBSJ1/06, the Submesic Queen's Cup subassociation. The s o i l s are c l a s s i f i e d as shallow (3cm) mor humus forms on a ferro-humic podzol. The s i t e i s t y p i c a l l y submesic to submesotrophic . The texture of the s o i l is a loamy sand with 10% coarse fragments, probably f l u v i a l . The s i t e has about a 4% slope, with a south aspect. The s i t e occurs on the lower slope. A2 40% Poputre, Betupap, Piceene, Pseumen A3 40% Piceene, Abielas B1 15% Abielas, Piceene B2 2% Abielas C variable 5%-80% Corncan, Rubuped D 100% Pleusch, P t i l c r i Species l i s t : Picea exg. Pseudotsuga menziesi i Pinus contorta Betula papyri fera Cornus sericea Lycopodium obscurum Goodyera ob l o n g i f o l i a Rubus pedatus Lycopodium annotinum Veratrum v i r i d e Orthi1ia secunda Clinto n i a u n i f l o r a Streptopus roseus T i a r e l l a t r i f o l i a t a Sphagnum capillaceum Ptilium c r i s t a - c a s t r e n s i s Pleurozium schreberi Polytrichum juniperinum Abies lasiocarpa Linnaea borealis Lonicera involucrata Streptopus amplexifolis Spiraea b e t u l i f o l i a Gymnocarpium dryopteris Rosa a c i c u l a r i s Vaccinium membranaceum Rhytidiadelphus triquetrus A r a l i a nudicaulis Populus tremuloides 56 Site f ive : Tabor Mountain Northern slope. Taken from survey stand. This s i t e i s atypical in vegetative nature. It appears to be in a serai stage. The s o i l s are t y p i c a l l y a morainal blanket mor, the s i t e i s north aspect on a 20% slope. A mid-slope s i t e with such a slope and morainal parent material would place th i s in the SBSj1/01. A2 80% Piceene, A3 20% Abielas, B1 - B2 - C 2% Streamp, D 5% Brachyl Betupap, Poputre Piceene Actarub, Streros Species l i s t : Betupap Piceene Abielas Streamp Actarub Streros CIinuni Braculy Poptre 57 APPENDIX B - STEM MAPS OF THE TEN STUDY PLOTS Ten maps are presented from the plot work in the Prince George East Forest D i s t r i c t . B1 to B4 are from four s i t e s at the Bowron River. DC1 to DC3 are from three s i t e s northwest of the l a t t e r . Two s i t e s , J567 and J568 are in the Jerry Creek drainage, and PLOTHIXON is from the Hixon area. A l l maps are scaled 1cm = 1m The codes for the maps are described as follows; Number 1 through 4 correspond to re l a t i v e amounts of Polyporus tomentosus on white spruce, such that 1 = healthy 2 = disease at roots only 3 = disease at roots and root c o l l a r 4 = disease at breast height An "x" represents a dead tree, and i f the dead tree had any sign of P. tomentosus i t was denoted as X . An "a" represents a non-spruce tree. N O R T H 8S N O R T H 69 N O R T H I D 09 61 « i a o N N O R T H 39 N O R T H n £9 N O R T H f9 N O R T H o 1*5 N O R T H 3 -1 99 N O R T H Cr, •44 LS 68 APPENDIX C - RELATIONSHIP BETWEEN TREE SIZE AND BASAL AREA INCREMENT. This contains four graphs showing the general shape of data points. tree volume is represented by DBH squared times height. Multiple occurrences of points in the same position are represented by numerical values which count the number of such overlaps. Rotcod 2 sp e c i f i e s a l l trees with any amount of evident P. tomentosus , while rotcod 1 s p e c i f i e s a l l healthy trees. The t h i r d and fourth graph show the resu l t i n g l i n e a r i t y of points when logs are taken for both the x and y axes. It is of note that four points from the f i r s t graph, two from the second, and one point from the fourth graph are missing due to the upper l i m i t of the y axis. SCATTER PLOT <\> ROTCOD : 1 BASAL AREA INCREMEN1 VS. (DBH + * 2 )+HEIGHT N= 121 OUT OF 125 27.BAI VS. 29.D2H 6AI 8000.O + 7 111.1 + 6222.2 + 5333.3 + 4444.4 + 3555.6 + 2666.7 + 1777.8 + 888.89 + 2* * * * * * * * * * * 2 * * * * * 3 • + * * * * * 3**2 * * * * •3524522 0. + 3333.3 6666.7 10000. 13333. D2H 1666.7 5000.0 8333.3 11667. 15000. SCATTER PLOT <2> ROTCOD:2 LN(BASAL AREA INCREMENT) VS. LN((OBH**2)*HEIGHT) N=, 169 OUT OF 170 33.LBAI VS. 34.LD2H LBAI 8.5369 + * 7.9918 + * * 2 • + • * + + * * * * i * * 7.44G7 + * * * 2 * * * 2 • * • * * < * + * * * * * * * * * * * 6.9016 + * * * * * * 2 * * * + * 6.3566 + * * * * * * * * * 2 * + * * * * * * * * * * * * * 5.8115 + * 2 + * * * * A * * * * 5.2664 +- * * * * 4.7213 + 4.1762 + 3.6312 + * + + + + + + + + + + + + + + + + + + + 5.1156 6.1325 7.1494 8.1663 9.1832 LD2H 5.6240 6.6410 7.6579 8.6748 9.6917 SCATTER PLOT <2> ROTCOD:2 BASAL AREA INCREMENT VS. (DBH**2)+HEIGHT N= 168 OUT OF 170 27.BAI VS. 29.D2H BAI 8000 .0 + + 7111.1 + + 6222.2 + + 5333.3 + * 4444.4 + 3555.6 + 2666.7 + 1777.8 + * * * * * * * * * * * + * * * * 2 * * * 2 *2 888.89 + 2 * * * * *2 * * * « * * *2 2 2 + 322 * 3 * * 2* * * 2 2 3 * * 2 2 •32X62*42* * * 0. + 22 * * * * * 3333.3 6666.7 1000O. 13333. D2H 1666.7 5000.0 8333.3 11667. 15000 <SCATTER BYSTRA TA VAR = LBAI.LD2H CASES=NEGBAI:0 STRAT = ROICOD HEAD=1 1 LN(BASAL AREA INCREMENT) 'VS . LN((DBH +* 2)+ HEIGHT)> SCATTER PLOT <1> ROTCOD:1 LN(BASAL AREA INCREMENT) VS. LN((DBH*+2 ) 'HE IGHT ) N= 125 OUT OF 125 33.1.BAI VS. 34 . LD2H LBA I 9.9882 + * 9.3744 + 8.7606 + 8.1469 + 6.9193 + 6.3055 + 5.6918 + 5.0780 + 4.4642 + * 2 2 + t * 2 * 7.5331 + •* *2 * * * -i * « * * '4: * * + + * * * 2 * * + + 2 * * * 4.7957 6.0492 7.3027 8.5562 9.8097 LD2H 5.4224 6.6759 7.9294 T . I830 10.436

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