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The influence of salal on planted hemlock and cedar saplings on northern Vancouver Island Fraser, Lauchlan 1993

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THE INFLUENCE OF SALALON PLANTED HEMLOCK AND CEDAR SAPLINGSON NORTHERN VANCOUVER ISLANDbyLAUCHLAN FRASERA THESIS SUBMITTED IN PARTIAL FULFILMENTOF THE REQUIREMENTS FOR THEMASTER OF SCIENCE DEGREEinTHE FACULTY OF GRADUATE STUDIESDEPARTMENT OF BOTANYWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIASeptember 1993© Lauchlan H. Fraser, 1993In presenting this thesis in partial fulfilment of the requirements for an advanceddegree at the University of British Columbia, I agree that the Library shall make itfreely available for reference and study. I further agree that permission for extensivecopying of this thesis for scholarly purposes may be granted by the head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.(Signature) Department ofThe University of British ColumbiaVancouver, CanadaDate^S 42-p+. 2J /9 3DE-6 (2/88)ABSTRACTThrough correlation analyses between 2- and 4-year-old conifer performance(western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western red cedar (Thujaplicata Donn ex D. Don)) and salal (Gaultheria shallon Pursh) leaf area index, and theeffect of salal leaf area index on the 2-year growth increment of western red cedar andwestern hemlock, this study determines the influence of salal on poorly growingwestern red cedar and western hemlock plantations growing on clear-cut and burnedold-growth western red cedar and western hemlock stands in the Coastal WesternHemlock biogeoclimatic zone. •This study was set up on a pre-existing experimentalsite involving 8 site x treatment combinations: 2 sites (cedar-hemlock and hemlock-fir)and 4 treatments (control, fertilized, scarified, and fertilized plus scarified).It is shown that increasing salal leaf area index reduces the growth of westernhemlock more than western red cedar. When growing with western hemlock, it isinferred that salal is strongly competitive in control plots on CH sites, fertilized plotson CH sites, control plots on HA sites, and fertilized plots on HA sites. When growingwith cedar, it is inferred that salal is wealdy competitive on fertilized plots on CH sites,and control plots on HA sites. However, the negative influence of salal on western redcedar only occurred on 2-year-old trees, not 4-year-old trees, suggesting that theinfluence is waning. For hemlock, the opposite occurred. It is concluded thatscarification is the best way to reduce the influence of salal on western hemlock andwestern red cedar.IITABLE OF CONTENTSAbstract^Table of Contents^List of Tables viList of Figures^Acknowledgements xiiIntroduction^ 1Description of ecosystem^  2The problem^ 7Hypotheses concerning ecosystem differences^ 7Literature reviewThe biology of salal ^  10The salal hypothesis  18Objectives^  21MethodsStudy area^  22Field manipulation  22Data collection  27Data analysisSite x treatment effect^  32Relationship between non-crop vegetation and conifer growth ^32The influence of the abundance of salal on the growth rate ofconifers between 1990 and 1992^  35ResultsPredictions ^  36Site x treatments effect using 3-way anova.western hemlocksoil variables ^  39salal performance  39western hemlock performance^  42western red cedarsoil variables ^  45salal performance  45western red cedar performance ^48Relationship between non-crop vegetation and conifer growth usingmultiple regression.western hemlockcontrol CH sites ^  51control HA sites  53fertilized CH sites  53fertilized HA sites ^  56scarified CH sites  ^56scarified HA sites  59fertilized + scarified CH sites ^59fertilized + scarified HA sites ^62western red cedarcontrol CH sites ^  64control HA sites  64fertilized CH sites  67fertilized HA sites ^  69scarified CH sites  ^69scarified HA sites  72fertilized + scarified CH sites ^74fertilized + scarified HA sites ^74Relationship between salal leaf area index and conifer growth usingmultiple regression^  77Relationship between soil variables and conifer growth, andsalal leaf area index using multiple regression ^80The influence of salal leaf area index on the growth of conifersbetween 1990 and 1992.western hemlock^  84western red cedar  88ivDiscussionWere the predictions of the salal hypothesis met? ^91Gaultheria shallon as a competitor of conifers.Relationship between neighbouring non-crop vegetationand conifer growth using multiple regression ^94The influence of the abundance of salal on the growth ofconifers from 1990 to 1992 ^96The influence of the leaf area index of non-crop species otherthan salal on conifer growth using multiple regression ^98Abiotic environmental factors influence on salal leaf area indexand conifer growth using multiple regression  ^100Site x treatment effect using 3-way anova.salal performance^  101western hemlock performance^  102western red cedar performance  102soil variables ^  103Competition theory related to salal ^  104Summary and ConclusionsSummary^  106Management implications for western hemlock and wester red cedargrowing on CH sites ^  107Future research  108Literature cited^  109LIST OF TABLESTable 1. Typical soil profile descriptions of the CH ecosystems(adapted from Germain, 1985)^Table 2. Typical soil profile descriptions of the HA ecosystems(adapted from Germain, 1985)^  5Table 3. Summary of the attributes of CH and HA sites beforeand after clear-cutting and slashburning ^6Table 4. Number of plots sampled from each site x treatmentcombination in the SCHIRP site at the highest plantingdensity of 2500 trees/ha^  26Table 5. Species list of the naturally growing vegetation withinthe study area on the CH and HA sites ^29Table 6. Transformations done on the variables within theANOVA models in order to meet assumptions of equalvariance^  33Table 7. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species andthe growth of 2- and 4-year-old western hemlocksaplings on control plots in CH sites measured in 1990 and1992, respectively^  52Table 8. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings oncontrol plots in HA sites measured in 1990 and 1992,respectively^  54Table 9. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings onfertilized plots in CH sites measured in 1990 and 1992,respectively^  55viTable 10. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings onfertilized plots in HA sites measured in 1990 and 1992,respectively^  57Table 11. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings onscarified plots in CH sites measured in 1990 and 1992,respectively^  58Table 12. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings onscarified plots in HA sites measured in 1990 and 1992,respectively^  60Table 13. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings onfertilized plus scarified plots in CH sites measured in 1990 and1992, respectively^  61Table 14. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western hemlock saplings onfertilized plus scarified plots in HA sites measured in 1990 and1992, respectively^  63Table 15. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings oncontrol plots in CH sites measured in 1990 and 1992,respectively^  65Table 16. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings oncontrol plots in HA sites measured in 1990 and 1992,respectively^  66viiTable 17. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings onfertilized plots in CH sites measured in 1990 and 1992,respectively^  68Table 18. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings onfertilized plots in HA sites measured in 1990 and 1992,respectively^  70Table 19. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings onscarified plots in CH sites measured in 1990 and 1992,respectively^  71Table 20. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings onscarified plots in HA sites measured in 1990 and 1992,respectively^  73Table 21. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings onfertilized plus scarified plots in CH sites measured in 1990and 1992, respectively  75Table 22. Multiple regression models determining the correlationbetween the leaf area index of neighbouring species and thegrowth of 2- and 4-year-old western red cedar saplings onfertilized plus scarified plots in HA sites measured in 1990and 1992, respectively  76Table 23. Summary of the correlations between the leaf area indexof salal and western hemlock height and root collar diameterusing the multiple regression models ^78Table 24. Summary of the correlations between the leaf area indexof salal and western red cedar height and root collar diameterusing the multiple regression models ^79viiiTable 25. Summary of the correlations between soil variables(moisture, coarse content, total carbon, total nitrogen,and total phosphorus) and the growth of 4- year-oldwestern hemlock measured in 1992 using the multipleregression models^  81Table 26. Summary of the correlations between soil variables(moisture, coarse content, total carbon, total nitrogen,and total phosphorus) and the growth of 4- year-oldwestern red cedar measured in 1992 using the multipleregression models^  82Table 27. Summary of the correlations between soil variables(moisture, coarse content, total carbon, total nitrogen,and total phosphorus) and the leaf area index of salalusing the multiple regression models ^83Table 28. Summary of the R2 values of the growth of westernhemlock and western cedar between 1990 and 1992 againstthe leaf area index of salal for each site x treatment combination...^87LIST OF FIGURESFigure 1. Hypothetical development of live-root, leaf, stemand rhizome abundance of Gaultheria shallonover a60-year period following the clear-cutting and burningof old-growth forests of western red cedar and westernhemlock on northern Vancouver Island (from Messier, 1991) ^14Figure 2. Map of the study area in northern Vancouver Island ^23Figure 3. Map of the SCHIRP site and layout of the experimentaldesign^  25Figure 4. Diagram illustrating the methods used to measure leaf area index ofnon-crop vegetation, leaf litter of salal and soil variables^ 28Figure 5. Predicted outcomes of thesis according to the salalhypothesis^  38Figure 6. Site x treatment effect on soil variables where westernhemlock were planted using 3-way ANOVA ^40Figure 7. Site x treatment effect on salal performance wherewestern hemlock were planted using 3-way ANOVA ^41figure 8. Site x treatment effect on western hemlock performanceusing 3-way ANOVA^Figure 9. Site x treatment effect on soil variables where westernred cedar were planted using 3-way ANOVA^Figure 10. Site x treatment effect on salal performance wherewestern red cedar were planted using 3-way ANOVA^Figure 11. Site x treatment effect on western red cedarperformance using 3-way ANOVA^Figure 12. The influence of salal on western hemlock growthrate on CH sites^Figure 13. The influence of salal on western hemlock growthrate on HA sites^43 &464749 &85864450Figure 14. The influence of salal on western red cedar growthrate on CH sites ^89Figure 15. The influence of salal on western red cedar growthrate on HA sites ^90Figure 16. The predicted outcomes compared to the observedoutcomes of western hemlock and western red cedar responseto high abundance of salal based on the salal hypothesis ^93xiACKNOWLEDGEMENTSI am very grateful to my supervisors, Dr. Roy Turkington and Dr. ChrisChanway, for their insight, editorial contributions, encouragement and effort. I wouldalso like to thank my other committee members, Dr. Gary Bradfield and Dr. GordonWeetman, for their advice and support.Many people helped in the inception, development and completion of thisproject. I wish to thank Tim Underhill and Heather Jones for their many hours of leafcounting in the field. I would also like to thank F. Dlott, S. Graham, S. Marcuitz, R.Keenan, C. Prescott, and B. Cade-Menum for their stimulating discussion,encouragement and help. Finally, I would like to thank B. Dumont, P. Bavis, and C.Fox for their continual support in Port McNeill.Western Forest Products Ltd. kindly provided lodging and resources for thefield work.Funding for this work was provided by a NSERC - Industrial Grant for theSalal/Cedar/Hemlock Integrated Research Program.My parents, family and friends have encouraged me throughout this project andI thank them dearly. Finally, a very special thank you to Julia for her love, support,patience and understanding throughout this project.xiiINTRODUCTIONOn northern Vancouver Island in the submontane variant of the CWHvmbiogeoclimatic subzone (Green et al. 1984)., poor regeneration, with associated slowgrowth and chlorosis has been reported in clear-cuts of western red cedar (Thuja plicataConn ex D. Don) - western hemlock (Tsuga heterophylla (Raf.) Sarg.) forests(Weetman et al. 1989a). The complexity of the observed phenomena lead a group ofscientists to adopt an integrated ecosystem-level approach to the problem. In 1985, theSalal-Cedar-Hemlock-Integrated-Research-Program was formed, or more simply theacronym SCHIRP. SCHIRP now involves many investigators from diverse fieldsincluding forestry, soil sciences and botany.Salal (Gaultheria shallon Pursh) is abundant in many parts of these cutovers andhas been shown to slow the growth of hemlock and cedar saplings (Weetman et al.1989b; Messier 1991; deMontigny 1992). However, it is not known to what extentsalal directly contributes to the poor plantation performance.Competition among plants has been studied intensively over the past centurybecause of its potential for influencing patterns of distribution and abundance.However, many papers that contend to observe competition have been shown byConnell (1983), Schoener (1983) and Underwood (1986) to be poorly designed andinconclusive. Furthermore, Goldberg and Barton (1992) observed that although manystudies have shown that competition is happening, the majority do not show whether ithas any major ecological and evolutionary consequence in nature. It is necessary,therefore, to conduct preliminary experiments in order to generate hypotheses whichmight predict the structure of plant communities before designing specific competitiontrials. My thesis examines the competitive influence of neighbouring non-crop species,particularly salal, on planted conifers. In order to generate hypotheses about theperformance of planted conifers, a range of biotic and abiotic factors were measured.2DESCRIPTION OF ECOSYSTEMThe large majority of northern Vancouver Island comprises the very-wetmaritime Coastal Western Hemlock biogeoclimatic subzone (CHWvm), which ischaracterized by the species association of Tsuga heterophylla, Thuja plicata, Abiesamabilis, Gaultheria shallon, Rhytidiadelphus loreus, and by a mean annualprecipitation of 2787 mm (Pojar et al. 1991). Out of an approximate area of 32000 ha,Lewis (1982) has identified numerous ecosystems within the CWHvm biogeoclimaticsubzone. The dominant ecosystem, occupying approximately 60% of the zone, Lewistermed the Si ("salal-moss") ecosystem association: 7huja plicata - Tsuga heterophylla- Abies amabilis - Gaultheria shallon - Rhytidiadelphus loreus. Within this ecosystem,different stand history allows the identification of two phases of Si, the cedar-hemlockphase (S1CH) and the hemlock-amabilis fir phase (S1HA) (Lewis 1982). These will bereferred to as CH and HA, respectively, in this thesis. Green et al. (1984) haveclassified the CH forest as CWHb 1(3)' and the HA forest as CWHb 1(4)'The CH phase is characterized by "old-growth" forests dominated by large7huja plicata Donn. (western red cedar), many with dead tops; poorly growing Tsugaheterophylla (Raf.) Sarg. (western hemlock); and a small number of very poorlygrowing Abies amabffis (Dougl.) Forbes (Pacific silver fir). Although accumulatedtree biomass of CH sites is high, annual productivity is low. This ecosystem does notappear to have been disturbed by events such as catastrophic wind storms for at least1000 years (Messier 1991). The canopy is open (i.e., not dense), thus permittingpenetration of sunlight to understory vegetation. As a result, Gaultheria shallon Pursh(salal), Vaccinium parvifollum Howell (red huckleberry), and V alaskaense Smith(Alaskan blueberry) form a fairly continuous and frequently dense understory.Blechnum spicant (L.) (deer fern), Hylocomium splendens (Hedw.) B.S.C. and3Rhytidiadelphus loreus (Hedw.) Warnst. grow sparsely under the Gaultheria-Vacciniumcover (Germain 1985).CH sites have a compacted humus layer that is approximately 45 cm thick(Klinka et al. 1981). This layer is rich in decaying wood and overlies a moderatelydrained Ferro-Humic Podzol. For a description of the typical soil profile of CH forestsee Table 1. The HA phase has a thin friable humus layer (10-40 cm)(Klinka et al.1981). Compared to the HA sites, the humus layer in CH sites is higher in tannincontent, higher in the ratio of carbohydrate to lignin, and has less advanceddecomposition in the non-woody horizons (Preston 1992). Analysis of each of the LFHlayers showed that CH forests have consistently lower availability of nitrogen andphosphorus (Prescott et al. 1992), and preliminary evidence suggests that the rates ofnutrient cycling are higher in HA forests (Keenan and Kimmins 1992). Furthermore,Keenan and Kimmins (1992) determined that the nutrient quality of the litter in HAforests was higher than CH forests. HA forests have a higher abundance and biomassof soil fauna than CH forests, but the diversity is similar (Battigelli et al. 1992).The HA phase is characterized by younger (i.e. < 100 years old) natural secondgrowth western hemlock and Pacific silver fir. The average tree biomass of the HAsites is 1100 m3/ha/yr (J. Barker, pers. comm.) and the productivity of these forests ishigh, with tree growth up to 12 m3/ha/yr (Anonymous 1991). Unlike the CH forests,HA forests have experienced repeated catastrophic disturbance caused by high winds(Lewis 1982). The canopy is dense, excluding light and consequently almost allunderstory vegetation, including salal. Sparse Vaccinium alas.kaense, V parvikilium,Blechnum spicant L., Polystichum munitum (Kaulf.) Presl and Tiarella trifoliata L.,and Hylocomium splendens (Hedw.) B.S.C. are present in the understory (Germain1985). The HA phase is predominantly situated on upper slopes (Messier 1991). For adescription of the typical soil profile of HA forests see Table 2. Table 3 summarizes4Table 1. Typical soil profile description of the CH ecosystem (adapted fromGermain, 1985).Horizon Depth (cm)^DescriptionLF^25-22^Mixed coniferous and moss litter; looseconsistency; many fine-roots andmycorrhizal hyphae; abrupt wavy boundaryto,H^22-0 black, dark reddish brown; highlydecomposed organic matter; granular,slightly greasy in lower horizon;abundant roots of all sizes; abrupt, wavyboundary to,Aeu^0-3 Grey to brown; sandy loam; mediumsubangular blocky; friable; few fine-roots; clear, broken boundary to,BhfuBfBfgj3-18 Reddish brown, strong brown; sandy loam;weak medium subangular blocky; friablewhen moist; non-sticky and slightlyplastic, wet: few to abundant fine- andmedium-roots; abrupt wavy boundary to,18-40 Strong brown, yellowish brown; gravellysandy loam; weak medium subangular block;friable when moist; non-sticky and non-plastic, wet; few fine-roots; some mediumto large roots; clear wavy boundary to,40-60 Yellowish brown, brownish yellow;gravelly sandy loam, weak, medium andcoarse subangular blocky, firm whenmoist; non-sticky and non-plastic, wet;very few roots; few faint mottles; abruptwavy boundary to,BCc^60+^Olive grey, strongly cemented toindurated gravelly sandy loam; no roots.5Table 2. Typical soil profile description of the HA ecosystem (adapted fromGermain, 1985).Horizon Depth (cm)^DescriptionLF^60-55 Mixed coniferous, salal and moss litter;loose consistency; many fine-roots andmycorrhizal hyphae; abrupt wavy boundaryto,H^55-0 Reddish black, dark reddish brown;massive; greasy; abundant roots of allsizes; abrupt wavy boundary to,Ae^0-4 Grey to brown; sandy loam; mediumsubangular blocky, friable; few fine andmedium roots; clear, broken boundary to,Bhf^4-19 Red, yellowish brown; sandy loam; weakmedium subangular blocky; firm whenmoist; non-sticky and slightly plastic,wet; few fine-roots, few medium andcoarse roots; abrupt wavy boundary to,BfBfgjBCc19-34 Yellowish red, yellowish brown; sandyloam; medium subangular block, firm whenmoist; non-sticky and non-plastic, wet;very few fine-roots, few medium andcoarse roots; abrupt wavy boundary to,34-55 Yellowish brown, gravelly sandy loam;weak, medium and coarse subangularblocky, extremely firm when moist; non-sticky and non-plastic; no roots; commonfaint mottles, seepage water present;abrupt wavy boundary to,55+^Olive grey, strongly cemented toindurated gravelly sandy loam; no roots.Table 3. Summary of the attributes of CH and HA sites before and after clear-cuttingand slashburning.CH (cedar/hemlock)^HA  (hemlock/fir)BEFORE: Dominant conifers western red cedar andwestern hemlockwestern hemlock andPacific silver firWind distubance absent repeated catastrophicdisturbanceAge of stand "old-growth" > 200 yearsoldyoung < 100 years old.Productivity of conifers low highCanopy open denseSalal abundance plentiful rareAFTER: Natural regeneration ofconifersPerformance of plantedconifersNon-crop vegetationregenerationslow prompt, dense, fast-growinggoodpoorplentiful salal,little fireweedlittle salal,plentiful fireweed67the attributes of the CH and HA phases before and after deforestation and broadcastburning.THE PROBLEMOn HA sites, following clear-cutting and slashburning, tree growth from plantedand naturally regenerated conifer seedlings is good. There is no sign of nutrientdeficiencies. Fireweed (Epilobium angustifolium) is abundant and salal does not form adense ground cover.On CH sites, however, following clear-cutting and slashburning, tree growthfrom planted and naturally regenerated seedlings is often good for the first few years,but shortly thereafter trees become chlorotic, show signs of nutrient deficiencies, andoften die. Salal re-establishes quickly on the clear-cuts and forms a dense groundcover.HYPOTHESES CONCERNING ECOSYSTEM DIFFERENCESA number of hypotheses have been proposed to account for the differences inconifer growth and productivity between the CH and HA sites, four of which will bepresented below. The first three hypotheses assume that the CH and HA sites aredifferent seral stages of a single forest ecosystem association, the fourth does not. It isgenerally accepted that HA sites are the pioneer stage and CH sites are the climax stage(Lewis 1982).81. The "disturbance hypothesis":It is argued that areas frequently disturbed by catastrophic windstorms willregenerate to western hemlock and Pacific silver fir, as is observed on HA sites. Windstorms causes tree falls resulting in soil mixing which promotes a well-drained andaerated soil with active organic matter decomposition and nutrient cycling. Improvedsoils increase the growth rate of trees and help to produce dense stands which excludesalal by shading. In areas that are not affected by the windstorms i.e., CH sites,western hemlock and Pacific silver fir stands thin, allowing the regeneration of westernred cedar. This improves the stand's ability to withstand windstorms because wind canpass through rather than strike against the forest stand.2. The "salal hypothesis":It is argued that salal (Gaultheria shallon) is a major competitor with coniferseedlings. There are two theories relevant to the salal hypothesis that SCHIRP isinvestigating. One theory proposes that salal suppresses the growth of conifer seedlingsthrough an allelopathic agent which inhibits either mycorrhizal development, rootdevelopment, or both (de Montigne 1992). This theory is related to observations ofother ericaceous species in eastern Canada (Meades 1983) and the heathlands of Europe(Malcolm 1975) which have been attributed to growth problems of planted coniferseedlings after deforestation. The second theory suggests that salal is simply a bettercompetitor than the conifer seedlings for soil nutrients in the CH clear-cuts. In eithercase, the reason for high productivity in HA sites following a major disturbance is thatthe dense regeneration of hemlock and fir excludes salal, thus eliminating eitherallelopathy, nutrient competition, or both. Because the CH stands are not dense, salalcan maintain a dense understory, and inhibit most conifer seedling growth. Therefore,little ecological succession occurs at CH sites and the "old-growth" cedar forestsremain relatively stable.93. The "western red cedar hypothesis":Western red cedar, unlike western hemlock and Pacific silver fir, is highlyresistant to decay due to the presence of a fungitoxic chemical (thujaplicin) and achemical (thujic acid) which repels a variety of insects (Swan et al. 1987).Consequently, a forest-floor dominated by decomposing western red cedar will have alow mineralization potential and will immobilize nitrogen in the decomposercommunity, thus lowering the rate of nutrient cycling and nutrient availability. It hasalso been postulated that western red cedar is not a climax species, but a long-livedpioneer species that requires exposed mineral soil, or decaying cedar logs, andmoderate levels of light to regenerate. Therefore, the conditions in windthrown HAsites are suitable for western red cedar, but because its initial growth is so slow, it isshaded out by the faster growing dense stands of western hemlock and Pacific silver fir.Because western red cedar is better able to regenerate on decaying cedar logs thanwestern hemlock and Pacific silver fir, it can regenerate slowly in the CH sites.4. The "site-difference hypothesis":This hypothesis proposes that HA and CH sites are not different seral stages inthe same succession, but rather are two different plant associations determined bytopography. HA sites are situated on knolls and upper slopes and are therefore moreexposed to wind and better drained than the CH sites which are situated in lower areas.In this study I focussed on the salal hypothesis. I made no attempt to make adistinction between the two salal theories but merely to test if the presence of salalsuppresses cedar or hemlock growth. According to this hypothesis salal restrictsconifer growth (particularly hemlock), therefore, the removal or absence of salal on theCH clear-cuts should promote the growth of an HA-type forest. Similarly, abundantgrowth of salal on the HA clear-cuts should promote the growth of a CH-type forest.LITERATURE REVIEWThe biology of salalGaultheria shallon has slow initial growth for approximately the first 2 years,but once it is established it spreads vegetatively very rapidly by means of rhizomes(Messier 1991). The length and complexity of the rhizomes of an individual salal plantin an area dominated by salal has not been determined but Koch (1983) found newshoots up to 2m from the parent plant. Bunnell (1990) observed a strong tendency fordaughter shoots to be clumped around the other shoot under sparse canopies, whereasdaughter shoots were farther away from the oldest shoots under closed canopy. Salalaccumulates considerable biomass in a growing season, but mainly through theexpansion of rhizomes leading to the production of new shoots, not through significantincrease in the height of preexisting shoots (Sabhasri 1961).Sale s ability to respond to a continuum of understory light conditions byproducing either sun leaves or shade leaves (Messier et al. 1989; Smith 1991) isimportant to its survival. Vales (1986) suggested that red and near infrared lightenrichment may be an environmental trigger for stem elongation. Sabhasri (1961)found that salal stem elongation was highest under red light.Individual shoots may survive for 10-15 years, but leaves are rarely older thanfour years before senescence (Haeussler and Coates 1986). Shoots will bear leavesonly during the first few years (Koch 1983). Rhizomes have the potential to reproducevegetatively indefinitely if there is sufficient light through the forest overstory (gapsand sunflecks or diffuse light conditions associated with denser stands) for above-ground stem and leaf growth. Bunnell (1990) found extensive mats of salal rhizomesbetween 80- 110 years old in conifer stands of the same age, even when above-groundsalal densities were low. During winter, salal is virtually dormant and is very sensitiveto frozen soils and frost (Sabhasri 1961).1 01 1Salal is at least a moderately shade tolerant species (Sabhasri 1961; Koch 1983)but its photosynthetic and respiration characteristics are consistent with a shadeintolerant plant species (Sabhasri 1961). For an actively growing plant it was foundthat at low light intensities (50 )imolm -2s1) respiration was greater thanphotosynthesis. Photosynthetic activity and seedling growth significantly increasedwith increased light intensities up to the maximum level tested (500 pimolm-2s4)(Sabhasri 1961). Salal shade leaves are thought to have a lower light compensationpoint (Sabhasri 1961; Vales 1986). Maximum growth occurs under red light (Sabhasri1961). Bunnell (1990) reported that the cost of flowering was shared across connectedshoots of a plant, showing there is physiological integration between ramets.The maximal growth of salal (roots, rhizomes, shoots and leaves) is betweenlate April to August, peaking in early June. Vegetative buds burst in early April(Sabhasri 1961). Flowering can occur anytime between March and July depending onthe area (Dimock et al. 1974). In Alaska, flowering occurs between March and June(Viereck and Little 1972). Near Vancouver, B.C., Pojar (1974) reported floweringbetween June 12 and July 4. In Washington state, flowering begins in the third weekof June. Fruits ripen between August and October and remain on the stem untilDecember (Dimock et al. 1974).Largent et al. (1980) have reported that G. shallon can be associated with threedifferent kinds of mycorrhizae: arbutoid, ericoid, and ectomycorrhime. Threedifferent fungal species have been identified, one is Oidioclendron griseum and thetaxonomic position of the other two species are being studied (Xiao and 13erch, 1992).This is the first repot of 0. griseum as an ericoid mycorrhizal fungus of Gaultheria.Gaultheria shallon flowers are pollinated by insects, primarily bumblebees andflies (Pojar 1974). The fruit is a many-seeded capsule, and each inflorescence has 5-15capsules. However, Bunnell (1990) found that salal will flower only when twoconditions are met; on vigorous stems greater than four years old, and at a mean crown12completeness (a measure of forest canopy closure) less than 30%. Hebda (1982) foundthat Gaultheria shallon contributed less than 2% of the pollen and spore rain in areasdominated by salal, indicating how little salal flowers.The fruits of salal remain on the stem until December and those seeds remainingare viable for up to one year following ripening (Dimock et al. 1974). Fruits have anaverage of 126 seeds each. When conditions are suitable for flowering, heavy crops offruit are produced on a regular basis (Haeussler et al. 1990). Seeds are dispersedmainly by the animals which feed upon the fruit; black-tailed deer, Roosevelt elk,mountain beaver, ruffed grouse, blue grouse, and other small mammals and birds(Halverson 1986).Seeds can remain viable for several years in cold, dry storage, but the viabilityof seeds under natural conditions is generally much reduced (Dimock et al. 1974).Sabhasri (1961) stored seeds at 4.4 °C for one year and found a decline in germinationfrom 31% to 21%. Seeds do not require chilling (Haeussler et al. 1990) orstratification (McKeever, 1938) to induce germination. Successful germinationrequires moist, acidic sites under partial shade (Dimock et al. 1974) and light for eighthours or more per day is essential (McKeever 1938). In Washington, germination ratesof 27-35% from fresh seed under lighted conditions were reported (Sabhasri 1961;Dimock et al. 1974). In British Columbia, Messier (pers. comm.) obtainedgermination rates of approximately 60% under the same conditions.Despite the large quantity of seeds produced and the many seeds which germinate,seedling survival is very low (Haeussler et. al. 1990). Sabhasri (1961) found that inWestern Washington, seedling establishment is most successful in the understory ofyoung Douglas- fir stands.The most significant and effective form of colonization is through vegetativespread, both in open habitats and in deep shade. Once salal is present on a site, furtherexpansion is almost exclusively by vegetative means (Sabhasri 1961; Koch 1983;13McGee 1988; Messier 1991) including layering and suckering from roots and stembases. However, among the 54 naturally growing plants that Bunnell (1990) examined,no evidence of stem layering was found; rhizomes were the only means of producingnew shoots. Bunnell (1990) forced stems into the organic mat and examined them oneyear later to find that they had grown adventitious roots, and concluded that layeringmust also occur naturally. He found, while monitoring the colonization of salal, that85% of the space occupied by salal after nine years of growth was occupied during thefirst three years. Bunnell also discovered that the vegetative reproduction of rametswas negatively associated with age (r2 =0.95) and no new shoots were produced after aplant reached nine years of age. Seed production may be significant in the initialcolonization of a newly disturbed area (eg. wind storms, clear-cut), but considering thata plant must be at least four years old before it will flower, and that most colonizationof an area occurs within the first three years, the vast majority of colonization occursthrough vegetative spread. Bunnell (1990) found no seed production, only vegetativespread, at a mean crown completeness greater than 30%.The rate of increase of salal populations depends largely on the stage ofsuccession of the area. Messier (1991) proposed a general growth model based on thework of Messier (1991), Messier and Kimmins (1991), Messier et al. (1989), Vogt etal. (1987), and Vales (1986) (Fig. 1) of the development of salal over a 60-year periodfollowing a major disturbance (eg. clear-cutting and slashburning) of old-growthwestern red cedar and western hemlock forests on northern Vancouver Island. Thedevelopment of the live fine-root, leaf, stem and rhizome biomass of salal has threedifferent stages. Stage one is between 1-15 years and is characterized by a rapidgrowth rate of rhizomes and fine-roots, in particular, between 8-15 years. Stage two,approximately between 16-45 years, begins with a rapid decline in salal live fine-rootbiomass followed by a more gradual decrease in leaf and stem biomass. The decline ofthe population is caused by shading due to an increase in the overstory tree canopy.Salal biomass (1000 kg/ha)100468— — — - Leaf   New-rhizome^ Fine-root   Stem4-- Stage 1 ^2 Stage 3..„......^_..........^— —....................14Old-growthforest0^15^30^45Years after clear-cutting and burning60Figure 1. Hypothetical development of live-root, leaf, stern and rhizome abundance ofGaultheria shallon over a 60 year period folowing the deaf-cutting andburning of old-growth forests of western red cedar and western hemlock onnorthern Vancouver Island (taken from Messier, 1991).15There are no data for rhizome biomass in the 10 to 60 year period, but it is believed tobe high (Messier 1991). The final stage, occurring from 46 years until the next majordisturbance, is the virtual exclusion of salal by the dense overstory canopy. However,it is not completely excluded and can quickly re-establish following a disturbance.Much research effort has been focused on the competitive interactions of salaland coniferous tree species in low-elevation coastal British Columbia forests (Tan et al.1978; Black et al. 1980; Price et al. 1986; Weetman et al. 1989a; Klink et al. 1989a;Messier et al. 1990; Messier 1991). The competitive influence of salal on the seedlingsof Douglas-fir, western hemlock, and Sitka spruce is believed to be much stronger thanon western red cedar and lodgepole pine (Bunnell et al. 1990). Competition is mostsevere during the early stages of stand development (Long 1977) but may continuethrough the rotation, in particular, if the canopy is open enough to allow a well-developed understory of salal to persist (Stanek et al. 1979).Young stands of Douglas-fir on sub-xeric sites are limited by soil waterpotential (Tan et al. 1977). At low values of soil water potential, the reduction instomatal conductance is greater for Douglas-fir than for salal, indicating that salaltranspiration would account for a higher proportion of total stand transpiration (Tan etal. 1978). Price et al. (1986), found that the removal of the salal understory of thinned32-year-old Douglas-fir significantly increased rates of photosynthesis and tree growthdue to an increase in the soil water potential. Other researchers have proposed thatsalal may be competing for nutrients in the Douglas-fir forests (Stanek et al. 1979;Haeussler and Coates 1986).There is evidence to suggest that salal may also be competitive in moistecosystems (Weetman et al. 1989b; Messier 1991). Two hypotheses have beenproposed to account for this. First, is the resource exploitation hypothesis. Weetmanet al. (1989a, 1989b) have shown that on northern Vancouver Island western red cedarand western hemlock cutovers that are dominated with salal are nutrient deficient.16Germain (1985) and Messier (1991) found that salal can have an impact on the nutrientbudget of conifers. Gaultheria shallon forms ericoid, arbutoid and ectomycorrhizae(Largent et al. 1980), whereas western hemlock only form ectomycorrhizae, andwestern red cedar only form vesicular-arbuscular mycorrhizae; therefore, because salalmight be more efficient at extracting nutrients such as nitrogen and phosphorous at lowpH, and accessing nutrients in complex organic forms (Xiao, Cade-Menum and Berchpers. comm.). Parke et al. (1983) suggest that dense salal can lower soil temperaturescausing reduced conifer growth by inhibiting root growth and mycorrhizal infection.The second hypothesis involves the possible allelopathic properties of salal. Del Moraland Cates (1971) did not find convincing evidence for allelopathy in salal, but Rose etal. (1983) have shown that allelochemicals in salal litter may inhibit seedling growth.It has been suggested that salal may have an allelopathic effect through the productionof tannins and phenolic acids (de Montigny, 1992).In general, salal is both resistant and resilient to many herbicides. The mostsuccessful herbicide in controlling salal is triclopyr ester (Garlon). Applying triclopyrester at 4 kg a.i./ha reduced salal cover by 78% (Barker 1988). Combining diesel withtriclopyr ester effectively controlled salal for three seasons in a Douglas-fir-salalecosystem on the southeast coast of Vancouver Island (Dunsworth 1986). In anexperiment conducted in a dry cedar-hemlock ecosystem, 4 kg a.i./ha trilopyr ester indiesel oil at 100 L/ha in early spring or late summer reduced salal cover by 60-90%.When using mineral oil as the carrier instead of diesel oil, salal cover was reduced byonly 40% (Haeussler et al. 1990).In all of the herbicidal tests to control salal, little is known about how thebelow-ground plant portion responds. D'Anjou (cited by Haeussler et al. 1990)showed that although above-ground parts of salal were well controlled by triclopyrester, living roots (dry weight basis) still comprised 89% of that in untreated controls,indicating that roots continue to survive despite substantial foliar control.17Several studies have reported that salal will rapidly increase in cover and vigourfollowing the removal or reduction of the forest canopy (Sabhasii 1961; Long andTurner 1975; Long 1977; Stanek et al. 1979; Black et al. 1980; Koch 1983; Gholz etal. 1985; Price et al. 1986; Vales and Bunnell 1988; Messier et al. 1989). Messier(1991) found that salal reestablishes relatively quickly below ground following clear-cutting and slashburning, but the above ground portion does not grow as rapidly andmay take many years to become dominant.Prescribed burning after logging can increase the growth of salal if the burn islight. Fire stimulates resprouting from roots and stem bases (Sabhasri 1961; Lafferty1980). Only severe burns that penetrate sufficiently deep to kill the roots can reducesalal cover. Vihanek (1985) reported that high severity burns on dry sites on easternVancouver Island decreased salal cover by 80% compared to adjacent unburned areaswhereas low to moderate burns decreased cover by only 40%.Fertilizer application, particularly nitrogen-rich fertilizer, increases both aboveand below-ground growth of salal (Sabhasri 1961; Anonymous 1970). However, inforest stands, applications of fertilizer that result in an increased tree canopy densitymay cause a decline in the vigour and cover of the salal understory due to shading(Long and Turner 1975; Stanek et al. 1979).Salal readily forms new plants from cutting of the stem and the roots (Sabhasri1961), so it can be expected that any form of soil disturbance that causes mechanicaldamage to the plant, but that does not physically remove it from the site, will stimulateresprouting. However, it has been reported by Muller (1989, cited in Haeussler et al.1990) that heavy scarification on areas on Vancouver Island has resulted in very slowre-invasion of salal. R. Green (pers. comm.) has reported slow colonization of accesslogging roads in Cameron Valley, southern Vancouver Island. R. Green observed thatif the organic layer is removed, exposing the mineral soil over a large area, salal willnot quickly recolonize. He postulated that because areas of southern Vancouver Island18are very dry, salal rhizomes are particularly vulnerable to mortality caused bydessication following heavy scarification.The salal hypothesisCentral to the salal hypothesis is the assumption that the presence of salal, dueto an as yet undetermined mechanism, markedly contributes to the decline of replantedforests on the CH sites. A number of studies have been conducted where the removalof salal improves the growth of neighbouring conifer seedlings (Weetman et al. 1989b;Messier 1991; Preston et al. 1992). However, although the evidence to support theidea that salal competition is central to conifer plantation stagnation at CH clear-cuts onVancouver Island is compelling, it is nevertheless inconclusive.A trial by Weetman et al. (1989b) was accomplished by manually "grubbingout" (removing with a pole-axe) the above-ground portion of salal, followed by a singleapplication of the herbicide GarIon 4E (3.5 kg/ha) at the end of the second growingseason to control re-establishment. Of the three conifer species tested (western redcedar, western hemlock, and Sitka spruce (Picea sitchensis (Bong.) Carr.), salalremoval resulted in increased nitrogen uptake and a slight increase in height only incedar. However, grubbing of the study sites to remove salal also caused mixing of thesoil which possibly confounded the results and renders interpretation inconclusive.Furthermore, the study by Weetman et al. (1989b) was designed to determine simply ifcompetition occurred. The occurrence of competition does not imply that it is centralto the distribution and structure of plant communities (Goldberg and Barton 1991).Messier (1991) studied the competitive effect of salal by planting Sitka spruceseedlings in the middle of 200 cm diameter patches from which all above-groundvegetation was continuously removed by clipping. Furthermore, below-groundcompetition from adjacent vegetation was eliminated by periodically trenching to adepth of 40 cm around the perimeter of these patches. Messier detected increased19growth of the Sitka spruce in the treated sites. However, Connell (1990) has criticizedthe practice of trenching because by severing the roots of competitors, the abundance ofnatural enemies (soil pathogens, root predators, etc.) in the vicinity of the roots of thetarget plants may be reduced and may lower the rate of attack on the plant. This maylead to an increase in the growth or survival of the target plant within trenched plots.This argument is supported by Gadgil and Gadgil (1971) who demonstrated thattrenching on a pine plantation in New Zealand resulted in an increased rate of litterdecomposition. They suggested that saprophytic fungal populations had increased inabundance or activity, or both, thus increasing nutrient availability. These effectswould both result in what Connell refers to as "apparent" competition. To partiallycontrol for the "trenching effect", Messier (1991) should have set up an additionaltreatment where trenches were dug around seedlings without the above-ground portionof salal removed. The strength of Messier's (1991) conclusions is based on hismeasurements of the nitrogen that the above and below-ground portions of salal areable to immobilize in the first 8 years: approximately 9 kg/ha/year. This indicates apotential temporary loss of nitrogen to the system, but it is not proof that salalcompetes with conifer seedlings. It has been shown recently (Berch and Xiao, 1992)that salal is capable of growing only on organic forms of nitrogen due to itsmycorrhizae. Therefore, the high rates of nitrogen that Messier (1991) reported beingimmobilized by salal may not have originally been in a form that was available to theconifers, regardless of whether salal was present or absent. The same may be true, andis currently under investigation (Berch and Cade-Menun 1992), for availablephosphorus.Preston et al. (1992) have preliminary results from a salal eradication and nitrogenfertilization experiment with western red cedar, western hemlock and Sitka spruceseedlings in which half of the plots salal was eradicated, and the remaining half were20control plots. ( 15NH4)2SO4 was applied at 200 kg N/ha to all the plots. They reportthat after one growing season following salal removal a significant increase in treeheight growth occurred for all the conifer species, especially western hemlock.However, salal removal did not significantly affect first year tree foliage nitrogenconcentrations. Furthermore, tree foliage N-15 concentration was greater in the controlplots than the salal eradicated plots. The researchers argued that this is a dilution effectcaused by an increase in tree growth, and expect overall N-15 content in tree foliage tobe greater in the salal eradicated plots.In light of the research that has been done it seems reasonable to conclude thatsalal has a negative influence on the growth of conifers, but data are inconclusive.However, rigorous data are difficult to gather because manipulative field experimentsoften yield confounding effects. Therefore, it was necessary to investigate theinfluence of salal on conifer seedlings from a different perspective.21OBJECTIVESThe specific objectives of my study were to:1. quantify the relationship between leaf area index of salal and performance ofneighbouring western hemlock and western red cedar saplings;2. quantify the influence of leaf area index of other neighbouring species on westernhemlock and western red cedar sapling performance;3. relate abiotic environmental factors i.e., soil moisture, soil coarse content, soilcarbon, soil total nitrogen, and soil total phosphorus to western hemlock, western redcedar and salal performance;4. determine the effects of treatment: fertilization, scarification (i.e. manual removalof salal), and fertilization plus scarification; and site: CH and HA on western hemlock,western red cedar and salal growth and foliar nutrient concentration, as well asenvironmental variables.METHODSStudy areaThe study was conducted at the SCHIRP site located approximately 20 km northof Port McNeill situated on Block 4 of Tree Farm Licence 25 operated by WesternForest Products Ltd. on northern Vancouver Island, B.C., Canada (50°60'/127°35')(Fig.2). The SCHIRP site is in the submontane variant of the CWHvm biogeoclimaticsubzone (Lewis 1982). The elevation of the site is approximately 100m above sealevel. The summers are cool and moist and winters mild and wet. The followingweather data were collected at the Port Hardy Airport weather station located about 20km north of the study area at an elevation of 50m above sea level. The data representan average from 1966-1992. The area receives approximately 1700 mm of rainfallannually, 65% occurring between October and February. From March to Septemberno less than 50 mm of precipitation falls monthly, indicating that drought is absentfrom the deep mineral soils in all but exceptional years (Lewis 1982). The hours ofdirect sunlight vary from an average high of 6.4 h/day in July to an average low of 1.5h/day in December. The frequent occurrence of fog in the summer and frontal cloudsin the winter account for the low hours of direct sunlight. Mean daily temperatureranges from a high of 13.7°C in July/August to a low of 3.0°C in January/February.Field manipulationsThe SCHIRP site was clear-cut logged in 1986, broadcast burned during thespring of 1987, and planted in 1988 (Barker et al. 1991). Therefore, the conifers were2- and 4-years-old during the study period (1990 - 1992). At the time of the study,vegetation, including salal, had between 3- to 5-years to reinvade after broadcastburning in 1987.22230^50^100kilometresRESEARCH AREAPACIFIC OCEANBRITISH COLUMBIA, CANADAV couver•WASHINGTON, U.S.A.Figure 2. Study area - northern Vancouver Island.24The SCHIRP site has 128 plots, with 64 trees per plot, involving severaltreatments (Barker eta]. 1991) (Fig.3):2 ecosystems2 pure conifer stands3 densitiesxx- CH- HA- western red cedar- western hemlock- 500 trees/ha- 1500 trees/ha- 2500 trees/hax2 fertilities^- fertilized- unfertilizedx4 replicatesIn addition, scarified and scarified plus fertilized plots were established, but only onthe highest planting density plots of 2500 trees/ha.2 ecosystems^-CH- HAx2 pure conifer stands2 treatmentsx- western red cedar- western hemlock- scarified- scarified plus fertilizedx4 replicatesEach tree was labelled and measured for height and root collar diameter in1988, 1989, 1990 and 1992 by Western Forest Products.25131kCHlois*Blk IVCH15SHFit$ 11640.....811c IVHA ser Blk IHAes4,4 Blk8414,MENEM•• • .....^........BIk IV--._^CH :.1:11k IScale - 1:10000...600 /.Figure 3. SCHIRP site - experimental design. The 97 ha site is located on the Rupert600 (R600) logging road. The site was clear-cut logged in 1986, burned in 1987, andplanted in 1988. C= western red cedar, H= western hemlock, F= fertilized,S =scarified (^ ) represents the CH (cedar-hemlock) HA (hemlock-fir) boundary.Blocks 1-4 represent the four replications in the design, each block having both CH andHA sites. The smallest to largest boxes indicate planting densities of 2500, 1500, and500 trees per hectare, respectively, with spacing between trees of 2.0 m, 2.63 m, and4.5 m, respectively.Table 4. Number of plots sampled from each site x treatment combination in theSCHIRP site at the highest planting density of 2500 trees/ha.26Western hemlock:Treatmentcontrolfertilizedscarifiedfertilized + scarifiedCH site HA site4 44 44 44 4Western red cedar:Treatmentcontrolfertilizedscarifiedfertilized + scarifiedCH site HA site4 44 44 44 4Total = 64 plots27Within the fertilized treatments, each tree was individually fertilized with 60g ofNutricoat controlled release fertilizer (Type: 360 16-10-10). Scarification was doneusing a backhoe (215 Cat Excavator) with a 3-tyned rake attachment. The purpose ofthe scarification was to remove salal rhizomes and to simulate windthrow by mixing theorganic forest floor and the mineral soil.In my study, only the high density (2500 trees/ha) plots, represented by thesmallest boxes in Figure 3, were used. It was reasoned that competition betweenplanted conifers would be minimal at this early stage in growth at all densities andtherefore the lower densities were not required. A total of 64 plots in the SCHIRP sitewere studied (Table 4).Data collectionDuring the summer of 1991, four conifer seedlings were selected from each ofthe 64 plots, except for one plot in which only three suitable conifers were found, for atotal of 255 seedlings. The conifers were chosen based on the percent cover of salalsurrounding them within a 1m 2 area. Four different abundances of salal were selected:approximately 0%, 33%, 66% and 100% salal cover. A 1m2 quadrat was centeredaround each conifer on a direct north/south orientation. The same quadrats weremeasured over two summers (1991 and 1992). The following measurements weremade on each of the quadrats:i) vegetation measurements: During both summers, the leaf area index (leaf area perunit of land area) of all plant species present was measured using 50 systematicallyarranged points per quadrat (Fig. 4). A list of the plant species found on either CH orHA sites is presented in Table 5. At each point, the number of leaves from eachspecies that passed through that point was counted. The mean leaf area per quadrat form281 mFigure 4. Diagram illustrating the methods used to measure leaf area index of non-crop vegetation, leaf litter of salal and soil variables. The conifer being measured isrepresented by • . At each intersection of horizontal and vertical lines, thenumbers of leaves of each species were counted for the leaf area index measurement.The areas represented by \ • were where the leaf litter of salal was collected. Thesolid boxes (^) were where the soil samples were collected.Table 5. Species list of the naturally growing vegetation within the study area on theCH and HA sites.29Scientific name and authority1. Anaphalis margaritaceae (L.) B. & H.2. Blechnum spicant (L.) Roth.3. Bryophytes4. Cornus canadensis L.5. Dryopteris expansa (Presl) Fraser-Jenkins & Jeremy6. Epilobium angustiMium L.7. Equisetum sylvaticum L.8. Gaultheria shallon Pursh9. Hypochoeris radicata L.10. Lysichitum americanum Hulten &St.John11. Menziesia krruginea Smith.12. Mycelis muralis (L.) Dumort.13. Pinus contorta Dougl.14. Poa L.15. Pteridium aquilinum (L.) Kuhn.16. Ribes laxiflorum Pursh17. Rubus spectabilis Pursh18. Sambucus rac,emosa L.19. Sthx sitchensis Sanson20. Thuja plicata Donn.21. Tsuga heterophylla (Raf.) Sarg.22. Vaccinium ovalikilium Smith23.^Vaccinium parvifiylium Smithcommon namepearly everlastingdeer fernmoss familybunchberryspiny wood fernfireweedhorsetailsalalhairy cat's earskunk cabbagefalse azaleaewall lettucelodgepole pinegrass familybracken ferntrailing black currantsalmonberryelderberrysitka willowwestern red cedarwestern hemlockoval leaved blueberryred huckleberry30each species was used for the analyses. Leaf area index is a measure of thephotosynthetic potential of plants.a) Conifer seedling performance as indicated by height and root collar diameterwas measured on the 255 seedlings at 2-years-old and 4-years-old (1990 and 1992) byWestern Forest Products. During a 3-day period in mid-July, 1992, four or five twigseach approximately 10-15cm long were clipped from each of the conifers for a foliaranalysis. The samples were oven-dried at 28°C for 24 hours, and ground in a standardBraun coffee grinder. Concentrations of total nitrogen, phosphorus and potassium weremeasured from oven-dried samples on an autoanalyzer following sulphuric acid -hydrogen peroxide digestion (Parkinson and Allen 1975). A colour index of conifertrees was also scored in 1992 in order to determine a relationship between foliarnutrient concentration and colour index of conifers. It is well known that a plant withnutrient deficiency has different colour leaves than a healthy plant (Lavender andWalker 1979). A number was assigned to each of the conifers according to the colourof their needles: 1 indicated dark green, 2-light green, 3-yellow-green, and 4-yellow-brown.b) Gaultheria shallon leaves were collected and analyzed for nitrogen,phosphorus, and potassium during the same time interval that conifer foliar analyseswas conducted (mid-July, 1992). Between fifteen and twenty salal leaves greater thanone year old were randomly selected from 48 of the 255 total number of quadrats.Gaultheri a shallon leaves less than one year old have less cuticle thickness and colourthan those greater than one year old. Older leaves had a thick waxy layer and weredark green in colour compared to the relatively thin, light green leaves less than oneyear old. Of the 48 quadrats, eight were randomly selected from each of threedifferent treatments; control, fertilized, and scarified, on both the CH and HA sites.Concentrations of total nitrogen, phosphorus and potassium were measured from oven-31dried samples on an autoanalyzer following sulphuric acid - hydrogen peroxidedigestion (Parkinson and Allen 1975).c) Gaultheria shallon leaf litter was also collected from each of the 255 quadratsduring the summer of 1992. The leaf litter was collected from four 10 cm 2 patcheswithin each quadrat (Fig. 4). The leaf litter from each quadrat was combined, ovendried at 28°C for 48 hours and weighed. Because salal leaves live for an average of 4years before shedding, a measurement of the abundance of salal leaf litter yielded anestimate of the length of time salal occupied the area immediately surrounding theconifers at these sites.ii) Environmental measurements: Environmental variables were measured onlyduring the summer of 1992. Soil samples from the rooting layers (humus layer and Ahlayer) were collected from within each 1m2 quadrat, and 4 subsamples from eachquadrat were combined (Fig. 4). In the field, soils were put in a cooler during the dayand transferred to a deep-freeze in the evening for storage where they remained frozenuntil analyzed. The following analyses were conducted for each of the samples: soilmoisture, coarse soil content, total carbon, total nitrogen and available phosphorus.After mixing the soil thoroughly, each of the soil samples was divided in half.Soil moisture was measured by weighing one half of each of the soil samples beforeand after oven drying at 27°C for 36 hours. Coarse soil content was measured bysieving the oven-dried soil through a 2mm sieve and weighing the portion of soil thatcould not filter through the sieve.The remaining soil from each of the soil samples was air-dried for one week,and finely ground in a standard Braun coffee grinder in preparation for nitrogen,phosphorus and carbon analysis. A Leco analyzer was used to measure total carbon(Anonymous 1981). Total nitrogen and potassium was measured by initially digestingthe soils. Because the soils were generally highly organic, 1 g of soil was digested32using lg of digestion mix (K2SO4, CuSO4-5H20, and Se), and 10 ml H2SO4. Totalnitrogen and potassium was measured by an autoanalyzer. To measure totalphosphorus, samples were air-dried and extracted with Bray' s solution (McKeague1978) and analyzed on an autoanalyzer.DATA ANALYSISSite x treatment effectsThree-way ANOVA' s were applied to the soil variables, salal performance, andconifer performance. The independent variables were site (CH and HA); fertilization(present and absent); and scarification (present and absent). Western red cedar andwestern hemlock saplings were analyzed separately. SYSTAT (Wilkinson 1990) wasused for all statistical procedures.Bartlett's test for homogeneity of group variances was applied to each ANOVA.If the data were heteroscedastic with a significance of p< 0.10 transformations wereperformed to meet the assumption of equal variances. Three transformations (Table 6)were applied: logarithmic (X' =logX), arcsine (P' =arcsinP), and square root (X' =/X).An appropriate means separation test for hypothesis generation is Fisher'sprotected least significant difference (LSD) (Saville 1990). This test was applied toeach of the ANOVA's to separate treatment means (p< 0.05).Relationship between non-crop vegetation and conifer performanceStepwise multiple regression was applied to determine which vegetationvariables (leaf area index) influenced height and root collar diameter of western redcedar and western hemlock saplings in each of the eight different site x treatmentcombinations: i.e. 2 ecosystems (CH and HA) x 4 treatments (control, fertilized,33Table 6. Transformations on western red cedar and western hemlock data in order tomeet the assumption of equal variances for the analysis of variance. "-" represents thatno transformation was necessary.Measurement Variables^Cedar HemlockHeight of conifers (1990) -Root collar diameter of conifers (1992)^-Height of conifers (1990)^ logRoot collar diameter of conifers (1992)^logColour index of conifersFoliar nitrogen of conifers^arcsineFoliar phosphorus of conifers logFoliar potassium of conifers^arcsineLeaf area index of salal (1991) -Leaf area index of salal (1992)Salal leaf litter^ log^square rootFoliar nitrogen of salal^ -Foliar phosphorus of salal -Foliar potassium of salal^ -Soil moisture^ -Soil coarse content log^logSoil total carbon^ arcsine^arcsineSoil total nitrogen -Soil total phosphorus^ log^log34scarified, and fertilized plus scarified). Leaf area index data from 1991 were used todetermine the variation in 2-year-old conifer performance measured in 1990. Ideally,conifer performance from 1991 should be used but the data were not available. Leafarea index data from 1992 were used to determine the variation in 4-year-old coniferperformance measured in 1992. By decreasing the number of independent variables inthe model, its predictive capability is enhanced. This is because the variance of theparameter estimates decreases. However, with the reduction of independent variables,bias may increase because the "true model" may have a higher dimension. The goal isto balance smaller variance against increased bias. Generally, variables within themodels which displayed an absolute t-value less than 2.0, a p-value greater than 0.5,and tolerance values less than 0.1 were removed; the exceptions to this general rulewere those variables that, when removed, the R2 and the analysis of variance p-valueof the multiple regression model were reduced. Tolerance is a measure of correlationbetween variables and is calculated as 1 minus the square multiple correlation betweena predictor and the other predictors included in the model. The multiple regressionmodels were tested for normal distribution, homogeneity of variance, independenterrors and to ensure that all the members of the population were described by the samelinear model.The primary emphasis of this study is to determine the influence of salal onconifer performance. Therefore, the individual R2 values of salal were calculated fromthe output of the multiple regression models to determine the variation of height androot collar diameter of the conifers by salal alone. The following method was used tocalculate the R2 values of salal from the output of the multiple regression models (Zar1984):35T2 = FF = regression MS residual MSregression SS = residual SS x dfR2 = regression SS total SSwhere; T= test statistic, F= test statistic, MS =mean square, SS =sum of squares.This method is not a rigorous statistical test because the independent variablesfrom a multiple regression model are not independent on their own. However it allowsan estimate of the influence of salal alone on the height and root collar diameter ofconifers.The influence of the abundance of salal on the growth of conifersbetween 1990 and 1992.The growth increment of hemlock and cedar height and root collar diameterover two years were measured when the conifers were 2- and 4-years-old. The 2 yeargrowth rates were separated by site (CH and HA) and treatment (control, fertilized,scarified, and fertilized plus scarified) for a total of 32 separate conditions: 2 conifers(hemlock and cedar) x 2 conifer performance variables (height and root collar diameter)x 2 sites (CH and HA) x 4 treatments (control, fertilized, scarified, and fertilized plusscarified). The growth rates of conifers were regressed against the leaf area index ofsalal for 1991, the mid-point of the 2-year time period, and the regression lines werecompared.36RESULTSPredictionsIn order to accept the "salal hypothesis", a number of outcomes from themultiple regression models must occur. These predictions are made based on researchconducted by SCHIRP researchers as to the response cedar and hemlock saplings haveto the abundance of salal according to the "salal hypothesis". The following fourparagraphs state the predictions. See Figure 5 for a summary of the predictedoutcomes.Growth of hemlock on CH sites: According to Bunnell (1990), hemlock growthis more sensitive to the abundance of salal than cedar, therefore it is predicted that theabundance of salal will be negatively correlated with growth performance of hemlockon control and scarified plots to a greater degree than cedar. Scarification is meant tomimic the disturbance of the soil following trees felled in a windstorm and increasenutrient availability of the soil due to increased aeration and mineralization. Therefore,hemlock on scarified plots will grow marginally better than on control plots. Weetman(1989b) found that hemlock had a greater growth response to the addition of nitrogenand phosphorus than cedar. Furthermore, Weetman (1989b) found that after salalremoval, increased nitrogen uptake was observed in cedar, not hemlock. Thereforesalal abundance on fertilized, and fertilized plus scarified plots would show lessinfluence on the growth of hemlock than cedar.Growth of hemlock on HA sites: It is predicted that salal abundance on controland scarified plots will be negatively correlated with hemlock growth. However, thegrowth of hemlock would be less sensitive to salal on HA sites compared to CH sites.37Salal abundance on fertilized, and fertilized plus scarified plots would show very little,if any, influence on the growth of hemlock.Growth of cedar on CH sites: It is predicted that salal abundance will benegatively correlated with height and root collar diameter of cedar on control andscarified plots, but that the correlation will not be strong because natural regenerationof cedar is better than hemlock on control CH sites (Weetman et al. 1989b). Becausescarification may increase the available nutrients in the soil, cedar will grow better onscarified plots than control plots. On fertilized and fertilized plus scarified plots theremay be a small negative correlation between cedar growth and salal abundance becausethe fertilization of the sites would diminish the effect of any resource depletion bysalal. However, although tolerant of low nutrient soils, cedar grows rapidly in nutrientrich environments (Krajina et al., 1982). Therefore cedar may be slightly inhibited bysalal growth even when the site is fertilized.Growth of cedar on HA sites: It is predicted that the abundance of salal oncontrol and scarified plots is negatively correlated with cedar growth but not as stronglyas on CH sites. Salal abundance on fertilized and fertilized plus scarified plots willhave very little negative influence, if any, on cedar growth but, similar to CH,fertilization will reduce the effect of salal, especially since HA sites are higher innutrients compared to CH sites.HEMLOCKCH site^HA site38treatmentasalal abundanceconifer responsebc f s f+ s c f s f+ shigh high high high high high high higha c bd b dc dCEDARCH site^HA sitetreatmentsalal abundanceconifer responsec f s f+ s c f s f+ shigh high high high high high high highb d c d c dc dFigure 5. The predicted western hemlock and western red cedar response to highabundance of salal based on the salal hypothesis.ac=control, f= fertilized, s= scarified.ba=a 50% or more reduction in conifer growth compared to a conifer growing inoptimum conditions, b=30-50% reduction in conifer growth compared to a conifergrowing in optimum conditions, c= >0-30% reduction in conifer growth compared toa conifer growing in optimum conditions, d =no influence from salal.39Site x treatment effect using 3-way ANOVAwestern hemlocka: Soil variablesGenerally, the soil moisture content was higher on CH sites than on HA sites(Fig. 6a), especially in control and in scarified sites. Also, the plots manipulated themost (fertilized plus scarified) on CH sites had the least soil moisture content.Although coarse content of soils increased with increasing field manipulation on CHsites, there was no significant difference (Fig. 6b). HA sites generally had a highercoarse soil content than CH sites, but fertilized HA sites were significantly greater thancontrol CH, fertilized CH and scarified CH sites. Fertilized HA sites were alsosignificantly greater than fertilized plus scarified HA sites. There was very littledifference in the total carbon concentration of soils except that scarified HA sites hadpredictably lower total carbon than control HA sites (Fig. 6c). There was no differencein the total nitrogen concentration of the soil between the treatments on the HA sites(Fig. 6d). Interestingly, soils in control CH sites had a greater total nitrogen than bothscarified CH sites and fertilized plus scarified CH sites. Also, soils of fertilized CHsites had a greater total nitrogen than scarified CH sites. An interesting pattern can beseen in the total phosphorus of soils (Fig. 6e); there was no difference between sites,however, soil from scarified plots in both CH and HA sites were significantly less thanall other site x treatment combination except fertilized HA sites.b: salal performanceThe leaf area index of salal in 1991 (Fig. 7a) and 1992 (Fig. 7b), and the leaflitter of salal (Fig. 7c) all show similar patterns. Generally, control and fertilized plotson CH sites had a higher leaf area index and leaf litter than all other site x treatmentcombinations, i.e. scarification reduced leaf area index and leaf litter. Scarification on90807060 -50-40 -30 -20 -lo -— bc bcab0bca abc–^c f s f+s^c f s +s25-20r 150coco 10co5ab oh• c^f^s c^f^5^i-A406050S 40-CHbsiteabHAobsiteaab025020dCHbcsitea ababcHAaLxsiteabcabcJD z0 30010-.6 20-1 0 - 0.05-c^f^s^f+s^C^t^s^f+s0.00c^f^s^f+s^c^f^s +sCH site HA site CH site HA site20011 1500_100 aab^a50c f s f+s^c f s +sCH site HA siteFigure 6. Site x treatment effect on soil variables (moisture, coarse content, totalcarbon, total nitrogen, and total phosphorus) where western hemlock was planted using3-way ANOVA. Fisher's protected least significant difference was applied to separatetreatment means. Within a group, bars sharing the same letter are not significantlydifferent (p> 0.05). On the x axis, c=control, f=fertilized, and s= scarified.41A3 3—9)-0 2 -0 2 bcci bc cd‘c.-13 abbcbc bccoa)cc1abr-b ab abaab "(Toa)UITa1 abacc0c^f^s f4-8^ C^ C ^f^s^4-8CH site^HA site^ CH site^HA site20151210-0.8aa _9_aaa10 - bc^oh 00'Cr; ab^ab ci0.47135 ab abCDa02 -00c^f^s^f+s s^f+s S^ SCH site HA site CH site HA site0.15 12 -a0.10 aaa a a1.0 -0.8 -a aaa aci0.6 -.2 0.05 0.402 -0.00C^f^s0.0C^fCH site^HA site CH site^HA siteFigure 7. Site x treatment effects on salal performance (LAI, leaf litter, foliar nitrogen,foliar phosphorus, and foliar potassium) where western hemlock was planted using 3-way ANOVA. Fisher's protected least significant difference was applied to separatetreatment means. Within a group, bars sharing the same letter are not significantlydifferent (p> 0.05). On the x axis, c = control, f= fertilized, and s= scarified.42HA sites showed that the lowest leaf area index and leaf litter values compared to allother site x treatment combinations. No significant differences were found between thetreatments or sites of salal foliar nitrogen, phosphorus, or potassium concentrations atp< 0.05 (Figures 7d,e,f), but foliar nitrogen concentration of salal on fertilized HAsites was greater (p< 0.10) than control CH sites. Furthermore, foliar potassiumconcentration of salal on scarified HA sites was significantly greater than scarified CHsites.c: western hemlock performanceHemlock height (Fig. 8a) and root collar diameter (Fig. 8b) in 1990 showedsimilar patterns. Hemlock growing on control CH sites were significantly smaller, thanall other site x treatment combinations. A treatment effect could be seen on CH siteswhere there was increasing height with increasing field manipulation, but this was notseen on HA sites. A noticeable site difference was evident, with height and root collardiameter of hemlock on fertilized CH sites and scarified CH sites being significantlysmaller than fertilized HA sites and scarified HA sites, respectively. In 1992, the height(Fig. 8c) and root collar diameter (Fig. 8d) of 4-year-old hemlocks again showedsimilar patterns. The only significant difference between height and root collardiameter measurements of 2- and 4-year-old hemlocks is that the effect of scarificationhad increased height and root collar diameter at a greater rate on both CH and HA sitesthan the other treatments. Therefore 4-year-old hemlocks grown on scarified CH siteswere not significantly shorter than 4-year-old hemlocks grown on fertilized CH sites,unlike 2-year-old hemlocks measured in 1990. Also, 4-year-old hemlocks grown onscarified HA sites were significantly taller than 4-year-old hemlocks grown on fertilizedplus scarified CH sites, unlike 2-year-old hemlocks measured in 1990. Finally, unlike1990, root collar diameter of hemlock on scarified HA sites was significantly greaterthan control HA sites.A3503009>6050uE 250- zi5 40o 200- cd — cd E(is 30 -cd cd cd-z 150 - bc bz.-0 20,_c 100 a50 -10-0o f^s^t+s c^f^s^f+s f^s^f+s^c^i^S^4-sCH site HA site CH site HA site350 60 d —300 - de — e (N.1 50cd0(NICD250 -200 -150 -100 -abc— b :5E'35zi--3754°3020 ab b50 -810 -E' 0S^f 4-S C^I^$^I+5 ci^s^+s^c^f^sf +sCH site HA site CH site HA siteFigure 8. Site x treatment effects on western hemlock performance (height and rootcollar diameter) using 3-way ANOVA. Fisher's protected least significant differencewas applied to separate treatment means. Within a group, bars sharing the same letterare not significantly different (p > 0.05). On the x axis, c=control, f=fertilized, ands= scarified.430.80.00200.050.0044d d—3.22.4-1.00.8cdC^f^s 11-CH sitebc^bc- abc f s +HA site?- 0.6-z0 0.4-02 -0.0_d dab aba ab —c f 5 1+5^c f s f+OH Slte HA dtebc1.0-0.8-ab ab^ ab aba^ a a —cdb bab^ aa —C f s +CH sitec f s f+HA sitec f s +s^cf s +sCH site HA sitez?- 0.60.4026.0Figure 8 (cont.). Site x treatment effects on western hemlock performance (colourindex, foliar nitrogen, foliar phosphorus, and foliar potassium) using 3-way ANOVA.Fisher's protected least significant difference was applied to separate treatment means.Within a group, bars sharing the same letter are not significantly different (p> 0.05).On the x axis, c=control, f=fertilized, and s=sc,arified.45There was a distinct site difference in the colour index of hemlock (Fig. 8e).For each treatment, the colour index of hemlock was less on HA sites than on CH sites,i.e. hemlock grown on HA sites were greener. Furthermore, hemlock grown onscarified plots have a significantly lower colour index than those on control plots ineach site. There was also a strong site difference in foliar nitrogen concentration (Fig.80, where hemlock grown on HA sites had higher concentrations than CH sites. Theonly condition in which hemlock grown on HA sites did not have a higher nitrogenconcentration was fertilized plus scarified HA sites. The total foliar phosphorusconcentration of hemlock varied little between CH and HA sites (Fig. 8g). However,foliar phosphorus concentration decreased with increasing field manipulation for bothCH and HA sites. There was little variation in total foliar potassium concentration ofhemlock between the site x treatment conditions (Fig. 8h). However, hemlock grownon the fertilized plus scarified treatment on the CH sites had a significantly higherfoliar potassium concentration than hemlock grown on control CH sites.Western red cedara: Soil variablesSoil moisture did not vary significantly between treatments or sites (Figure 9a),and predictably, some fertilized sites had higher levels of nitrogen (HA on Fig. 9d) andphosphorus (CH and HA on Fig. 9e), although not always. The response of totalcarbon to the treatments was variable and showed no real pattern (Fig. 9c). Soil coarsecontent was greater on scarified sites compared to fertilized sites, but not control sites(Fig. 9b).b: Salal perbrmanceIn 1991, salal on scarified HA sites had a significantly lower mean leaf areaindex than all other treatments at both site types except for scarified CH sites (Fig.2520C15 -00co incd c d46bcababab cdcd —aCH site^HA siteCH site^HA site025020 -z 0.15 -To0.10Zo)005 -c f s f+s^c f s f+sababaaaa a0.00f^sf1-s^C^f^s f+sbcA908070^• a^a - _a a60_p6, 50-5 403020c f^fls^c f s f+sCH site HA site60^50- ab a ab oh^ab^a ab40 --aD0• 30O• 20c f s f+s^c f s +sCH site HA siteE250200-ab150a_^100^a^a^a50^0^c f s f+s^of s +sCH site HA siteFigure 9. Site x treatment effects on soil variables (moisture, coarse content, totalcarbon, total nitrogen and total phosphorus) where western red cedar was planted using3-way ANOVA. Fisher's protected least significant difference was applied to separatetreatment means. Within a group, bars sharing the same letter are not significantlydifferent (p> 0.05). On the x axis, c=c,ontrol, f=fertilized, and s= scarified.abc^f^s f4-CH siteac^f^f4.-sHA site0CO2015Ui1050ababcabas f+s25CH site^HA siteaac^f^sHA site0.0f^sCH sitea1.00.8 -0.60.4 -02a a1 2 -473 ab ab aba0f s +s^of s 4-8CH site^HA site0.15ab^ab0.10 aaa a a0.80.6abaab°-Caz 0.05Ui 0.4020.00c^f^s s0.0^sT^f^sCH site HA site CH site HA siteFigure 10. Site x treatment effects on salal performance (LAI, leaf litter, foliarnitrogen, foliar phosphorus, and foliar potassium) where western red cedar was plantedusing 3-way ANOVA. Fisher's protected least significant difference was applied toseparate treatment means. Within a group, bars sharing the same letter are notsignificantly different (p> 0.05). On the x axis, c=control, f= fertilized, ands=scarified.4810a). The highest mean leaf area index (1.8) was found on control HA sites. Asimilar, but less strong pattern was found in 1992 (Fig. 10b). Despite the large leafarea index of salal on fertilized plus scarified CH sites in both 1991 and 1992, salal leaflitter was lowest in those plots (Fig. 10c). There were no significant differencesbetween treatments or sites in either the salal foliar nitrogen (Fig. 10d) or phosphorusconcentrations (Fig. 10e). The mean foliar potassium concentration of salal onfertilized CH sites was significantly greater than that of salal at fertilized HA sites (Fig.100.c: Western red cedar performance2-year-old cedars height (Fig. 11a) and root collar diameter (Fig. 11b) measuredin 1990 on fertilized plus scarified CH sites (132.9cm and 23.8mm, respectively) wasmostly significantly greater than all other treatments in both sites. 4-year-old cedarsheight and root collar diameter measurements measured in 1992 showed that,predictably, fertilization and scarification significantly increased height in both CH andHA sites except for fertilized CH sites (Figures 11c and d). The added effect offertilization plus scarification significantly increased height and root collar diameter ofcedar on CH sites whereas on HA sites there was little difference in height and rootcollar diameter between field manipulations.The colour index of cedar on CH sites showed little difference betweentreatments (Fig. 11e). However, on HA sites, colour index decreased with increasingfield manipulation, i.e. cedar growing on fertilized plus scarified HA sites weresignificantly greener than control HA sites. Fertilization plus scarification increasedfoliar nitrogen and phosphorus of cedar in both CH and HA sites (Figures 1 if and g).However, the only significant differences were that fertilized plus scarified CH siteshad a higher foliar nitrogen than control CH and HA sites and fertilized CH sites.Also, fertilized plus scarified CH sites had a significantly higher foliar phosphorus thanaa a aaaba —_A300—E-u 20010060o 50-a 40-30-aki 20ao 10••-•0049b b ba ac f s f+s^c is +sCH site HA sitec f s f+s^c f s f+sCH site HA site300 — 60-50200 — cd —ab bc bcabcy a aa ac f s f+s^c f s f4-CH site HA sitef 5f4^C f S f4-SCH site HA siteFigure 11. Site x treatment effects on western red cedar performance (height and rootcollar diameter) using 3-way ANOVA. Fisher's protected least significant differencewas applied to separate treatment means. Within a group, bars sharing the same letterare not significantly different (p> 0.05). On the x axis, c=control, f=fertilized, ands=scarified.ab^ab ab abciba aa aab bc bc—bc a bc— bca0200.050.00ab050ab ab obc f s f+s^c f s I+sCH site^HA sitec f s f+s^c f. s f+sCH site HA site1.51.02 0,50.00.8g 0.6a— a0.4-C f sf+s^c f s f+sCH site HA sitef+s^c f s f+sCH site^HA site020.0Figure 11 (cont.). Site x treatment effects on western red cedar performance (colourindex, foliar nitrogen, foliar phosphorus, and foliar potassium) using 3-way ANOVA.Fisher's protected least significant difference was applied to separate treatment means.Within a group, bars sharing the same letter are not significantly different (p> 0.05).On the x axis, c=control, f=fertilized, and s=scarified.51control HA sites. There were no significant differences in total foliar potassiumconcentration of cedar saplings between treatments at both sites (Fig. 11h).Relationship between neighbouring non-crop vegetation and conifergrowth using multiple regression.WES7ERN HEMLOCKWestern hemlock saplings on conhyl plots in CH sites:Over 67% of the variation in height (Table 7a) and over 56% of the variation inroot collar diameter (Table 7b) of 2-year-old hemlocks were attributed to the presenceof neighbours. Hypochoeris radicata and G. shallon were negatively correlated withheight, while B. spicant and E. angustik•lium were positively correlated. As withheight, G. shallon was also negatively correlated with root collar diameter of hemlock,while E. angustiklium was positively correlated.Over 70% of the variation in height (Table 7c) and over 82% of the variation inroot collar diameter (Table 7d) of 4-year-old hemlocks were attributed to the presenceof neighbours. Unlike the height model of 2-year-old hemlocks, G. shallon was nolonger a significant variable. Hypochoeris radicata was still negatively correlated withheight, while A. margaritaceae, M muralis, and Vaccinium sp. were positivelycorrelated with height. However, M muralis was not significant in the model on itsown. Anaphalis margaritaceae, M muralis, and Vaccinium sp. were positivelycorrelated with root collar diameter, while H radicata and G. shallon were negativelycorrelated with root collar diameter.52Table 7.^Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on control plots in CH sites measured in 1990 and1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.821; R2=0.675; adjusted Rz=0.556ANOVA p-value=0.010Independent variables^std coef T P-valueEpilobium angustifolium 0.486 2.770 0.018Hypochoeris radicata -0.458 -2.553 0.027Gaultheria shallon -0.385 -2.010 0.070Blechnum spicant 0.366 1.876 0.087b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.749; R2=0.561; adjusted R2=0.493ANOVA p-value=0.005Independent variables^std coef^P-valueGaultheria shallon -0.580^-3.118^0.008Epilobium angustifolium^0.571^3.068 0.009c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.840; R2=0.706; adjusted R4=0.599ANOVA p-value=0.006Independent variables std coef T P-valueMenziesia ferruginea 7.833 4.670 0.001Vaccinium sp. 3.751 4.510 0.001Hypochoeris radicata -8.056 -4.466 0.001Mycelis muralis 0.282 1.699 0.117d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.907; R2=0.823;ANOVA p-value=0.002adjusted R2=0.734Independent variables std coef T P-valueMenziesia ferruginea 6.770 4.947 0.001Vaccinium sp. 3.257 4.806 0.001Hypochoeris radicata -6.963 -4.740 0.001Gaultheria shallon -0.447 -2.869 0.017Mycelis muralis 0.353 2.474 0.033std coef = standard partial coefficient53Western hemlock saplings on control plots in HA sites:Only 21.7% of the variation in height of 2-year-old hemlock (Table 8a) wasattributed to neighbours, but 81% of the variation in root collar diameter (Table 8b) of2-year-old hemlocks were attributed to neighbours. The only variable in the heightmodel was G. shallon, which was negatively correlated. The only variable positivelycorrelated with root collar diameter of hemlock was B. spicant, all the other variableswere negatively correlated.Over 85% of the variation in height (Table 8c) and over 64% of the variation inroot collar diameter (Table 8d) of 4-year-old hemlocks could be attributed to thepresence of neighbours. All the variables, except for B. spicant, were negativelycorrelated with height of hemlock. Both variables in the root collar diameter model,G. shallon and V oxycoccus, were negatively correlated with root collar diameter.Western hemlock saplings on fertilized plots in CH sites:Over 48% of the variation in height (Table 9a) and over 64% of the variation inroot collar diameter (Table 9b) of 2-year-old hemlocks could be attributed to thepresence of neighbours. Cornus canadensis was negatively correlated with heightwhile R. lald &rum and R. spectabilis showed positive correlations. Cornus canadensiswas also negatively correlated with root collar diameter but, in contrast to the modelfor height, R. laxiBorum was negatively correlated with root collar diameter.Gaultheria shallon, which was removed from the height model because it was notsignificant, was negatively correlated with root collar diameter. Epilobiumangustikdium, like R. laxiflorum, was positively correlated with root collar diameter.Over 53% of the variation in height (Table 9c) and over 74% of the variation inroot collar diameter (Table 9d) of 4-year-old hemlocks were attributed to the presenceof neighbours. Gaultheria shallon showed a negative correlation to height of hemlock,while M muralis and T plicata were positively correlated. Similar to the height54Table 8. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on control plots in HA sites measured in 1990 and1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.466; R2=0.217; adjusted re=0.161ANOVA p-value=0.069Independent variables^std coef^T^P-valueGaultheria shallon -0.466^-1.969^0.069b. Dependent variable: root collar diameter of 4-year-oldhemlocks (1990)N=16; R=0.900; R2=0.810; adjusted R2=0.684ANOVA p-value=0.007Independent variables^std coef T P-valueCornus canadensis -0.938 -4.253 0.002Dryopteris expansa -5.704 -4.105 0.003Blechnum spicant 5.555 3.874 0.004Ribes laxiflorum -2.049 -3.793 0.004Gaultheria shallon -0.557 -3.612 0.006Hypochoeris radicata -0.423 -2.228 0.053c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.923; R2=0.852; adjusted 1,2=0.777ANOVA p-value=0.001Independent variables std coef T P-valueGaultheria shallon -0.638 -4.726 0.001Rubus spectabilis -1.016 -3.703 0.004Blechnum spi cant 1.000 3.393 0.007Vaccinium oxycoccus -0.448 -2.510 0.031Sambucus racemosa -0.301 -1.923 0.083d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.800; R2=0.641; adjusted R2=0.585ANOVA p-value=0.001Independent variables^std coef^T^P-valueGaultheria shallon -0.628^-3.739^0.002Vaccinium oxycoccus -0.413^-2.458 0.029std coef = standard partial coefficient55Table 9. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on fertilized plots in CH sites measured in 1990and 1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.694; R2=0.482; adjusted 12=0.353ANOVA p-value=0.042Independent variables^std coef^T^P-valueRubus spectabilis 0.448 2.131 0.054Ribes laxiflorum 0.434 2.067 0.061Cornus canadensis -0.371 -1.761 0.104b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.804; R2=0.647; adjusted R2=0.519ANOVA p-value=0.015Independent variables^std coef^P-valueCornus canadensis -0.871^-3.536^0.005Epilobium angustifolium^1.692^3.345 0.007Ribes laxiflorum -1.397^-2.791^0.018Gaultheria shallon^-0.507^-2.547 0.027c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.732; R2=0.537; adjusted R4=0.421ANOVA p-value=0.023Independent variables^std coef^P-valueMycelis muralis 0.470^2.307^0.040Gaultheria shallon -0.419^-2.036 0.064Thuja plicata^ 0.384^1.910^0.080d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.861; R2=0.742; adjusted R2=0.677ANOVA p-value=0.001Independent variables^std coef^P-valueGaultheria shallon -0.674^-4.459^0.001Vaccinium sp.^ -0.748^-4.358 0.001Epilobium angustifolium^0.638^3.777^0.003std coef = standard partial coefficient56model, G. shallon was negatively correlated with root collar diameter, as wasVaccinium sp., while E. angustifolium was positively correlated.Western hemlock saplings on fertilimd plots in HA sites:About one-third of the variation in height (Table 10a) and over 55% of thevariation in root collar diameter (Table 10b) of 2-year-old hemlocks were attributed tothe presence of neighbouring non-crop vegetation. Epilobium angustiblium wasnegatively correlated with height and M muralis was positively correlated. Similar tothe height model, E. angusti.alium was negatively correlated with root collar diameterand M muralis was positively correlated with root collar diameter.68% of the variation in height (Table 10c) and over 80% of the variation in rootcollar diameter (Table 10d) of 4-year-old hemlocks were attributed to the presence ofneighbours. Of the four variables in the model B. spicant was the only one negativelycorrelated with height. However, B. spicant and D. eApansa were significantlycorrelated with each other with tolerance values of 0.054 and 0.053, respectively.Blechnum spic,ant and E. angustiMium were both negatively correlated with root collardiameter, while H. radicata, M muralis, R spectabilis, and D. eApansa werepositively correlated with root collar diameter. As in the height model, B. spicant andDrypoteris e. were significantly correlated with each other with tolerance values of0.054 and 0.052, respectively.Western hemlock saplings on scarified plots in CH sites:Only about one quarter of the variation in height (Table 11a) and root collardiameter (Table 11b) of 2-year-old hemlocks could be attributed to the presence ofneighbouring non-crop vegetation. The height model was not statistically significant.The root collar diameter model was also not significant but is noteworthy that G.shallon was negatively correlated with root collar diameter.57Table 10. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on fertilized plots in HA sites measured in 1990and 1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.594; R2=0.353; adjusted R4=0.253ANOVA p-value=0.059Independent variables^std coef^T^P-valueMycelis muralis 0.691^2.619^0.021Epilobium angustifolium^-0.472 -1.790 0.097b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.744; R2=0.554; adjusted R2=0.486ANOVA p-value=0.005Independent variables^std coef^P-valueEpilobium angustifolium^-0.849 -3.879^0.002Mycelis muralis 0.649^2.963 0.011c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.824; R2=0.680; adjusted R4=0.563ANOVA p-value=0.009Independent variables std coef T P-valueMycelis muralis 0.720 3.678 0.004Blechnum spicant -1.722 -2.342 0.039Dryopteris expansa 1.418 1.906 0.083Hypochoeris radicata 0.324 1.775 0.104d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.895; R2=0.802; adjusted R2=0.669ANOVA p-value=0.009Independent variables^std coef^T^P-valueMycelis muralis 0.812 4.478 0.002Hypochoeris radiacata 0.684 3.605 0.006Epilobium angustifolium -0.567 -2.832 0.020Blechnum spicant -1.704 -2.660 0.026Dryopteris expansa 1.629 2.491 0.034Rubus spectabilis 0.352 2.237 0.052std coef = standard partial coefficient58Table 11. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on scarified plots in CH sites measured in 1990 and1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.481; R2=0.231; adjusted R4=0.039ANOVA p-value=0.350Independent variables^std coef^T^P-valueRubus spectabilis -0.367 -1.444 0.174Vaccinium oxycoccus 4.068 1.309 0.215Cornus canadensis -4.026 -1.295 0.220b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.498; R2=0.248; adjusted R2=0.060ANOVA p-value=0.314Independent variables^std coef^T^P-valueGaultheria shallon -0.364^-1.433^0.177Vaccinium oxycoccus 3.901^1.272 0.228Cornus canadensis^-3.810 -1.242^0.238C. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.552; R2=0.305; adjusted R4=0.131ANOVA p-value=0.210Independent variables std coef T P-valueCornus canadensis -2.408 -1.969 0.072Vaccinium oxycoccus 2.256 1.877 0.085Hypochoeris radicata 0.447 1.707 0.114d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.696; R2=0.485; adjusted R2=0.356ANOVA p-value=0.041Independent variables std coef T P-valueBlechnum spicant -0.532 -2.559 0.025Cornus canadensis -2.353 -2.333 0.038Vaccinium oxycoccus 2.191 2.174 0.050std coef = standard partial coefficient59Over 30% of the variation in height (Table 11c) and over 48% of the variationin root collar diameter (Table 11d) of 4-year-old hemlocks could be attributed to thepresence of neighbours. The height model was not significant. Blechnum spicant andC. canadensis were negatively correlated with root collar diameter, while Vovalifikum was positively correlated. However, V ovalifolium and C. canadensiswere significantly correlated with each other with tolerance values of 0.042.Western hemlock saplings on scarified plots in HA sites:Over 45% of the variation in height (Table 12a) and over 35% of the variationin root collar diameter (Table 12b) of 2-year-old hemlocks could be accounted for bythe presence of neighbours. Epilobium angustifolium was negatively correlated withheight but R. laxiflorum showed a positive correlation. The only species variable in theroot collar diameter model was Epilobium angustifikum, which was negativelycorrelated with root collar diameter.Approximately one half of the variation in height (Table 12c) and over 67% ofthe variation in root collar diameter (Table 12d) of 4-year-old hemlocks could beattributed to the presence of neighbours. All the variables in the height model werenegatively correlated, however G. shallon was not a significant variable on its own.The only species variable in the root collar diameter model was Bryophyte sp., whichwas negatively correlated.Western hemlock saplings on fertilized plus scarified plots in CH sites:Only 13.2% of the variation in height (Table 13a) and 18.4% of the variation inroot collar diameter (Table 13b) of 2-year-old hemlocks were attributed toneighbouring non-crop vegetation. Both variables in the height model, Corn uscanadensis and Sambucus racemosa, were negatively correlated, however, the modelwas not significant. Blechnum spicant was positively correlated with root collar60Table 12. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on scarified plots in HA sites measured in 1990 and1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.678; R2=0.459; adjusted R4=0.369ANOVA p-value=0.025Independent variables^std coef^T^P-valueEpilobium angustifolium^-0.498^-2.316^0.039Ribes laxiflorum 0.385^1.791 0.098b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.597; R2=0.356; adjusted R2=0.306ANOVA p-value=0.019Independent variables^std coef^P-valueEpilobium angustifolium^-0.597^-2.680^0.019c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.721; R2=0.519; adjusted R4=0.388ANOVA p-value=0.039Independent variables std coef P-valueBryophyte sp. -0.518 -2.325 0.040Rubus spectabilis -0.448 -1.987 0.072Gaultheria shallon -0.314 -1.395 0.191d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.676; R2=0.458; adjusted R2=0.416ANOVA p-value=0.006Independent variables^std coef^P-valueBryophyte sp.^ -0.676^-3.311^0.006std coef = standard partial coefficient61Table 13. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western hemlocksaplings on fertilized plus scarified plots in CH sitesmeasured in 1990 and 1992, respectively.a. Dependent variable: height of 2-year-old hemlocks (1990)N=16; R=0.363; R2=0.132; adjusted Rz=0.000ANOVA p-value=0.400Independent variables^std coef^T^P-valueSambucus racemosa -0.282^-1.085^0.298Cornus canadensis -0.262^-1.007 0.332b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.428; R2=0.184; adjusted R2=0.058ANOVA p-value=0.268Independent variables^std coef^_T_^P-valueBlechnum spicant 0.390^1.490 0.160Mycelis muralis -0.323^-1.234^0.239c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.502; R2=0.252; adjusted Rz=0.137ANOVA p-value=0.152Independent variables^std coef^P-valueVaccinium oxycoccus -3.215 -2.012^0.065Mycelis muralis 3.040^1.902 0.080d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.813; R2=0.661; adjusted R2=0.537ANOVA p-value=0.012Independent variables std coef T P-valueVaccinium oxycoccus -4.104 -3.367 0.006Mycelis muralis 3.881 3.170 0.009Cornus canadensis 0.463 2.474 0.031Bryophyte sp. 0.396 2.193 0.051std coef = standard partial coefficient62diameter, while M muralis was negatively correlated. However, like the model forheight, both variables were not significant.Approximately one-quarter of the variation in height (Table 13c) and over 66%of the variation in root collar diameter (Table 13d) of 4-year-old hemlocks wereattributed to the presence of neighboring non-crop vegetation. Cornus canadensis wasnegatively correlated with height but M muralis was positively correlated. However,the model was not significant. Vaccinium ovalifolium was negatively correlated withroot collar diameter, while M muralis, C. canadensis, and Bryophyte sp. werepositively correlated. However, R. laydflorum and M muralis were correlated witheach other with tolerance values of 0.021.Western hemlock saplings on fertilized plus scarified plots in HA sites:Over 40% of the variation in height (Table 14a) and over 29% of the variationin root collar diameter (Table 14b) of 2-year-old hemlocks could be accountable for bythe presence of neighbours. Although two of the variables, E. angustiblium and Mmuralis were significant in the height model, the p-value for the entire model was notsignificant. Mycelis =rails, the only species variable in the root collar diametermodel, was negatively correlated.Only approximately one-tenth of the variation in height (Table 14c) and rootcollar diameter (Table 14d) of 4-year-old hemlocks were attributed to neighbours, butneither of the models was significant.63Table^14.^Multiple^regression^models^determining^thecorrelation^between^the^leaf^area^index^of^neighbouringspecies and the growth of to 2- and 4-year-old westernhemlock saplings on fertilized plus scarified plots in HAsites measured in 1991 and 1992, respectively.a. Dependent variable: height of 2-year-old hemlocksN=16; R=0.634; R2=0.402; adjusted R4=0.185(1990)ANOVA p-value=0.190Independent variables std coef T P-valueEpilobium angustifolium 1.736 2.530 0.028Mycelis muralis -1.372 -2.144 0.055Blechnum spicant 0.569 1.561 0.147Rubus spectabilis -0.538 -1.341 0.207b. Dependent variable: root collar diameter of 2-year-oldhemlocks (1990)N=16; R=0.544; R2=0.296; adjusted R2=0.246ANOVA p-value=0.029Independent variables^std coef^T^P-valueMycelis muralis -0.544^-2.426^0.029c. Dependent variable: height of 4-year-old hemlocks (1992)N=16; R=0.349; R2=0.122; adjusted R4=0.059ANOVA p-value=0.185Independent variables^std coef^T^P-valueRibes laxiflorum 0.349^1.394^0.185d. Dependent variable: root collar diameter of 4-year-oldhemlocks (1992)N=16; R=0.342; R2=0.117; adjusted R2=0.054ANOVA p-value=0.195Independent variables^std coef^T^P-valueRubus spectabilis -0.342^-1.361^0.195std coef = standard partial coefficientWESTERN RED CEDARWestern red cedar saplings on contivi plots in CH sites:The models for height (Table 15a) and root collar diameter (Table 15b) of 2-year-oldcedars in 1990 were similar, however, G. shallon and R. sylvaticus were included inthe height model but not in the root collar diameter model. Over 72% of the variationin height and over 59% of the variation in root collar diameter was attributed to theabundance of neighbours. Although G. shallon was included in the height model, itwas positively associated with the height of cedars. None of the variables werenegatively correlated with height or root collar diameter. Cornus canadensis accountedfor the most variation in the height (T=3.064) and the root collar diameter model(T = 3.456).72.0% of the variation in height (Table 15c) and over 51% of the variation inroot collar diameter (Table 15d) of 4-year-old cedars were attributed to neighbours.Although G. shallon was included in the height model it was not significant. Pteridiumaquilinum and Mycdis muralis were negatively associated with height, while E.angustiblium, C. canadensis, Poa sp., H. radicata and G. shallon were positivelyassociated. Unlike height, the abundance of Poa sp. was negatively associated withroot collar diameter.Western red cedar saplings on contnd plots in HA sites:Over 86% of the variation in height (Table 16a) and over 93% of the variationin root collar diameter (Table 16b) of 2-year-old cedars were attributed to neighbours(Tables 16a,b). Gaultheria shallon, D. expansa and Vaccinium sp. were negativelycorrelated with height, but the influence of Vaccinium sp. was not statisticallysignificant. In contrast, H. radicata and B. spicant were positively correlated withheight. Similar to the height model, H. radicata, B. spicant, and E. angustikdiumwere positively correlated with root collar diameter, but Drypoteris e., R. spectabilis,6465Table 15. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2-and 4-year-old western red cedarsaplings on control plots in CH sites measured in 1990 and1992, repectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.849; R2=0.721; adjusted R4=0.536ANOVA p-value=0.034Independent variables std coef T P-valueCornus canadensis 0.599 3.064 0.013Hypochoeris radicata 0.555 2.887 0.018Epilobium angustifolium 0.485 2.300 0.047Gaultheria shallon 0.478 2.256 0.050Blechnum spicant 0.510 1.989 0.078Rubus spectabilis 0.358 1.666 0.130b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.773; R2=0.597; adjusted R2=0.451ANOVA p-value=0.029Independent variables std coef T P-valueCornus canadensis 0.729 3.456 0.005Hypochoeris radicata 0.527 2.634 0.023Bpilobium angustifolium 0.432 1.957 0.081Blechnum spicant 0.404 1.924 0.081c. Dependent variable: height of 4-year-old cedars (1992)N=16; R=0.848; R2=0.720; adjusted R4=0.474ANOVA p-value=0.077Independent variables std coef T P-valueEpilobium angustifolium 0.979 3.632 0.007Mycelis muralis -0.747 -2.834 0.022Poa sp. 1.733 2.755 0.025Hypochoeris radicata 0.623 2.735 0.026Cornus canadensis 0.626 2.647 0.029Pteridium aguilinum -1.127 -2.135 0.065Gaultheria shallon 0.506 1.844 0.102d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.715; R2=0.511; adjusted R2=0.388ANOVA p-value=0.031Independent variables std coef P-valuePoa sp. -0.843 -2.846 0.015Rubus spectabilis 0.827 2.757 0.017Cornus canadensis 0.407 1.948 0.075std coef = standard partial coefficient66Table 16. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on control plots in HA sites measured in 1990and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.930; R2=0.866; adjusted Rz=0.799ANOVA p-value=0.000Independent variables std coef T P-valueBlechnum spicant 0.851 4.856 0.001Hypochoeris radicata 0.976 2.959 0.014Gaultheria shallon -0.356 -2.421 0.036Dryopteris expansa -0.404 -2.408 0.037Vaccinium sp. -0.351 -1.105 0.295b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.968; R2=0.936; adjusted R2=0.894ANOVA p-value=0.000Independent variables^std coef^T^P-valueBlechnum spicant 1.481 5.001 0.001Hypochoeris radicata 0.468 4.315 0.002Rubus spectabilis -1.035 -3.349 0.009Epilobium angustifolium 0.455 1.991 0.078Dryopteris expansa -0.405 -1.913 0.088Gaultheria shallon -0.189 -1.402 0.194c. Dependent variable: height of 4-year-old cedarsN=16; R=0.824; R2=0.679; adjusted It=0.598(1992)ANOVA p-value=0.003Independent variables std coef T P-valueDryopteris expansa 11.289 4.081 0.002Sambucus racemosa -10.916 -3.949 0.002Vaccinium sp. 0.473 2.842 0.015d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.844; R2=0.713; adjusted R2=0.641ANOVA p-value=0.001Independent variables std coef T P-valueRubus spectabilis 0.767 4.870 0.000Pteridium aguilinum 1.795 3.037 0.010Poa sp. -1.526 -2.593 0.024std coef = standard partial coefficient67and G. shallon were negatively correlated. However, the influence of G. shallon wasnot statistically significant.Over 67% of the variation in height (Table 16c) and over 71% of the variationin root collar diameter (Table 16d) of 4-year-old cedars could be attributed to thepresence of neighbours. Sambucus racemosa was negatively correlated with heightwhile Vaccinium sp. and D. expansa were positively correlated. However, S.racemosa and D. expansa were highly correlated with each other as indicated bytolerance levels of 0.004 and 0.003, respectively. Similar to the height model, S.racemosa was negatively correlated with root collar diameter, but P. aquilinum and H.radicata were positively correlated. Also similar to the height model, S. racemosa andP. aquilinum were significantly correlated with a tolerance of 0.069 and 0.068,respectively.Western red cedar saplings on fertilized plots in CH sites:Only 19.0% of the variation in height (Table 17a) of 2-year-old cedars wereattributed to neighbouring non-crop vegetation, but over 74% of the variation in rootcollar diameter (Table 17b) of 2-year-old cedar was attributed to neighbours.Gaultheria shallon was negatively correlated with root collar diameter, and accountedfor most of the observed variation (T=-3.930). Rubus spectabilis, B. spicant, and H.radicata were also negatively correlated with root collar diameter. In contrast, P.aquilinum, E. angustifikum, and C. canadensis were positively correlated with rootcollar diameter.Over 83% of the variation in height (Table 17c) and 70% of the variation inroot collar diameter (Table 17d) of 4-year-old cedars were attributed to the presence ofneighbours. Rubus spectabilis and R laxiflorum were negatively correlated withheight, while H. radicata, M muralis, and Bryophyte sp. showed positive correlations.However, H. radicata and R laydfiorum were not significant to p > 0.05 on their own,68Table 17. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on fertilized plots in CH sites measured in1990 and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.436; R2=0.190; adjusted R4=0.000ANOVA p-value=0.453Independent variables std coef T P-valueBlechnum spicant 0.327 1.227 0.243Vaccinium oxycoccus 0.321 1.185 0.259Gaultheria shallon -0.134 -0.491 0.632b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.865; R2=0.748; adjusted R2=0.528ANOVA p-value=0.054Independent variables^std coef^T^P-valueGaultheria shallon -1.271^-3.930^0.004Pteridium aguilinum 1.285^3.438 0.009Rubus spectabilis^-0.581^-2.881^0.020Blechnum spicant -1.100^-2.876 0.021Cornus canadensis 0.554^2.250^0.055Epilobium angustifolium^0.671^2.166 0.062Hypochoeris radicata -0.413^-1.858^0.100c. Dependent variable: height of 4-year-old cedars (1992)N=16; R=0.912; R2=0.833; adjusted R4=0.749ANOVA p-value=0.001Independent variables^std coef^T^P-valueMycelis muralis 0.764 5.370 0.000Rubus spectabilis -0.809 -5.282 0.000Bryophyte sp. 0.637 4.237 0.002Ribes laxiflorum -0.360 -2.019 0.071Hypochoeris radicata 0.340 1.901 0.087d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.837; R2=0.700; adjusted R2=0.625ANOVA p-value=0.002Independent variables std coef T P-valueBryophyte sp. 0.755 4.248 0.001Rubus spectabilis -0.786 -4.204 0.001Mycelis muralis 0.607 3.530 0.004std coef = standard partial coefficient69but they were significant to p > 0.10. As with height, root collar diameter was alsonegatively correlated with the presence of R spectabilis, and positively correlated withM muralis and Bryophyte sp.Western red cedar saplings on fertilized plots in HA sites:Over 52% of the variation in height (Table 18a) and over 59% of the variationin root collar diameter (Table 18b) of 2-year-old cedars were attributed to the presenceof neighbours. Pterithum aquilinum and Dryopteris evansa were negatively correlatedwith height while R. laxiflorum and M muralis were positively correlated with height.However, both P. aquilinum and D. expansa were not significant in the model on theirown. Pteridium aquilinum and Vaccinium sp. were negatively correlated with rootcollar diameter but both were not significant in the model on their own, while R.laxfflorum was positively correlated with root collar diameter.Over 62% of the variation in height (Table 18c) and over 73% of the variationin root collar diameter (Table 18d) of 4-year-old cedars could be attributed toneighbours. Although T. heterophylla was negatively correlated with height, it was notsignificant in the model on its own. Epilobium angustifolium and R. laxiflorum wereboth positively correlated with height. Tsuga heterophylla and P. aquilinum werenegatively correlated with root collar diameter but the effect of P. aquilinum on its ownwas not significant in the model. Ribes laxiflOrum was positively correlated with rootcollar diameter as it was for all height and root collar diameter measurements of cedarsaplings on fertilized plots in HA sites (Tables 18a,b,c,d).Western red cedar saplings on scarified plots in CH sites:Over 47% of the variation in height (Table 19a) and only about one third of thevariation in root collar diameter (Table 19b) of 2-year-old cedars were attributed toneighbouring non-crop vegetation. Blechnum spicant and Vaccinium sp. were70Table 18. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on fertilized plots in HA sites measured in1990 and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.724; R2=0.525; adjusted 12=0.352ANOVA p-value=0.065Independent variables std coef T P-valueRibes laxiflorus 0.767 3.051 0.011Mycelis muralis 0.606 2.094 0.060Pteridium aguilinum -0.410 -1.750 0.108Dryopteris expansa -0.442 -1.485 0.166b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.773; R2=0.598; adjusted R2=0.498ANOVA p-value=0.010Independent variables std coef T P-valueRibes laxiflorum 0.679 3.667 0.003Pteridium aguilinum -0.237 -1.277 0.226Vaccinium sp. -0.184 -0.998 0.338C. Dependent variable: height of 4-year-old cedars (1992)N=16; R=0.788; R2=0.621; adjusted R&--0.526ANOVA p-value=0.007Independent variables^std coef^T^P-valueRibes laxiflorum 0.516 2.851 0.015Epilobium angustifolium 0.361 1.887 0.084Tsuga heteropohylla -0.297 -1.533 0.151d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.859; R2=0.738; adjusted R2=0.673ANOVA p-value=0.001Independent variables std coef T P-valueRibes laxiflorum 0.641 4.237 0.001Tsuga heterophylla -0.293 -1.880 0.085Pteridium aquilinum -0.269 -1.731 0.109std coef = standard partial coefficient71Table 19. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on scarified plots in CH sites measured in1990 and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.687; R2=0.472; adjusted Rz=0.340ANOVA p-value=0.047Independent variables std coef P-valueRubus spectabilis 2.772 2.982 0.011Blechnum spicant -1.403 -2.885 0.014Vaccinium sp. -2.213 -2.587 0.024b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.566; R2=0.321; adjusted R2=0.151ANOVA p-value=0.185Independent variables std coef T P-valueBlechnum spicant -0.560 -1.990 0.070Rubus spectabilis 0.529 1.938 0.076Gaultheria shallon 0.397 1.521 0.154c. Dependent variable: height of 4-year-o1d cedars (1992)N=16; R=0.434; R2=0.188; adjusted 11=0.063ANOVA p-value=0.258Independent variables^std coef^P-valueRubus spectabilis 0.380 1.519 0.153Ribes laxiflorum -0.185 -0.739 0.473d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.687; R2=0.472; adjusted R2=0.435ANOVA p-value=0.003Independent variables^std coef^T^P-valueRubus spectabilis 0.687^3.539^0.003std coef = standard partial coefficient72negatively correlated with height but I?. spectabilis was positively correlated withheight. Gaultheria shallon was positively correlated with root collar diameter but themodel was not statistically significant.Only 18.8% of the variation in height (Table 19c) of 4-year-old cedar wasattributed to neighbours, but over 47% of the variation in root collar diameter (Table19d) of 4-year-old cedars were attributed to neighbours. Rubus spectabilis waspositively correlated and R. laxiflorum was negatively correlated with height, howeverthe model was not significant. Rubus spectabilis, the only variable in the root collardiameter model, was positively correlated.Western ird cedar saplings on scarified plots in HA sites:Over 35% of the variation in height (Table 20a) and approximately one half ofthe variation in root collar diameter (Table 20b) of 2-year-old cedars were attributed tothe presence of neighbours. Gaultheria shallon and Rubus spectabilis were positivelycorrelated with cedar height. Also, Anaphalis margaritaceae and G. shallon werepositively correlated with root collar diameter, but the influence of G. shallon was notsignificant in the root collar diameter model on its own.Over 96% of the variation in height (Table 20c) and over 98% of the variationin root collar diameter (Table 20d) of 4-year-old cedars were attributed to the presenceof neighbours. Although much of the variation is accounted for, the large number ofvariables included in the model make it difficult to determine the principle variables.There was little difference between the models except that the root collar diametermodel included two more variables, S. racemosa and R. spectabilis, which werenegatively and positively correlated, respectively. It is important to note that G.shallon was positively correlated with height and root collar diameter.c. Dependent variable: height of 4-year-old cedars (1992)N=16; R=0.980; R2=0.961; adjusted R4=0.903ANOVA p-value=0.001Independent variables^std coef^T^P-valueEguisetum sylvaticumV'accinium sp.Gaultheria shallonEpilobium angustifoliumAnaphalis margaritaceaeDryopteris expansaBryophyte sp.Blechnum spicantHypochoeris radicata-0.814 -6.500 0.001-0.502 -5.670 0.0010.616 5.077 0.002-0.958 -3.985 0.0070.485 3.957 0.0070.523 3.611 0.0110.330 2.900 0.027-0.335 -2.777 0.0320.622 2.564 0.04373Table 20. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on scarified plots in HA sites measured in1990 and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.598; R2=0.357; adjusted R4=0.258ANOVA p-value=0.057Independent variables^std coef^T^P-valueRubus spectabilis 0.513^2.259^0.042Gaultheria shallon 0.425^1.875 0.083b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.693; R2=0.481; adjusted R2=0.401ANOVA p-value=0.014Independent variables^std coef^P-valueAnaphalis margaritaceae^0.611^3.053^0.009Gaultheria shallon 0.341^1.707 0.111d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.994; R2=0.989;ANOVA p-value=0.002Independent variables Epilobium angustifoliumGaultheria shallonEguisetum sylvaticumHypochoeris radicataVaccinium sp.Bryophyte sp.Dryopteris expansaAnaphalis margaritaceaeBlechnum spicantSambucus racemosaRubus spectabilisadjusted R2=0.959std coef^T P-value-1.630 -10.085 0.0010.815 9.519 0.001-0.766 -8.819 0.0011.308 7.267 0.002-0.388 -6.548 0.0030.527 6.222 0.0030.478 5.049 0.0070.759 4.818 0.009-0.606 -4.668 0.010-0.624 -4.320 0.0120.379 3.787 0.01974Western red cedar saplings on fertilized + scarified plots in CH sites:Only 20.2% of the variation in height (Table 21a) and 9.5% of the variation inroot collar diameter (Table 21b) of 2-year-old cedars could be attributed toneighbouring non-crop vegetation. Both models were not statistically significant.Over 33% of the variation in height (Table 21c) and over 39% of the variationin root collar diameter (Table 21d) of 4-year-old cedars were attributed to neighbours.Bryophyte sp., the only species associated with height of cedar, was negativelycorrelated. Bryophyte sp. was also negatively correlated with root collar diameter butT heterophylla was positively correlated.Western red cedar saplings on fertilized + scarified plots in HA sites:Approximately three-quarters of the variation in height (Table 22a) and over63% of the variation in root collar diameter (Table 22b) of 2-year-old cedars could beattributed to the presence of neighbours. All four variables included in the heightmodel were positively correlated with height. As with the height model all the speciesexcept Mycelis a. were positively correlated with root collar diameter of cedar.However, the effect of B. spicant and E. angustiMium on their own were notsignificant in the model.71% of the variation in height (Table 22c) and over 72% of the variation in rootcollar diameter (Table 22d) of 4-year-old cedars could be attributed to the presence ofneighbours. Hypochoeris radicata, B. spicant, and E. angustifollum were positivelycorrelated with height, while R. laAiflorum and 7huja plicata showed a negativecorrelation. Similar to the height model, H. radicata, B. spicant, and E. angustifoliumwere positively correlated with root collar diameter, while T. plicata was negativelycorrelated.75Table 21. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on fertilized plus scarified plots in CHsites measured in 1990 and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.449; R2=0.202; adjusted Rz=0.079ANOVA p-value=0.231Independent variables^std coef^T^P-valueCornus canadensis -0.710^-1.769^0.100Hypochoeris radicata 0.657^1.635 0.126b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.308; R2=0.095; adjusted R2=0.030ANOVA p-value=0.246Independent variables^std coef^T^P-valueEpilobium angustifolium^-0.308 -1.210^0.246C. Dependent variable: height of 4-year-old cedars (1992)N=16; R=0.576; R2=0.332; adjusted Rz=0.285ANOVA p-value=0.019Independent variables^std coef^T^P-valueBryophyte sp.^ -0.576^-2.640^0.019d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.630; R2=0.397; adjusted R2=0.304ANOVA p-value=0.037Independent variables^std coef^P-valueTsuga heterophylla 0.582^2.515^0.026Bryophyte sp.^ -0.533^-2.307 0.038std coef = standard partial coefficient76Table 22. Multiple regression models determining thecorrelation between the leaf area index of neighbouringspecies and the growth of 2- and 4-year-old western redcedar saplings on fertilized plus scarified plots in HAsites measured in 1990 and 1992, respectively.a. Dependent variable: height of 2-year-old cedars (1990)N=16; R=0.858; R2=0.735; adjusted R4=0.639ANOVA p-value=0.003Independent variables std coef T P-valueBlechnum spicant 0.642 4.082 0.002Epilobium angustifolium 0.444 2.741 0.019Pinus contorta 0.353 2.236 0.047Bypochoeris radicata 0.352 2.190 0.051b. Dependent variable: root collar diameter of 2-year-oldcedars (1990)N=16; R=0.795; R2=0.631; adjusted R2=0.386ANOVA p-value=0.098Independent variables^std coef^T^P-valueHypochoeris radicata 1.392 3.077 0.013Mycelis muralis -2.528 -2.465 0.036Ribes laxiflorum 2.116 2.297 0.047Rubus spectabilis 0.936 1.894 0.091Blechnum spicant 0.369 1.788 0.107Epilobium angustifolium 0.362 1.654 0.132c. Dependent variable: height of 4-year-old cedars (1992)N=16; R=0.843; R2=0.710; adjusted R4=0.565ANOVA p-value=0.016Independent variables std coef T P-valueBlechnum spicant 0.431 2.455 0.034Epilobium angustifolium 0.440 2.452 0.034Thuja plicata -2.991 -2.145 0.058Hypochoeris radicata 2.966 2.119 0.060Ribes laxiflorum -0.353 -2.049 0.068d. Dependent variable: root collar diameter of 4-year-oldcedars (1992)N=16; R=0.854; R2=0.729; adjusted R2=0.630ANOVA p-value=0.004Independent variables std coef T P-valueEpilobium angustifolium 0.417 2.770 0.028Hypochoeris radicata 5.421 -2.553 0.001Thuja plicata -5.396 -2.010 0.001Blechnum spicant 0.411 1.876 0.027std coef = standard partial coefficient77Relationship between salal leaf area index and conifer growth using themultiple regression models.Tables 23 and 24 summarize the influence of the leaf area index of salal onheight and root collar diameter of 2- and 4-year-old western hemlock and western redcedar, respectively, measured in 1990 and 1992.Height and root collar diameter of 2- and 4-year-old hemlock was significantlynegatively correlated with salal abundance on control CH sites, fertilized CH sites, andcontrol HA sites. The greatest influence from salal on hemlock was on the root collardiameter of 4-year-old hemlock on fertilized CH sites, R2 =0.428. From 1990 to1992, the influence of salal appeared to diminish on control CH sites but increased onfertilized CH sites and control HA sites.Height and root collar diameter of 2-year-old cedars were significantlynegatively correlated with the abundance of salal on control HA sites and fertilized CHsites, but not 4-year-old cedars. Cedar performance was significantly positivelycorrelated with salal abundance on control CH sites, scarified CH sites, and scarifiedHA sites.78Table 23. Summary of the correlations between the leaf area index of salal andwestern hemlock height and root collar diameter using the multiple regressionmodels. "np" means salal is not present in model. "+" and "-" mean that salal ispositively and negatively correlated with hemlock growth, respectively.correlation 122CH control sites:1990 (height)1990 (root collar1992 (height)1992 (root collarHA control sites:1990 (height)1990 (root collar1992 (height)1992 (root collarCH fertilized sites:^0.119^0.070diameter)^0.328^0.008np^np npdiameter) 0.146^0.017^0.217^0.069diameter)^0.275^0.0060.332^0.001diameter) 0.387^0.0021990 (height)1990 (root collar diameter)1992 (height)1992 (root collar diameter)HA fertilized sitesnp np0.2080.1600.428np0.0270.0640.0011990 (height) np np np1990 (root collar diameter) np np np1992 (height) np np np1992 (root collar diameter) np np npCH scarified sites:1990 (height) np np np1990 (root collar diameter) - 0.129 0.1771992 (height) np np np1992 (root collar diameter) np np npHA scarified sites:1990 (height) np np np1990 (root collar diameter) np np np1992 (height) - 0.085 0.1911992 (root collar diameter) np np npCH fertilized plus scarified sites:1990 (height) np np np1990 (root collar diameter) np np np1992 (height) np np np1992 (root collar diameter) np np npHA fertilized plus scarified sites:1990 (height) np np np1990 (root collar diameter) np np np1992 (height) np np np1992 (root collar diameter) np np np79Table 24. Summary of the correlations between the leaf area index of salal andwestern red cedar height and root collar diameter using the multiple regressionmodels. "np" means salal is not present in model. "+" and "2 mean that salal ispositively and negatively correlated with cedar growth, respectively.CH control sites:correlation^R2 p1990 (height) 0.158 0.0501990 (root collar diameter) np np np1992 (height) 0.119 0.1021992 (root collar diameter) np np npHA control sites:1990 (height) 0.079 0.0361990 (root collar diameter) 0.014 0.1941992 (height) np np np1992 (root collar diameter) np np npCH fertilized sites:1990 (height) 0.016 0.6321990 (root collar diameter) 0.486 0.0041992 (height) np np np1992 (root collar diameter) np np npHA fertilized sites:1990 (height) np np np1990 (root collar diameter) np np np1992 (height) np np np1992 (root collar diameter) np np npCH scarified sites:1990 (height) np np np1990 (root collar diameter) 0.131 0.1541992 (height) np np np1992 (root collar diameter) np np npHA scarified sites:1990 (height)1990 (root collar diameter)1992 (height)1992 (root collar diameter)CH fertilized plus scarified sites:0.1740.1160.1670.2490.0830.1110.0020.0011990 (height) np np np1990 (root collar diameter) np np np1992 (height) np np np1992 (root collar diameter) np np npHA fertilized plus scarified sites:1990 (height) np np np1990 (root collar diameter) np np np1992 (height) np np np1992 (root collar diameter) np np np80Relationship between soil variables and conifer growth, and soilvariables and salal growth using multiple regression.Tables 25, 26, and 27 summarize the multiple regression models determiningthe correlation between soil variables and 4-year-old hemlock height and root collardiameter, 4-year-old cedar height and root collar diameter, and salal leaf area index,respectively. The complete multiple regression models including the standardcoefficients of the independent variables are not presented because the models weregenerally not significant. Some general trends found in the models were that increasedheight and root collar diameter of western hemlock and western red cedar wereassociated with high soil moisture and total nitrogen. Also, higher percentages of totalcarbon were associated with poor growth of hemlock and cedar. Soil coarse contentand total phosphorus showed no trends.Increasing salal leaf area index was associated with increasing soil totalphosphorus on CH and HA scarified sites. Otherwise, there was no significantcorrelation between salal leaf area index and the other soil variables (moisture, coarsecontent, total nitrogen, and total potassium).Table 25. Summary of correlations between soil variables (moisture, coarse content,total carbon, total nitrogen, and total phosphorus) and the growth of 4-year-old western hemlock saplings measured in 1992 using the multipleregression models.SITE 'TREATMENT PERFORMANCE N R^R2 P-valueVARIABLECH CONTROL HEIGHT 16 0.361 0.131 0.902CH CONTROL RCD 16 0.348 0.121 0.916CH FERTILIZED HEIGHT 16 0.501 0.251 0.655CH FERTILIZED RCD 16 0.428 0.183 0.805CH SCARIFIED HEIGHT 16 0.512 0.262 0.630CH SCARIFIED RCD 16 0.606 0.367 0.392CH FERTILIZED +SCARIFIEDHEIGHT 16 0.177 0.031 0.996CH FERTILIZED +SCARIFIEDRCD 16 0.731 0.535 0.123HA CONTROL HEIGHT 16 0.570 0.324 0.485HA CONTROL RCD 16 0.595 0.355 0.419HA FERTILIZED _ HEIGHT 16 0.755 0.570 0.089HA FERTILIZED RCD 16 0.706 0.498 0.167HA SCARIFIED HEIGHT 15 0.666 0.444 0.299HA SCARIFIED RCD 15 0.666 0.444 0.300HA FERTILIZED +SCARIFIEDHEIGHT 16 0.647 0.419 0.291HA FERTILIZED+SCARIFIEDRCD 16 0.579 0.335 0.461N=number of hemlock included in the model.RCD = root collar diameter.8182Table 26. Summary of the correlations between soil variables (moisture, coarsecontent, total carbon, total nitrogen, and total phosphorus) and the growth of4-year-old western red cedar saplings measured in 1992 using the multipleregression models.SITE TREATMENT PERFORMANCE N R^R2 P-valueVARIABLECH CONTROL HEIGHT 16 0.729 0.531 0.128CH CONTROL RCD 16 0.609 0.371 0.383CH FERTILIZED HEIGHT 16 0.538 0.289 0.566CH FERTILIZED RCD 16 0.509 0.259 0.637CH SCARIFIED HEIGHT 16 0.576 0.332 0.469CH SCARIFIED RCD 16 0.515 0.265 0.469CH FERTILIZED +SCARIFIEDHEIGHT 16 0.459 0.211 0.747CH FERTILIZED +SCARIFIEDRCD 16 0.448 0.201 0.769HA CONTROL HEIGHT 16 0.473 0.224 0.717HA CONTROL RCD 16 0.402 0.161 0.848HA FERTILIZED HEIGHT 16 0.731 0.534 0.124HA FERTILIZED RCD 16 0.753 0.567 0.092HA SCARIFIED HEIGHT 16 0.409 0.167 0.837HA SCARIFIED RCD 16 0.547 0.299 0.542HA FERTILIZED +SCARIFIEDHEIGHT 16 0.729 0.531 0.127HA FERTILIZED+SCARIFIEDRCD 16 0.710 0.504 0.159N=number of hemlock included in the model.RCD = root collar diameter.83Table 27. Summary of the correlations between soil variables (moisture, coarsecontent, total carbon, total nitrogen, and total phosphorus) and the leaf areaindex of salal using the multiple regression models.SITE TREATMENT N R^P-valueCH CONTROL 32 0.537 0.288 0.097CH FERTILIZED 32 0.494 0.244 0.175CH SCARIFIED 32 0.567 0.321 0.059CH FERTILIZED +SCARIFIED32 0.502 0.252 0.157HA CONTROL 32 0.358 0.128 0.585HA FERTILIZED 32 0.403 0.162 0.434HA SCARIFIED 31 0.681 0.464 0.006HA F^ERTILIZED+ SCARIFIED32 0.351 0.123 0.607N=number of independent leaf area index measurements taken for each multipleregression model.84The influence of the abundance of salal on the growth of conifersbetween 1990 and 1992western hemlockHeight increase (Fig. 12a) and root collar diameter increase (Fig. 12b) ofhemlock between 1990 and 1992 in most cases was reduced with increasing amounts ofsalal (Table 23).The growth rate of hemlock height and root collar diameter on CH sites showeda strong treatment effect. Hemlock growing on control plots had the lowest growthrate, followed by fertilized plots, scarified plots, and fertilized plus scarified plots.Salal had a greater influence on the root collar diameter of hemlock than on its height.The slopes of the three root collar diameter regressions (Fig. 12b) were similar,indicating that salal had a similar influence in each of the treatments. The growth rateof the height and root collar diameter of hemlock growing on scarified plots showedlittle difference with increasing abundance of salal.Similar to CH sites, the growth rate of hemlock height and root collar diameteron HA sites showed a treatment effect but it was not as strong. The two year growthincrement of height and root collar diameter of hemlock growing on control plotsshowed the greatest response to increasing salal leaf area index than any other site xtreatment combination for both hemlock and cedar. The growth rate of height and rootcollar diameter when salal was absent was approximately 170 cm/2yr, and 33 mm/2yr,respectively, while at a leaf area index of 3, the growth rate was close to 0 for bothheight and root collar diameter. Hemlock growing on fertilized plots also showed asignificant decrease with increasing abundance of salal. The growth rate of hemlockgrowing on scarified and fertilized plus scarified plots showed no significant influenceto increasing abundance of salal.controlfertilizedscarifiedfertilized +scarified40 oolit^v./0••■•■•■•■E 20A200E 150100501^2^3^4Leaf area index of salal851^2^3^4Leaf area index of soledFigure 12. The relationship between salal LAI measured in 1991 and the 2-yeargrowth increment of western hemlock height and root collar diameter (between 2- and4-years after planting) on CH sites within four different treatments (control, fertilized,scarified, and fertilized plus scarified). The regression lines for each treatment extendto the maximum salal LAI measured.2 3 42002 3 410A^ 86Leaf area index of salal5040 controlfertilizedscarifiedfertilized +scarifieda.* ■•••■■• ■••■.at 3017, 200Leaf area index of salalFigure 13. The relationship between salal LAI measured in 1991 and the 2-yeargrowth increment of western hemlock height and root collar diameter (between 2- and4-years after planting) on HA sites within four different treatments (control, fertilized,scarified, and fertilized plus scarified). The regression lines for each treatment extendto the maximum salal LA! measured.87Table 28. Summary of the R2 values of the growth of western hemlock and westernred cedar between 1990 and 1992 against the leaf area index of salal foreach site x treatment combination.R2^P -valueHemlock Height on CH sites control^ 0.021^0.591fertilized 0.354 0.015scarified 0.042^0.444fertilized + scarified^ 0.029 0.527Hemlock Root Collar Diameter on CH sites control^ 0.310^0.025fertilized 0.232 0.059scarified 0.006^0.774fertilized + scarified^ 0.077 0.299Hemlock Height on HA sites control^ 0.445^0.005fertilized 0.256 0.045scarified 0.009^0.744fertilized + scarified^ 0.162 0.122Hemlock Root Collar Diameter on HA sites control^ 0.503^0.002fertilized 0.314 0.024scarified 0.022^0.600fertilized + scarified^ 0.015 0.654Cedar Height on CH sites control^ 0.013^0.669fertilized 0.214 0.071scarified 0.003^0.832fertilized + scarified^ 0.035 0.488Cedar Root Collar Diameter on CH sites control^ 0.081^0.285fertilized 0.162 0.122scarified 0.124^0.182fertilized + scarified^ 0.055 0.381Cedar Height on HA sites control^ 0.201^0.081fertilized 0.094 0.248scarified 0.099^0.235fertilized + scarified^ 0.006 0.770Cedar Root Collar Diameter on HA sites control^ 0.286^0.033fertilized 0.081 0.285scarified 0.011^0.697fertilized + scarified^ 0.030 0.52488western red cedarThe relationship between the growth rate of cedar and the leaf area index ofsalal was far less clear than with hemlock and salal (Figs. 14, 15; Table 24).Furthermore, there were fewer R2 values with a P-value< 0.1 than hemlock.The growth rate of height and root collar diameter of cedar growing on controlplots in CH sites increased with increasing abundance of salal. The same can be saidfor the growth rate of height of cedar growing on fertilized plus scarified plots in CHsites. The growth rate of the height and root collar diameter of cedar was greatest onfertilized plus scarified plots. The growth rate of height and root collar diameter ofcedar grown on fertilized plots showed the greatest influence to increasing abundanceof salal. When salal was absent, the growth rate of height and root collar diameter wasapproximately 75 cm/2yr, and 15 mm/2yr, respectively, while at a salal leaf area indexof 6, the growth rate of height and root collar diameter was approximately 40 cm/2yr,and 7mm/2yr, respectively. Cedar grown on scarified plots showed the least change ingrowth rate with the change in salal abundance.The growth rate of cedar growing on HA sites differed considerably from cedargrowing on CH sites. Instead of an increasing growth rate with increasing abundanceof salal, cedar growing on control plots on HA sites showed a decreasing growth rate.Furthermore, instead of a decreasing growth rate with increasing abundance of sala1,cedar growing on scarified plots on HA sites showed an increasing growth rate. Thegrowth rate of cedar growing on fertilized, scarified and fertilized plus scarified plotswere all roughly equal, and they were all greater than the growth rate of cedar growingon control plots.A89150a 100------.050'NS00 1 2^3^4 5 6Leaf area index of salal4030^ controlfertilizedscarifiedfertilized +scarified20 -0C.)ct 1000^1^2^3^4^5^6Leaf area index of saladFigure 14. The relationship between salal LAI measured in 1991 and the 2-yeargrowth increment of western red cedar height and root collar diameter (between 2- and4-years after planting) on CH sites within four different treatments (control, fertilized,scarified, and fertilized plus scarified). The regression lines for each treatment extendto the maximum salal LA! measured.— — ....m.o.^•••••••••••••controlfertilizedscarifiedfertilized +scarified403041.■•■•■1 1^2^3^4^5A 90150.•■••ale-----41.".••••■••■■••••••••00^1^2^3^4^5Leaf area index of 88181Leaf area index of salalFigure 15. The relationship between salal LAI measured in 1991 and the 2-yeargrowth increment of western red cedar height and root collar diameter (between 2- and4-years after planting) on HA sites within four different treatments (control, fertilized,scarified, and fertilized plus scarified). The regression lines for each treatment extendto the maximum salal LAI measured.1005091DISCUSSIONWere the predictions of the salal hypothesis met?The influence of salal on growth of trees can be assessed in two ways. First,correlation and regressions between conifer growth and salal abundance at any onepoint in time. These, of course, can only lead to speculative interpretations and do notallow a direct assessment of the impact of the presence of salal on growth of trees.Secondly, and more realistically, we can correlate the abundance of salal and the treeheight and root collar diameter increments from 1990 to 1992. A number ofpredictions about the influence of salal on conifer growth were presented earlier in thisthesis based on the salal hypothesis. To support the salal hypothesis alone, all of thesepredictions must be met. Figure 16 summarizes the major findings of this study todetermine if the salal hypothesis is supported.Growth of hemlock on CH sites: The results of this study corroborate many ofthe predictions for hemlock growing on CH sites. Hemlock was more sensitive to salalthan cedar, and hemlock growth was reduced with increasing abundance of salal oncontrol plots. However, scarification reduced the influence of salal on hemlockconsiderably, and salal growing on fertilized CH sites reduced the performance ofhemlock.Growth of hemlock on HA sites: The greatest reduction in hemlock growth bythe abundance of salal occurred on control HA sites. The salal hypothesis predicts thatsalal would be competitive on control HA sites, but it does not predict that the strongestcompetition would occur here. Scarification on HA sites, like CH sites, reduced theinfluence of the abundance of salal considerably on hemlock growth, which is contraryto the prediction. As predicted, fertilization of HA sites, contrary to CH sites, alsoreduced the influence of salal on the growth of hemlock.92Growth of cedar on CH sites: Unexpectedly, cedar growth seemed to beencouraged by salal on control CH sites and scarified CH sites. This of course isdirectly opposite to the prediction. Furthermore, cedar growth was reduced by salal onfertilized CH sites which is also contrary to the prediction.Growth of cedar on HA sites: As predicted, cedar growth was reduced by salalon control HA sites, but the correlation was stronger than control CH sites. Cedargrowing on scarified HA sites seemed to be encouraged by salal which is directlyopposite to the prediction. As predicted, cedar growing on fertilized HA sites were notinfluenced by salal.The predictions of the salal hypothesis were not all met. Therefore, thepresence of salal cannot be accepted as the principal factor contributing to the poorgrowth of conifers on CH sites. However, salal clearly does have some impact onconifers, especially hemlock, and lends at least partial support to the hypothesis.HEMLOCKCH site^HA site93predictions:treatmentasalal abundanceconifer responsebobserved:treatmentsalal abundanceconifer responsec f s f+ s c f s f+ shigh high high high high high high higha c b d b d c dc f s f+ s c f s f+ shigh high high high high high high higha* a d d* a a d d*CEDARCH site^HA sitepredictions:treatmentsalal abundanceconifer responseobserved:treatmentsalal abundanceconifer responsec f s f+ s c f s f+ shigh high high high high high high highb d c d c dc dc f s f+ s c f s f+ shigh high high high high high high high+ b + d* b d* + d*Figure 16. The predicted outcomes compared to the observed outcomes of westernhemlock and western red cedar response to high abundance of salal based on the salalhypothesis.ac=control, f= fertilized, s= scarified.ba-=a 50% or more reduction in conifer growth compared to a conifer growing inoptimum conditions, b=30-50% reduction in conifer growth compared to a conifergrowing in optimum conditions, c= >0-30% reduction in conifer growth compared toa conifer growing in optimum conditions, d=no influence from salal.* = the prediction was the same as the observed.+ = an increase in conifer growth with increasing salal abundance.94Gaultheria shallon as a competitor of conifersRelationship between salal leaf area index and conifer performance using multipleregirssionWestern red cedar and western hemlock responded differently to the abundanceof salal indicating that there is a species effect, with cedar less sensitive to salal thanhemlock, which supports the general view (Bunnell 1990).A strong case can be made for the competitive influence of salal on hemlock.With increasing leaf area index of salal, both height and root collar diameter ofhemlock was reduced in control plots on CH and HA sites and on fertilized plots onCH sites. Salal on scarified plots generally had no influence on the height and rootcollar diameter of hemlock. It is possible that the minimal influence of salal onscarified plots was because scarification effectively removed most of the salal rhizomes.Therefore, salal would have to establish by seed propagation on scarified sites which isa slow method of colonization for salal because salal does not readily produce seeds,and the percentage of successful seed germination is low (Fraser et al. 1993). Becausesalal is slower at establishing it may not be exerting much of an influence on conifergrowth at the time of this study. The leaf litter of salal was much less on scarified sitesthan other treatments which is an indication that salal was recently established. Leaflitter may be considered a relative measure of the age of salal, i.e. a large leaf littermeans salal has been established for a long time. The areas which were fertilized didnot show any big differences in leaf area index or leaf litter of salal from those areaswhich were not fertilized. This indicates that any effect of salal on the resources didnot affect the performance of hemlock in fertilized, high-nutrient soils. To explain thenegative correlation of salal and hemlock in fertilized CH sites, it must by assumed thatthese sites are still comparatively low in nutrients. However, the measurements of soiltotal nitrogen do not reflect this assumption. This may be explained by the fact that the95sites were fertilized 4 years ago, therefore, any available nitrogen from the fertilizationtreatment has probably been incorporated by other plants or lost from the system.Also, total nitrogen is an imperfect measurement which doesn't account for the entirenitrogen cycle. Based on what is known about the soil properties of CH and HA sites(Lewis 1982; Messier 1991; Prescott et al. 1993) it seems evident that HA sites have ahigher nutrient availability than CH sites.There is evidence in this study that increasing leaf area index of salal reducedthe growth of western red cedar under certain conditions. However, control plots onCH sites showed that the abundance of salal was positively correlated with both theheight and root collar diameter of 2-year-old cedars measured in 1990, which rejectsthe salal hypothesis. Also, the root collar diameter of 2-year-old cedars growing inscarified plots on CH sites, and both height and root collar diameter of 2- and 4-year-old cedars growing in scarified plots on HA sites showed a positive correlation withsalal. This also rejects the salal hypothesis. Scarified plots on HA sites had the lowestleaf area index and leaf litter during 1991 and 1992, therefore not only was salalsparse, but the minimal leaf litter suggests that it had only recently been establishedwithin the area. This may account for the observed anomaly where the abundance ofsalal seemed to increase cedar growth.Evidence for the competitive influence of salal on 2-year-old cedars height androot collar diameter was found in control plots on HA sites and fertilized plots on CHsites. Salal had a greater negative influence on control plots on HA sites than fertilizedplots on CH sites. This agrees with the salal hypothesis but because of the other resultsthe hypothesis is rejected for cedar. The fertilized plots on CH sites and the controlplots on HA sites had the two highest mean leaf area index for 1991 and the highestsalal leaf litter. Both sites may be considered as nutrient medium because HA siteshave higher concentrations of available soil nutrients than CH sites (Prescott et al.1993), and in this case, the CH sites were fertilized. Nutrient medium soils appear to96be conducive to good salal growth, and abundant levels of salal on nutrient mediumsoils were competitive with cedar. The abundance of salal was not correlated withcedar growth during the 1992 measurements which may mean that salal is competitiveonly during the first few years following clear-cutting and slashburning. Messier(1991) projected that the expansion of salal will cease between 10 and 20 years afterclear-cutting and slashburning. Until that time, Messier suggested that salal wouldcontinue exerting a large effect on the nutrient resources. There is no evidence of anegative effect of salal on cedar growth after 7 years following clear-cutting andslashburning in this study, which suggests that the growth of cedar is not influenced bya possible depletion of resources by salal after 7 years. This may be due to thetolerance of western red cedar to limited resources (Gregory 1957), even though theymay require very high nutrient levels for optimum nutrition (Krajina 1969), or that theexpansion of salal has ceased. However, western hemlock is tolerant of equally lowlevels of nutrients, in fact, it has been shown that western hemlock survives anydeficiency treatment better than any other conifer (Krajina et al. 1982).The influence of the abundance of salal on the gmwth of conifers from 1990 to1992The 2-year growth increment of hemlock was reduced by the presence of salalto a much greater extent than cedar. The rate of height increase of hemlock on CHsites did not vary much with increasing abundance of salal. For hemlock growing oncontrol CH sites, presumably there was such a large deficit of nutrients that hemlocksdid poorly regardless of the abundance of salal. Scarification of CH sites may haveincreased the fertility of the sites and delayed the establishment of salal, therefore,although hemlocks may have had abundant salal growing nearby, the salal was recentlyestablished and not exerting a strong influence. The 2-year growth rate of hemlockgrowing on fertilized plots were influenced the most by salal abundance. This shows97that although the rate of height increase of hemlock can be increased with thefertilization of CH sites, the presence of salal will reduce the rate. Root collardiameter may be a more accurate estimate of biomass of hemlock than height.Hemlock is faster growing than cedar and allocates more biomass to leader growth,characteristic of a shade-tolerant species (Packee 1990). This may explain why rootcollar diameter was more sensitive to the abundance of sa1a1 than height. The onlycondition in which the abundance of salal had no influence on the rate of root collardiameter increase of hemlock was on scarified CH sites, presumably becausescarification increased the fertility of the sites and delayed the establishment of salal.Western hemlock was more sensitive to the abundance of salal on HA sites thanon CH sites. The greatest influence that salal had on the growth rates of height androot collar diameter increase of hemlock was found on control plots on HA sites. HAsites have higher levels of available nutrients than CH sites (Weetman et al. 1989b;Prescott et al. 1993). This shows that salal is more strongly competitive with hemlockwhen there are relatively more available nutrients. With fertilization and scarificationthe rate of height and root collar diameter increase of hemlock when salal was absentwas approximately the same as control plots. However, the rate of height and rootcollar diameter increase of hemlock planted on plots which had been scarified weremore resistant to increasing leaf area index of salal. Hemlock height and root collardiameter growth rate were reduced with increasing leaf area index of salal on fertilizedHA sites. This was a different response than the results from the multiple regressionmodels. Therefore, salal is a serious competitor with hemlock under specific fieldconditions: control CH sites, fertilized CH sites, control HA sites, and fertilized HAsites.There is very little evidence to suggest that salal is competitive with western redcedar. There were only two significantly negative relationships between the growthrate of cedar and the leaf area index of salal: height of cedar on fertilized CH plots and98on fertilized HA plots. Unlike hemlock, the height of cedar was more sensitive to theabundance of salal than root collar diameter, i.e. cedar allocates more biomass to rootcollar diameter. Scarification eliminates any negative influence from sala1 presumablyby delaying its establishment. Unless the leaf area index of salal is kept below 1, itwould not be beneficial to fertilize CH sites to improve the growth rate of cedar.The influence of the leaf area index of non-crop species other than salalon conifer growthThe multiple regression models of the leaf area index of all non-crop specieswere more effective at predicting cedar and hemlock growth on control and fertilizedplots than on scarification plots and fertilization plus scarification plots. Thedisturbance caused by scarification may have delayed the establishment and propagationof non-crop species, therefore delaying the onset of competition effects. It is possiblethat competition from non-crop species on scarified plots will never significantly hinderthe growth of conifers because after 4 years of growth the conifers may be largeenough to inhibit the establishment of non-crop species through shading.Generally, the non-crop species which were correlated with height of hemlockand cedar were also correlated with root collar diameter during the same year andunder the same conditions. However, the multiple regression models for root collardiameter more often had a higher R2 value than height, particularly for hemlock.Hemlock allocates more biomass to leader growth than cedar, and although a hemlockmay be relatively high, it may not have a correspondingly large root collar diameter.In this case, root collar diameter on hemlock may be a more accurate measurement ofcompetition than height because it is more sensitive to limitation of resources.99For only three species could generalities be made about their relationship withthe conifers over all of the site x treatments conditions.The abundance of Epilobium angustifolium is an indicator of nutrient-rich soils(Klinka et al. 1989b), and generally, the abundance of E. angustifolium was positivelycorrelated with conifer growth. However, conifer growth on some of the sites thatwere scarified was negatively correlated with E. angustifolium, especially hemlockgrowth. Scarification increased the abundance of E. angustifolium, thus increasing itsinfluence on conifer growth. The fact that the abundance of E. angustifolium wasnegatively correlated with hemlock growth on fertilized HA sites indicates that hemlockis more sensitive to competition from E. angustifolium than cedar.The abundance of Hypochoeris radicata, an indicator of exposed mineral soil(Klinka et al. 1989b), was positively correlated with cedar growth in practically everycondition where it was significant in the multiple regression models. Hemlock growthwas predominantly negatively correlated with the abundance of H. radicata.Therefore, it is likely that cedar grows well on exposed mineral soil whereas hemlockgrows better with a high amount of organic matter. This is consistent with researchconducted on sites suitable for the development of cedar (Minore 1990) and hemlock(Packee 1990) seedlings.The abundance of Cornus canadensis, an indicator of nitrogen-poor soils(Klinka et al. 1989b), was predominantly positively correlated with the growth of cedarwhere it was included in the multiple regression models. In contrast, the abundance ofC. canadensis was predominantly negatively correlated with the growth of hemlock.The fact that cedar was positively correlated with C. canadensis, an indicator ofnitrogen-poor soils, suggests that cedar can tolerate low nutrient environments and thatit is not negatively influenced by C. canadensis. It is interesting to note that C.canadensis was more abundant where cedar was planted compared to hemlock. Thereis a strong association between the abundance of C. canadensis and cedar growth.100It is evident that not only is hemlock more sensitive to salal than cedar, hemlockis also generally more sensitive to the abundance of non-crop vegetation and tonitrogen-poor soils. The abundance of Blechnum spicant and Mycelis muralis,indicators of low and high soil nitrogen, respectively, (Klinka et al. 1989b), areexceptions, where, at least for control plots, they were positively correlated withhemlock growth. The abundance of Blechnum spicant and Mycelis muralis were alsopositively correlated with cedar growth.Abiotic environmental factors influence on salal leaf area index andconifer growth using multiple regressionThe soil variables (soil moisture, soil coarse content, soil total carbon, soil totalnitrogen, and soil total phosphorus) were poor predictors of conifer growth, andequally poor at predicting salal abundance. Generally, high levels of soil total nitrogenand soil total moisture were positively correlated with hemlock and cedar growth, andhigh levels of soil total carbon were negatively correlated with hemlock and cedargrowth. This corroborates the known requirements for good hemlock and cedar growth(Burns 1990). The influence of soil coarse content and soil total phosphorus onhemlock and cedar growth was variable and indeterminate. The only soil variablethat showed any significance in predicting salal leaf area index was total phosphorus.Increasing soil total phosphorus was correlated with increasing salal leaf litter onscarified CH and HA sites. This indicates that phosphorus is limiting salal growth. Ithas been shown that salal can obtain access to organic nitrogen (Xiao and Berch 1993),therefore, phosphorus, not nitrogen, may be the limiting nutrient to salal growth. Ifthis is true, nitrogen fertilization alone may be a preferable treatment for improvingconifer growth by limiting salal growth.101The reason for the lack of correlation between soil variables and coniferperformance are numerous. Although it is relatively easy to determine the totalquantity of nutrients present in a soil sample, only a small fraction of the total pools areavailable for nutrient uptake by plants each year and nutrient availability variestemporally. Therefore, measurements of total nutrients may not relate well to thequantities available to plants. It would be more beneficial to determine the rate atwhich nutrients are cycled each year than to know the total quantity of nutrients withinan ecosystem. Furthermore, nutrient availability varies spatially, with more nutrientsin the upper profile. This coincides with the maximum occurrence of fine-root growth.But, in some cases, nutrient supplies from deeper than 50 cm are important (Binkley1986). It is not surprising that fertilized plots generally had no greater levels of soiltotal nutrients than control plots because the sites were fertilized 4 years before theanalysis. Therefore, most of the nutrients from the fertilizer treatment would beincorporated by plants or leached out of the system.Site x treatment effect using 3-way ANOVASalal performance:The growth of salal was analyzed separately according to the neighbouringconifer. Generally, there was no difference in salal growth whether in association withcedar or with hemlock. However, in control plots in HA sites there was more salal leaflitter and a higher salal LAI with cedar than with hemlock. It would seem thathemlock suppresses salal growth to a greater degree than cedar or that the soil type thatencourages hemlock discourages salal, or perhaps that cedar facilitates salal growth.Not surprisingly, scarification decreased leaf area index and leaf litter of salal.However, the greatest increase in leaf area index of salal from 1991 to 1992 occured onthe scarified plots. This indicates that salal had expanded its above-ground growth to102near its maximum potential on control and fertilized plots by 1991, i.e. 4 years afterestablishment. This agrees with Bunnell's (1990) findings that 85% of the spaceoccupied by salal after nine years of growth was occupied during the first three years.On scarified plots, salal appears to be still expanding, indicating that scarificationdelays the establishment of salal, therefore reducing the influence salal may have onconifers. The fact that salal showed little difference in foliar nutrients between site xtreatment combinations indicates that salal is tolerant of low nutrient environments orthat it does not have the capacity to retain high levels of nutrients in its foliage whengrown on high nutrient environments. However, this does not mean that salal does notincrease its uptake of nutrients in high nutrient environments. In higher nutrientenvironments it is likely that salal will turn over its leaves at a faster rate, increasingleaf litter.Western hemlock performance:There was a strong site effect where the growth of hemlock was greater on HAsites, probably due to the greater availability of nutrients. A treatment effect wasobserved on CH sites, where fertilization and scarification increased the growth ofhemlock. Nutrients do not appear to be limiting hemlock growth on HA sites.Fertilization and scarification decreased foliar nitrogen and foliar potassium, howeverthe concentration of nitrogen and potassium may decrease with increasing total biomassof the hemlocks. Therefore, the net concentration of nitrogen and potassium of thehemlock in the treated plots may be equal to, or even greater than, the control plots.Western red cedar performance:The site effect on western red cedar was not as obvious as for western hemlock.Cedar growth on control plots on CH and HA sites were similar. But fertilization andscarification increased the growth of cedar more on HA sites than CH sites. The effect103of scarification increased dramatically from 1990 to 1992, surpassing the effect offertilization. Therefore, the effects of soil mixing is delayed but, perhaps, ultimatelypreferable because there is very little competition from non-crop species. By the timenon-crop species can establish, shading from the conifers will suppress growth. OnHA sites, treatment had little effect on height, root collar diameter, colour index, andfoliar nitrogen compared to the control plots. This indicates that cedar growing oncontrol plots on CH sites are nutrient deficient to a greater degree than control plots onHA sites. This supports the findings that HA sites are higher in nutrients than CH sites(Weetman et al. 1989b; Prescott and McDonald 1992). This also shows that cedar areslower growing species than hemlock. Cedar had higher foliar nitrogen, phosphorus,and potassium concentrations than hemlock. Perhaps on a net foliar nutrient basis,hemlock may be higher because they are taller. In any case, slower growth andaccumulation of nutrients of cedar may be one reason why salal had minimal influenceon cedar performance.Soil variables:Soil moisture did not differ between site x treatment combinations. Thissuggests that soil moisture does not limit conifer growth, which Messier (1991) alsoreported. Soil total carbon also did not differ between site x treatment combinations,but Messier (1991) found that HA soils were lower in soil total carbon than CH soils.The coarse content of soils on HA sites where hemlock were grown were higher thanthe soils on CH sites. A higher coarse content is conducive to a well-drained soil andincreased mineralization of nutrients (Binkley 1986), therefore increasing the growthpotential of the conifers. Soils where cedar were grown did not show the same patternin coarse content as where hemlock was grown. This may mean that there is adifference in the degree to which the growth of hemlock and cedar alter the soilstructure, or that the disturbance of the soil caused by windthrow alters the soil104structure. Fertilization and scarification had varying effects on nutrient availability ofthe soil. For the soils where hemlock was growing, fertilization had no effect on totalnitrogen or phosphorus. This may be due to the fact that the soils were fertilized fouryears before the analysis and hemlock and neighbouring vegetation have incorporatedall of the available nutrients. Scarification, on the other hand, seemed to reduce thetotal soil phosphorus. For the soils where cedar was growing, fertilization increasedthe total nitrogen and phosphorus, which could mean that cedar is slower at extractingnutrients than hemlock.Competition theory related to salalBased on the growth of salal, and the sites where the abundance of salal reducedconifer growth, salal may be termed a "competitive - stress-tolerant" strategist (Grime1977, 1979). Much attention has been centered on Grime's theories (Harper 1982;Grubb 1985; Loehle 1988; Grace 1990; Turkington et al. 1993) as they predict theresponse of plants under different environmental conditions. Grime's theory is basedon the life history characteristics of a plant's established phase depending on thedegrees of "stress" (phenomena which restrict photosynthetic production) and"disturbance" (partial or total destruction of plant biomass) to which they are adapted.According to this classification, those plants adapted to low levels of both disturbanceand stress are referred to as "competitive," those adapted to low disturbance and highstress are "stress-tolerant," and those adapted to high disturbance and low stress are"ruderal." In this study, low levels of both disturbance and stress are fertilized plots,low disturbance and high stress are control plots, high disturbance and low stress arescarified, and fertilized plus scarified plots. One of the most important characteristicsof this classification is the maximum relative growth rate (RGRmax). Plants with a105high RGRmax are better able to utilize nutrients in a high nutrient environment and aretherefore the best competitors. Good competitors develop biomass rapidly, allocatinglittle energy to sexual reproduction, in order to dominate both above- and below-ground resources.The relative growth rate of salal is high when nutrients are high which is evidentby the high abundance of salal on the higher nutrient sites. This suggests that salal hasa high RGRmax which is indicative of a competitor-type strategist. Only afterapproximately 4 years will salal flower (Fraser et al. 1993). The delay in sexualreproduction allows for the expansion of salal both above- and below-ground (Messier,1991). Although salal is able to persist in low-nutrient conditions (Fraser et al. 1993),the limited distribution range of salal indicates that it does not have a wide tolerance.Scarification, i.e. disturbance, significantly reduced the leaf area index and leaf litter ofsalal and effectively eliminated the negative influence of salal on conifer performance.In this case, salal is not a strong "ruderal" strategist. However, salal does resproutfrom severed rhizomes and lightly burnt stems (Fraser et al. 1993), therefore,conferring limited "ruderal" strategist traits. Based on sale s characteristics, Grimewould predict that salal would be competitively dominant in nutrient rich, undisturbedsoils, which holds true for this study.106SUMMARY AND CONCLUSIONSThis study shows that the presence of salal reduces the growth of westernhemlock more than western red cedar. Both the correlations of salal abundance onhemlock height and root collar diameter from the multiple regression models, and theinfluence of salal on height and root collar diameter growth from 1990 to 1992 showthat salal abundance is strongly associated with poor hemlock growth. The multipleregression models show that in control plots on CH sites, control plots on HA sites,and fertilized plots on CH sites salal could account for over 32%, 38%, and 42% of thevariation in conifer performance, respectively. The analysis of the 2-year growth ofhemlocks between 1990 and 1992 show that saial reduces hemlock growth rate incontrol plots on CH sites, fertilized plots on CH sites, control plots on HA sites andfertilized plots on HA sites. Scarification appears to reduce the influence of salal onhemlock, perhaps because salal present on scarified plots are recently established andare not exerting a strong nutrient drain on the system. When growing with cedar, salalappears to be weakly competitive in control plots on HA sites, fertilized plots on CHsites and fertilized plots on HA sites. However, this negative association of salal oncedar only occurred on 2-year-old trees, not 4-year-old trees, suggesting that theinfluence is waning. For hemlock, the influence of salal was greatest on 4-year-oldsaplings, suggesting that the influence of salal is increasing.Foliar nitrogen, phosphorus, and potassium concentrations were greater forcedar than hemlock, indicating that cedar utilizes nutrients more effectively. This mayaccount for the minimal influence of salal on cedar performance.Soil variables showed no strong trends for predicting the performance ofhemlock or cedar. There is some evidence to suggest that salal is limited byphosphorus.107Management implications for hemlock and cedar growing on CH sitesIt is important to recognize the difference between the influence of salal oncedar and hemlock growing on CH sites because cedar and hemlock require differenttreatments to control against the competitive influence of salal. Fertilization,scarification and fertilization plus scarification increases the growth rate of hemlock onCH sites. However, with increasing abundance of salal, the growth rate of hemlock onfertilized sites is reduced rapidly compared to hemlock on scarified and fertilized plusscarified sites. Therefore, scarification or fertilization plus scarification is therecommended treatment. Cedar increases its growth rate with increasing abundance ofsalal on control CH sites. Therefore, no treatment is necessary to control against thecompetitive influence of salal. However, it is shown that fertilization, scarification andfertilization plus scarification increases the performance of cedar, especially when theleaf area index of salal is below 1. Fertilization would not be recommended as atreatment because with salal leaf area index over approximately 1, there is a significantdecrease in the growth rate of salal, i.e. fertilization increases the competitiveness ofsalal. The recommended treatment would be either no treatment, or fertilization plusscarification.More research needs to be conducted on the effect of phosphorus on salal. Ifphosphorus is a limiting nutrient for salal, a fertilization treatment of nitrogen alonewould not encourage salal growth but would increase conifer growth and quickly shadeout any salal.108Future researchThis research has revealed the need for additional studies to improve ourunderstanding of the influence of salal on the growth of cedar and hemlock saplingsfollowing clear-cut logging and slashburning of CH sites on northern Vancouver Island.The following 5 suggestions outline the most important studies needed:1. A manipulative replacement series experiment in a controlled environmentto determine the point when the abundance of saIal inhibits hemlock andcedar growth.2. Age effect of saIal on the growth of hemlock and cedar.3. Fertilization trials to determine the nutrient requirements of salal andwhether it is limited by phosphorus.4. Long-term effects of scarification on sala1 growth in association withhemlock and cedar growth.5. Determine why cedar appears to be more resistant to the influence ofsa1a1 than hemlock.LITERATURE CITEDANONYMOUS 1970. Gaultheria shallon Pursh. Davidsonia 1:29 -31.ANONYMOUS 1981. UBC Pedalogy laboratory "Methods Manual". Dept. of SoilScience, UBC, Van., B.C.BARKER, J.E. 1988. Control of salal with Garlon (1988 update). Expert Committeeon Weeds. Research report. p.194. Western Canada Section Meeting.Winnipeg, Man.BARKER, J.E., VVEETMAN, G.F. and FOURNIER, R.M. 1987. Growth andnutrition of sitka spruce,^western hemlock and western red cedar followingfertilization of coastal cedar/hemlock sites. Western Forest Products. 14pp.BARKER, J.E., JOYCE S., BAVIS P., DUMONT B. 1991.! SCHIRPestablishment trial. 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