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Classification of trembling aspen ecosystems in British Columbia. Full report. Krestov, Pavel; Klinka, Karel; Chourmouzis, Christine; Hanel, Claudia 2000

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CLASSIFICATION OF TREMBLING ASPEN ECOSYSTEMS IN BRITISH COLUMBIAP.V. Krestov, K. Klinka, C. Chourmouzis, and C. HanelForest Sciences DepartmentTHE UNIVERSITY OF BRITISH COLUMBIAMarch 2000CLASSIFICATION OF TREMBLING ASPEN ECOSYSTEMS IN BRITISH COLUMBIAbyP. V.  K r e s t o v1,2, K. Klinka2, C. Chourmouzis2, C. Hanel21Institute of Biology and PedologyRussian Academy of Sciences, Far Eastern BranchVladivostok 690022 Russia2Forest Sciences DepartmentUniversity of British Columbia3036-2424 Main Mall, Vancouver, BC V6T 1Z4 CanadaScientia Silvica Extension SeriesNumber 27Forest Sciences DepartmentTHE UNIVERSITY OF BRITISH COLUMBIAMarch 2000Scientia Silvicais published by the Forest Sciences Department, The University of British Columbia, ISSN 1209-952XEditor: Karel Klinka (klinka@interchange.ubc.ca)Production and design: Christine Chourmouzis (chourmou@interchange.ubc.ca)Financial support: Site Productivity Working Group of the BC Ministry of ForestsiiiSUMMARYSUMMARYThis report presents the first approximation of vegetation classification of trembling aspen ecosystems in interior British Columbia. The classification is based on a total of 186 plots sampled during the summers of 1995, 1997 and 1998. We used multivariate and tabular methods to synthesize and classify ecosystems according to the Braun-Blanquet approach and the methods of biogeoclimatic ecosystem classification. The aspen ecosystems were classified into 15 basic vegetation units (associations or subassociations) that were grouped into four alliances. Communities of the Populus tremuloides – Mertensia paniculata, and Populus tremuloides – Elymus innovatus alliances were aligned with the boreal Picea glauca & mariana order and were distributed predominantly in the Boreal White and Black Spruce zone; communities of the Populus tremuloides – Thalictrum occidentale alliance were also aligned with the same order, but were distributed predominantly in the Sub-Boreal Spruce zone; communities of the Populus tremuloides – Symphoricarpos albus alliance were aligned with the wetter cool temperate Tsuga heterophylla order and the drier cool temperate Pseudotsuga menziesii order and were distributed in the Sub-boreal Spruce, Interior Western Hemlock, Montane Spruce, and Interior Douglas-fir zones. We describe the vegetation and environmental features of these units and present vegetation and environmental tables for individual plots and units.ACKNOWLEDGEMENTSWe thank the following individuals for helping in the preparation of this report: David New, David Brisco, Brad Collins, David Affleck, and Katherine Zidek for field assistance and sample preparation, Pal Varga for digitizing the photographs, Hong Qian for contributing the section on plant diversity, and Mike Ryan for the identification of byrophytes and lichens.We thank R. Kabzems (Fort St. John Forest District) for contributing vegetation and environmental data from aspen plots in northeastern BC sampled in 1995. We also thank the BC Forest Service Staff from the Dawson Creek, Fort St. James, Ft. Nelson, Mackenzie, and Morice Forest Districts for assistance in locating study stands and permits for cutting site trees. We gratefully acknowledge the financial support from the Site Productivity Working Group of the BC Ministry of Forests.ivScientica Silvica Extension Series, Number 27, 2000TABLE OF CONTENTSSUMMARY ........................................................................................................................... iiiACKNOWLEDGEMENTS..................................................................................................... iiiINTRODUCTION.................................................................................................................. 1METHODSStudy Area .................................................................................................................. 3Sampling ..................................................................................................................... 6Vegetation Classification ............................................................................................. 7Similarity and Cluster Analysis ........................................................................................... 9Spectral Analysis ................................................................................................................ 9Diversity Analysis .............................................................................................................10RESULTS AND DISCUSSIONVegetation Classification ........................................................................................... 11Vegetation-Environment Relationships ..................................................................... 26Description of Plant Associations .............................................................................. 33111 Populus tremuloides - Mertensia paniculata: Festuca altaica subassociation ........... 33112 Populus tremuloides - Mertensia paniculata: Arnica cordifolia subassociation .......... 35113 Populus tremuloides - Mertensia paniculata: Petasites frigidus subassociation ........ 37210 Populus tremuloides - Ledum groelandicum association ........................................... 39221 Populus tremuloides - Lathyrus ochroleucus: Hedysarum boreale subassociation ... 41222 Populus tremuloides - Lathyrus ochroleucus: typic subassociation ........................... 43223 Populus tremuloides - Lathyrus ochroleucus: Actaea rubra subassociation .............. 45310 Populus tremuloides - Thalictrum occidentale association ........................................ 48411 Populus tremuloides - Viburnum edule: Spiraea betulifolia subassociation ............... 50412 Populus tremuloides - Viburnum edule: Paxistima myrsinites subassociation .......... 52421 Populus tremuloides - Rosa nutkana: Aralia nudicaulis subassociation .................... 54422 Populus tremuloides - Rosa nutkana: Arnica cordifolia subassociation ..................... 55423 Populus tremuloides - Rosa nutkana: Angelica genuflexa subassociation ................ 56424 Populus tremuloides - Rosa nutkana: Senecio pseudoaureus subassociation ......... 57425 Populus tremuloides - Rosa nutkana: Shepherdia  canadensis  subassociation ....... 58REFERENCES................................................................................................................... 59APPENDICES .................................................................................................................... 631INTRODUCTIONTrembling Aspen EcosystemsINTRODUCTIONTrembling aspen (Populus tremuloides Michx.) is one of the most common tree species in the second-growth forests of the boreal and temperate zones of North America (Little 1979). It occurs across all of non-arctic Alaska, Canada and the northern USA and reaches south to the west coast of Mexico. In British Columbia (BC), aspen grows in all forested biogeoclimatic zones, except the Mountain Hemlock (MH) zone.  It is common in the Boreal White and Black Spruce (BWBS), Sub-Boreal Spruce (SBS), Sub-Boreal Pine – Spruce (SBPS), Montane Spruce (MS), Interior Douglas-fir (IDF), and Interior Cedar - Hemlock (ICH) zones.  Its occurrence is marginal in the Costal Douglas-fir (CDF), Coastal Western Hemlock (CWH), Spruce – Willow – Birch (SWB), Engelmann Spruce – Subalpine Fir (ESSF), and Ponderosa Pine (PP) zones.Aspen has become an important timber crop species in the province, yet the full ecological value of aspen in the boreal forest is not yet fully understood.  The classic successional sequence of a boreal forest begins with the removal or disturbance of a coniferous stand by wildfire and the establishment of a broad-leaved stand. Over time the boreal conifers, such as white (Picea glauca (Moench) Voss) and black spruce (Picea mariana (Mill.) B.S.P) re-establish  and remain until the next stand-disturbing event. The increasing presence of seral aspen stands across the landscape and the increasing demand for timber has motivated forest managers to search for ways to utilize the aspen timber resource as well as to establish and grow coniferous trees in association with the aspen.  An improved knowledge of aspen ecology and ecosystems, and stand productivity and dynamics is needed in this pursuit, which presupposes classification of aspen ecosystems. There have been only a few ecological studies carried out in aspen ecosystems in BC. These studies included local classification of aspen ecosystems (e.g., DeLong 1988), aspen site index modelling and prediction from environmental factors (Chen et al. 1998a, 1998b), relationships between aspen site index and soil properties (Chen et al. 1998b), and humus form characterization (Fons et al. 1998). While this information has added to our knowledge base, many of these studies have been carried out on a local level. In order to integrate this information and provide a complimentary tool for further studies of aspen ecosystems in BC and their comparison with others across North America, we have developed a regional vegetation classification. The classification, which follows the biogeoclimatic ecosystem classification system, is based on samples of aspen-dominated stands across the BWBS, SBS, SBPS, IDF, MS and ICH zones of BC. Our aim was to organize aspen communities into groups that show the greatest number of vegetation and vegetation-environment relationships, are easily retained in memory and are easily conveyed through instruction. However, we do not claim that we have accounted for all of the many different aspen communities; thus the classification presented is but the first approximation. Other aspects of aspen growth and boreal ecology, such as height/age and site index models, the integration of these productivity relationships into the ecosystem classification, a characterization of understory plant diversity, humus forms, and soil nutrient conditions of aspen ecosystems, and a comparison of the above features between aspen and black spruce ecosystems are discussed in the following reports prepared for publication: Trembling aspen site index in relation to environmental measures of site quality at two spatial scales (Chen et al.),  Height growth models for trembling aspen in BC (Nigh et al.), Comparison of forest floor and mineral soil properties between black spruce and trembling aspen stands in the BWBS zone of BC (Kayahara 2INTRODUCTIONScientica Silvica Extension Series, Number 27, 2000et al.), and Plant diversity of mid-seral black spruce and trembling aspen stands in the BWBS and SBS zones (Qian et al.).In this report we present the vegetation classification, which includes, from the lowest to the highest hierarchical level: 13 subassociations, 6 associations, and 4 alliances. We present the summary and diagnostic tables and indicator plant analysis used to show floristic affinities among the units, and to interpret their relationships to climatic and edaphic gradients. The vegetation and environmental data for individual plots are also included in the appendices.This report is available in full colour or B&W printed versions or in electronic format on Scientia Silvica CD-ROM. For further information or to order a copy visit www.forestry.ubc.ca/klinka or contact Karel Klinka, Forest Sciences Department, University of British Columbia, 3036-2424 Main Mall, Vancouver BC  V6T 1Z4 (e-mail:  klinka@interchange.ubc.ca).3METHODSStudy AreaTrembling Aspen EcosystemsMETHODS Study AreaThe study area encompassed nearly the entire interior area of the province where aspen stands form a significant landscape component (Table 1, Figure 1). The area included (in order from north to south) the BWBS, SBS, SBPS, ICH, IDF, and MS biogeoclimatic zones (Meidinger and Pojar 1991).The BWBS, SBPS, and SBS zones are part of the Canadian Boreal Forest Region (Krajina 1969). The BWBS zone is influenced by a continental, montane boreal climate and subject to frequent outbreaks of arctic masses, while the climate influencing the SBS and SBPS zones is milder. Forest fires are frequent in all these zones, maintaining a large portion of the landscape in early and mid-seral stages. White spruce, hybrid spruce (Picea engelmannii x glauca), black spruce, subalpine fir (Abies lasiocarpa (Hook.) Nutt.), lodgepole pine (Pinus contorta var. latifolia Dougl. ex Loud), trembling aspen, balsam poplar (Populus balsamifera L.) and black cottonwood  (P. trichocarpa Torr. & Gray), paper birch (Betula papyrifera Marsh.) and Alaska paper birch (Betula neoalaskana Sarg.) are the major tree species. In upland ecosystems, aspen typically forms pure stands of various sizes ranging form small cohorts to large-area stands. The IDF, ICH, and MS zones are part of the Cordilleran Montane Forests Region (Krajina 1969) and are influenced by a cool continental temperate climate (with the MS zone grading into a continental subalpine boreal climate). These temperate zones are much warmer than the BWBS, SBS and SBPS zones but have about the same annual precipitation (Table 1). Aspen stands are not as extensive as in the boreal zones. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western redcedar (Thuja plicata (Donn ex D.Don) Spach), western hemlock (Tsuga heterophylla (Raf.) Sarg.), western larch (Larix occidentalis Nutt.), lodgepole pine, subalpine fir, and hybrid white spruce are the major tree species in these temperate zones. The soils typically associated with aspen communities in the province are Brunisols, Luvisols, and Podzols (rarely Gleysols, Regosols, or Organic soils), developed from a variety of parent materials. Regardless of site characteristics, the associated humus forms are Mormoders, Moders (frequently laminated), Hemimors, Mullmoders and Mulls (Fons et al. 1998). More detailed information about the vegetation and environment of the zones studied is given in Krajina (1969) and Meidinger and Pojar (1991).4METHODSStudy AreaScientica Silvica Extension Series, Number 27, 2000Table 1. General spatial, climatic, and growth characteristics of the trembling aspen study plots stratified by biogeoclimatic zones.Biogeoclimatic zone Number of plots Elevation (m) Latitude (°N) Longitude (°W) Mean annual precipitation (mm)Mean annual temperature (°C)Site index (m) (standard deviation)All plots Site index plotsBoreal White and Black Spruce (BWBS) 88 59 525-980 55°42'-59°35' 120°26'-133°10'446 [46]11. Number of climatic stations with precipitation records0.6 [84]22. Number of climatic stations with temperature records13.7 (4.64)Sub-boreal Spruce (SBS) 25 20 790-1025 52°08'-54°35' 121°21'-124°32' 645 [78] 2.1 [129] 16.7 (3.13)Sub-boreal Pine - Spruce (SBPS) 7 6 870-1040 52°34'-52°35' 123°01'-123°20' 479 [14] 2.4 [11] 18.7 (3.45)Interior Douglas Fir (IDF) 23 20 960-1285 49°22'-52°11' 119°05'-123°31' 442 [90] 5.1 [73] 16.3 (5.25)Montane Spruce (MS) 19 17 980-1285 49°01'-49°31' 115°30'-119°35' 598 [13] 3.1 [12] 22.8 (4.96)Interior Cedar-Hemlock (ICH) 24 19 380-1025 49°02'-55°28' 116°11'-128°31' 795 [60] 5.5 [60] 21.7 (4.81)Total or total range 186 141 380-1285 49°01'-59°35' '115°30'-133°10'276 (IDF) to 1916 (SBS)-3.2 (SBS) to 9.7 (IDF)5.5 - 30.75METHODSStudy AreaTrembling Aspen Ecosystems Figure 1. Map showing the native range of trembling aspen in British Columbia and the location of plots sampled in 1997 and 1998; the plots sampled by Kabzems in northeastern BC in 1995 are not shown on this map.Distribution frequencySample plotsinfrequentfrequentvery frequentisolated standplot locationnumber of plots at a location(4)(8)(5)(3)(3)(3)(3)(4)(7)(3)(3)(3)(3)(3)(8)(2)(4)(4)(4)(5)(6)(2)(2)(9)(5)(2)(2)6METHODSSamplingScientica Silvica Extension Series, Number 27, 2000SamplingSampling in the northeastern portion of the BWBS zone was carried out in 1995 by R. Kabzems, Fort St. John Forest District. We continued the sampling in other areas in 1997 and 1998. The candidate stands were located close to access roads branching off from the Cassiar and Alaska Highways, around Tumbler Ridge, and north of Fort St. James, and from highways in southern BC (Figure 1). During the summer of 1997 we (i) carried out a reconnaissance, (ii) located candidate stands for sampling, and (iii) described 50 plots; during the summer of 1998 we completed description and sampling of selected stands. The complete data set includes vegetation and environment information obtained from 186 plots. These study plots were deliberately located over the widest possible range in climate (latitude, longitude, elevation), topography (aspect, slope gradient), soil moisture and soil nutrient conditions throughout six biogeoclimatic zones: BWBS, SBS, SBPS, IDF, ICH, and MS (Table 1). The study plots, 20 by 20 m squares (0.04 ha), were selected in naturally established, unmanaged, fully stocked, even-aged (immature, early mature, and mature >50 but <150 years at breast height) stands without a history of suppression. The developmental stage of the selected stands ranged from stem exclusion to understory reinitiation (Oliver and Larson 1996). Each stand had a uniform canopy layer formed by trembling aspen and uniform understory vegetation, with the floristic composition varying from site to site. Biogeoclimatic subzone was identified using maps obtained from the regional offices of the BC Ministry of Forests. Latitude and longitude were determined from topographic maps, elevation was measured with a Thommen pocket altimeter, and aspect was measured with a pocket compass. Site, vegetation, and soil of each plot were described according to Luttmerding et al. (1990).All plant species present within the plot were identified and their cover percentage was estimated. These cover values were converted to classes (+ to 9) of the Domin-Krajina scale of species significance. The plant nomenclature followed Qian and Klinka (1998). Unknown plants were collected and identified in the laboratory. A soil pit was dug at each plot and soils were described and identified according to the Canadian Soil Classification System (Agriculture Canada Expert Committeee on Soil Survey 1987). Humus samples were taken from each plot for a visual analysis and identification in the laboratory using the humus form classification of Green et al. (1993). The type of ground cover (forest floor, decaying wood, mineral soil, coarse fragments, and open water) was recorded. A more complete description of the field methods is given in Brooke et al. (1970) and Luttmerding et al. (1990). Soil moisture and nutrient regimes were estimated in the field by a systematically guided evaluation of a selected number of topographic (slope, aspect, gradient, and position) and soil morphological properties (humus form, rooting depth, soil texture, coarse fragment content, soil aeration, soil mineralogy, and the presence and depth of the growing-season water table). This procedure is based on interpreting relationships between these properties, soil water-holding capacity, and available nutrient levels in the soil (Green and Klinka 1994). Field-estimates of SNRs were substantiated by soil nutrient analysis (Kayahara et al. 2000), while SMRs were only field-estimated and not directly measured. Using the criteria proposed by Klinka et al. (1989), we converted relative SMRs to actual SMRs by consulting Wang et al. (1994) for the SBS zone, Banner et al. (1993) for the BWBS zone and New (1999) for the IDF, ICH, and MS zones (Table 2). For field estimates of SNR we used the following mean relative frequencies of nitrophytic species: 1% for very poor SNR, 4% for poor SNR, 9% for medium SNR, 25% 7METHODSVegetation ClassificationTrembling Aspen Ecosystemsfor rich SNR, and 38% for very rich SNR Wang (1992). A complete description of indicator plant analysis is given in Klinka et al. (1989).Table 2. Estimated generalized relationships between relative and actual soil moisture regimes (SMRs) for the study zones. Actual SMRs are abbreviated as follows: ED - excessively dry, VD - very dry, MD - moderately dry, SD slightly dry, F - fresh, M - moist, VM - very moist, W - wet. Definitions of actual SMRs are given in Klinka et al. (1989).Vegetation ClassificationOur objective was to produce ecologically meaningful classes of ecosystems that could be identified and used as a framework for examining vegetation-environment relationships. Consistent with the methods of the biogeoclimatic ecosystem classification, the plots within each group had to represent communities that had affinities in floristic composition and physiognomy.  The groups of plots were required to (1) be floristically distinct, and (2) occupy a floristically defined segment of the edaphic and local climatic gradients.We classified the ecosystems into vegetation units at three categorical levels (subassociation, association, and alliance) using the Braun-Blanquet approach (Mueller-Dombois and Ellenberg 1974: 177-210; Westhoff and van der Maarel 1980: 287-399). This method consists of grouping the plots in a way that each group is separated from all other groups by an exclusive diagnostic combination of species. These diagnostic species must be either differential species, which have a much higher presence (proportion of plots of a group that it occurs in) than in other groups, or a dominant differential species, which have higher species significance (percent cover) than in other groups. The exact criteria are as follows (Becking 1957):differential species: species that may be associated with more than one vegetation unit in a hierarchy; presence class ≥ III (occurring in ≥ 40% of the plots of this unit) and at least two presence classes greater than in other units of the same hierarchical level within the same higher level unit. dominant-differential species: species that may be associated with more than one vegetation unit in a hierarchy; presence class ≥ III, mean species significance ≥ 5 (≥ 10% cover) and two or more species significance classes greater than in other units of the same hierarchical level within the same higher level unit.Biogeoclimatic zone Relative Soil Moisture Regime1234567Boreal White and Black Spruce VD MD SD SD F-M VM WSub-boreal Spruce VD MD SD F M VM WSub-boreal Pine – Spruce VD VD MD MD SD F-M VM-WMontane Spruce VD MD SD SD F M-VM WInterior Cedar – Hemlock VD MD SD F M VM WInterior Douglas-fir ED VD VD MD SD F-M VM-W8METHODSVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000There is no universally accepted methodology for, nor agreement upon, the required composition of the diagnostic combination of species for a particular category (Becking 1957; Mueller-Dombois and Ellenberg 1974; Westhoff and van Maarel 1980). We used the principle of relative differentiation that allows delineation of a subassociation or association by an exclusive diagnostic combination of species. The diagnostic combination must include at least one differential species or dominant-differential species. However, a subassociation or association that represents the central concept, i.e. typic, of a higher circumscribing unit can be recognized without a diagnostic combination of species. A typic unit can be differentiated by the absence or low occurrence of species that characterize other subassociations or associations of the same hierarchical level within the same higher level unit (Pojar et al. 1987: 131-132). The major tool used to achieve this objective was a computer-aided program, VTAB-Ecosystem Reporter, Revision 19907a (Emanuel 1999), which produces the various tables required in the analysis and synthesis of vegetation data. It arranges columns (plots or groups of plots) and rows (species) according to the criteria specified by the user for each step of the tabular analysis and synthesis.The following four analytical steps were used to synthesize the data:Step 1 Plots were stratified into floristically similar groups using a two-way indicator species analysis (TWINSPAN, Hill 1979). This program divides the plots into two groups, then further subdivides each of these groups in subsequent steps. When all the plots in a group are relatively uniform according to predetermined criteria, subdivision of this group stops.Step 2 For each of the groups obtained in step 1, a tentative vegetation plot table, which shows the species significance of each species in all plots of the group (e.g., Appendices 2 through 16), was produced and examined for within-group similarities and differences. A tentative differentiated summary vegetation table (e.g., Table 5), showing species presence and average species significance for each group, was used to examine floristic affinities and differences between groups. Step 3 Tentative environmental plot tables, which show selected environmental characteristics for all plots within each group (e.g., Appendices 17 through 31), were used to determine whether the floristically similar plots were also similar in environmental characteristics. Floristically and environmentally aberrant plots were reassigned to the group to which they were most closely related. After reassignment, the summary vegetation tables were inspected to determine to which extent the groups of plots could be differentiated from each other in a hierarchical manner. The groups that could not be differentiated were merged. Steps 2 and 3 were repeated iteratively in a process of successive approximation (Poore 1962), in which the production of revised vegetation and environmental tables continued until there were no more plot re-assignments and group mergers. Step 4 A tentative hierarchy of groups was then proposed, where each group was considered to be either an association or a subassociation depending on its relationship to the hierarchy. A preliminary diagnostic table showing the diagnostic combination of species for every group was produced. Step 4 was repeated in a process of successive approximation in which the production of tentative diagnostic tables continued until exclusive diagnostic combinations of species were obtained for each group of the hierarchy. This process typically required 9METHODSVegetation ClassificationTrembling Aspen Ecosystemschanges in the structure of the hierarchy and occasionally merging of some of the groups lacking a diagnostic combination of species.Instead of using phytosociological nomenclature (Barkman et al. 1976) we used the scientific names without suffixes for naming vegetation units. Plant alliances and associations were named using the generic and specific names of two dominant species from the diagnostic combination of species for that association, e.g., the Populus tremuloides – Lathyrus ochroleucus plant association. Plant subassociations were named by adding a colon (:) to the association name, followed either by the term ‘typic’ (to represent what we believed to be the central concept of that association) or the name of one diagnostic species, e.g., the Populus tremuloides – Lathyrus ochroleucus: Actaea rubra plant subassociation. All units based on the synthesis of <10 sample plots were considered tentative.Similarity and Cluster AnalysisUsing VTAB, we compared floristic similarities between pairs of vegetation units using Sørenson’s index based on presence/absence of species (Equation 1, Magurran 1988), as well as on species cover (Equation 2, Qian et al. 1997). The presence/absence index is a simple but effective measure of the number of species shared between two vegetation units. Both indices enable the comparison of floristic similarity between vegetation units. Equation 1. , whereEquation 2. , whereWe carried out a cluster analysis using the average linkage method with values of the Sørenson presence/absence index as the distance measure. A dendrogram based on this cluster analysis was constructed to illustrate the relationships between the units.Spectral AnalysisTo provide a simple means for characterizing the vegetation of a group of plots complementary to tabular analysis, VTAB-assisted ‘spectral analysis’ was carried out (Mueller-Dombois & Ellenberg 1974:315-319). Spectral analysis was performed on indicator species groups for climate (CL), soil moisture regime (SMR), and soil nutrient regime (SNR), and on life forms (LF) (coniferous trees, broad-leaved trees, evergreen shrubs, deciduous shrubs, ferns, graminoids, herbs, mosses, liverworts, lichens, parasites and saprophytes, and dwarf woody plants) (Klinka et al. 1989). Spectra presenting the relative frequency of each life form (or indicator species group) were constructed for each vegetation unit. Relative frequencies were calculated using Equation 3 (Klinka et al. 1996). The plots were not standardized, i.e., plots with a greater total vegetation cover or indicator species cover contribute relatively more to the spectrum of the vegetation unit.SI2cab+()-----------------=SI2CAB+()------------------=a = the number of species in the first unit, b = the number of species in the second unit, andc = the number of species common to both units.A = the cover sum of all species in the first unit, B = the cover sum of all species in the second unit, and C = the sum of the lower of the two cover values for the species common to both units.10METHODSVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000Equation 3. , where Diversity AnalysisTo compare diversity in the understory vegetation of study stands, we used the number of plant species in each sample plot as index of species diversity. Mean species diversity per plot and standard deviations of the means were calculated for each delineated vegetation unit. Analysis of variance (ANOVA) and Tukey's honestly significantly different (HSD) tests were used to detect significant differences between the means.FjCii 1=n∑Ciji 1=n∑j 1=m∑---------------------------=  = relative frequency (%) of species group j (j = 1,2,3...m) for attribute LF (m= 12), CL (m= 6), SMR (m= 6), SNR (m= 3); and = midpoint percent cover value of species i (i= 1,2,3...n).FjCi11RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen EcosystemsRESULTS AND DISCUSSIONVegetation ClassificationAll 186 study plots were classified into a 3-level hierarchy of vegetation units that included 13 subassociations, 6 associations, and 4 alliances (Table 3). These units were delineated according to floristic differences (diagnostic combinations of species) that are summarized in Table 4 and Table 5; non-diagnostic species are shown in Appendix 1. The significance values of all species in each plot of each of the fifteen basic vegetation units (vegetation plot tables) are given in Appendices 2 through 16; environmental characteristics of each plot in each of the fifteen units (environmental plot tables) are given in Appendices 17 through 31. For brevity, when referring to vegetation units in the text, we avoided using 'Populus tremuloides' and the specific names without creating ambiguities; e.g., Mertensia alliance instead of Populus tremuloides - Mertensia paniculata alliance.The diagnostic table indicates that differentiation of 15 basic units was reasonably strong as each unit in the proposed hierarchy has several differential species (usually more than five), except for the Rosa - Senecio subassociation with only one differential species. The summary table provides a useful overview of distribution of the species that occur at least in one unit with the presence ≥III (41 to 60%) across a given unit.Table 3. Synopsis of delineated vegetation units in trembling aspen ecosystems indicating levels of generalization and relationships. The row containing the names of associations are printed in bold fonts. Numerical codes indicate position of a unit in the hierarchy; the same codes are used in diagnostic and summary vegetation tables. Asterisk indicates an insufficient sampled unit (<10 plots).Code Plant alliancePlant associationPlant subassociation100 Populus tremuloides - Mertensia paniculata110 Populus tremuloides - Mertensia paniculata 111 Populus tremuloides - Mertensia paniculata: Festuca altaica* (4 plots)112 Populus tremuloides - Mertensia paniculata: Arnica cordifolia (14 plots)113 Populus tremuloides - Mertensia paniculata: Petasites frigidus (13 plots)200 Populus tremuloides - Elymus innovatus210 Populus tremuloides - Ledum groelandicum (10 plots)220 Populus tremuloides - Lathyrus ochroleucus 221 Populus tremuloides- Lathyrus ochroleucus: Hedysarum boreale (11 plots)222 Populus tremuloides- Lathyrus ochroleucus: typic (31 plots)223 Populus tremuloides- Lathyrus ochroleucus: Actaea rubra (10 plots)300 Populus tremuloides - Thalictrum occidentale 310 Populus tremuloides - Thalictrum occidentale (10 plots)400 Populus tremuloides - Symphoricarpos albus410 Populus tremuloides - Viburnum edule411 Populus tremuloides - Viburnum edule: Spiraea betulifolia (17 plots)412 Populus tremuloides - Viburnum edule: Paxistima myrsinites (10 plots)420 Populus tremuloides - Rosa nutkana421 Populus tremuloides - Rosa nutkana: Aralia nudicaulis (14 plots)422 Populus tremuloides - Rosa nutkana: Arnica cordifolia* (9 plots)423 Populus tremuloides - Rosa nutkana: Angelica genuflexa* (9 plots)424 Populus tremuloides - Rosa nutkana: Senecio pseudoaureus * (9 plots)425 Populus tremuloides - Rosa nutkana: Shepherdia canadensis (15 plots)12RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000Table 4. Diagnostic combinations of species for the vegetation units in aspen ecosystems. The diagnostic combination of species for each vegetation unit is shaded in grey. Presence values ≥III are printed in bold. An asterisk (*) indicates an insufficiently sampled unit (<10 plots).Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14131011311010171014 9 9 9 15SpeciesDiagnosticvalue1Species presence2 and species significance3100 & 110 Populus tremuloides - Mertensia paniculata alliance and association Cladina stellaris (ic) II h I h I hCladonia ecmocyna (ic) II h I h I hEmpetrum nigrum (ic) II h I h II 2Festuca altaica (d) IV 6 II + III 1Geocaulon lividum (d) IV 3 V 2 IV 1 IV 3 I h I h I hMertensia paniculata (d) III 1 IV 3 IV 2 III 2 IV 3 I h I h I h I hPedicularis labradorica (ic) III + I + II hPeltigera membranacea (ic) II h II h II 2 I hPleurozium schreberi (dd) IV 3 IV 7 IV 6 IV 4 I h I + I h III 4 III 4 III + I h I h I hSalix scouleriana (d) IV 6 II 4 III 4 II 4 I 3 II 2 I + I hShepherdia canadensis (d) V 5 V 7 IV 3 I 1 IV 4 IV 4 I 1 I 4 II 4 II 1 I h III 4 I 3 III 5 IV 6111 Populus tremuloides - Mertensia paniculata: Festuca altaica subassociation* (4 plots)  Arctostaphylos uva-ursi (d) IV 5 II 4 I 2 I 2 III 5 I h I h II 4 III 6Festuca altaica (dd) IV 6 II + III 1Galium boreale (d) V 3 I h III 1 IV 4 IV 3 II 2 III + IV 1 II + II + II h I + III +Juniperus communis (d) IV 5 II 3 I h I h II 3 III 5Pulsatilla patens  (d) III + I h I h II hTrisetum spicatum (d) III + I h I h I h I hViburnum edule (dd) IV 6 IV 3 III 4 I 2 V 4 V 5 III 4 IV 6 IV 4 I + II 1112 Populus tremuloides - Mertensia paniculata: Arnica cordifolia subassociation (14 plots)  Arnica cordifolia (d) V 4 II 2 I 1 I + I h II h II h II 4 IV 4 II + II 1 I hOrthilia secunda (d) III + V 1 III h I h III 1 I 2 II h II h III + I h II h I h II h II +Shepherdia canadensis (dd) V 5 V 7 IV 3 I 1 IV 4 IV 4 I 1 I 4 II 4 II 1 I h III 4 I 3 III 5 IV  6113 Populus tremuloides - Mertensia paniculata: Petasites frigidus subassociation (13 plots)  Lupinus arcticus (d) II 2 II 1 IV 3 II 3 I 2Mitella nuda (d) III + I h III 2 I h II h I hPetasites frigidus (d) I h IV 3 V 4 III 3 III 3 IV 3 III 2 II + I h I h200 Populus tremuloides - Elymus innovatus alliance  Calamagrostis canadensis (d) II h I h III 2 IV 3 III 3 IV 3 II h II h I h III 6 II h IV + I 2Elymus innovatus (d) III 1 V 5 IV 4 II 1Salix sp. (d) IV 3 III 4 V 4 II 313RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen Ecosystems210 Populus tremuloides - Ledum groenlandicum association (10 plots)  Abies lasiocarpa (d) II 2 II 4 I h IV 2 I 1 I h I 2 II 4 I + I + II 4 I 3Cladina rangiferina (d) IV 4 I tGeocaulon lividum (d) IV 3 V 2 IV 1 IV 3 I h I h I hLedum groenlandicum (d) I 1 II 3 V 7 II 4 II 4Lycopodium clavatum (d) III 3 I 1Lycopodium complanatum (d) I h IV 5 I + I hMelampyrum lineare (d) IV 2 I h I h I hPeltigera aphthosa (d) II h II 2 II 1 IV 4 I t I h I h I h I h I h I hPicea mariana (d) III 4 IV 5 III 4 I 2 I 2 I 2Pinus contorta (d) II h I 4 II 5 III 3 I h I 2 I 2 I 2 I 2 I 4 III 5 II 4 II 5 IV 5 IV 6Pleurozium schreberi (d) IV 3 IV 7 IV 6 IV 4 I h I + I h III 4 III 4 III + I h I h I hPolytrichum juniperinum (d) V 3 I h I hSpiraea betulifolia (d) I + V 3 II 2 II 2 II + I 3 IV 4 I + II 1 IV 1 III 3 III 1 I hStereocaulon tomentosum (d) II + III 2Vaccinium vitis-idaea (d) II 3 I h III 3 V 5 III 3 II 3220 Populus tremuloides - Lathyrus ochroleucus association Amelanchier alnifolia (d) II 1 I h I h III 4 II + III 2 I h IV 4 III + III 2 II + V 6 IV 2 II hAster conspicuus (d) I + I 3 IV 5 IV 4 III 4 III 3 III 4 I h I h I 1 V 3 III 3 II 3Fragaria virginiana (d) IV + III 2 III 2 IV 2 IV 2 III 1 III 1 III + I h II + II h II 1 IV + III +Galium boreale (d) V 3 I h III 1 IV 4 IV 3 II 2 III + IV 1 II + II + II h I + III +Lathyrus ochroleucus (d) I + II 2 V 4 V 3 III 3 III 2 III 2 I + II hPyrola asarifolia (d) I h II 1 V 4 IV 4 I 2 II h III + II + II hRosa acicularis (d) V 4 V 4 V 3 I 2 V 4 V 5 V 4 IV 5 V 5 IV 4 II 3 II h I h II +221 Populus tremuloides - Lathyrus ochroleucus: Hedysarum boreale subassociation (11 plots)  Achillea millefolium (d) III + III + III + IV 1 I h I h III + III h I h II h I h III + III 2Arctostaphylos uva-ursi (d) IV 5 II 4 I 2 I 2 III 5 I h I h II 4 III 6Hedysarum boreale (d) IV 4Oryzopsis asperifolia (d) I + I h III 4 I + I h II h I 3Vaccinium myrtilloides (d) V 7 IV 4 I 4222 Populus tremuloides - Lathyrus ochroleucus: typic subassociation (31 plots)  Cornus canadensis (dd) IV 5 IV 6 V 5 II 5 V 6 IV 4 III 2 III 3 IV 3 IV 5 II 5 III 4Hylocomium splendens (d) II h V 7 IV 7 I h I 3 IV 3 I h III 4 I + II + I + I hOrthilia secunda (d) III + V 1 III h I h III 1 I 2 II h II h III + I h II h I h II h II +Rubus pubescens (d) I + II 2 V 4 III 3 III 2 IV 3 III 1 I +Salix sp. (d) IV 3 III 4 V 4 II 3Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14131011311010171014 9 9 9 15SpeciesDiagnosticvalue1Species presence2 and species significance314RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000223 Populus tremuloides - Lathyrus ochroleucus: Actaea rubra subassociation (10 plots)  Actaea rubra (d) I h I + I h V 4 II + III 2 I h I h I h III 4 I 2Aralia nudicaulis (d) I h I + I 1 II 4 IV 5 II 3 IV 5 V 4 IV 5 II 4 I + I 3Cornus sericea (d) I + V 4Delphinium glaucum (d) IV + III + I h IV 4Equisetum pratense (d) I h I h I 4 II h IV 5 III + I h II h I h II hGalium triflorum (d) I h I h I h V 4 II h II h II h III + IV + IV + IV +Heracleum maximum (d) I h III 4 I 2 I 1 I + I +Lonicera involucrata (d) I 2 I + I h II 1 IV 4 III 4 III 4 III 2 I + I h II 5 I hMitella nuda (d) III + I h III 2 I h II h I hOsmorhiza berteroi (d) II h II + I + I h I h III 2 I h V 2 III + IV 2 IV 1 V 3 IV + I hPopulus balsamifera (d) II 2 I 2 I 1 III 5 I 4 I 3 III 5 I 1 I 2 I 4Ribes oxyacanthoides (d) I h III 3Viola canadensis (d) I h III 4 II 1 I + I h III 2 II + I h300 & 310 Populus tremuloides - Thalictrum occidentale alliance and association (10 plots) 400 Populus tremuloides - Symphoricarpos albus alliance Amelanchier alnifolia (d) II 1 I h I h III 4 II + III 2 I h IV 4 III + III 2 II + V 6 IV 2 II hElymus glaucus (d) I h I h I + I h IV + III + IV 1 IV + III h V 1 II hMaianthemum racemosum  (ic) I h I + I + I h III 3 III 2 II 3 II + IV 4 III 3 I hMaianthemum stellatum  (ic) I 1 I h III 1 II h III 3 IV 2 III + I hOsmorhiza berteroi (ic) II h II + I + I h I h III 2 I h V 2 III + IV 2 IV 1 V 3 IV + I hPaxistima myrsinites  (d) I h II 5 V 7 II 2 III 2 II 5 III 4 II 3Symphoricarpos albus (d) II 2 I + II + IV 4 III + IV 3 III + IV 6 IV 5 II +410 Populus tremuloides - Viburnum edule associationAralia nudicaulis (d) I h I + I 1 II 4 IV 5 II 3 IV 5 V 4 IV 5 II 4 I + I 3Cornus stolonifera (ic) I h I 2 I h II 3 IV 5 IV 5 III 4 III 2 III 3 II 5Epilobium angustifolium (ic) V 6 V 6 IV 3 IV 3 III 2 V 4 IV 3 V 6 III 2 III + I h I h I h II + II +Lathyrus ochroleucus (d) I + II 2 V 4 V 3 III 3 III 2 III 2 I + II hLonicera involucrata (d) I 2 I + I h II 1 IV 4 III 4 III 4 III 2 I + I h II 5 I hPleurozium schreberi (d) IV 3 IV 7 IV 6 IV 4 I h I + I h III 4 III 4 III + I h I h I hPyrola asarifolia (ic) I h II 1 V 4 IV 4 I 2 II h III + II + II hRosa acicularis (d) V 4 V 4 V 3 I 2 V 4 V 5 V 4 IV 5 V 5 IV 4 II 3 II h I h II +Rubus pubescens (d) I + II 2 V 4 III 3 III 2 IV 3 III 1 I +Viburnum edule (d) IV 6 IV 3 III 4 I 2 V 4 V 5 III 4 IV 6 IV 4 I + II 1Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14131011311010171014 9 9 9 15SpeciesDiagnosticvalue1Species presence2 and species significance315RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen Ecosystems411 Populus tremuloides - Viburnum edule: Spiraea betulifolia subassociation (17 plots)Achillea millefolium (d) III + III + III + IV 1 I h I h III + III h I h II h I h III + III 2Actaea rubra (d) I h I + I h V 4 II + III 2 I h I h I h III 4 I 2Aster ciliolatus (d) I h I h II + I + I h I h III 1 I h II + II h III + II hAster conspicuus (d) I + I 3 IV 5 IV 4 III 4 III 3 III 4 I h I h I 1 V 3 III 3 II 3Fragaria virginiana (d) IV + III 2 III 2 IV 2 IV 2 III 1 III 1 III + I h II + II h II 1 IV + III +Galium boreale (d) V 3 I h III 1 IV 4 IV 3 II 2 III + IV 1 II + II + II h I + III +Osmorhiza berteroi (ic) II h II + I + I h I h III 2 I h V 2 III + IV 2 IV 1 V 3 IV + I hPicea glauca (d) II 1 IV 6 IV 5 III 5 V 5 IV 4 III 5 IV 7 V 6 II 3 III 4 II 4 III 4 III 4 I +Ribes lacustre (d) I h I h I h II 2 II 3 III 2 I h II 1 II h I h I hSpiraea betulifolia (d) I + V 3 II 2 II 2 II + I 3 IV 4 I + II 1 IV 1 III 3 III 1 I hThalictrum occidentale (d) I 3 I + III 3 V 2 II 2 I h II 1 V 5 III 3 I +Viburnum edule (dd) IV 6 IV 3 III 4 I 2 V 4 V 5 III 4 IV 6 IV 4 I + II 1412 Populus tremuloides - Viburnum edule: Paxistima myrsinites subassociation (10 plots)Betula papyrifera (d) I h I h II 1 I 2 I + I 2 III 6 III 5 IV 6 I hCorylus cornuta (d) I 4 III 6Paxistima myrsinites  (d) I h II 5 V 7 II 2 III 2 II 5 III 4 II 3Rhytidiadelphus triquetrus (d) I 4 I + I h II 2 IV 3 I 3Thuja plicata (d) III 5 II 6 II 2 II 2Tsuga heterophylla (d) III 3 I + II 5420 Populus tremuloides - Rosa nutkana association Acer glabrum (ic) II 4 III 5 III 5 II 3 II 4 I hAlnus incana  (ic) I h I 1 I 3 II 4 III 5 II 3 II 5 III 5 I 3Festuca subuliflora (ic) I h I h I h I h IV 2 III h II h III + II hGalium triflorum (ic) I h I h I h V 4 II h II h II h III + IV + IV + IV +Hieracium scouleri (ic) I h II h I h II h II hLonicera utahensis (ic) I h II 4 I h II 4 II 4 I hMahonia aquifolium (d) I 3 I h II h III 2 IV 3 IV 4 II 2Pinus contorta (ic) II h I 4 II 5 III 3 I h I 2 I 2 I 2 I 2 I 4 III 5 II 4 II 5 IV 5 IV 6Pseudotsuga menziesii (ic) I 3 I 2 II 4 I 3 I + IV 6 III 5 IV 5 II 5Rosa nutkana (d) I h III + III + IV 4 IV 4 III 2421 Populus tremuloides - Rosa nutkana: Aralia nudicaulis subassociation (14 plots)Aralia nudicaulis (d) I h I + I 1 II 4 IV 5 II 3 IV 5 V 4 IV 5 II 4 I + I 3Calamagrostis canadensis (dd) II h I h III 2 IV 3 III 3 IV 3 II h II h I h III 6 II h IV + I 2Populus balsamifera (d) II 2 I 2 I 1 III 5 I 4 I 3 III 5 I 1 I 2 I 4Tiarella trifoliata (d) III +422 Populus tremuloides - Rosa nutkana: Arnica cordifolia subassociation* (9 plots)Arnica cordifolia (d) V 4 II 2 I 1 I + I h II h II h II 4 IV 4 II + II 1 I hChimaphila umbellata (ic) I + I + III 2 II h I h I 1Pinus monticola (dd) I 2 II 3 III 5 I hVaccinium caespitosum (dd) I + I 3 I 1 I h II h III 6 I 1Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14131011311010171014 9 9 9 15SpeciesDiagnosticvalue1Species presence2 and species significance316RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000423 Populus tremuloides - Rosa nutkana: Angelica genuflexa subassociation* (9 plots)Actaea rubra (d) I h I + I h V 4 II + III 2 I h I h I h III 4 I 2Amelanchier alnifolia (dd) II 1 I h I h III 4 II + III 2 I h IV 4 III + III 2 II + V 6 IV 2 II hAngelica genuflexa (d) I h I h IV 4 I hAster conspicuus (d) I + I 3 IV 5 IV 4 III 4 III 3 III 4 I h I h I 1 V 3 III 3 II 3Disporum hookeri (d) I h III 4 II 2 I 2 II 1 IV 5 II h I hLilium columbianum (d) I h II h V + II h I hThalictrum occidentale (d) I 3 I + III 3 V 2 II 2 I h II 1 V 5 III 3 I +424 Populus tremuloides - Rosa nutkana: Senecio pseudoaureus subassociation* (9 plots)Senecio pseudaureus (d) I h II + I h II h IV 1 I h425 Populus tremuloides - Rosa nutkana: Shepherdia canadensis subassociation (15 plots)Arctostaphylos uva-ursi (dd) IV 5 II 4 I 2 I 2 III 5 I h I h II 4 III 6Galium boreale (ic) V 3 I h III 1 IV 4 IV 3 II 2 III + IV 1 II + II + II h I + III +Juniperus communis (ic) IV 5 II 3 I h I h II 3 III 51 Species diagnostic values: d = differential, dd = dominant differential, ic = important companion (Pojar et al. 1987).2 Species presence classes (the percentage of plots in which the species occurs): I = 1-20%, II = 21-40%, III = 41-60%, IV = 61-80%, V = 81-100%.3 Species significance classes and the corresponding mid-point and range (in parentheses) of cover: t = 0.005 (0.001-0.009), h = 0.05 (0.01 - 0.099), + = 0.2 (0.1-0.299), 1 = 0.4 (0.3-0.499), 2 = 0.75 (0.5-0.999), 3 = 1.5 (1-1.999), 4 = 3.5 (2-4.999), 5 = 7.5 (5-9.999), 6 = 15 (10-19.999), 7 = 35 (20-49.999), 8 = 60 (50-69.999), 9 = 85 (70-100). Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14131011311010171014 9 9 9 15SpeciesDiagnosticvalue1Species presence2 and species significance317RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen EcosystemsTable 5. Differentiated (in descending order of presence from left to right) summary table of the vegetation units in aspen ecosystems. This table contains only plant species present in ≥ 41% of the plots in at least one vegetation unit (presence class ≥III ). As most of these species were diagnostic (differential, dominant-differential, and important companion species, Table 6) for a vegetation unit, only non-diagnostic species are shaded in grey. Presence values >III are  printed in bold.Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14 13 10 11 31 10 10 17 10 14 9 9 9 15Species Species presence and species significance1Pulsatilla patens III + I h I h II hPedicularis labradorica III + I + II hTrisetum spicatum III + I h I h I h I hFestuca altaica IV 6 II + III 1Juniperus communis IV 5 II 3 I h I h II 3 III 5Salix scouleriana IV 6 II 4 III 4 II 4 I 3 II 2 I + I hArctostaphylos uva-ursi IV 5 II 4 I 2 I 2 III 5 I h I h II 4 III 6Delphinium glaucum IV + III + I h IV 4Geocaulon lividum IV 3 V 2 IV 1 IV 3 I h I h I hMertensia paniculata III 1 IV 3 IV 2 III 2 IV 3 I h I h I h I hOrthilia secunda III + V 1 III h I h III 1 I 2 II h II h III + I h II h I h II h II +Galium boreale V 3 I h III 1 IV 4 IV 3 II 2 III + IV 1 II + II + II h I + III +Pleurozium schreberi IV 3 IV 7 IV 6 IV 4 I h I + I h III 4 III 4 III + I h I h I hAchillea millefolium III + III + III + IV 1 I h I h III + III h I h II h I h III + III 2Shepherdia canadensis V 5 V 7 IV 3 I 1 IV 4 IV 4 I 1 I 4 II 4 II 1 I h III 4 I 3 III 5 IV 6Viburnum edule IV 6 IV 3 III 4 I 2 V 4 V 5 III 4 IV 6 IV 4 I + II 1Rosa acicularis V 4 V 4 V 3 I 2 V 4 V 5 V 4 IV 5 V 5 IV 4 II 3 II h I h II +Epilobium angustifolium V 6 V 6 IV 3 IV 3 III 2 V 4 IV 3 V 6 III 2 III + I h I h I h II + II +Fragaria virginiana IV + III 2 III 2 IV 2 IV 2 III 1 III 1 III + I h II + II h II 1 IV + III +Linnaea borealis IV 4 V 5 V 5 V 3 V 3 V 4 III 3 III 3 IV + III 4 II + III 4 II 3 II 4Populus tremuloides V 7 V 7 V 7 V 8 V 8 V 8 V 8 V 8 V 8 V 7 V 8 V 8 V 8 V 8 V 7Goodyera repens III + II + I h I hArnica cordifolia V 4 II 2 I 1 I + I h II h II h II 4 IV 4 II + II 1 I hPicea mariana III 4 IV 5 III 4 I 2 I 2 I 2Hylocomium splendens II h V 7 IV 7 I h I 3 IV 3 I h III 4 I + II + I + I hCornus canadensis IV 5 IV 6 V 5 II 5 V 6 IV 4 III 2 III 3 IV 3 IV 5 II 5 III 4Picea glauca II 1 IV 6 IV 5 III 5 V 5 IV 4 III 5 IV 7 V 6 II 3 III 4 II 4 III 4 III 4 I +Lupinus arcticus II 2 II 1 IV 3 II 3 I 2Mitella nuda III + I h III 2 I h II h I hPetasites frigidus I h IV 3 V 4 III 3 III 3 IV 3 III 2 II + I h I hPtilium crista-castrensis II 2 III 3 I h I h II 3 III + I hVaccinium vitis-idaea II 3 I h III 3 V 5 III 3 II 3Abies lasiocarpa II 2 II 4 I h IV 2 I 1 I h I 2 II 4 I + I + II 4 I 3Cladina rangiferina IV 4 I tLedum groenlandicum I 1 II 3 V 7 II 4 II 4Lycopodium clavatum III 3 I 1Lycopodium complanatum I h IV 5 I + I h18RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000Melampyrum lineare IV 2 I h I h I hPeltigera aphthosa II h II 2 II 1 IV 4 I t I h I h I h I h I h I hPolytrichum juniperinum V 3 I h I hStereocaulon tomentosum II + III 2Vaccinium myrtilloides V 7 IV 4 I 4Elymus innovatus III 1 V 5 IV 4 II 1Maianthemum canadense I + III 3 V 4 IV 3 I + I hSalix sp. IV 3 III 4 V 4 II 3Pinus contorta II h I 4 II 5 III 3 I h I 2 I 2 I 2 I 2 I 4 III 5 II 4 II 5 IV 5 IV 6Spiraea betulifolia I + V 3 II 2 II 2 II + I 3 IV 4 I + II 1 IV 1 III 3 III 1 I hCalamagrostis canadensis II h I h III 2 IV 3 III 3 IV 3 II h II h I h III 6 II h IV + I 2Hedysarum boreale IV 4Oryzopsis asperifolia I + I h III 4 I + I h II h I 3Vicia americana I h I h III 3 II 1 I h III + II + II h II + I h II hLathyrus ochroleucus I + II 2 V 4 V 3 III 3 III 2 III 2 I + II hAmelanchier alnifolia II 1 I h I h III 4 II + III 2 I h IV 4 III + III 2 II + V 6 IV 2 II hAster conspicuus I + I 3 IV 5 IV 4 III 4 III 3 III 4 I h I h I 1 V 3 III 3 II 3Pyrola asarifolia I h II 1 V 4 IV 4 I 2 II h III + II + II hRubus pubescens I + II 2 V 4 III 3 III 2 IV 3 III 1 I +Cornus sericea I + V 4Galium triflorum I h I h I h V 4 II h II h II h III + IV + IV + IV +Ribes oxyacanthoides I h III 3Heracleum maximum I h III 4 I 2 I 1 I + I +Equisetum pratense I h I h I 4 II h IV 5 III + I h II h I h II hPopulus balsamifera II 2 I 2 I 1 III 5 I 4 I 3 III 5 I 1 I 2 I 4Viola canadensis I h III 4 II 1 I + I h III 2 II + I hOsmorhiza berteroi II h II + I + I h I h III 2 I h V 2 III + IV 2 IV 1 V 3 IV + I hActaea rubra I h I + I h V 4 II + III 2 I h I h I h III 4 I 2Aralia nudicaulis I h I + I 1 II 4 IV 5 II 3 IV 5 V 4 IV 5 II 4 I + I 3Lonicera involucrata I 2 I + I h II 1 IV 4 III 4 III 4 III 2 I + I h II 5 I hCalamagrostis rubescens I h I 4 III 3 I 1 II 2 III 4 I h V 6 V 6Thalictrum occidentale I 3 I + III 3 V 2 II 2 I h II 1 V 5 III 3 I +Ribes lacustre I h I h I h II 2 II 3 III 2 I h II 1 II h I h I hAster ciliolatus I h I h II + I + I h I h III 1 I h II + II h III + II hDisporum hookeri I h III 4 II 2 I 2 II 1 IV 5 II h I hMaianthemum racemosum  I h I + I + I h III 3 III 2 II 3 II + IV 4 III 3 I hMaianthemum stellatum  I 1 I h III 1 II h III 3 IV 2 III + I hClintonia uniflora I + I h I h III 3 IV 2 III 2 III 4 III 3 I hCornus stolonifera I h I 2 I h II 3 IV 5 IV 5 III 4 III 2 III 3 II 5Elymus glaucus I h I h I + I h IV + III + IV 1 IV + III h V 1 II hRubus parviflorus I h I + IV 5 V 4 III 5 V 4 IV 6 III 4Symphoricarpos albus II 2 I + II + IV 4 III + IV 3 III + IV 6 IV 5 II +Corylus cornuta I 4 III 6Rhytidiadelphus triquetrus I 4 I + I h II 2 IV 3 I 3Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14 13 10 11 31 10 10 17 10 14 9 9 9 15Species Species presence and species significance119RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen EcosystemsThuja plicata III 5 II 6 II 2 II 2Tsuga heterophylla III 3 I + II 5Betula papyrifera I h I h II 1 I 2 I + I 2 III 6 III 5 IV 6 I hPaxistima myrsinites  I h II 5 V 7 II 2 III 2 II 5 III 4 II 3Tiarella trifoliata III +Alnus incana  I h I 1 I 3 II 4 III 5 II 3 II 5 III 5 I 3Acer glabrum II 4 III 5 III 5 II 3 II 4 I hRanunculus acris I h I h I h III + I h II h III hFestuca subuliflora I h I h I h I h IV 2 III h II h III + II hRosa nutkana I h III + III + IV 4 IV 4 III 2Chimaphila umbellata I + I + III 2 II h I h I 1Pinus monticola I 2 II 3 III 5 I hVaccinium caespitosum I + I 3 I 1 I h II h III 6 I 1Mahonia aquifolium I 3 I h II h III 2 IV 3 IV 4 II 2Pseudotsuga menziesii I 3 I 2 II 4 I 3 I + IV 6 III 5 IV 5 II 5Angelica genuflexa I h I h IV 4 I hLilium columbianum I h II h V + II h I hSenecio pseudaureus I h II + I h II h IV 1 I hViola renifolia I h II + I h I h I h II + II h III h I h1 Species presence and significance values as defined in Table 4.Vegetation unit 111 112 113 210 221 222 223 300 411 412 421 422 423 424 425Number of plots 4 14 13 10 11 31 10 10 17 10 14 9 9 9 15Species Species presence and species significance120RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000The hierarchy of the proposed classification (Table 3) reflects the distribution of study stands according to regional climates (biogeoclimatic zones). The Mertensia, Elymus, and Thalictrum alliances represent stands located in montane boreal climates (predominantly in the BWBS and SBS zones); and the Symphoricarpos alliance represents stands located predominantly in cool temperate climates (predominantly in the IDF, ICH, and MS zones). This stratification is corroborated by climatic spectra which show two broad groups: the first group including units from 111 through 310 (the units of the Mertensia, Elymus, and Thalictrum alliances) and the second group including units 411 through 425 (the units of the Symphoricarpos alliance) (Figure 2). While the spectra of the first group are dominated by the indicators of montane boreal and cool temperate climates, the spectra of the second group feature also indicators of cool temperate & mesothermal and  cool temperate & semiarid climates. This suggests the stands of the Symphoricarpos alliance are influenced by warmer and milder climates (i.e., cool temperate) than the other stands.Figure 2. Climatic spectra for the 15 basic vegetation units delineated in trembling aspen stands across British Columbia. Codes for vegetation units as in Ta ble  3.Although all study stands, in general, can be considered to represent mid-seral successional stages, some stands featured well-established, regeneration of shade-tolerant conifers while some other stands featured only aspen regeneration in canopy gaps and not conifers (Figure 3). On montane boreal sites the understory conifers were Abies lasiocarpa and Picea mariana; regeneration of Picea glauca was present across the study area. Pinus monticola, Pseudotsuga menziesii, Thuja plicata, and Tsuga heterophylla were established in the understory on cool temperate sites. Montane boreal stands of the Mertensia (100), Elymus (200), and Thalictrum (300) alliances and Viburnum - Spiraea (411) subassociation appear to be floristically aligned with the Picea glauca & mariana order (Krajina 1969) and will likely develop into white spruce and/or black spruce dominated stands, with a variable admixture of subalpine fir in the eastern portion of the BWBS zone and in the SBS zone. The stands of the Symphoricarpos (400) alliance (except for Viburnum - Spiraea (411) subassociation) shows floristic affinities to the interior Tsuga heterophylla order (Krajina 1969), and will likely develop into western hemlock and western redcedar dominated stands in the ICH zone, and Douglas-fir dominated stands in the IDF zone.0% 20% 40% 60% 80% 100%Relative frequency of climate indicator speciesTundra & borealSubalpine boreal & cool mesothermalMontane boreal & cool temperateCool mesothermalCool temperate & mesothermalCool temperate & semiaridIndicator species groups for climate:111112113210221222223310411412421422423424425Vegetation unit21RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen EcosystemsWhile on some sites, aspen may be replaced by conifers within a single aspen generation, replacement on some other sites may be as long as 1,000 years (Perala 1990). Also, the presence of uneven-aged aspen stands in northern Montana, Wyoming, eastern Idaho, Colorado, and North Dakota suggests that under certain conditions, aspen may be self-perpetuating without major disturbance; however, aspen regeneration can fail when apical dominance prevents suckering during gradual deterioration of clones (Mueggler 1985). In the absence of replacement by shade tolerant conifers, aspen stands, especially on moist and nutrient-rich sites, usually gradually deteriorate to shrub-dominated woodlands, with a few scattered aspen suckers and occasional conifers (Perala 1990).Figure 3. Three scenarios encountered in the understory of study stands: 1 - no regeneration of aspen or shade-tolerant conifers, 2 - advance regeneration of shade-tolerant conifers was present, and 3 - natural regeneration of aspen from root suckers was present, providing semi-open canopy conditions.Since a majority of the study stands were young and many stands lacked abundant advance regeneration of conifers, we refrained from explicitly predicting succession trends. Ignoring succession trends might have resulted in framing different vegetation units on ecologically-equivalent sites, i.e., in two different aspen communities that can be differentiated only by the differences in the floristic composition. We also avoided resolving a related issue concerning classification at the order level: could the delineated units form a Populus tremuloides order (similar to the Populus balsamifera order (Krajina 1969)) or should they be attached to the proposed 'coniferous' orders (Krajina 1969) according to the similarity in understory vegetation?  While the constant occurrence of Populus tremuloides was a consequence of the sampling design, several other species, such as Epilobium angustifolium, Fragaria virginiana, Linnaea borealis, Hylocomium splendens, Cornus canadensis, and Picea glauca occurred nearly in all study plots. Somewhat less widespread but frequently occurring species were Achillea milefolium, Galium boreale, Orthilia secunda, Pleurozium schreberi, Shepherdia canadensis, and Viburnum edule (Table 5). When all these commonly occurring species as well as other species with low presence and species significance (e.g., Alnus viridis, Antennaria neglecta, Cladina stellaris, Cladonia ecmocyna, Empetrum nigrum, and others (Table 5)) showed affinity to one or more units vegetation units they were used in the diagnostic table (Table 4) as differential or companion species. The physiognomic appearance of study stands was relatively consistent. Compared to neighbouring coniferous stands, a well developed, frequently luxuriant understory was the characteristic feature of aspen stands. 1 3222RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000Regardless of the differences in floristic composition and site characteristics, there were generally minor differences in life forms profiles between the study stands (Figure 4). The understory vegetation was typically dominated by deciduous shrubs (e.g., Shepherdia canadensis, Rosa acicularis, R. nutkana, and Viburnum edule) and herbs (e.g., Epilobium angustifolium, Fragaria virginiana, and Cornus canadensis). Stands in boreal climates had a somewhat higher proportion of mosses and lichens, while stands in drier cool temperate climates had a higher proportion of graminoids. Figure 4. Life from spectra for the 15 basic vegetation units delineated in trembling aspen stands across British Columbia. Codes for vegetation units as in Ta ble  3. The floristic individuality of the delineated vegetation units was described by two sets of similarity indices (Table 6). Vegetation units adjacent in Table 3 were climatically equivalent, and were more similar to each other that the climatically disjunct units that were distant in the table. The most poorly differentiated unit was the Thalictrum (310) association, which was similar to nearly all other units. The Arnica (112) and Petasites (113) subassociations of the Mertensia (110) association were floristically equivalent (Table 5a), and the boreal Festuca (111) subassociation was quite similar to the cool temperate Shepherdia (425) subassociation of the Rosa (420) association. The subassociations of the cool temperate Rosa nutkana (420) association had a high similarity to each other according to both indices. In view of a large number of study stands from climatically and edaphically different environments, it was surprising to frame only 15 units (6 associations and 13 subassociations). It appears that in mid-seral communities the uniform aspen overstory creates favourable light and edaphic conditions for the development of understory vegetation that has similar structure, life forms, and floristic composition over large areas. The major changes in the composition of understory vegetation appear to coincide with major changes in climate and regional flora. 0% 20% 40% 60% 80% 100%Life Form Groups:Coniferous treesBroad-leaved treesEvergreen shrubsDeciduous shrubsFernsGraminoidsHerbsParasites & saprophytesMossesLiverwortsLichensDwarf woody plantsRelative frequency of life form groups111112113210221222223310411412421422423424425Vegetation unit23RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen EcosystemsTable 6. Matrix of floristic similarities for vegetation units delineated in trembling aspen ecosystems across British Columbia. Higher values indicate a greater number of shared species and greater floristic similarity. Codes for vegetation units as in Table 3 .A. Sørensen (coincidence) coefficient of floristic similarity based on presence/absenceVegetation unit111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Vegetation unit111 1.00112 0.48 1.00113 0.42 0.70 1.00210 0.35 0.31 0.32 1.00221 0.30 0.37 0.46 0.53 1.00222 0.31 0.42 0.47 0.56 0.61 1.00223 0.27 0.39 0.46 0.35 0.53 0.67 1.00310 0.32 0.59 0.65 0.26 0.47 0.47 0.53 1.00411 0.28 0.55 0.57 0.24 0.44 0.44 0.55 0.69 1.00412 0.27 0.56 0.53 0.28 0.41 0.44 0.54 0.55 0.67 1.00421 0.24 0.41 0.48 0.22 0.38 0.43 0.54 0.59 0.61 0.59 1.00422 0.26 0.45 0.41 0.27 0.33 0.41 0.48 0.52 0.57 0.55 0.68 1.00423 0.24 0.38 0.41 0.16 0.33 0.38 0.48 0.53 0.60 0.55 0.58 0.65 1.00424 0.28 0.43 0.43 0.23 0.32 0.38 0.48 0.50 0.52 0.48 0.69 0.63 0.58 1.00425 0.32 0.41 0.41 0.24 0.31 0.32 0.37 0.50 0.50 0.47 0.55 0.52 0.49 0.65 1.00B. Sorensen (coincidence) coefficient of floristic similarity based on coverVegetation unit111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Vegetation unit111 1.00112 0.49 1.00113 0.34 0.67 1.00210 0.10 0.20 0.23 1.00221 0.22 0.29 0.28 0.32 1.00222 0.24 0.29 0.26 0.29 0.52 1.00223 0.26 0.33 0.31 0.16 0.35 0.44 1.00310 0.50 0.49 0.41 0.13 0.29 0.28 0.41 1.00411 0.47 0.41 0.38 0.12 0.28 0.29 0.47 0.63 1.00412 0.34 0.35 0.34 0.07 0.17 0.15 0.30 0.40 0.54 1.00421 0.34 0.33 0.35 0.11 0.20 0.20 0.36 0.44 0.51 0.54 1.00422 0.35 0.37 0.38 0.12 0.19 0.17 0.27 0.41 0.51 0.54 0.59 1.00423 0.35 0.31 0.29 0.06 0.17 0.10 0.27 0.45 0.59 0.44 0.53 0.51 1.00424 0.41 0.38 0.37 0.10 0.21 0.17 0.30 0.50 0.57 0.49 0.60 0.58 0.62 1.00425 0.53 0.39 0.33 0.05 0.20 0.12 0.20 0.44 0.43 0.37 0.40 0.47 0.45 0.66 1.0024RESULTS AND DISCUSSIONVegetation ClassificationScientica Silvica Extension Series, Number 27, 2000Cluster analysis using the Sørensen index based on presence/absence showed a hierarchical structure somewhat similar to that based on the tabular analysis (Table 3; Figure 5). The dendrogram shows two major clusters joined at approximately the same distance (0.3), and a smaller cluster joined at a slightly greater distance (0.34). The first cluster joined the units of the montane boreal Mertensia (100) and Elymus (200) alliances. Different from the tabular analysis was the connection of the Thalictrum (300) alliance, with stands occurring in montane boreal and cool temperate climates, to the second cluster, and separation of the Senecio (424) and Shepherdia (425) subassociations of the Rosa nutkana (420) association. These subassociations were connected with the other units at larger distance indicating that they might have been considered to form a different association. Figure 5. Dendrogram showing the groupings of the vegetation units produced by cluster analysis using the Sørensen index based on presence/absence as a distance measure.There were only few significant differences in the mean species diversity among 15 basic vegetation units (Tables 7 and 8). The three units with the highest (>30) mean species diversity were: Viburnum - Spiraea (411), Viburnum - Paxistima (412), and Rosa - Senecio (424) subassociations; the three units with lowest (≤22) mean species diversity were: Rosa - Shepherdia (425) subassociation, Ledum (210) association, and Lathyrus - Hedysarum (221). The most species-diverse Viburnum - Spiraea (411) subassociation a had significantly higher mean species diversity that the Ledum (210) association and Lathyrus - Hedysarum (211) and Lathyrus - typic (222) subassociations; and the least species-diverse, Rosa - Shepherdia (425) subassociation had a significantly lower mean species diversity than the Viburnum - Spiraea (411), Viburnum - Paxistima (412), and the Rosa - Senecio (424) subassociations. Comparison of the most and least species-diverse units seems to indicate that more species-diverse communities develop in wetter cool temperate climate (ICH zone) and less species-diverse communities develop in montane boreal climate and on sites transitional to grasslands. However, despite a few exceptions, the results of species diversity comparisons suggest that species richness in aspen communities is relatively consistent regardless of community type and the type of the associated environment. This inference is corroborated by consistency in the life form spectra (Figure 4) and, to some degree, by floristic similarity of the communities (Table 6). Thus, it can be expected, that the understory vegetation in aspen communities will be similar in life forms, species richness, and floristic composition over large areas, with the major changes in the composition coinciding with major changes in climate and regional flora.0.0 0.1 0.2 0.3 0.4 0.5 0.6Distances11111211321022122222331041141242142242342442525RESULTS AND DISCUSSIONVegetation ClassificationTrembling Aspen EcosystemsTable 7. Means and standard deviations of number of species according to the 15 vegetation units.Table 8. Probability in pair-wise comparisons of means of the number of species among the 15 vegetation units (Table 7 ) based on Tukey HSD test. The values in boldface indicate that two vegetation units in a pair have significantly different means (P≤0.05).Number of speciesNumerical codeNumber of plotsMean Standard deviation111 4 25.75 8.54112 14 24.50 4.94113 13 25.92 6.50210 10 21.90 3.67221 11 22.00 3.07222 31 23.74 3.51223 10 28.20 5.96310 10 25.80 5.25411 17 31.24 6.70412 10 30.60 7.34421 14 26.86 9.42422 9 25.67 3.35423 9 27.33 7.55424 9 30.89 8.55425 15 21.47 6.73ProbabilityCode111 112 113 210 221 222 223 310 411 412 421 422 423 424 425111 1.000112 1.000 1.000113 1.000 1.000 1.000210 0.999 0.999 0.964 1.000221 0.999 1.000 0.964 1.000 1.000222 1.000 1.000 0.999 1.000 1.000 1.000223 1.000 0.980 1.000 0.577 0.564 0.789 1.000310 1.000 1.000 1.000 0.984 0.985 1.000 1.000 1.000411 0.954 0.127 0.536 0.010 0.008 0.004 0.996 0.633 1.000412 0.991 0.497 0.887 0.089 0.080 0.117 1.000 0.912 1.000 1.000421 1.000 1.000 1.000 0.816 0.809 0.961 1.000 1.000 0.801 0.978 1.000422 1.000 1.000 1.000 0.991 0.992 1.000 1.000 1.000 0.648 0.911 1.000 1.000423 1.000 0.999 1.000 0.830 0.826 0.967 1.000 1.000 0.967 0.998 1.000 1.000 1.000424 0.987 0.469 0.862 0.084 0.076 0.116 1.000 0.890 1.000 1.000 0.968 0.889 0.996 1.000425 0.996 0.992 0.836 1.000 1.000 0.998 0.296 0.919 0.001 0.019 0.525 0.950 0.599 0.019 1.00026RESULTS AND DISCUSSIONVegetation-Environment RelationshipsScientica Silvica Extension Series, Number 27, 2000Vegetation-Environment RelationshipsConsidering uncertainties in predicting succession trends, we refrained from deriving site units from delineated vegetation units. Instead, we characterized each basic vegetation units (association or subassociation) by climate (zone) and the range of soil moisture regimes (SMRs) and soil nutrient regimes (SNRs). The climatic and edaphic individuality of each of the 15 basic vegetation units is portrayed on the edatopic grid (Figure 6 and Figure 7) and summarized in the summary environmental table (Table 9). The ranges for each unit were derived by integrating and generalizing the results of environmental and indicator plant analysis for each plot of the unit. Diagnosis of SNRs is also supported by soil chemical analysis (Kayahara et al. 2000).Figure 6. Edatopic grid showing the generalized relationships of the seven vegetation units to soil moisture and soil nutrient regimes in the BWBS zone. The units are named using the generic names of the understory species and vegetation unit numbers in Ta ble  3.  Abbreviations for soil nutrient and moisture regimes are defined in Ta bl e 9 .VPVDMDSD(f)F(f)M(f)VM(f)W(f)PMRVRSoil nutrient regimeSoil moisture regime223 Lathyrus – ActaeaBWBSdk subzoneBWBSmw subzoneSBS zoneSBPS zonegrasslands, shrubs, and/or stunted tree black/white spruce coniferous communities> 50%20 - 50%< 20%Zone/subzoneDistribution of plots accordingto zone/subzone113 Mertensia – Petasites210 Ledum 221 Lathyrus – Hedysarum222 Lathyrus – typic112 Mertensia – Arnica 111 Mertensia – Festuca27RESULTS AND DISCUSSIONVegetation-Environment RelationshipsTrembling Aspen EcosystemsFigure 7. Edatopic grid showing the generalized relationships of the eight vegetation units to soil moisture and soil nutrient regimes in the SBS, MS, ICH, and IDF zones. The units are named using the generic names of the understory species and vegetation unit numbers in Ta bl e  3 .  Abbreviations for soil nutrient and moisture regimes are defined in Ta bl e 9 .VPVDMDSD(f)F(f)M(f)VM(f)W(f)PMRVRSoil nutrient regimeSoil moisture regimeZone/subzoneDistribution of plots accordingto zone/subzone425 Rosa – Shepherdia IDF zoneMS zoneICH zoneSBS zoneSBPS zonewhite/black spruce coniferous communities422 Rosa – Arnica424 Rosa – Senecio423 Rosa – Angelica310 Thalictrum 421 Rosa – Aralia412 Viburnum – Paxistima> 50%20 - 50%< 20%411 Viburnum – SpireaBWBSdk subzone28RESULTS AND DISCUSSIONVegetation-Environment RelationshipsScientica Silvica Extension Series, Number 27, 2000Table 9. Summary environmental table for the vegetation units in aspen ecosystems.  Continuous properties are characterized by mean and range; categorical properties are described by the percentage of the sample plots in each class.Vegetation unit 111 112 113 210 221 222 223Number of plots 4 14 13 10 11 31 10PropertyZone/subzone BWBSdk - 100 BWBSdk - 86 BWBSdk - 85 BWBSmw -100 BWBSmw - 91 BWBSmw - 100BWBSmw - 90SBS - 7 SBS - 8 SBS - 9 SBS - 10SBPS - 7 SBPS - 8Actual soil moisture regime11 Actual moisture regime: VD-very dry, MD-moderately dry, SD-slightly dry, F-fresh, M-moist, VM-moist, f-fluctuating water tableMD - 100 MD - 86 SD - 85 SD - 80 SD - 91 SD - 26 M - 80SD - 14 F - 15 F - 20 M - 9 F - 71 VM - 20M - 3Soil nutrient regime22 VP-very poor, P-poor, M-medium, R-rich, VR-very richM - 25 P - 7 P - 15 VP - 60 P - 27 P - 13 R - 90R -75 M - 71 M - 54 P - 40 M - 73 M - 77 VR - 10R -21 R - 31 R - 10Elevation (m) 838 (770-950) 900 (720-1040)824 (590-900)750 728 (710-790) 632 (450-750) 666 (450-1025)Slope gradient (%) 15 (7-22) 19 (0-33) 12 (0-49) 2 (0-6) 15 (0-40) 4 (0-15) 7 (2-12)Aspect3 3 N-north, E-east, S-south, W-west, F-flatS - 50 E - 36 N - 23 N - 30 S - 45 N - 3 N - 20W - 50 S - 29 E - 8 W - 10 W - 18 E - 10 S - 50W - 29 S - 15 F - 60 F - 36 S - 13 W - 10F - 7 W - 23 W - 26F - 31 F - 48Forest floor thickness (cm) 9 (6-11) 12 (5-22) 11 (6-17) 3 (2-4) 7 (3-32) 6 (3-9) 10 (4-14)Textural class44 S-sand, SL-sandy loam, LS-loamy sand, L-loam, SiL-silt loam, CL-clay loam, SCL-sandy clay loam, SC-sandy clay, SiCL-silty clay loam, O-organicL -25 L -14 L - 31 LS - 30 LS - 9 LS - 10 SL - 10LS - 25 LS - 50 SL - 62 SL -20 S - 82 SL - 13 S - 30SL - 50 SL - 21 SCL - 8 S - 50 SCL - 9 S - 16 SiL - 20S - 7 SiL - 10 CL - 30SC - 7 CL - 35 SCL - 10SiCL - 16Actual rooting depth (cm) 50 (40-60) 54 (40-70) 59 (30-80) 63 (46-80) 60 (25-80) 49 (20-90) 48 (30-60)Potential rooting depth (cm)59 (40-75) 60 (50-75) 65 (30-80) 63 (46-80) 60 (25-80) 42 (15-90) 47 (26-70)Seepage depth (cm) N/A N/A N/A or >60 N/A N/A or >65 N/A or >30 N/A or 35-85Soil drainage5 5 R-rapid, W-well, M- moderately well, I-imperfect, P-poorR - 25 R - 7 W - 54 W - 20 R - 9 M - 52 M - 40W - 25 W - 64 M - 38 M - 60 W - 55 I - 48 I - 60M - 29 I - 8 I - 20 M -27I - 9Humus form group66 F-Mor, D-Moder, L-MullD - 100 R - 57 R - 38 R - 100 R - 18 R - 39 R - 10D - 43 D - 62 D - 82 D - 61 D - 80L -10Soil Order77 B-Brunisol, P-Podzol, R-Regosol, O-Organic, L-Luvisol, G-GleysolB - 50 B - 78 B - 54 B - 100 B - 91 B - 42 B - 70P - 25 P - 22 P - 31 G - 9 L - 58 L - 30R - 25 L - 16Stand age (years @ bh)8117 (59-152) 124 (67-164) 103 (50-181) 54 (51-58) (>50-154) (>50-70) (>50-96)Site index (m@50 yrs bh)88 Site index and stand age data are missing for some plots. See Appendices 10 - 16 for details.8 (6-9) 12 (10-16) 13 (10-15) 8 (7-10) 13 (11-16) 19 (15-23) 22 (20-25)Tree layer cover (%) 36 (10-70) 47 (21-90) 46 (30-81) 25 (15-36) 36 (27-86) 35 (4-43) 44 (26-100)Shrub layer cover (%) 40 (20-64) 33 (13-77) 20 (4-63) 53 (33-65) 27 (23-47) 35 (4-83) 31 (7-67)Herb layer cover (%) 25 (2-55) 15 (3-32) 17 (1-38) 15 (6-30) 36 (21-58) 33 (11-58) 38 (8-60)Moss layer cover (%) 3 (0-6) 36 (0-92) 55 (0-100) 19 (3-34) 5 (0-50) 2 (0-5) 0 (0-1)29RESULTS AND DISCUSSIONVegetation-Environment RelationshipsTrembling Aspen Ecosystems310 411 412 421 422 423 424 42510 17 10 14 9 9 9 15BWBSdk - 10 SBS - 94 ICH - 100 MS - 57 MS - 56 ICH - 67 MS - 44 MS - 13SBS - 50 ICH - 6 ICH - 29 ICH - 33 IDF - 33 IDF - 56 IDF - 67SBPS - 20 IDF - 14 IDF - 11 SBPS - 20IDF - 20SD - 30 SD - 53 SD - 80 F - 14 MD - 44 SD - 22 MD - 89 VD - 80F - 50 F - 41 F - 20 M - 71 SD - 56 F - 78 SD - 11 MD - 20M - 20 M - 6 VM - 14P - 10  M - 6 M - 50 M - 14 M - 67 M - 22 M -22 P - 40M - 60 R - 82 R - 50 R - 64 R - 33 R - 67 R - 67 M - 40R - 30 VR - 12 VR - 22 VR -11 VR - 11 R - 20891 (595-1115) 860 (390-1025)540 (380-1020) 959 (520-1115) 989 (785-1285) 945 (795-1285) 1073 (1005-1220)1058 (960-1258)13 (0-67) 6 (0-30) 19 (0-33) 8 (0-33) 36 (0-65) 20 (0-48) 22 (0-59) 22 (0-85)N - 20 N - 18 N - 10 N - 21 N - 44 E - 11 E - 44 E - 7E - 20 E - 6 E - 10 E - 29 E - 11 S - 67 S - 22 S - 33S - 10 W - 24 S - 30 W - 7 W - 33 F - 22 W - 22 W - 13W - 20 F - 53 W - 40 F - 43 F - 11 F - 11 F - 47F - 30 F - 1012 (4-40) 9 (4-19) 7 (4-10) 8 (3-30) 6 (3-10) 9 (7-10) 7 (3-13) 6 (3-10)L - 30 4L - 53 L - 20 L - 14 L - 11 L - 44 LS - 22 L - 20SL - 30 SL - 24 LS - 50 SL - 29 LS - 56 LS - 11 SL - 56 LS - 20CL - 20 S - 12 SL - 30 S - 21 SL - 22 SL - 22 S - 11 SL - 33SCL -10 SCL - 12 SC - 7 S - 11 S - 11 SCL - 11 S - 7O - 10 SCL - 29 SCL - 11 CL - 7SCL - 1371 (30-120) 56 (30-90) 56 (35-70) 54 (30-100) 55 (30-90) 59 (45-70) 71 (40-100) 60 (25-120)77 (35-120) 62 (30-90) 59 (35-70) 57 (20-100) 55 (30-90) 60 (50-70) 71 (40-100) 61 (25-120)N/A or 60-90 N/A N/A N/A or 20-100 N/A N/A or 55-65 N/A or >75 N/AW - 60 R - 6 W - 60 W - 14 R - 33 W - 67 W - 89 R - 60M - 20 W - 88 M - 40 M - 36 W - 56 I - 22 M - 11 W - 33I - 10 M - 6 I - 21 M - 11 P - 11 M - 7P - 10 P - 29R - 30 R - 12 R - 10 D - 57 R - 11 D - 33 R - 11 R - 13D - 70 D - 88 D - 90 L - 43 D - 78 L - 67 D - 22 D - 74L - 11 L - 67 L - 13B - 50 B - 88 B - 90 B - 21 B - 22 B - 78 B - 67 B - 94P - 10 P - 12 P - 10 P - 29 P - 67 L - 22 P - 22 L - 7L - 30 R - 14 R - 11 L - 11O - 10 L - 3673 (46-135) 90 (48-116) 79 (47-103) 70 (56-95) 65 (54-76) 70 (56-100) 75 (57-96) 82 (61-122)19 (17-22) 16 (12-19) 18 (15-23) 26 (21-31) 23 (20-27) 22 (19-27) 21 (15-25) 12 (9-16)72 (40-100) 82 (30-100) 63 (20-100) 82 (45-100) 88 (70-100) 74 (42-93) 67 (41-90) 52 (25-95)33 (5-85) 54 (18-97) 46 (15-95) 26 (1-92) 33 (4-66) 47 (13-84) 37 (3-77) 27 (0-69)17 (2-84) 15 (2-35) 6 (2-14) 32 (0-80) 18 (2-53) 29 (13-48) 22 (5-78) 18 (0-74)4 (0-20) 4 (0-35) 2 (0-9) 1 (0-11) 0 0 0 (0-1) 0 (0-2)30RESULTS AND DISCUSSIONVegetation-Environment RelationshipsScientica Silvica Extension Series, Number 27, 2000It appears that each delineated vegetation units is not environmentally exclusive: they overlap and cannot be characterized by an exclusive edaphic range. The generalized plots illustrated on the two grids show overlaps in climatic range for some units that is an artifact of placing on one grid units associated with different climates (Figure 5 and Figure 6). For example, two edaphically different units (Lathyrus - Hedysarum (221) and Lathyrus typic (222)) overlap with Mertensia - Petasites (113); however, the former are from the wetter portion of the BWBS zone (BWBSmw subzone) and the latter is from the drier portion of the BWBS zone (BWBSdk subzone). The vegetation units extend from very dry to very moist sites but are infrequent on very poor and poor sites. Except for three units (Mertensia - Arnica (112), Ledum (210), and Thalictrum (310)) all other units occupy medium and richer portion of the grids. In general, indicator plant analysis supported characterization of soil moisture conditions for the units (Figure 8). For example, the Mahonia - Shepherdia (425) subassociation, with the soil moisture range restricted to very dry SMR, has the highest (about 90%) mean relative frequency of very dry to moderately dry indicators. The moderately dry Mertensia - Festuca (111), Mertensia - Arnica (112), and Rosa - Senecio (424) subassociations have lower and similar mean relative frequencies of very dry to moderately dry indicators than the Mahonia - Shepherdia (425) subassociation, and the similar proportion of other indicator species groups in their soil moisture spectra. Similarly, the moist to very moist Lathyrus - Actaea (223) and Rosa - Aralia (421) subassociations have very similar soil moisture spectra that are dominated by indicators of fresh to very moist and very moist to wet soil moisture conditions. Except the Ledum (210) association, the mean relative frequency of nitrogen-rich indicators of all other units is over 40% suggesting rich or very rich SNRs (Figure 9). In general, the units of the cool temperate Symphoricarpos alliance appear to be richer than those of the montane boreal Mertensia (100) and Elymus (200) alliances. However, as soil nutrient spectra reflect nutrient conditions of the forest floor (predominantly Moder humus forms) more strongly than the associated mineral soil, occurrence of very rich sites will likely be infrequent. We made edaphic comparisons of the vegetation units of this study with those recognized by DeLong (1988) in the BWBSmw subzone (Figure 10). The comparison indicates some differences but predominantly similarities, despite different nomenclature, difficulties in comparing actual to relative SMRs, and ambiguous edaphic ranges in DeLong's units. Our Mertensia - Festuca (111) subassociation appears to be edaphically as well as floristically very similar to DeLong's Kinnikinnick unit; similarly, our Ledum (210) association and DeLong's Ledum unit occupy a very similar edaphic range and have the similar floristic composition. Although DeLong's Soopalallie and Creamy Peavine units are considered to be associated predominantly with the medium SNR, they correspond to our medium to rich Lathyrus - Hedysarum (221) and Lathyrus typic (222) subassociations. On moist to very moist, nutrient medium to very rich sites we recognized only one unit (Lathyrus - Actaea (223) subassociation) while DeLong delineated three closely related units: Oak Fern, Black Twinberry, and Cow Parsnip. Our Lathyrus - Actaea (223) subassociation included Lonicera involucrata as a diagnostic species but Gymnocarpium dryopteris and Heracleum sphondylium were very infrequent species. 31RESULTS AND DISCUSSIONVegetation-Environment RelationshipsTrembling Aspen EcosystemsFigure 8. Soil moisture spectra for the 15 basic vegetation units delineated in trembling aspen stands across British Columbia. Codes for vegetation units as in Ta bl e 3 . Figure 9. Soil nutrient spectra for the 15 basic vegetation units delineated in trembling aspen stands across British Columbia. Codes for vegetation units as in Ta bl e 3 . 0% 20% 40% 60% 80% 100%Indicator species groups for soil moisture:Excessively to very dryVery to moderately dryModerately dry to freshFresh to very moistVery moist to wetWet to very wetRelative frequency of soil moisture indicator species111112113210221222223310411412421422423424425Vegetation Unit0% 20% 40% 60% 80% 100%111112113210221222223310411412421422423424425 poor medium richIndicator species groups for soil nutrients:Vegetation UnitRelative frequency of soil nutrient indicator species32RESULTS AND DISCUSSIONVegetation-Environment RelationshipsScientica Silvica Extension Series, Number 27, 2000Figure 10. Edatopic grid showing the relationships to soil moisture and soil nutrient regimes of the seven vegetation units recognized by DeLong (1988) in seral aspen ecosystems in the BWBSmw subzone. The units are named by Trembling Aspen (At) and the common name of one understory species.VP1234567VDMDSD(f)F -M(f)VM(f)W(f)PMRVRSoil nutrient regimeSoil moisture regime0101 At – Creamy PeavineBWBSmw2 Seral Aspen Units 02 At – Kinnikinnick 03 At – Soopolallie04 At – Labrador Tea05 At – Black Twinberry06 At – Oak Fern07 At – Cow Parsnip04030205060733RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen EcosystemsDescription of Plant AssociationsThis section expands upon the vegetation classification by emphasizing floristic and stand characteristics of the delineated units. As much of this information is presented in diagnostic, summary, plot vegetation, and plot environmental tables, the description is brief and focused on the most salient features. We describe and illustrate each of the 15 basic vegetation units that represent the lowest level of the hierarchy - either associations or subassociations. Vegetation units are organized according to the order given in Table 3.111 Populus tremuloides - Mertensia paniculata: Festuca altaica (Mertensia - Festuca) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, 11, 12 and 13; Appendices 2 and 17)Moderately dry, medium to rich (very rich) sites in drier montane boreal climatesMertensia - Festuca communities occur on water-shedding ridge crests or warm-aspect upper slopes, often bordering grassland communities, in the Dry Cool BWBS (BWBSdk) subzone. These water-deficient sites support marginal to poor, often distorted, aspen growth with site index (@ 50 yrs bh) ranging from 6 to 9 m (Figures 11 to 13). The associated soils are shallow, coarse-skeletal, Dystric or Eutric Brunisols, Podzols or Regosols with Mormoder Leptomoder, or Mullmoder (when grass cover is high) humus forms (Table 9).The canopy of the Mertensia - Festuca community is exposed to wind and early frost; however the frost damage is never so severe as on the large, cool air-receiving flats that do not support forest growth. The canopy is usually open and includes only aspen. As a result of the open-canopy conditions, the shrub and herb layers are well developed, but the cover of the moss layer is very low (Table 9, Figures 11, 12 and 13). In order of decreasing presence, the most common shrub species are: Rosa acicularis, Shepherdia  canadensis (a diagnostic species for the Mertensia association), Viburnum edule, and Arctostaphylos uva-ursi and Juniperus communis (both diagnostic species for the Mertensia - Festuca subassociation). The most common species in the herb layer are: Galium boreale and Festuca altaica (both diagnostic species for this subassociation), Epilobium angustifolium, Delphinium glaucum, Fragaria virginiana, Geocaulon lividum, and Linnaea borealis (Tables 4 and 5).Figure 11. An exposed, open-canopy, distorted, stunted, grass-dominated aspen stand on an upper slope in the Atlin Lake area bordering a grassland ecosystem (BWBSdk subzone). This stand represents the driest variation of the Mertensia - Festuca (111) subassociation.34RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 12. A semi-open canopy, soopalallie-dominated aspen stand on an upper slope in the Atlin Lake area (BWBSdk subzone). This stand represents the typic variation of the Mertensia - Festuca (111) subassociation. Note the white and black spruce understory on the mid-slope (in the background), which is occupied by a Mertensia - Arnica (112) community. Figure 13. A wind-exposed, closed-canopy, cranberry-dominated aspen stand on an upper slope in the Atlin Lake area (BWBSdk subzone). This stand represents the wettest variation of the Mertensia - Festuca (111) subassociation. 35RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems112 Populus tremuloides - Mertensia paniculata: Arnica cordifolia (Mertensia - Arnica) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, 14 to 17; Appendices 3 and 18)Moderately dry (slightly dry), (poor) medium to rich sites in drier montane boreal climatesMertensia - Arnica communities occur predominantly on water-shedding mid-slopes, less frequently on flats, in the Dry Cool BWBS (BWBSdk) subzone. These water-deficient sites support low- to medium-productivity aspen growth, with site index (@ 50 yrs bh) ranging from 10 to 16 m. The associated soils are moderately deep, coarse-skeletal, Dystric or Eutric Brunisols or Podzols, with Hemimor, Mormoder, or Leptomoder humus forms (Table 9). The cover of the tree canopy is variable and, in addition to aspen, it may include white spruce, black spruce, and subalpine fir. These shade-tolerant tree species also occur in the understory of many stands (Figures 14, 15,16 and 17). Lodgepole pine occurs very infrequently in the tree layer. All the understory layers may be well developed, with their cover varying from stand to stand (Table 9). In order of decreasing presence, the most common shrub species are Shepherdia canadensis (a diagnostic species for the Mertensia association and this subassociation), Rosa acicularis, Viburnum edule (a diagnostic species for this subassociation), and Salix scouleriana (a diagnostic species for the Mertensia association). The most common herbs are: Arnica cordifolia and Orthilia secunda (the diagnostic species for this subassociation), and Epilobium angustifolium, Geocaulon lividum, Linnaea borealis, Mertensia paniculata (a diagnostic species for the Mertensia association), Cornus canadensis, Delphinium glaucum, Goodyera repens, Achillea millefolium, Fragaria virginiana, Lupinus arcticus, Osmorhiza berteroi, and Festuca altaica. The most common moss species are Hylocomium splendens and Pleurozium schreberi (Tables 4 and 5).Figure 14.  An open-canopy, fireweed-dominated aspen stand on a mid-slope north of Dease Lake (BWBSdk subzone). This stand represents the drier variation of the Mertensia - Arnica (112) subassociation. Figure 15. An semi-open canopy, fireweed- and highbush cranberry-dominated aspen stand on a mid-slope north of Dease Lake (BWBSdk subzone). This stand represents the wetter variation of the Mertensia - Arnica (112) subassociation.36RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 16. A closed-canopy, grass- and herb-dominated, old-growth aspen stand on a flat in the Atlin Lake area (BWBSdk subzone). This stand represents the drier and richer variation of the Mertensia - Arnica (112) subassociation. Figure 17. An old growth, grass- and herb-dominated aspen stand with large canopy gaps on a flat in the Atlin Lake area (BWBSdk subzone). This stand also represents the drier and richer variation of the Mertensia - Arnica (112) subassociation. Willows and infrequently, white spruce regenerate in canopy gaps. 37RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems113 Populus tremuloides - Mertensia paniculata: Petasites frigidus (Mertensia - Petasites) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, 18 and 19; Appendices 4 and 19)Slightly dry to fresh (often with fluctuating water table), (poor) medium to rich sites in drier montane boreal climates More or less water-receiving Mertensia - Petasites communities occur predominantly on lower slopes, with intermittent seepage, less frequently on flats affected by a fluctuating water table, in the Dry Cool BWBS (BWBSdk) subzone. These slightly dry to fresh sites support low- to medium-productivity aspen growth, with site index (@ 50 yrs bh) ranging from 10 to 15 m. The commonly associated soils are moderately deep, sandy loam to loamy, skeletal, occasionally gleyed, Eutric Brunisols or Podzols, with Hemimor, Humimor, Mormoder, or Leptomoder humus forms (Table 9).The cover of the tree canopy is variable and, in addition to aspen, it usually includes shade-intolerant lodgepole pine and shade-tolerant white spruce, black spruce and subalpine fir, with shade-tolerant species also regenerating in the understory of many stands (Figures 18 and 19). All the understory layers are moderately well developed, with the moss layer having the highest average cover (Table 9). In order of decreasing presence the most common shrub species are: Rosa acicularis, Shepherdia  canadensis (a diagnostic species for the Mertensia association), Vaccinium vitis-idaea, Viburnum edule, Empetrum nigrum, and Ledum groelandicum. The most common herb species are: Linnaea borealis, Cornus canadensis, Petasites frigidus (a diagnostic species for this subassociation), Epilobium angustifolium, Geocaulon lividum, Lupinus arcticus (a diagnostic species for this subassociation), Mertensia paniculata (a diagnostic species for the Mertensia association), Achillea millefolium, Festuca altaica, Galium boreale, Fragaria virginiana, Mitella nuda (a diagnostic species for this subassociation), Orthilia secunda, and Goodyera repens. The most common species in the moss layer are: Hylocomium splendens, Pleurozium schreberi, Ptilium crista-castrensis, and Peltigera membranacea (Tables 4 and 5). Figure 18. View of a closed-canopy, dense aspen stand on a lower slope with a scattered understory of white spruce in the Iskut Lake area (BWBSdk subzone). This stand represents the drier variation of the Mertensia - Petasites (113) subassociation.38RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 19. A closed-canopy, dense aspen stand on a lower slope with a scattered understory of white spruce in the Iskut Lake area (BWBSdk subzone). This stand represents the typic variation of the Mertensia - Petasites (113) subassociation.39RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems210 Populus tremuloides - Ledum groelandicum (Ledum) association(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, 20, 21 and 22; Appendices 5 and 20)Slightly dry to fresh, very poor to poor sites in wetter montane boreal climates Ledum communities occur most often on very poor and slightly dry sites, and less frequently on poor and fresh sites. They occupy variable mesoslope positions but are most common on flats or very gentle lower slopes. These communities are restricted to wetter subzones of the BWBS zone, and were described from the Dawson Creek area. Aspen productivity is low, with site index (@ 50 yrs bh) ranging from 7 to 10 m. Commonly associated soils are moderately deep, sandy to loamy, skeletal, Dystric Brunisols, with thin Hemimor or Humimor (infrequently Mormoder) humus forms (Table 9).Due to floristic distinctiveness and uniformity, Ledum communities are represented by a single unit at the association level within the Elymus alliance. The cover of the tree layer is variable and, in addition to aspen, it may include shade-intolerant lodgepole pine and shade tolerant white spruce, black spruce, and subalpine fir, with shade-tolerant species also regenerating in the understory of many stands (Figures 20, 21 and 22). All the understory layers are moderately well developed, with the shrub layer having on the average the highest cover (Table 9). In order of decreasing presence, the most common shrub species are: Ledum groelandicum and Spiraea betulifolia (both diagnostic species for this association), Vaccinium myrtilloides, and V. vitis-idaea (a diagnostic species for this association). The most common herb species are: Linnaea borealis, Cornus canadensis, Epilobium angustifolium, Geocaulon lividum, Petasites frigidus (a diagnostic species for the Elymus alliance and this association), Lycopodium complanatum and Melampyrum lineare (both diagnostic species for this association). The most common species in the moss layer are Polytrichum juniperinum (a diagnostic species for this association), Pleurozium schreberi, Cladina rangiferina, and Peltigera aphthosa (Tables 4 and 5). Figure 20. An immature aspen cohort on a gentle upper slope with sparsely developed understory vegetation in the Fort St. John area (BWBSmw subzone). This stand represents the drier variation of the Ledum (210) association.40RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 21. A closed-canopy, immature aspen stand on a mid-slope with sparsely developed understory vegetation and scattered pine and white spruce in the Fort St. John area (BWBSmw subzone). This stand represents the typic variation of the Ledum (210) association.Figure 22. An immature, Labrador tea-dominated aspen cohort on a flat in the Tumbler Ridge area (BWBSmw subzone). This stand represents the wetter and poorer variation of the Ledum (210) association.41RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems221 Populus tremuloides - Lathyrus ochroleucus: Hedysarum boreale (Lathyrus - Hedysarum) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, 23 and 24; Appendices 6 and 21)Slightly dry, poor to medium sites in wetter montane boreal climates Lathyrus - Hedysarum communities occupy variable mesoslope positions but are most common on warm-aspect, upper or mid-slopes and flats. These communities are restricted to wetter subzones of the BWBS zone, and were described from the Dawson Creek area. Aspen productivity is low to medium, with site index (@ 50 yrs bh) ranging from 11 to 15 m. The associated soils are moderately deep, sandy-skeletal, Dystric or Eutric Brunisols, with or Mor or Mormoder humus forms (Table 9).Lathyrus - Hedysarum communities represent the driest segment of the Lathyrus association (Figure 6). The cover of the tree layer is generally high, and in addition to aspen, it may include shade tolerant white spruce and subalpine fir, which also regenerate in the understory. The shrub and graminoid-dominated herb layers are well developed, but the moss layer is generally absent or very poorly developed (Table 9, Figures 23 and 24). In order of decreasing presence, the most common shrub species are: Rosa acicularis, Vaccinium myrtilloides (the diagnostic species for this subassociation), Shepherdia  canadensis, Amelanchier alnifolia (the diagnostic species for the Lathyrus association), Vaccinium vitis-idaea, and Ledum groelandicum. The most common herb species are: Elymus innovatus (a diagnostic species for the Elymus alliance), Lathyrus ochroleucus (a diagnostic species for the Lathyrus association), Maianthemum canadense, Linnaea borealis, Calamagrostis canadensis, Aster conspicuus (a diagnostic species for the Lathyrus association), Achillea millefolium (a diagnostic species for this subassociation), Galium boreale (a diagnostic species for the Lathyrus association), and Hedysarum boreale (a diagnostic species for this subassociation).Figure 23. An immature, dense aspen stand on a gentle mid-slope in the Dawson Creek area (BWBSmw subzone) dominated by grasses (Calamagrostis canadensis, Elymus innovatus, and Oryzopsis asperifolia). This stand represents the typic variation of the Lathyrus - Hedysarum (221) subassociation.42RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 24. A closed-canopy, low-productivity, mature aspen stand on a gentle mid-slope in the Dawson Creek area (BWBSmw subzone). The understory is grass-dominated (Calamagrostis canadensis, Elymus innovatus, and Oryzopsis asperifolia) with scattered low shrubs. This stand represents the drier variation of the Lathyrus - Hedysarum (221) subassociation.43RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems222 Populus tremuloides - Lathyrus ochroleucus: typic (Lathyrus typic) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, 25, 26 and 27; Appendices 7 and 22)Slightly dry to fresh (moist), (poor) medium (rich) sites in wetter montane boreal climates Typic Lathyrus communities occur on intermediate sites in the BWBSmw subzone, predominately on slightly dry or fresh, nutrient-medium sites. Occasionally they are found on poor or rich sites and very infrequently on moist sites. They occur most commonly on gentle mid-slopes or flats, and less frequently on lower slopes. This subassociation probably accounts for about half of the aspen communities in the wetter subzones of the BWBS zone, and, unlike the Ledum association and Lathyrus - Hedysarum subassociation, typic Lathyrus typic communities are distributed across the entire Liard Plain (Ft. Nelson, Ft. St. John, and Dawson Creek areas). Aspen productivity is medium, with site index (@ 50 yrs bh) ranging from 15 to 23 m, but timber quality is high as reflected in good growth form and absence of stem rot. The commonly associated soils are moderately deep, sandy to loamy-skeletal, Dystric or Eutric Brunisols and Gray Luvisols with Hemimor or Mormoder humus forms (Table 9).The cover of the tree layer is generally high, and a high stand density is typical for immature stands (Figures 26 and 27). This is the result of prolific suckering after disturbance (Figure 25). In addition to aspen, the tree layer may include white spruce, subalpine fir, lodgepole pine, paper birch, and balsam poplar, with shade-tolerant species occurring in the understory. The shrub and herb layers are very well developed, but the moss layer consistently has a low cover (Table 9). In order of decreasing presence, the most common shrub species are: Rosa acicularis (a diagnostic species for the Lathyrus association), Viburnum edule, and Shepherdia canadensis. The most common herb species are: Cornus canadensis (a diagnostic species for this subassociation), Epilobium angustifolium (Figure 27), Lathyrus ochroleucus (a diagnostic species for the Lathyrus association), Linnaea borealis, Rubus pubescens (a diagnostic species for this subassociation), Pyrola asarifolia (a diagnostic species for the Lathyrus association), Maianthemum canadense, Galium boreale (a diagnostic species for the Lathyrus association), and Elymus innovatus (a diagnostic species for the Elymus alliance). The most common species in the moss layer is Hylocomium splendens (a diagnostic species for this subassociation) (Tables 4 and 5).Figure 25. Vigorous regeneration of aspen following the cutting of conifers on a flat in the Fort St. John area (BWBSmw subzone). This stand represents an early initiation stage in stand development of the Lathyrus typic (222) subassociation. 44RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 26. A dense, immature, herb-dominated aspen stand on a flat in the Fort St. John area (BWBSmw subzone). This stand represents the drier variation of the Lathyrus typic (222) subassociation. Figure 27. A dense, immature, fireweed-dominated aspen stand on a flat in the Fort St. John area (BWBSmw subzone). This stand represents the wetter variation of the Lathyrus typic (222) subassociation. 45RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems223 Populus tremuloides - Lathyrus ochroleucus: Actaea rubra (Lathyrus - Actaea) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 6, 8, 9, and 28, 29, 30, and 31; Appendices 8 and 23)Moist to very moist, rich (very rich) sites in wetter montane boreal climates Lathyrus - Actaea communities represent the wettest segment of the Lathyrus association: in fact, the wettest sites supporting aspen growth in the BWBS zone. On these moist to very moist sites, aspen stands feature a high admixture of balsam poplar, which has a higher tolerance of water-surplus than aspen. Lathyrus - Actaea communities occupy lower slopes, which are often affected by intermittent seepage, or flats, which are often affected by a fluctuating water table. Similar to the Lathyrus typic subassociation, the Lathyrus - Actaea subassociation is distributed in the wetter subzones of the BWBS zone across the entire Laird Plain (Ft. Nelson, Ft. St. John, and Dawson Creek areas). Aspen productivity is high, with site index (@ 50 yrs bh) ranging from 20 to 25 m. Timber quality is also high as reflected in good growth form and absence of stem rot, particularly in the Fort Nelson area. The commonly associated soils are moderately deep, coase to fine-textured, Gleyed Dystric or Eutric Brunisols, occasionally Gleyed Gray Luvisols, with Mormdoder, Hydromoder, Mullmoder, or Vermimull humus forms  (Table 9).The cover of the tree layer is generally high; a high stand density is typical for immature stands (Figures 28 and 29). In addition to aspen, the tree layer usually includes white spruce and paper birch, with shade-tolerant spruce occurring in the understory (Figures 30 and 31). The shrub and herb layers are very well developed, with the moss layer usually absent (Table 9). In order of decreasing presence, the most common shrub species are: Rosa acicularis (a diagnostic species for the Lathyrus association), Viburnum edule, and Cornus sericea and Lonicera involucrata (a diagnostic species for this subassociation). The most common herbs are: Actaea rubra and Aralia nudicaulis (both diagnostic species for this subassociation), Calamagrostis canadensis (a diagnostic species for the Elymus alliance), Epilobium angustifolium, Galium triflorum (a diagnostic species for this subassociation), Pyrola asarifolia (a diagnostic species for the Lathyrus association), Cornus canadensis, Delphinium glaucum (a diagnostic species for this subassociation), Equisetum pratense (a diagnostic species for this subassociation), and Mertensia paniculata (Tables 4 and 5). 46RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000Figure 28. A dense, immature aspen stand on a lower slope in early spring in the Fort St. John area (BWBSmw subzone). This stand represents the typic variation of the Lathyrus - Actaea (223) subassociation.Figure 29. A dense, immature, herb-dominated aspen stand on a flat in the Fort St. John area (BWBSmw subzone). This stand represents the wetter variation of the Lathyrus - Actaea (223) subassociation.47RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen EcosystemsFigure 30. A semi-open canopy, mature, shrub-dominated aspen stand with scattered white spruce regeneration on an alluvial terrace in the Fort St. John area (BWBSmw subzone). This stand represents the wetter and richer variation of the Lathyrus - Actaea (223) subassociation.Figure 31. A dense cohort of old aspen on a flat with a scattered understory of white spruce in the Fort Nelson area (BWBSdk subzone). This stand representing the wetter and richer variation of the Lathyrus - Actaea (223) subassociation is one of many with high-quality aspen timber in the area.48RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000310 Populus tremuloides - Thalictrum occidentale (Thalictrum) association(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, 32, 33 and 34; Appendices 9 and 24)Slightly dry to moist (often with fluctuating water table), (poor) medium to rich sites in montane boreal and cool temperate climates The Thalictrum association represents floristically variable communities occurring in montane boreal and cool temperate climates (BWBS, SBS, SBPS, and IDF zones), with most of the communities located in the SBS zone. The floristic variability is indicated by the plot vegetation table, which shows that few species occur in more than 60% of the plots (presence class ≥ IV) (Table 5). This association lacks a diagnostic combination of species, but is defined by the low presence of species diagnostic of other units (Table 4). Thalictrum communities occur over a wide edaphic range, but are most common on fresh, nutrient-medium sites. They occupy various meso-slope positions, depending on climate, but most frequently depressions or flats with a fluctuating water table in drier climates (BWBS, SBPS, and IDF zones) (Figures 32 and 33) or the mid- or lower slopes (affected by intermittent seepage) in wetter climates (SBS zone). In the SBPS zone, Thalictrum communities typically form a narrow fringe in the transition between water surplus sites and water-deficient, upland lodgepole pine forest (Figure 34). Aspen productivity is medium, with site index (@ 50 yrs bh) ranging from 17 to 22 m. The commonly associated soils are shallow to moderately deep, loamy-skeletal, Gleyed Dystric or Eutric Brunisols, occasionally Gleyed Gray Luvisols, with Mormoder, or Leptomdoder humus forms (Table 9).The cover of the tree layer is generally high. In addition to aspen, the tree layer nearly always includes white spruce, occasionally lodgepole pine and black spruce; white spruce, willows, and scrub birch are common in the understory (Table 9). The cover of the understory vegetation decreases in order form the shrub to the herb to the moss layer. In order of decreasing presence, the most common shrub species are: Rosa acicularis, Viburnum edule, Lonicera involucrata, Salix spp., and Ribes lacustre. The most common herbs are: Epilobium angustifolium, Aster conspicuus, Fragaria virginiana, Galium boreale, Thalictrum occidentale, Achillea millefolium, Calamagrostis rubescens, and Cornus canadensis (Tables 4 and 5). Figure 32. An aspen fringe occupying a transitional area between a non-forested, mounded, graminoid community and an 'upland' lodgepole pine forest in the Nimpo Lake area (SBPS zone). The fringe and graminoid community are affected by a fluctuating water table. This stand represents the poorer variation of the Thalictrum (310) association. 49RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen EcosystemsFigure 33. An immature aspen stand surrounded by lodgepole pine in a shallow depression in the 100 Mile House area (IDF zone). This stand represents the drier and poorer variation of the Thalictrum (310) association on a site with a fluctuating water table. Figure 34. A closed-canopy, mature aspen stand with scattered scrub birch bordering a non-forested, frost-affected wetland (in the background) in the 100 Mile House area (IDF zone). This stand represents the wetter, most productive variation of the Thalictrum (310) association on a site with a fluctuating water table.50RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000411 Populus tremuloides - Viburnum edule: Spiraea betulifolia (Viburnum - Spiraea) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, 35, 36 and 37; Appendices 10 and 25)Slightly dry to fresh (moist), (medium) rich to very rich sites in wetter montane boreal climates The Viburnum - Spirea subassociation represents a sub-boreal segment of the Symphoricarpos alliance and Viburnum association (Tables 3 and 4). These slightly dry to fresh, nutrient-rich communities occupy flats or warm-aspect, mid- and lower slopes in the SBS zone, and feature a mixture of montane boreal and cool temperate species. The mean area of aspen stands is rather small compared to the BWBS zone. Aspen productivity is medium (Figures 35, 36 and 37), with site index (@ 50 yrs bh) ranging from 12 to 19 m. The commonly associated soils are moderately deep,  well-drained, coarse or fine textured, skeletal, Dystric or Eutric Brunisols, Gray Luvisols, or Humo-Ferric Podzols, with Mormoder, or Mullmoder humus forms (Table 9).The cover of the tree layer is generally high. In addition to aspen, the tree layer nearly always includes white spruce, and occasionally subalpine fir and Douglas-fir. White spruce, subalpine fir, and Sitka alder are common in the understory (Figure 37). The understory vegetation is always well developed; its cover decreases in order from the shrub to the herb to the moss layer (Table 9, Figures 35 and 36). In order of decreasing presence, the most common shrub species are: Rosa acicularis (a diagnostic species for the Viburnum association), Amelanchier alnifolia (a diagnostic species for the Symphoricarpos alliance), Cornus stolonifera (a diagnostic species for the Viburnum association), Spiraea betulifolia, Symphoricarpos albus (a diagnostic species for the Symphoricarpos alliance), Viburnum edule (a diagnostic species for the Viburnum association), and Rubus parviflorus. The most common herbs are: Osmorhiza berteroi and Thalictrum occidentale (both diagnostic species for this subassociation), Aralia nudicaulis (a diagnostic species for the Viburnum association), Elymus glaucus (a diagnostic species for the Symphoricarpos alliance), Galium boreale (a diagnostic species for this subassociation), Linnaea borealis, Epilobium angustifolium, Rubus pubescens, Aster conspicuus and Fragaria virginiana (both diagnostic species for this subassociation), Clintonia uniflora, and Cornus canadensis (Tables 4 and 5). Figure 35. An immature, closed-canopy, herb-dominated aspen stand on a gentle mid-slope north of Vanderhoof (SBS zone). This stand represents the drier variation of the Viburnum - Spiraea (411) subassociation. 51RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen EcosystemsFigure 36. A late-immature, closed-canopy, shrub- and herb-dominated aspen stand on a flat near Cranberry Junction (ICH zone). This stand represents the wetter variation of the Viburnum - Spiraea (411) subassociation. Figure 37. A late-immature, semi-open canopy, shrub-dominated aspen stand with scattered understory hybrid spruce on flat north of Fort St. James (SBS zone). This stand represents the wetter and richer variation of the Viburnum - Spiraea (411) subassociation. 52RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000412 Populus tremuloides - Viburnum edule: Paxistima myrsinites (Viburnum - Paxistima) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, and 38, 39, 40, and 41; Appendices 11 and 26)Slightly dry (fresh), medium to rich sites in wetter cool temperate climates The Viburnum - Paxistima subassociation represents a segment of the Symphoricarpos alliance and Viburnum association that is located entirely within the ICH (Tables 3 and 4). These slightly dry to fresh, nutrient-rich communities occupy variable meso-slope positions but they occur most frequently on warm-aspect mid-slopes (Figures 39, 40 and 41), rarely on flats. Similarly to the Viburnum - Spiraea communities, the Viburnum - Paxistima stands occupy small areas compared to the montane boreal stands. Aspen productivity is medium, with site index (@ 50 yrs bh) ranging from 15 to 23 m. The commonly associated soils are moderately deep, moderately well-drained, coarse or fine textured, skeletal, Eutric Brunisols, with Mormoder or Leptomoder humus forms (Table 9).The cover of the tree layer is variable but generally high (Figures 39, 40 and 41). The tree layer may include paper birch , western redcedar, and western hemlock (all diagnostic species for this subassociation); occasionally balsam poplar, subalpine fir, western white pine, and Douglas-fir. Shade tolerant tree species, Alnus sitchensis, and Corylus cornuta (a diagnostic species for this subassociation) are common in the understory (Table 9, Figure 41). The understory vegetation is always well developed; its cover decreases in order from the shrub to the herb to the moss layer, which has a low cover. In order of decreasing presence, the most common shrub species are: Paxistima myrsinites (a diagnostic species for the Symphoricarpos alliance and Viburnum - Paxistima subassociation), Rubus parviflorus, Cornus stolonifera (a diagnostic species for the Viburnum association), Rosa acicularis, Viburnum edule, and Lonicera involucrata (a diagnostic species for the Viburnum association). The most common herbs are: Aralia nudicaulis (a diagnostic species for the Viburnum association), Clintonia uniflora, Cornus canadensis, Elymus glaucus, Epilobium angustifolium, Linnaea borealis, and Maianthemum racemosum. The most common bryophytes are: Rhytidiadelphus triqetrus (a diagnostic species for this subassociation), Pleurozium schreberi, and Ptilium crista-castrensis (Tables 4 and 5). Figure 38. An immature mixture of aspen and birch dominated by falsebox on a mid-slope in the Horsefly area (ICH zone). This stand represents the drier variation of the Viburnum - Paxistima (412) subassociation.53RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen EcosystemsFigure 39. A uniform, immature, closed-canopy, falsebox-dominated aspen stand on a gentle mid-slope near Cranberry Junction (ICH zone). This stand represents the typic variation of the Viburnum - Paxistima (412) subassociation.Figure 40. An immature mixture of aspen, black cottonwood, and birch on a mid-slope near Horsefly (ICH zone). This stand represents the wetter variation of the Viburnum - Paxistima (412) subassociation.Figure 41. A mature aspen with Corylus cornuta in the upper shrub layer stand on a flat near St Marry Lake (ICH zone). This stand represents the wetter and richer variation of the Viburnum - Paxistima (412) subassociation.54RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000421 Populus tremuloides - Rosa nutkana: Aralia nudicaulis (Rosa - Aralia) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, 42, and 43; Appendices 12 and 27)(Fresh) moist to very moist, (medium) rich to very rich sites in wetter cool temperate climates Rosa - Aralia communities are most common on moister and richer sites, but occasionally occur on fresh, or nutrient-medium sites. They are found almost exclusively on cool-aspect lower slopes, sometimes affected by seepage, or on flats influenced by a strongly fluctuating water table. These communities were described from the MS, ICH, and wetter IDF subzones. These water surplus sites support high-productivity aspen growth with site index (@ 50 yrs bh) ranging from 21 to 31 m (Figure 42). The associated soils in the MS and ICH zones include coarse-skeletal Humo-Ferric Podzols, loamy-skeletal Eutric Brunisols or loamy-skeletal Gray Luvisols; the associated humus forms are predominantly Mormoders, Leptomoders or Vermimulls (Table 9).The tree layer of the Rosa - Aralia communities includes frequently hybrid spruce, paper birch, lodgepole pine, and black cottonwood (on very moist sites); the sub-canopy may include hybrid spruce and/or western redcedar (Figure 43). Rosa - Aralia communities usually have well developed shrub and herb layer, but sometimes both of these layers have a very low cover (Table 9). The moss layer is absent or its cover is low. In order of decreasing presence, the most common shrubs are: Symphoricarpos albus (a diagnostic species for the Symphoricarpos alliance), Acer glabrum (an important companion for the Rosa association), Rubus parviflorus, and Cornus stolonifera. The most common species in the herb layer are: Elymus glaucus (a diagnostic species for the Symphoricarpos alliance), Osmorhiza berteroi (an important companion for the Symphoricarpos alliance), Festuca subuliflora (a diagnostic species for the Rosa association), Aralia nudicaulis (a diagnostic species for the Aralia subassociation), Cornus canadensis, Galium triflorum (an important companion for the Rosa association), and Mainathemum stellatum (an important companion for the Symphoricarpos alliance) (Tables 4 and 5).Figure 42. View of the canopy of one of the most productive aspen stands on a moist and rich site in the SBS-ICH transition near Gavin Lake. This stand represents the wetter and richer variation of the Rosa - Aralia (421) subassociation. Figure 43. An open-canopy aspen stand with abundant regeneration of Douglas-fir, hybrid spruce, and subalpine in the understory near Horsefly (ICH zone). This stand represents the drier variation of the Rosa - Aralia (421) subassociation. 55RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems422 Populus tremuloides - Rosa nutkana: Arnica cordifolia (Rosa - Arnica) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, and 44; Appendices 13 and 28)Moderately to slightly dry, medium to rich sites in montane cool temperate climates Rosa - Arnica communities occur predominantly on mid-slopes in the MS, ICH, and IDF zones. Although water-deficient, these sites support high-productivity aspen growth, with site index (@ 50 yrs bh) ranging from 20 to 27 m. The associated soils in the MS and ICH zones are typically coarse-skeletal Humo-Ferric Podzols or, in the IDF zone, loamy-skeletal Eutric Brunisols. The associated humus forms are Mormoders and Leptomoders in the MS and ICH zones, and Hemimors in the IDF zone (Table 9).Rosa - Shepherdia communities may include paper birch, and occasionally western white pine and western larch, in the canopy. Douglas-fir may occur in the canopy or sub-canopy in the IDF zone, and hybrid spruce in the MS, ICH, and IDF zones. In the ICH zone, western redcedar and western hemlock can be found in the sub-canopy. Most stands are structurally diversified into well developed, species-rich shrub and herb layers, either layer or both layers may be poorly developed in some cases (Table 9, Figure 44). The moss layer is essentially absent. In order of decreasing presence, the most common shrubs are: Rubus parviflorus, Spiraea betulifolia, Acer glabrum (an important companion for the Rosa association), Mahonia aquifolium (a diagnostic species for the Rosa association), and Shepherdia canadensis. In order of decreasing presence, the most common species in the herb layer are: Osmorhiza berteroi (an important companion for the Symphoricarpos alliance), Arnica cordifolia (a diagnostic species for this subassociation), Galium triflorum (an important companion for the Rosa association), Calamagrostis rubescens, Chimaphila umbellata (a diagnostic species for this subassociation), Clintonia uniflora, and Linnaea borealis (Tables 4 and 5). Figure 44. A mature, small shrub- and herb-dominated aspen stand on a mid-slope on the side of a gully west of Williams Lake (IDF zone). This stand represents the drier variation of the Rosa - Arnica (422) subassociation.56RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000423 Populus tremuloides - Rosa nutkana: Angelica genuflexa (Rosa - Angelica) subassociation(References: TTables 3, 4, 5, and 9; Figures 4, 7, 8, 9, and 45; Appendices 14 and 29)(Slightly dry) fresh, medium to rich (very rich) sites in cool temperate climates Rosa - Angelica communities occur predominantly on south-aspect mid- or lower slopes or on flats affected by intermittent seepage in the ICH and IDF zones. These sites support medium- to high-productivity aspen growth with site index (@ 50 yrs bh) ranging from 19 to 26 m. The associated soils are typically sandy to loamy-skeletal Eutric Brunisols, occasionally Gray Luvisols, with Vermimull or Moder humus forms (Table 9).In the IDF zone, Rosa - Angelica communities may include Douglas-fir in the canopy or sub-canopy while hybrid spruce can be present in both the IDF and ICH zones (Figure 45). Lodgepole pine in the canopy and western hemlock in the sub-canopy are infrequent. The stand structure is typically diversified into well developed, species-rich shrub and herb layers, but the moss layer is essentially absent (Table 9). In order of decreasing presence, the most common shrubs are: Amelanchier alnifolia (a diagnostic species for this subassociation), Sympricarpos albus (a diagnostic species for the Symphoricarpos alliance), Rubus parviflorus, Cornus stolonifera, Lonicera involucrata, and L. utahensis (an important companion for the Rosa association). The common herbs include: Actaea rubra, Angelica genuflexa, Aster conspicuus, Disporum hookeri, Lilium columbianum, and Thalictrum occidentale (all diagnostic species for this subassociation) (Tables 4 and 5).Figure 45. An immature, open-canopy, clumpy aspen stand with western hemlock and hybrid spruce in the understory on a flat near Horsefly (ICH zone). This stand represents the typic variation of the Rosa - Angelica (423) subassociation associated with a fluctuating water table.57RESULTS AND DISCUSSIONDescription of Plant AssociationsTrembling Aspen Ecosystems424 Populus tremuloides - Rosa nutkana: Senecio pseudoaureus (Rosa - Senecio) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, and 46; Appendices 15 and 30)Moderately dry (slightly dry), (medium) to rich (very rich) sites in drier cool temperate climates Rosa - Senecio communities occur on water-deficient sites, typically on upper or mid-slopes or on flats associated with fluvial deposits in the IDF and MS zones. While most common on moderately dry and rich sites, these communities are occasionally found on slightly dry and on medium or very rich sites. Although dry, these sites represent medium- to high-productivity conditions for aspen growth with site index @ 50 yrs bh ranging from 15 to 25 m; however, there is a high incidence of stem rot. The associated soils are loamy-skeletal Eutric Brunisols, occasionally Humo-Ferric Podzols or Grey Luvisols, with Vermimull or Leptomoder humus forms (Table 9).Rosa - Senecio communities may include lodgepole pine in the upper canopy or Douglas-fir (in the IDF zone) or hybrid spruce (in the MS zone) in the canopy or sub-canopy, or western redcedar in the sub-canopy (in the IDF zone). The stand structure is usually simple, with either the shrub or herb layer (or both) being poorly developed (Table 9, Figure 46). The moss layer is essentially absent. Common shub species include: Amelanchier alnifolia (a diagnostic species for the Symphoricarpos alliance), Mahonia aquifolium (a diagnostic species for the Rosa association), Rosa nutkana, Paxistima myrsinites and Symphoricarpos albus (both diagnostic species for the Symphoricarpos alliance). Calamagrostis rubescens and Elymus glaucus (a diagnostic species for the Symphoricarpos alliance) are constant dominants, and Senecio pseudoaureus (a diagnostic species for this subassociation) and Fragaria virginiana are other common herbs. The Rosa - Senecio subassociation has only one, albeit weak, diagnostic species (Senecio pseudoaureus). This means that these communities are identified by the absence of diagnostic species identified for the other four subassociations of the Rosa nutkana association (Tables 4 and 5).Figure 46. A uniform, closed-canopy mature aspen stand with a shrub (Shepherdia canadensis), grass (Calamagrostis rubescens), and herb-dominated understory near Yahk (MS zone). This stand represents the poorer variation of the Rosa - Senecio (424) subassociation.58RESULTS AND DISCUSSIONDescription of Plant AssociationsScientica Silvica Extension Series, Number 27, 2000425 Populus tremuloides - Rosa nutkana: Shepherdia  canadensis (Rosa - Shepherdia) subassociation(References: Tables 3, 4, 5, and 9; Figures 4, 7, 8, 9, and 47; Appendices 16 and 31)Very dry (moderately dry), poor to rich sites in drier cool temperate climates The Rosa - Shepherdia subassociation represents aspen communities characterized by severe water deficit. They occur on the driest and warmest sites, which are mostly very dry, and occasionally moderately dry, but have a wide range of nutrient conditions. These communities are typically found on ridge crests and warm-aspect, upper slopes in the IDF, SBPS, and MS zones, often bordering grassland communities, but sometimes occur on flats. The marginal environmental conditions for aspen growth are indicated by the occasional presence of Juniperus scopulorum. In the driest IDF subzones, Rosa - Shepherdia communities are located in gullies that feature ephemeral streams. The associated soils are typically loamy-skeletal Eutric Brunisols, occasionally Luvisols, with thin Leptomoder or Mull (when the cover of graminoids is high) humus forms. Small patches of exposed mineral soil are common, especially on steep slopes. Aspen growth is poor to medium (site index (@ 50 yrs bh) ranges form 8 to 16 m), often with a distorted growth form  and a high incidence of stem rot (Table 9, Figure 47).Rosa - Shepherdia communities may include lodgepole pine in the upper canopy or Douglas-fir in the canopy or sub-canopy. The stand structure is variable, typically both a shrub and herb layer are present, but either, or both may be poorly developed (Table 9). The cover of mosses is very low. Shepherdia canadensis and Arctostaphylos uva-ursi (a dominant differential species for this subassociation), Rosa nutkana (diagnostic for the Rosa association) and Juniperus communis ursi (a dominant differential species for this subassociation) are the most common shrubs. Calamagrostis rubescens is a constant dominant understory species; other associated grasses may include Elymus glaucus, E. repens, Festuca subuliflora, Poa nemoralis, Oryzopsis asperifolia, and Stipa richardsonii. Common forb species include: Achillea millefolium, Fragaria virginiana, and Galium boreale (an important companion for this subassociation) (Tables 4 and 5). Figure 47. A distorted, mature aspen stand with a graminoid-dominated (Calamagrostis rubescens) understory on an upper slope near Dog Creek (IDF zone). This stand represents the drier and richer variation of the Rosa - Shepherdia (425) subassociation. 59REFERENCESTrembling Aspen EcosystemsREFERENCESAgriculture Canada Expert Committeee on Soil Survey. 1987. The Canadian system of soil classification. 2nd ed. Agric. Can. Publ. 1646. Agriculture Canada, Ottawa, ON. 164 pp.Banner, A., W. MacKenzie, S. Haeussler, S. Thomson, J. Pojar, and R. Trowbridge. 1993. A field guide to site identification and interpretation for the Prince Rupert Forest Region. Land Management Handbook No 26. B.C. Min. For., Victoria, B.C. Barkman, J.J., J. Moravec, and S. Rauschert. 1976. Code of phytosociological nomenclature. Vegetatio 32:131-185.BC Ministy of Forests. no date. Biogeoclimatic units of the Prince George Forest Region. Map, scale 1:800,000. B.C. Min. For., Prince George, B.C.BC Ministy of Forests. 1988. Biogeoclimatic and ecoregion units of the Prince Rupert Forest Region. Map, scale 1:500,000. B.C. Min. For., Prince George, B.C.BC Ministry of Forests. 1997. Site index estimates by site series for coniferous tree species in British Columbia. Forest Renewal BC and BC Ministry of Forests, Victoria, B.C. 265 pp.Becking, R.W. 1957. The Zurich-Montepellier School of phytosociology. Bot. Rev. 23:411-488.Brooke, R.C., E.B. Peterson, and V.J. Krajina. 1970. The subalpine Mountain Hemlock zone. Ecol. Western N. Amer. 2:148-349.Chen, H.Y.H., K. Klinka, and R.D. Kabzems. 1998a. Height growth and site index models for trembling aspen (Populus tremuloides (Michx.) in northern British Columbia. For. Ecol. Manage. 102: 157-165.Chen, H.Y.H., K. Klinka, and R.D. Kabzems. 1998b. Site index, site quality, and foliar nutrients of trembling aspen: relationships and predictions. Can. J. For. Res. 28:1743-1755.DeLong, C. 1988. A field guide for identification of seral aspen ecosystems of the BWBSc1, Prince George Forest Region. Land Manage. Handbook No. 16., BC Ministry of Forests, Victoria BC. 36 pp.Emanuel, J. 1999. VTAB Ecosystem Reporter Revision 199907a. Department of Forest Sciences, University of British Columbia, Vancouver, B.C. Fons, J., K. Klinka, and R.D. Kabzems. 1998. Humus forms of trembling aspen ecosystems in northeastern British Columbia. Forest Ecol. Manage. 105: 241-250. Green, R.N., R.L. Towbridge, and K. Klinka. 1993. Towards a taxonomic classification of humus forms. For. Sci. Monog. 29. 49pp.Green, R.N. and K. Klinka. 1994. A field guide to site identification and interpretaion for the Vancouver Forest Region. B.C. Min. For., Victoria, B.C. 285 pp.Hill, M.O. 1979. TWINSPAN - a FORTRAN program for arranging multivariate data in an ordered two-way table by classification of the individuals and attributes. Cornell University, Ithaca, N.Y.60REFERENCESScientica Silvica Extension Series, Number 27, 2000Kayahara, G.J., K. Klinka, P.V. Krestov, and H. Qian. 2000. Comparison of vegetation and soil nutrient properties between black spruce and trembling aspen ecosystems in the boreal black and white spruce zone of British Columbia. Submitted for publication in Can. J. For. Res.Klinka, K., V.J. Krajina, A. Ceska and A.M. Scagel. 1989. Indicator plants of coastal British Columbia. University of British Columbia Press, Vancouver, B.C. 138 pp.Klinka, K., H. Qian, J. Pojar, and D.V. Meidinger. 1996. Classification of natural forest communities of coastal British Columbia, Canada. Vegetatio 125: 149-168.Krajina, V.J. 1969. Ecology of forest trees in British Columbia. Ecol. Western N. Amer. 2:1-146.Little, E.L. Jr. 1979. Checklist of United States Trees. USDA For. Serv. Agricultural Handbook 541. Washington, D.C., 373 pp.Luttmerding, H.A, D.A. Demarchi. E.C. Lea, D.V. Meidinger and T. Vold (eds.) 1990. Describing ecosystems in the field. 2nd ed. B.C. Min. For., Victoria, B.C.Magurran, A.E. 1988. Ecological diversity and its measurement. Princeton University Press, Princeton, N.Y. 179 pp.Meidinger, D.V. and J. Pojar (eds.) 1991. Ecosystems of British Columbia. Special Rep. Series no. 6, B.C. Min. For., Victoria, B.C.Mueggler, W.F. Vegetation associations. Pp. 45-55 in N.V. DeByle and R.P. Vinokur (editors). Aspen: Ecology and management in the western  United States. USDA For. Serv. General Technical Report RM-119, Rocky Mountain For. and Range Exp. Stat., Fort Collins, Colorado. Mueller-Dombois, D., and H. Ellenberg. 1974. Aims and methods of vegetation ecology. John Wiley and Sons, Toronto, ON.New, D. 1999. Productivity of western larch in relation to categorical measures of climate, soil moisture, and soil nutrients. M.Sc.Thesis, Faculty of Forestry, University of British Columbia. 47 pp.Nigh, G.D. 1996. Growth intercept models for species without distinct annual branch whorls: western hemlock. Can. J. For. Res. 26:1407-1415.Oliver, C.D. and B.C. Larson. 1996. Forest stand dynamics. McGraw-Hill, Inc., New York. 467 pp.Perala, D.A. 1990. Populus tremuloides (Michx). Pp. 555 -569 in R.M. Burns and B.H. Honkala (editors). Silvics of North America. Vol. 2. Hardwoods. USDA For. Serv. Agri. Handbook 445, Washington, D.C. 877 pp.Pojar, J. , K. Klinka, and D.V. Meidinger. 1987. Biogeoclimatic ecosystem classification in British Columbia. For. Ecol. Manage. 22:119-154.Poore, M.E.D. 1962. The methods of successive approximation in descriptive ecology. Adv. Ecol. Res. 1:35-68.Qian, H. and K. Klinka. 1998. Plants of British Columbia: scientific and common names of vascular plants, bryophytes, and lichens. University of British Columbia Press, Vancouver, B.C. 534 pp.Qian, H., K. Kinka, and B. Sivak. 1997. Diversity of the understory vascular vegetation in 40 year-old and old-growth forest stands on Vancouver Island, British Columbia. J. Veg. Sci. 8:773-780.61REFERENCESTrembling Aspen EcosystemsWang, Q. 1992. Ecological and height growth analysis of some sub-boreal immature lodgepole pine stands in central British Columbia. Ph.D. thesis, Fac. For., Univ. B.C. Vancouver, B.C. 207 pp.Wang, Q., G.G. Wang, K.D. Coates, and K. Klinka. 1994. Use of site factors to predict lodgepole pine and interior spruce site index in the Sub-Boreal Spruce Zone. Research Note No. 114, B.C. Min. For., Victoria, B.C.Westhoff, V. and E. van der Maarel. 1980. The Braun-Blanquet approach. In: R.H. Whittaker (ed). Classification of Plant Communities. Edited by R.H. Whittaker. Dr. Junk bv Publishers, The Hague.62Scientica Silvica Extension Series, Number 27, 200063APPENDICESAppendix 1Trembling Aspen EcosystemsAPPENDICESAppendix 1. Summary vegetation table (in alphabetical order) for vegetation units delineated in trembling aspen ecosystems in British Columbia. This table presents non-diagnostic species and those that occur with the presence ≤40% (= presence class ≤II) in one or more columns. Weak diagnostic species (usually important companion species) that were used in the diagnostic combinations of species (Table 4 on page 12) are shaded in grey. Codes for vegetation units as in Table 3 on page 11.Code 111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Number of sample plots 4 14131011311010171014 9 9 9 15Number of plant species 62 101 111 41 72 78 87 103 119 102 112 87 81 115 103Species Species presence and species significance1Aconitum columbianum II +Adenocaulon bicolor II 4 II 2 II + I hAdoxa moschatellina I h I h II hAgoseris aurantiaca I h I hAgropyron pauciflorum I hAgrostis mertensii I h I hAlectoria sarmentosa I hAllium cernuum I h II +Alnus viridis I h I 4 I 1 I 2 II 4 II 3 I 4 I 2 II 4 I 1Anaphalis margaritacea II h II h I hAnemone multifida II +Anemone parviflora I hAntennaria microphylla I hAntennaria neglecta II h I h II +Antennaria pulcherrima I hApocynum androsaemifolium I 3 I h II 2Aquilegia brevistyla I t I 1Aquilegia formosa II h I h II h I h II 1Arabis holboellii I hArctostaphylos alpina I h I hAsplenium viride I hAster engelmannii I +Aster modestus I h I hAster sibiricus II h I h I h II 1 I + I 1 II +Asterella lindenbergiana I +Athyrium filix-femina I h II + II hAulacomnium palustre I hBetula nana II h I 3 I +Botrychium lunaria I h I h I hBotrychium virginianum I h II hBromus inermis II 1 I h II 1 I h I h I hCalliergon giganteum I h II h II h I hCalliergon stramineum I 3 I h II 1 I h I h II h I h I hCalochortus apiculatus I hCalypso bulbosa I h I hCampanula rotundifolia I h I h I h I hCarex concinna I hCarex disperma I h I h I h64APPENDICESAppendix 1Scientica Silvica Extension Series, Number 27, 2000Carex obtusata I hCarex rossii I 2Carex spectabilis I h I hCastilleja hyetophila I h II +Castilleja miniata I h I h I h I h I +Castilleja sulphurea I hCeanothus velutinus I hCerastium arvense I hCinna latifolia I h I h I h I h I hCladina arbuscula II h I hCladina stellaris II h I h I hCladonia borealis  II 1Cladonia cornuta II h I hCladonia crispata II h I hCladonia ecmocyna II h I h I hCladonia gracilis II hCladonia multiformis I h I h I h I h I hCladonia ochrochlora II hCladonia phyllophora II h I hCladonia pyxidata II hClematis occidentalis I h I hCoeloglossum viride I hCorallorhiza maculata I hCorallorhiza trifida I h I h I h II h II h I hCrataegus douglasii I hCypripedium montanum I h I hDactylis glomerata I h II 1Deschampsia cespitosa I h I hDicranella palustris II h I + I h I h I hDicranum fragilifolium I hDicranum fuscescens I h I h I h I h I h I h I h I h I hDicranum polysetum I + I hDicranum scoparium I h I h I h I h I hDisporum trachycarpum I hDryopteris expansa I hDryopteris fragrans I h I hElymus repens I h II h I h I 1Elymus smithii I hEmpetrum nigrum II h I h II 2Epilobium ciliatum I + I h I hEquisetum arvense I h I t I h I h I hEquisetum hyemale I hEquisetum scirpoides I h I h I hEquisetum sylvaticum I h I h I h II hEurhynchium pulchellum I h I hFestuca brachyphylla I hFestuca occidentalis I h I h I h I h I hFlavocetraria nivalis II hCode 111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Number of sample plots 4 14131011311010171014 9 9 9 15Number of plant species 62 101 111 41 72 78 87 103 119 102 112 87 81 115 103Species Species presence and species significance165APPENDICESAppendix 1Trembling Aspen EcosystemsFrangula purshiana I +Fritillaria affinis I h I hGentianella amarella II h I h I h I hGeranium richardsonii I h II + I hGeum macrophyllum I hGlyceria elata I h I +Goodyera oblongifolia I h I h I h II h I h I h II h I hGymnocarpium dryopteris I 3 I 4 I 3 I hHedysarum sulphurescens I hHieracium scouleri I h II h I h II h II hHieracium umbellatum I hHypopitys monotropa I hJuniperus horizontalis I +Juniperus scopulorum I 2Larix occidentalis I 3 I 3 II 4Lathyrus nevadensis I h II h I h I 2 I + I hLetharia vulpina I h I hLeucanthemum vulgare II hLeymus innovatus I 3 I 2Listera convallarioides I hListera cordata I hLobaria pulmonaria I h I h I hLonicera utahensis I h II 4 I h II 4 II 4 I hLycopodium annotinum I 2 I h I 2 I h I 1Lycopodium dendroideum I hLycopodium obscurum II 2 I 2Maianthemum racemosum I h I 1Maianthemum stellatum I h I hMaianthemum trifoliatum  I hMalus fusca I h I +Matteuccia struthiopteris I hMedicago sativa II 2 I 3Mnium spinulosum I hMoehringia lateriflora II hMoneses uniflora I 1Oplopanax horridus I + I hParmelia saxatilis II hPedicularis bracteosa I hPedicularis racemosa I h I 1Peltigera malacea I + I h I h I hPeltigera membranacea II h II h II 2 I hPeltigera praetextata I h I h I h I h II h I hPeltigera scabrosa I h I hPenstemon procerus  I h I hPetasites sagittatus I hPhleum pratense I h I h I hPiperia unalascensis I h I h I hPlagiomnium ciliare II hCode 111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Number of sample plots 4 14131011311010171014 9 9 9 15Number of plant species 62 101 111 41 72 78 87 103 119 102 112 87 81 115 103Species Species presence and species significance166APPENDICESAppendix 1Scientica Silvica Extension Series, Number 27, 2000Plagiomnium drummondii I 4 I h I h I h I h I hPlagiomnium medium I h I hPlatanthera obtusata II h I h I hPlatanthera orbiculata I h I h I + I t I h I h I hPoa nemorosa I h II hPoa palustis  I h I h II h I hPogonatum contortum I hPolemonium boreale II +Polemonium caeruleum I hPolytrichum strictum I h II h II hPotentilla glandulosa I h I hPrunella vulgaris II 2 II h I hPrunus virginiana I 1Pteridium aquilinum II 3 II 3 II 4Ptilidium pulcherrimum II hPyrola chlorantha I h I h I hPyrola elliptica II h I h I hPyrola minor II + II h I h I h I hRanunculus eschscholtzii I hRhododendron albiflorum I hRhytidiadelphus squarrosus I h I + I hRibes triste I h I h I h I 2 I +Rubus idaeus I h I + II 2 I 2 I h I h II + II 2 I hRubus pedatus I +Salix bebbiana I + I + I 3 I 2 I hSalix glauca I 3 I 6 I h II 1Salix lucida I 2 II hSalix myrtillifolia I hSalix sitchensis I 1Sambucus racemosa I hSanicula marilandica I hSanionia uncinata II 2 I h I h I h I h II hSaxifraga nelsoniana I hSaxifraga tricuspidata II +Schizachne purpurascens I h I +Senecio triangularis I 1Silene menziesii I h I hSolidago canadensis I h I h II + I h I h I hSolidago spathulata II h I h I h I h I hSorbus scopulina I + II h II + II +Spiraea douglasii I 1Stellaria calycantha I h I h I h I h II h I hStenanthium occidentale I h I hStipa richardsonii I hStreptopus amplexifolius I hTaraxacum officinale I h I h I + I h I h I h II h II +Thalictrum venulosum II 2Thamnolia vermicularis II h I hCode 111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Number of sample plots 4 14131011311010171014 9 9 9 15Number of plant species 62 101 111 41 72 78 87 103 119 102 112 87 81 115 103Species Species presence and species significance167APPENDICESAppendix 1Trembling Aspen EcosystemsTomentypnum nitens II hTortula ruraliformis II h I hTrifolium pratense I h I +Trifolium repens I h II h I hTrillium ovatum I h I hTrimorpha acris  I hTrisetum cernuum I h I h I h I h I + I h II h I hUrtica dioica I +Vaccinium membranaceum I h I h I h II + I h I h I h I hVaccinium scoparium I 2Viola lanceolata I hViola orbiculata I h I h I hViola palustris I h I h I h I hViola septentrionalis I h I h II hVulpia microstachys I h I hZigadenus elegans I h1 Species presence and significance classes defined in Table 4 on pag e12.Code 111 112 113 210 221 222 223 310 411 412 421 422 423 424 425Number of sample plots 4 14131011311010171014 9 9 9 15Number of plant species 62 101 111 41 72 78 87 103 119 102 112 87 81 115 103Species Species presence and species significance168APPENDICESAppendix 2Scientica Silvica Extension Series, Number 27, 2000Appendix 2. Plot vegetation table for the 111 Populus tremuloides – Mertensia paniculata: Festuca altaica subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.1234SpeciesSpecies significance22 Species significance classes see Table 4 on page12 .Epilobium angustifolium 7++4Galium boreale +242Populus tremuloides 7769Rosa acicularis 43+4Shepherdia canadensis 6365Arctostaphylos uva-ursi 446Delphinium glaucum ++2Festuca altaica 284Fragaria virginiana +++Geocaulon lividum 42 +Juniperus communis 665Linnaea borealis 53 3Pleurozium schreberi 44 2Salix scouleriana 447Viburnum edule 53 7Achillea millefolium ++Mertensia paniculata +3Orthilia secunda Pulsatilla patens ++Pedicularis labradorica ++Trisetum spicatum ++Abies lasiocarpa 4Amelanchier alnifolia 3Antennaria neglecta +Aquilegia formosa +Aster sibiricus +Cladonia borealis  3Calamagrostis canadensis +Cladina arbuscula ssp. mitis +Cladina stellaris +Cladonia cornuta +Cladonia crispata +Cladonia ecmocyna +Cladonia gracilis +Cladonia ochrochlora +Cladonia phyllophora +Cladonia pyxidata +Drepanocladus uncinatus 4Empetrum nigrum +Flavocetraria nivalis +Gentianella amarella +Hylocomium splendens +Lupinus arcticus 4Moehringia lateriflora +Osmorhiza berteroi  +Parmelia saxatilis +Peltigera aphthosa +Peltigera membranacea +Picea glauca 3Pinus contorta +Plagiomnium ciliare +Polemonium boreale 2Ptilidium pulcherrimum +Rhizomnium glabrescens +Saxifraga tricuspidata 2Solidago spathulata +Stereocaulon tomentosum 1Thamnolia vermicularis +Tomentypnum nitens +Vaccinium vitis-idaea 569APPENDICESAppendix 3Trembling Aspen EcosystemsAppendix 3. Plot vegetation table for the 112 Populus tremuloides – Mertensia paniculata:  Arnica cordifolia subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number15 6 7 8 9 10 11 12 13 14 15 16 17 18Species Species significance2Hylocomium splendens 687+7237776++6Populus tremuloides 87677876787786Shepherdia canadensis 4757668657765Arnica cordifolia 4+5+++36 ++++Epilobium angustifolium 3+737742 +62+Geocaulon lividum 4+3++++33++ +Linnaea borealis 5475+3 4+562+Orthilia secunda 4+++++++ + +++Rosa acicularis 2+ 3335 25+46+Picea glauca 6764545 766 5Mertensia paniculata 3+++3533 +4Pleurozium schreberi 778+ +5674 9Viburnum edule 5434343+ 4 +Cornus canadensis +47 35555 +Delphinium glaucum +++ ++ 3 ++Goodyera repens ++ + ++++ +Achillea millefolium + ++++++Picea mariana 5444554Fragaria virginiana +5++++Lupinus arcticus ++4+3Osmorhiza berteroi + +++3Salix scouleriana 2375Abies lasiocarpa 6553Festuca altaica +++3Juniperus communis +5+6Peltigera aphthosa ++ 44Arctostaphylos uva-ursi 447Dicranella palustris +++Peltigera membranacea 2+ +Platanthera obtusata ++Populus balsamifera +35Ptilium crista-castrensis 5+ +Pyrola elliptica ++ +Pyrola minor 3Rhizomnium glabrescens +++Actaea rubra ++Amelanchier alnifolia Castilleja sulphurea ++Cladonia ecmocyna ++Corallorhiza trifida ++Dicranum scoparium Elymus glaucus ++Empetrum nigrum ++Galium boreale Goodyera oblongifolia Ledum groenlandicum 43Lobaria pulmonaria ++Lycopodium annotinum +5Oryzopsis asperifolia +3Pedicularis labradorica 3+Peltigera scabrosa ++Pinus contorta 47Rhytidiadelphus triquetrus 7+Ribes lacustre Spiraea betulifolia 4+Alnus viridis 2Adoxa moschatellina +70APPENDICESAppendix 3Scientica Silvica Extension Series, Number 27, 2000Aralia nudicaulis +Arctostaphylos alpina +Aster conspicuus 3Aster sibiricus +Calamagrostis canadensis +Calamagrostis rubescens +Carex spectabilis +Castilleja miniata +Cerastium arvense +Cladina arbuscula +Cladina stellaris +Cladonia multiformis +Clintonia uniflora 3Deschampsia cespitosa +Dicranum fragilifolium +Dicranum fuscescens +Dicranum polysetum 4Drepanocladus uncinatus +Equisetum scirpoides +Festuca occidentalis +Galium trifidum +Juniperus horizontalis 3Leymus innovatus 6Lonicera involucrata 5Lycopodium complanatum +Maianthemum racemosum 1Pulsatilla patens +Peltigera praetextata +Petasites frigidus +Platanthera orbiculata +Pseudotsuga menziesii 6Salix bebbiana 3Salix glauca 6Solidago spathulata +Stellaria calycantha +Trisetum cernuum +Vaccinium caespitosum 4Vaccinium membranaceum +Vaccinium scoparium 5Vaccinium vitis-idaea 2Vicia americana +Zigadenus elegans +1 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes defined in Table 4 on page 12.Plot number15678910112131415161718Species Species significance271APPENDICESAppendix 4Trembling Aspen EcosystemsAppendix 4. Plot vegetation table for the 113 Populus tremuloides – Mertensia paniculata: Petasites frigidus subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number119 20 21 22 23 24 25 26 27 28 29 30 31Species Species significance2Populus tremuloides 5776696787597Linnaea borealis 24 45557234+Rosa acicularis +++++246+22Hylocomium splendens 67 99787 895Shepherdia canadensis 4 + ++34 ++52Cornus canadensis 7776 +66 + 4Petasites frigidus +33332+6 4Pleurozium schreberi 7875666 76Epilobium angustifolium 63 3 33++3Geocaulon lividum +4+ +++ +3Lupinus arcticus 354444+ 2Mertensia paniculata 43+33+++Picea glauca 56 347 653Picea mariana 7 6643 6 55Achillea millefolium +++++Festuca altaica +33+ 2+Galium boreale ++ +3+ 3+Salix scouleriana 533 55 4 4Vaccinium vitis-idaea 2543 4 +4Viburnum edule 333 74 +3Fragaria virginiana ++4+4 2Mitella nuda + +++3+Orthilia secunda + +++++Ptilium crista-castrensis 53 +5 + 4Goodyera repens 3+ +Peltigera membranacea 11 5 42Pinus contorta 67 665Arnica cordifolia +34 4Empetrum nigrum 3+ + 5Ledum groenlandicum 45 5+Pedicularis labradorica ++ + +Peltigera aphthosa ++ 3 4Pyrola minor ++ + +Betula nana ++ +Abies lasiocarpa 1+Arctostaphylos alpina Arctostaphylos uva-ursi 5+Aster conspicuus 56Aulacomnium palustre ++Calypso bulbosa ++Cladina stellaris Delphinium glaucum 2+Dicranella palustris 3+Equisetum scirpoides ++Galium triflorum Leymus innovatus 45Platanthera obtusata ++Platanthera orbiculata Populus balsamifera 5+Pyrola elliptica ++Rubus pedatus 3+Rubus pubescens Salix bebbiana 33Thamnolia vermicularis ++Vaccinium caespitosum 65Viola lanceolata ++Alnus incana 272APPENDICESAppendix 4Scientica Silvica Extension Series, Number 27, 2000Alnus viridis 7Actaea rubra 3Amelanchier alnifolia 2Aralia nudicaulis 4Aster ciliolatus 1Aster sibiricus +Betula papyrifera 2Botrychium virginianum +Calamagrostis rubescens 7Cladonia cornuta +Cladonia ecmocyna +Cladonia multiformis 1Corallorhiza trifida +Cornus stolonifera +Dicranum polysetum +Elymus glaucus +Elymus repens +Elymus smithii +Epilobium ciliatum 4Equisetum arvense +Equisetum pratense +Equisetum sylvaticum +Festuca subuliflora +Geranium richardsonii 2Goodyera oblongifolia +Juniperus communis +Lathyrus nevadensis +Lathyrus ochroleucus 3Lonicera involucrata 3Lycopodium annotinum +Maianthemum racemosum 4Maianthemum canadense 4Osmorhiza berteroi 4Oryzopsis asperifolia +Poa palustris +Peltigera scabrosa 2Polemonium caeruleum +Pyrola asarifolia +Pyrola chlorantha +Rhytidiadelphus squarrosus +Rhytidiadelphus triquetrus 4Ribes lacustre 2Ribes triste 2Rubus idaeus +Salix sp. 2Salix myrtillifolia +Solidago spathulata +Taraxacum officinalis +Thalictrum occidentale 6Trisetum cernuum +Vaccinium membranaceum +Vicia americana +Viola palustris +1 Plot numbers have been simplified in this report. See Appendix 32 on page112  for original plot codes.2 Species significance classes defined in Table 4 on page12 .Plot number119 20 21 22 23 24 25 26 27 28 29 30 31Species Species significance273APPENDICESAppendix 5Trembling Aspen EcosystemsAppendix 5. Plot vegetation table for the 210 Populus tremuloides – Ledum groenlandicum association. Species are arranged in order of decreasing presence and alphabetically.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.32 33 34 35 36 37 38 39 40 41Species Species significance22 Species significance classes defined in Table 4 on page12 .Populus tremuloides 8998877799Cornus canadensis 4444566554Ledum groenlandicum 6467767767Petasites palmatus 22+4444433Spiraea betulifolia 3334334+24Vaccinium myrtilloides 7777655577Vaccinium vitis-idaea 5554444255Linnaea borealis 222 344323Polytrichum juniperinum 434 ++3343Epilobium angustifolium 23+ 2 4522Geocaulon lividum 332333 43Lycopodium complanatum 44454565Pleurozium schreberi 435 44344Abies lasiocarpa 3222 22 +Cladina rangiferina 545 53 45Melampyrum lineare 22+ 323 +Peltigera aphthosa 444 43 44Salix sp. 2223 343Picea glauca 65465Picea mariana 4444 44Calamagrostis canadensis + 2334Elymus innovatus 322 3+Lycopodium clavatum 44435Maianthemum canadense 3+443Pinus contorta 4424 4Stereocaulon tomentosum 33 + 3Lathyrus ochroleucus 32 44Tortula ruraliformis ++ ++Lycopodium obscurum 4+Alnus viridis 33Arctostaphylos uva-ursi 44Rosa acicularis 34Aster ciliolatus +Betula papyrifera +Castilleja hyetophila +Cladonia crispata 2Equisetum pratense +Hylocomium splendens +Juniperus communis +Shepherdia canadensis 4Vaccinium caespitosum 474APPENDICESAppendix 6Scientica Silvica Extension Series, Number 27, 2000Appendix 6. Plot vegetation table for the 221 Populus tremuloides – Lathyrus ochroleucus: Hedysarum boreale subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number142 43 44 45 46 47 48 49 50 51 52Species Species significance2Populus tremuloides 79899898889Elymus innovatus 6464666343Lathyrus ochroleucus 5343444334Maianthemum canadense 4232454442Linnaea borealis 42 +2++ 44+Picea glauca 55 643 4446Rosa acicularis 44344 4444Aster conspicuus 63334744Calamagrostis canadensis 24 422 443Galium boreale 44444454Vaccinium myrtilloides 65 434 454Achillea millefolium 222+2 3+Fragaria virginiana 222334 2Hedysarum boreale 4+43643Salix sp. 45 4 4 346Shepherdia canadensis 34 44Amelanchier alnifolia 42 6544Oryzopsis asperifolia 45454 4Vaccinium vitis-idaea +233 5 3Vicia americana 42+2 54Arctostaphylos uva-ursi 6 4656Epilobium angustifolium 3 2 244Petasites frigidus 42 44+Aster ciliolatus 2+3 2Cornus canadensis 476Ledum groenlandicum 46 6Spiraea betulifolia 3324Anemone multifida 2++Bromus inermis 34+Castilleja hyetophila 222Pyrola asarifolia 32 3Rubus pubescens 244Symphoricarpos albus 32 4Abies lasiocarpa 43Alnus viridis ssp. fruticosa 44Asterella lindenbergiana 32Hylocomium splendens +6Lycopodium obscurum 44Platanthera orbiculata 3+Apocynum androsaemifolium 6Arabis holboellii +Aralia nudicaulis 4Aster modestus 2Calliergon stramineum 6Calypso bulbosa +Carex disperma +Cinna latifolia +Coeloglossum viride +Cornus stolonifera 5Epilobium ciliatum +Equisetum pratense 7Geum macrophyllum 2Lonicera involucrata +Maianthemum stellatum +Melampyrum lineare 2Mitella nuda +Osmorhiza berteroi +75APPENDICESAppendix 6Trembling Aspen EcosystemsOrthilia secunda +Picea mariana 5Pinus contorta 2Plagiomnium drummondii 7Platanthera obtusata +Pleurozium schreberi +Ranunculus eschscholtzii +Ribes triste 2Schizachne purpurascens 2Tortula ruraliformis +Viburnum edule 5Viola renifolia +1 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.2 Species significance classes defined in Table 4 on page12 .Plot number142 43 44 45 46 47 48 49 50 51 52Species Species significance276APPENDICESAppendix 7Scientica Silvica Extension Series, Number 27, 2000Appendix 7. Plot vegetation table for the 222 Populus tremuloides – Lathyrus ochroleucus: typic subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number153 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83Species Species significance2Populus tremuloides 8978988799877999797898777888977Rosa acicularis 6656344574666665446665554453454Cornus canadensis 364 4544455554476755557644 3764Epilobium angustifolium 4623435544624443 3644444 555542Lathyrus ochroleucus 534324434333+ +33243+3 33333333Linnaea borealis 42+3333 4444444444443443 23534Viburnum edule 45554 44544555534+344 664 42355Rubus pubescens 224432444434 43444 434444333 4Salix sp. 344434 3 465445445344 43 443435Pyrola asarifolia 23 443423353424 44544442 3632Maianthemum canadense 42+4422+24544 3334354 443 2Shepherdia canadensis 5544 25 4 44555455435 464232Galium boreale 3242 4332 33323 323 2433 34Hylocomium splendens 2 3 2+ 4 3334554223544+ 43Picea glauca 4544 46 244645334544+2 5Elymus innovatus 542++63354 544444 55 5 5Aster conspicuus 4445 2 6 4322+ 3 3654453Fragaria virginiana ++33 4443 33 3 3+22 4233Calamagrostis canadensis + 42+342 3 4442343443Orthilia secunda ++22322+333 ++33++Petasites frigidus 3 33464442 2 4 3 3 4 2 24Mertensia paniculata 4+43 2 4 32 2 2442 3Alnus viridis 35 65 454 534 44Aralia nudicaulis 5 7 6 45 + 5445 4 4Ledum groenlandicum + 46 + 6 666+ 5 + 2Vaccinium vitis-idaea + 33+ 244 44454Lonicera involucrata 2 +23+ +++ +5+Spiraea betulifolia 4 54+3444 + 2 3Vicia americana ++4 + ++2 + + 2Amelanchier alnifolia +++ 2 2 2+ 32Betula papyrifera 33342 +Viola renifolia + 343 + ++ 2Equisetum pratense + + 222+ +Achillea millefolium +2 +2 +Arnica cordifolia 43 333 4Lycopodium clavatum 2 3 34 44Symphoricarpos albus 322 33 +Vaccinium myrtilloides 53 7 766Corallorhiza maculata +++++Cornus sericea +32+277APPENDICESAppendix 7Trembling Aspen Ecosystems  Rubus idaeus +4 2+ 2Aster ciliolatus 2+ 4 +Pinus contorta 25 5 3Populus balsamifera 344Galium triflorum ++ +Picea mariana 4 65Pleurozium schreberi + 34Ribes oxyacanthoides 3+ 2Ribes triste 2++Vaccinium caespitosum 32 2Actaea rubra Aster engelmannii 42Elymus glaucus 44Lycopodium annotinum 64Maianthemum racemosum ++Oryzopsis asperifolia 43Ptilium crista-castrensis 33Ribes lacustre +3Sorbus scopulina 34Taraxacum officinale +2Viola canadensis 3+Abies lasiocarpa 2Aquilegia brevistyla +Arctostaphylos uva-ursi 2Cladina rangiferina +Equisetum arvense +Heracleum maximum 2Lycopodium complanatum 5Osmorhiza berteroi 2Peltigera aphthosa +Platanthera orbiculata +Rubus parviflorus 2Schizachne purpurascens 41 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.2 Species significance classes as defined in Table 4 on page 12.Plot number153 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83Species Species significance278APPENDICESAppendix 8Scientica Silvica Extension Series, Number 27, 2000Appendix 8. Plot vegetation table for the 223 Populus tremuloides – Lathyrus ochroleucus: Actaea rubra subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number184 85 86 87 88 89 90 91 92 93Species Species significance2Populus tremuloides 9979888879Actaea rubra +5 4433322Cornus sericea 34+355645Galium triflorum 343 44434+Rosa acicularis 4444 5445+Viburnum edule 5 44556664Aralia nudicaulis 4 6444546Calamagrostis canadensis 33233444Epilobium angustifolium 343432 44Lonicera involucrata 62 333 254Pyrola asarifolia 3344444 +Cornus canadensis 24 34 553Delphinium glaucum 4 534344Equisetum pratense +332537Mertensia paniculata 542333 4Petasites frigidus 34 3344 +Aster conspicuus 44 54 55Lathyrus ochroleucus 344+ 2 4Picea glauca 34 4 3 + 7Rubus pubescens 4 45 242Amelanchier alnifolia +24 4 +Fragaria virginiana 233+Heracleum maximum 646 4 +Linnaea borealis +3 44 4Mitella nuda +32 44Osmorhiza berteroi 443 23Populus balsamifera 52 44 7Ribes oxyacanthoides 34534Viola canadensis 56 63 3Elymus innovatus +42+Galium boreale 2+4Ribes lacustre 443+Alnus viridis 55 4Botrychium virginianum ++ +Rubus idaeus 44Salix sp. 544Spiraea betulifolia +3 +Symphoricarpos albus 23Thalictrum venulosum 3+ 4Agropyron pauciflorum 2+Aquilegia brevistyla 33Maianthemum canadense 23Maianthemum racemosum 42Maianthemum stellatum +2Orthilia secunda 44Ribes triste 44Taraxacum officinale +3Alnus incana 4Achillea millefolium 2Arnica cordifolia 3Aster ciliolatus 2Betula papyrifera 5Betulaceae 4Bromus inermis +Calliergon stramineum +Clintonia uniflora +Cornus stolonifera 179APPENDICESAppendix 8Trembling Aspen EcosystemsDicranum scoparium +Disporum trachycarpum 2Drepanocladus uncinatus +Equisetum sylvaticum +Festuca subuliflora +Gymnocarpium dryopteris 6Hylocomium splendens 2Maianthemum racemosum 3Maianthemum stellatum 4Matteuccia struthiopteris +Moneses uniflora 4Paxistima myrsinites +Peltigera aphthosa +Pinus contorta 5Plagiomnium drummondii +Pleurozium schreberi +Pseudotsuga menziesii 5Ranunculus acris +Rubus parviflorus 3Shepherdia canadensis 4Solidago canadensis +Thalictrum occidentale 3Vicia americana +Viola renifolia 21 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes defined in Table 4 on page12 .Plot number184 85 86 87 88 89 90 91 92 93Species Species significance280APPENDICESAppendix 9Scientica Silvica Extension Series, Number 27, 2000Appendix 9. Plot vegetation table for the 310 Populus tremuloides – Thalictrum occidentale association. Species are arranged in order of decreasing presence and alphabetically.Plot number194 95 96 97 98 99 100 101 102 103Species Species significance2Populus tremuloides 8998987778Epilobium angustifolium +3+64+39+Picea glauca 66 93677 7Rosa acicularis 4645654 3Aster conspicuus 633 3++Fragaria virginiana +3+2+ +Galium boreale + +++ ++Thalictrum occidentale + + +542Viburnum edule 6 + 55 1+Achillea millefolium +++ ++Calamagrostis rubescens ++3+ 6Cornus canadensis ++4 +Equisetum pratense ++++Hylocomium splendens 4+336Linnaea borealis 5 +Lonicera involucrata +5+71Petasites frigidus +++5 +Pleurozium schreberi 2+256Rubus pubescens +4+4 +Vicia americana ++1++Actaea rubra 23Aster sibiricus ++ 4 +Elymus repens ++ + +Lathyrus nevadensis +++ +Ribes lacustre +362Aralia nudicaulis 264Bromus inermis 4++Calamagrostis canadensis ++ +Calliergon stramineum ++4Cornus stolonifera 2+6Galium triflorum +++Geranium richardsonii 3+2Orthilia secunda +++Salix scouleriana 456Viola canadensis ++ 4Alnus incana 45Arnica cordifolia Betula nana 6+Carex disperma ++Disporum hookeri +2Elymus glaucus ++Equisetum scirpoides Festuca subuliflora ++Hieracium umbellatum ++Maianthemum racemosum +2Maianthemum stellatum ++Mitella nuda 1+Osmorhiza berteroi ++Poa palustris ++Populus balsamifera 27Pyrola asarifolia 34Rhytidiadelphus triquetrus ++Salix glauca 87Senecio pseudaureus ++Shepherdia canadensis 7+Abies lasiocarpa 5Amelanchier alnifolia +81APPENDICESAppendix 9Trembling Aspen EcosystemsAntennaria pulcherrima 2Aquilegia formosa +Arctostaphylos uva-ursi +Aster ciliolatus +Betula papyrifera 3Carex obtusata        +    Carex rossii  5        Carex spectabilis   +         Castilleja miniata      +      Clintonia uniflora           + Dicranella palustris 2         Dicranum fuscescens     +       Drepanocladus uncinatus           + Epilobium ciliatum   +         Gentianella amarella   +         Glyceria elata   +         Goodyera oblongifolia           + Goodyera repens     +       Heracleum maximum         5 Lycopodium annotinum  +          Maianthemum trifolium   +         Maianthemum canadense  +          Mertensia paniculata  +          Oryzopsis asperifolia    +        Pulsatilla patens    +        Peltigera praetextata     +       Petasites sagittatus    +        Picea mariana          5Pinus contorta          5Platanthera orbiculata  +          Ptilium crista-castrensis         +   Pyrola minor   +         Ranunculus acris        +    Rubus idaeus         5 Salix sp.       6   Salix bebbiana  6        Salix lucida   5       Salix sitchensis      4    Spiraea betulifolia          6Stellaria calycantha         +   Taraxacum officinalis    +        Trisetum cernuum      +      Vaccinium membranaceum           + Viola palustris   +         Viola renifolia   +         1 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes defined in Table 4 on page12 .Plot number194 95 96 97 98 99 100 101 102 103Species Species significance282APPENDICESAppendix 10Scientica Silvica Extension Series, Number 27, 2000Appendix 10. Plot vegetation table for the 411 Populus tremuloides – Viburnum edule: Spiraea betulifolia subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120Species Species significance2Populus tremuloides 98899999897779789Rosa acicularis 5 2 1464564657+36Osmorhiza berteroi +44 +4++++++++ +Picea glauca 57556 56 +736785Thalictrum occidentale 432 3++34++++ ++Amelanchier alnifolia +336536655 3+ +Aralia nudicaulis 7644646353643Elymus glaucus ++++ +++++ ++ ++Cornus stolonifera 55455764 4+3 5Spiraea betulifolia 72356 43+++ 32Symphoricarpos albus 3+ 42335+465 4Viburnum edule 77376774 ++ 2 5Galium boreale 412++ ++++ + +Linnaea borealis 31 +++ +++ +++Rubus parviflorus 56 633 4 ++5 27Rubus pubescens 45 1333 1+++ +Aster conspicuus 64552 35 ++6Clintonia uniflora 61 43+ 5 ++ 2+Cornus canadensis 523443++++Disporum hookeri +45 52+ 46 ++Fragaria virginiana 2+ ++3 ++++ +Lonicera involucrata 274541+ 5 +2Maianthemum racemosum 45+2443+ 44Epilobium angustifolium +24 243+ +4Maianthemum stellatum +41+2 + +++Pleurozium schreberi 55332 3+ 65Ribes lacustre 144 33 + ++Achillea millefolium ++ ++++ +Actaea rubra 2+4125 +Aster ciliolatus 422++++Lathyrus ochroleucus 41 4+42 2Abies lasiocarpa 2566 5 5Mitella nuda +++ + + +Pyrola asarifolia + +++Shepherdia canadensis 754+25Calamagrostis canadensis +1 + + +Galium triflorum ++ + + +Oryzopsis asperifolia Petasites frigidus 21 + 2 1Vicia americana ++4 + +Alnus incana 55 56Aquilegia formosa ++ + +Arnica cordifolia ++ + +Goodyera oblongifolia ++ + +Orthilia secunda +2Paxistima myrsinites 7+ 85Pseudotsuga menziesii 567Ptilium crista-castrensis 4263Rhytidiadelphus triquetrus 1+2Sorbus scopulina ++ +2Vaccinium membranaceum 124 +Alnus viridis 66 6Calamagrostis rubescens ++ 5Cinna latifolia +++Heracleum maximum +4 4Salix scouleriana 264Viola canadensis ++4Aster modestus 1+Aster sibiricus 3+Betula papyrifera 6283APPENDICESAppendix 10Trembling Aspen EcosystemsBromus inermis ++Equisetum arvense ++Eurhynchium pulchellum ++Festuca occidentalis Festuca subuliflora ++Gymnocarpium dryopteris 75Hylocomium splendens 43Lathyrus nevadensis ++Lilium columbianum ++Lycopodium annotinum 5+Mahonia aquifolium 66Malus fusca ++Ribes triste 33Rubus idaeus ++Sambucus racemosa ++Trisetum cernuum ++Viola palustris +2Adoxa moschatellina +Angelica genuflexa +Apocynum androsaemifolium +Athyrium filix-femina 3Calliergon stramineum +Carex disperma +Castilleja miniata 1Clematis occidentalis +Corylus cornuta 7Deschampsia cespitosa +Dicranella palustris +Dicranum fuscescens +Drepanocladus uncinatus +Equisetum pratense +Fritillaria affinis +Geocaulon lividum +Geranium richardsonii +Listera cordata +Lobaria pulmonaria +Lonicera utahensis +Mertensia paniculata +Oplopanax horridus 4Peltigera aphthosa +Peltigera praetextata +Pinus contorta 6Plagiomnium drummondii 1Plagiomnium medium +Platanthera orbiculata +Prunus virginiana 5Pyrola minor +Ranunculus acris +Rhytidiadelphus squarrosus 4Salix bebbiana 6Solidago canadensis +Spiraea douglasii 5Stellaria calycantha +Streptopus amplexifolius 1Taraxacum officinalis +Trifolium pratense +Viola septentrionalis 2Vulpia microstachys +1 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.2 Species significance classes defined in Table 4 on pag e12.Plot number1104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120Species Species significance284APPENDICESAppendix 11Scientica Silvica Extension Series, Number 27, 2000Appendix 11. Plot vegetation table for the 412 Populus tremuloides – Viburnum edule: Paxistima myrsinites subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1121 122 123 124 125 126 127 128 129 130Species Species Significance2Paxistima myrsinites 6785677555Populus tremuloides 7789777767Aralia nudicaulis +4634++23Rubus parviflorus +35+65454Clintonia uniflora ++++ 3+ 42Cornus canadensis +++ 3+532Cornus stolonifera 3674635+Rosa acicularis 33+44645Viburnum edule 533 4335+Rhytidiadelphus triquetrus +1+3++5Betula papyrifera +8 5 75 6Elymus glaucus + + ++++Epilobium angustifolium ++ ++++Linnaea borealis +337+4Lonicera involucrata 42+3 3 +Maianthemum racemosum +434+ +Osmorhiza berteroi ++3+ + +Pyrola asarifolia +++ 3++Symphoricarpos albus ++ + 3++Amelanchier alnifolia 2+ + 3+Corylus cornuta 77753Lathyrus ochroleucus 433 3+Orthilia secunda +++ ++Pleurozium schreberi +23++Ptilium crista-castrensis + ++++Rubus pubescens +++ 33Thuja plicata +63 67Tsuga heterophylla 35352Acer glabrum 2 256Adoxa moschatellina ++++Arnica cordifolia ++++Hylocomium splendens +++2Picea glauca 3344Sorbus scopulina +23+Disporum hookeri 44 3Galium boreale +3Galium triflorum ++ +Maianthemum stellatum ++Shepherdia canadensis 3+3Thalictrum occidentale +4 3Vicia americana +++Abies lasiocarpa 22Aster ciliolatus ++Aster conspicuus ++Calamagrostis canadensis ++Fragaria virginiana Goodyera oblongifolia ++Goodyera repens ++Lobaria pulmonaria ++Lycopodium complanatum ++Mahonia aquifolium +1Mitella nuda ++Petasites frigidus Platanthera orbiculata ++Pyrola elliptica ++Sanicula marilandica ++Vaccinium membranaceum 85APPENDICESAppendix 11Trembling Aspen EcosystemsAlnus viridis 5Actaea rubra +Alectoria sarmentosa +Aster sibiricus 4Chimaphila umbellata 3Cinna latifolia +Dicranella palustris +Dicranum fuscescens +Dicranum scoparium +Equisetum sylvaticum +Eurhynchium pulchellum +Festuca occidentalis +Geocaulon lividum +Gymnocarpium dryopteris 6Hypopitys monotropa +Larix occidentalis 6Lathyrus nevadensis 5Lycopodium dendroideum +Malus fusca 3Melampyrum lineare +Pedicularis racemosa 2Peltigera aphthosa +Peltigera malacea 3Peltigera membranacea +Pinus contorta 7Pinus monticola 5Plagiomnium drummondii +Populus balsamifera 6Pseudotsuga menziesii 6Rhizomnium glabrescens +Rhododendron albiflorum +Rhytidiadelphus squarrosus +Ribes lacustre +Rosa nutkana 2Rubus idaeus +Salix glauca +Spiraea betulifolia 3Stellaria calycantha +Stenanthium occidentale +Trisetum cernuum 3Viola orbiculata +Viola renifolia +Viola septentrionalis +Vulpia microstachys +1 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes defined in Table 4 on page12 .Plot number1121 122 123 124 125 126 127 128 129 130Species Species Significance286APPENDICESAppendix 12Scientica Silvica Extension Series, Number 27, 2000Appendix 12. Plot vegetation table for the 421 Populus tremuloides – Rosa nutkana: Aralia nudicaulis subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1131 132 133 134 135 136 137 138 139 140 141 142 143 144Species Species significance2Populus tremuloides 78789999988877Elymus glaucus 3+++++3+ ++Festuca subuliflora +++++235 2+Osmorhiza berteroi +3++1+ + + 44Aralia nudicaulis 5776 22 11 6Cornus canadensis 35+275 7 + 6Symphoricarpos albus +5 4+ 4+4++Acer glabrum +375 +37+Clintonia uniflora 31333 ++ +Rubus parviflorus 6573+ + 67Alnus incana 65645 66Cornus stolonifera 63+33 + 6Galium trifidum 3 +++ + ++Maianthemum stellatum 3+ +63 2Picea glauca 555555 6Populus balsamifera 76666 6 6Ranunculus acris +++2+ 2+Rosa nutkana +++ 2+ ++Amelanchier alnifolia +34++ 3Betula papyrifera 67 6 3 4 2Calamagrostis canadensis 7 7968 +Pinus contorta 4756 75Tiarella trifoliata + 2++++Adenocaulon bicolor 6+46Arnica cordifolia 273 +2Athyrium filix-femina +22 3 +Calamagrostis rubescens 53+ 2 +Equisetum pratense +++1Fragaria virginiana ++ 2Linnaea borealis 3+ ++Solidago canadensis +2Spiraea betulifolia +++ 43Thuja plicata 3 7895Pteridium aquilinum 563 +Pyrola asarifolia 23 3+Ribes lacustre 4+3Senecio pseudaureus ++4+Viola renifolia ++4 +Aconitum columbianum ++ 3Anaphalis margaritacea ++ 2Equisetum sylvaticum +++Galium boreale 4++Lonicera utahensis 573Maianthemum racemosum 6+ +Mahonia aquifolium 1+ +Paxistima myrsinites 52Poa palustris ++2Pinus monticola 455Prunella vulgaris 5Rosa acicularis 44 5Rubus idaeus 2+ 2Vaccinium caespitosum +2 +Vicia americana 4+ +Actaea rubra ++Agrostis mertensii ++Calliergon giganteum Chimaphila umbellata +387APPENDICESAppendix 12Trembling Aspen EcosystemsDicranum fuscescens ++Disporum hookeri 5+Epilobium angustifolium ++Equisetum arvense ++Frangula purshiana +4Heracleum maximum 33Larix occidentalis 56Lonicera involucrata 33Peltigera praetextata ++Phleum pratense ++Pseudotsuga menziesii 4+Rhytidiadelphus triquetrus 6+Taraxacum officinalis ++Thalictrum occidentale +2Trillium ovatum ++Trisetum cernuum ++Trisetum spicatum ++Abies lasiocarpa 4Achillea millefolium +Aster conspicuus +Botrychium lunaria +Bromus inermis +Calliergon stramineum +Campanula rotundifolia +Cladonia phyllophora +Corallorhiza trifida +Crataegus douglasii 2Dactylis glomerata +Glyceria elata 3Gymnocarpium dryopteris +Hieracium scouleri +Hylocomium splendens 3Lathyrus nevadensis 3Oplopanax horridus +Orthilia secunda +Plagiothecium sp. +Poa nemoralis +Peltigera aphthosa +Petasites frigidus +Piperia unalascensis +Plagiomnium drummondii +Plagiomnium medium +Pleurozium schreberi 2Polytrichum strictum +Ptilium crista-castrensis 1Rubus pubescens 3Salix sp. +Shepherdia canadensis +Trifolium repens +Tsuga heterophylla 3Vaccinium membranaceum +Viburnum edule 41 Plot numbers have been simplified in this report. See Appendix 32 on page112  for original plot codes.2 Species significance classes defined in Table 4 on page12 .Plot number1131 132 133 134 135 136 137 138 139 140 141 142 143 144Species Species significance288APPENDICESAppendix 13Scientica Silvica Extension Series, Number 27, 2000Appendix 13. Plot vegetation table for the 422 Populus tremuloides – Rosa nutkana: Arnica cordifolia subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1145 146 147 148 149 150 151 152 153Species Species significance2Populus tremuloides 877877979Rubus parviflorus 43 +266+4Osmorhiza berteroi 3++ + ++3Pseudotsuga menziesii 546 664 7Arnica cordifolia 6354 ++Betula papyrifera 6 +776 +Elymus glaucus +++++ +Galium trifidum +++ ++ +Spiraea betulifolia 2+ 3 2+1Acer glabrum 4+ 376Calamagrostis rubescens 65 4+6Chimaphila umbellata 2+ ++5Clintonia uniflora +554+Linnaea borealis +555+Mahonia aquifolium 4+2++Shepherdia canadensis 34 36 3Cornus stolonifera 34 + 3Festuca subuliflora ++ ++Paxistima myrsinites +2 43Pinus monticola 67 6+Rosa nutkana 32++Symphoricarpos albus ++2Vaccinium caespitosum 2688Alnus incana 32 6Alnus viridis 56 6Adenocaulon bicolor 44+Amelanchier alnifolia +32Apocynum androsaemifolium 423Cornus canadensis 756Hieracium scouleri +++Larix occidentalis 66 5Peltigera praetextata +++Picea glauca 56 6Pinus contorta 665Abies lasiocarpa 27Achillea millefolium ++Anaphalis margaritacea ++Aralia nudicaulis 66Aster ciliolatus 3+Calamagrostis canadensis ++Calliergon giganteum ++Calliergon stramineum Corallorhiza trifida ++Disporum hookeri 41Fragaria virginiana ++Lilium columbianum ++Maianthemum racemosum 32Orthilia secunda ++Polytrichum strictum ++Pteridium aquilinum 54Rosa acicularis ++Thalictrum occidentale +4Thuja plicata +5Tsuga heterophylla 67Viola renifolia ++Actaea rubra 1Anemone parviflora +89APPENDICESAppendix 13Trembling Aspen EcosystemsAngelica genuflexa +Aquilegia formosa +Aster conspicuus 4Castilleja miniata +Ceanothus velutinus 2Cladonia multiformis +Dicranum fuscescens +Dicranum scoparium +Epilobium angustifolium +Equisetum arvense +Geocaulon lividum +Goodyera oblongifolia +Lonicera involucrata +Lonicera utahensis +Mertensia paniculata +Peltigera malacea +Pleurozium schreberi +Polytrichum juniperinum +Populus balsamifera 4Pyrola minor +Ranunculus acris +Senecio pseudaureus +Solidago canadensis +Trillium ovatum +Trisetum spicatum +Vaccinium membranaceum +Viola canadensis +Viola orbiculata +1 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes as defined in Table 4 on page 12.Plot number1145 146 147 148 149 150 151 152 153Species Species significance290APPENDICESAppendix 14Scientica Silvica Extension Series, Number 27, 2000Appendix 14. Plot vegetation table for the 423 Populus tremuloides – Rosa nutkana: Angelica genuflexa subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1154 155 156 157 158 159 160 161 162Species Species significance2Populus tremuloides 889998878Amelanchier alnifolia 56667652Aster conspicuus 3++ 44+2+Lilium columbianum +++++2 ++Osmorhiza berteroi ++2 452+2Thalictrum occidentale 464 54565Angelica genuflexa 22+3 +66Maianthemum racemosum +5 3 3444Maianthemum stellatum +++++24Symphoricarpos albus 367466 1Calamagrostis canadensis ++ ++++Disporum hookeri 56556 3Galium triflorum +++3++Mahonia aquifolium 52 3++2Rosa nutkana 23 64+ 2Rubus parviflorus 77766 3Actaea rubra 453 5+Clintonia uniflora +2 61+Pseudotsuga menziesii 67 636Viola canadensis 42 ++ +Cornus stolonifera +5 4 4Elymus glaucus ++++Picea glauca 5 653Spiraea betulifolia 325Acer glabrum 53 +Arnica cordifolia 3++Aster ciliolatus +++Calliergon giganteum +1Festuca subuliflora +++Fragaria virginiana 24+Lonicera involucrata 47+Lonicera utahensis 461Trisetum cernuum ++ +Alnus incana 67Adenocaulon bicolor 12Aquilegia formosa 4+Chimaphila umbellata ++Galium boreale Goodyera oblongifolia Paxistima myrsinites 57Pinus contorta 47Pteridium aquilinum 65Pyrola asarifolia ++Ranunculus acris ++Ribes lacustre ++Rubus idaeus +5Salix lucida ++Salix scouleriana 25Senecio pseudaureus ++Sorbus scopulina +2Viburnum edule 33Viola septentrionalis ++Alnus viridis 4Abies lasiocarpa 6Achillea millefolium +Aralia nudicaulis 3Calamagrostis rubescens +91APPENDICESAppendix 14Trembling Aspen EcosystemsCalliergon stramineum +Campanula rotundifolia +Cinna latifolia +Clematis occidentalis 2Cypripedium montanum +Dicranum fuscescens +Epilobium angustifolium 2Equisetum pratense +Festuca occidentalis +Hieracium scouleri +Listera convallarioides +Orthilia secunda 1Pedicularis bracteosa +Pedicularis racemosa 4Peltigera malacea +Populus balsamifera 5Pyrola chlorantha +Salix bebbiana 2Senecio triangularis 4Shepherdia canadensis 6Solidago canadensis +Urtica dioica 3Viola palustris +1 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes defined in Table 4 on pag e12.Plot number1154 155 156 157 158 159 160 161 162Species Species significance292APPENDICESAppendix 15Scientica Silvica Extension Series, Number 27, 2000Appendix 15. Plot vegetation table for the 424 Populus tremuloides – Rosa nutkana: Senecio pseudoaureus subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1163 164 165 166 167 168 169 170 171Species Species significance2Populus tremuloides 989777789Calamagrostis rubescens 468662+ 6Elymus glaucus ++++ +2+2Amelanchier alnifolia 22+++4 +Mahonia aquifolium +462++1Pseudotsuga menziesii 53+2766Rosa nutkana 322 +++6Senecio pseudaureus ++++ 3++Fragaria virginiana ++3 +++Galium trifidum +++ +++Osmorhiza berteroi ++++1+Pinus contorta 457625Symphoricarpos albus 52 6465Alnus viridis 3+ 7 63Festuca subuliflora +22 +1Paxistima myrsinites + 426 +Spiraea betulifolia 32 ++ 2Thalictrum occidentale 523 +5Achillea millefolium + ++3Aster ciliolatus 222Aster conspicuus +3 52Cornus canadensis 56 4+Maianthemum racemosum 1361Maianthemum stellatum +1 + 2Picea glauca 53 6 6Ranunculus acris +++ +Rubus parviflorus +66+Shepherdia canadensis +++ 8Viola renifolia +++Acer glabrum 17 2Cornus stolonifera +77Hieracium scouleri ++ +Juniperus communis 552Linnaea borealis 26 +Viola canadensis ++2Arctostaphylos uva-ursi 64Arnica cordifolia 4+Athyrium filix-femina ++Corallorhiza trifida ++Dactylis glomerata +4Disporum hookeri +1Drepanocladus uncinatus 1+Epilobium angustifolium 2+Equisetum pratense ++Leucanthemum vulgare ++Lilium columbianum Lonicera utahensis 56Lupinus arcticus 45Medicago sativa +5Orthilia secunda ++Polytrichum strictum Prunella vulgaris ++Stellaria calycantha ++Taraxacum officinalis ++Thuja plicata 52Trifolium repens ++Actaea rubra 593APPENDICESAppendix 15Trembling Aspen EcosystemsAdenocaulon bicolor +Agoseris aurantiaca +Allium cernuum +Anaphalis margaritacea +Angelica genuflexa +Antennaria microphylla +Antennaria neglecta +Aralia nudicaulis 6Asplenium viride +Betula papyrifera +Botrychium lunaria +Calamagrostis canadensis 5Calliergon giganteum +Calochortus apiculatus +Campanula rotundifolia +Carex concinna +Chimaphila umbellata +Cinna latifolia +Cladonia multiformis +Clintonia uniflora +Cypripedium montanum +Dicranum fuscescens +Dicranum scoparium +Dryopteris expansa +Dryopteris fragrans +Elymus repens +Equisetum hyemale +Galium boreale 3Gentianella amarella +Heracleum maximum +Lathyrus ochroleucus 3Letharia vulpina +Lonicera involucrata +Mertensia paniculata +Penstemon procerus +Poa palustris +Peltigera aphthosa +Peltigera praetextata +Phleum pratense +Pinus monticola 2Piperia unalascensis +Plagiomnium drummondii +Populus balsamifera 7Potentilla glandulosa +Pyrola chlorantha +Ribes lacustre 2Rosa acicularis +Salix scouleriana 3Saxifraga nelsoniana +Silene menziesii +Solidago spathulata 2Trisetum cernuum +Trisetum spicatum +Vaccinium caespitosum 4Vicia americana 21 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.2 Species significance classes as defined in Table 4 on page 12.Plot number1163 164 165 166 167 168 169 170 171Species Species significance294APPENDICESAppendix 16Scientica Silvica Extension Series, Number 27, 2000Appendix 16. Plot vegetation table for the 425 Populus tremuloides – Rosa nutkana: Shepherdia canadensis subassociation. Species are arranged in order of decreasing presence and alphabetically.Plot number1172 173 174 175 176 177 178 179 180 181 182 183 184 185 186Species Species significance2Populus tremuloides 778976697789777Calamagrostis rubescens +842+2+54578 +7Pinus contorta 76 4666 356 77Shepherdia canadensis 8+ 35623466 7Arctostaphylos uva-ursi 61 +75468 7Rosa nutkana 3+++ 432++Achillea millefolium + + 3++5 ++Fragaria virginiana ++ ++2+ ++Galium boreale ++322+++Juniperus communis 3766+673Linnaea borealis ++72 + +Orthilia secunda 3 +++2Taraxacum officinalis + 3 ++++Antennaria neglecta ++3+Aster conspicuus +226Elymus glaucus +++Pseudotsuga menziesii 7 6753Rosa acicularis 3+++ 2Salix glauca 23332Vicia americana +++ + +Allium cernuum +3 ++Amelanchier alnifolia ++Aster ciliolatus +2 + +Aster sibiricus 23+ +Epilobium angustifolium 3+ + +Festuca subuliflora +++ +Hieracium scouleri ++ ++Lathyrus ochroleucus +++2Mahonia aquifolium 443+Paxistima myrsinites 2+46Poa nemoralis ++++Pulsatilla patens +2 ++Symphoricarpos albus 33Agoseris aurantiaca ++ 1Castilleja miniata +3Chimaphila umbellata +34Elymus repens 4+3Gentianella amarella +++Lupinus arcticus 54 4Maianthemum racemosum +++Oryzopsis asperifolia 635Salix scouleriana ++Senecio pseudaureus ++ +Stipa richardsonii 2++Thalictrum occidentale ++ 3Agrostis mertensii Arnica cordifolia +1Campanula rotundifolia ++Dicranum fuscescens ++Dryopteris fragrans ++Goodyera oblongifolia ++Juniperus scopulorum 25Letharia vulpina Lonicera utahensis ++Medicago sativa 6+Osmorhiza berteroi ++Penstemon procerus 2+95APPENDICESAppendix 16Trembling Aspen EcosystemsPiperia unalascensis ++Pleurozium schreberi ++Potentilla glandulosa ++Solidago canadensis 2+Solidago spathulata Spiraea betulifolia ++Trisetum spicatum ++Viola canadensis Viola renifolia Alnus incana 6Acer glabrum 2Betula nana 4Botrychium lunaria +Bromus inermis +Calliergon stramineum 2Cladonia multiformis 2Corallorhiza trifida +Disporum hookeri +Festuca brachyphylla +Festuca occidentalis +Fritillaria affinis +Hedysarum sulphurescens 2Hylocomium splendens +Lathyrus nevadensis 1Lilium columbianum +Maianthemum stellatum +Melampyrum lineare +Peltigera aphthosa 2Peltigera malacea +Phleum pratense +Picea glauca 4Pogonatum contortum +Polytrichum juniperinum +Prunella vulgaris +Ribes lacustre +Rubus idaeus +Silene menziesii +Stellaria calycantha +Stenanthium occidentale +Trimorpha acris +Trifolium pratense 4Trifolium repens +Vaccinium membranaceum +Viola orbiculata +1 Plot numbers have been simplified in this report. See Appendix 32 on page112  for original plot codes.2 Species significance classes defined in Table 4 on pag e12.Plot number1172 173 174 175 176 177 178 179 180 181 182 183 184 185 186Species Species significance296APPENDICESAppendix 17Scientica Silvica Extension Series, Number 27, 2000Appendix 17. Selected environmental characteristics for plots of the 111 Populus tremuloides – Mertensia paniculata: Festuca altaica subassociation.Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on pag e112 for original plot codes.1234Zone/subzone BWBS dkBWBS dkBWBS dkBWBS dkSoil moisture regime22 Relative soil moisture regime: 1-xeric, 2-subxeric, 3-submesic, 4-mesic, 5-subhygric, 6-hygricActual soil moisture regime: VD-very dry, MD-moderately dry, SD-slightly dry, F-fresh, M-moist, VM-very moist,f-fluctuating water table2/MD 2/MD 2/MD 2/MDSoil nutrient regime33 VP-very poor, P-poor, M-medium, R-rich, VR-very richRMRRElevation (m) 950 850 780 770Slope gradient (%) 18 22 11 7Aspect4 4 N-north, E-east, S-south, W-west, F-flatSSWWForest floor thickness (cm) 9 11 6 9.5Textural class55 S-sand, SL-sandy loam, LS-loamy sand, L-loam, SiL-silt loam, CL-clay loam, SCL-sandy clay loam, SC-sandy clay, SiCL-silty clay loam, O-organicSL L SL LSActual rooting depth (cm) 60 40 40 60Potential rooting depth (cm) 65 40 55 75Seepage depth (cm) N/A66 N/A - not applicable; N/D - not determinedN/A N/A N/ASoil drainage7 7 R-rapid, W-well, M- moderately well, I-imperfect, P-poorWRWWHumus form group88 HR-Hemimor, UR-Humimor, YR-Hydromor, RD-Mormoder, TD-Leptomoder, MD-Mullmoder, YD-Hydromoder, VL-Vermimull, YL-HydromullTD RD TD TDSoil great group99 EB-Eutric Brunisol, DYB-Dystric Brunisol, MB-Melanic Brunisol, SB-Sombric Brunisol, GL-Grey Luvisol, GBL- Grey Brown Luvisol, HG-Humic Gleysol, G-Gleysol, LG-Luvic Gleysol, HFP-Humo-Ferric Podzol, FHP-Ferro-Humic Podzol, R-Regosol, HR-Humic Regosol, H-HumisolEB R DYB FHPStand age (years @ bh) 152 114 59 144Site index (m @ 50 yrs bh) 8 8.8 5.5 9.1Tree layer cover (%) 44 20 10 70Shrub layer cover (%) 43 33 20 64Herb layer cover (%) 33 2 55 11Mos layer cover (%) 650197APPENDICESAppendix 18Trembling Aspen EcosystemsAppendix 18. Selected environmental characteristics for plots of the 112 Populus tremuloides – Mertensia paniculata: Arnica cordifolia subassociation. * Abbreviations defined in Appendix 17 on pag e96.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on page112  for original plot codes.5 6 7 8 9 10 11 12 13 14 15 16 17 18Zone/subzone SBS dwBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkSBPS xcSoil moisture regime* 3/SD 2/MD 2/MD 2/MD 2/MD 2/MD 2/MD 2/MD 2/MD 2/MD 2/MD 3/SD 2/MD 3/MDSoil nutrient regime* MMMRMRRMMMMMMPElevation (m) 890 930 930 930 1005 970 980 910 950 720 800 780 770 1040Slope gradient (%) 4 27 18 33 33 27 31 27 0 4 18 31 9 7Aspect* EWWSSEESFESWWEForest floor thickness (cm) 13 22 12 12 14 17 18 13 8 5.5 5 9 8 5Textural clas* L LSLSLSLSLSSLSLSLSCLS L S LSActual rooting depth (cm) 50 60 60 70 60 60 60 60 40 50 40 40 60 50Potential rooting depth (cm) 60 60 60 70 60 60 60 60 50 55 55 58 75 50Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* W W W M M M W M W W W W W RHumus form group* HR UR HR TD RD TD TD RD HR HR HR RD HR HRSoil great group* HFP EB EB EB EB EB EB EB EB HFP FHP DYB DYB EBStand age (years @ bh) 120 151 N/D 139 N/D 160 164 154 90 94 67 138 143 69Site index (m @ 50 yrs bh) 14.8 10.5 N/D 10 N/D 11.5 11.5 12.9 11.9 14.8 12.9 10.4 11.5 15.5Tre layer cover (%) 9048273035723821606340405041Shrub layer cover (%) 14 13 25 29 37 19 17 52 13 16 51 77 76 24Herb layer cover (%) 8 13 32 31 3 27 31 15 19 11 3 13 3 3Moss layer cover (%) 41 86 90 0 61 1 6.2 37 62 23 10 0 0 9298APPENDICESAppendix 19Scientica Silvica Extension Series, Number 27, 2000Appendix 19. Selected environmental characteristics for plots of the 113 Populus tremuloides – Mertensia paniculata: Petasites frigidus subassociation.* Abbreviations defined in Appendix 17 on pag e96.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.19 20 21 22 23 24 25 26 27 28 29 30 31Zone/subzone SBS dwBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkBWBS dkSBPS xcSoil moisture regime* 4/Ff 4/SDf 4/SD 3/SD 3/SD 3/SDf 3/SDf 3/SDf 3/SD 3/SDf 3/SD 3/SD 5/FSoil nutrient regime* RMMMMR PMMPMRRElevation (m) 870 900 805 790 780 810 840 850 860 890 850 590 880Slope gradient (%) 0 2 18 18 18 0 0 4 49 4 11 16 18Aspect* FFENNFFWSNWSWForest floor thickness (cm) 16.5 13 6 9 11 13 9 12 10 12 9 9 8Textural clas* LSCLL SLSLSLSLSL L SLSLSL LActual rooting depth (cm) 30 60 60 60 60 60 60 60 60 60 60 80 60Potential rooting depth (cm) 30 70 60 70 70 70 60 70 70 65 72 80 60Seepage depth (cm) N/A N/A N/A N/A N/A N/A 60 N/A N/A N/A N/A N/A N/ASoil drainage* W I M W W W M M W M M W WHumus form group* MD MD RD HR HR RD HR TD HR RD HR RD RDSoil great group* EB GBL EB EB EB EB EB GL HFP HFP HFP HFP EBStand age (years @ bh) 97 157 66 63 63 145 102 62 68 181 156 124 50Site index (m @ 50 yrs bh) 10.5 11 9.6 13.8 14.4 14.4 12.7 15.4 15.1 10.8 10.8 15.4 N/DTree layer cover (%) 40 30 35 35 48 74 40 40 70 35 30 81 41Shrub layer cover (%) 63 5 15 16 5 51 18 16 35 15 5 17 4Herb layer cover (%) 13 36 38 17 9 9 19 26 1 4 4 14 33Moss layer cover (%) 40 97 42 100 95 40 70 41 0 93 97 5 099APPENDICESAppendix 20Trembling Aspen EcosystemsAppendix 20. Selected environmental characteristics for plots of the 210 Populus tremuloides – Ledum groenlandicum association.* Abbreviations defined in Appendix 17 on page96 .Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on page112  for original plot codes.32 33 34 35 36 37 38 39 40 41Zone/subzone BWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwSoil moisture regime* 4/SD 4/SD 4/SD 5/F 4/SD 4/SD 4/SD 5/F 4/SD 4/SDSoil nutrient regime* VP VP VP P VP P P P VP VPElevation (m) 750 750 750 750 750 750 750 750 750 750Slope gradient (%) 0005054600Aspect* F F F N F W N N F FForest flor thicknes (cm)42344233.532.5Textural class* LS S LS SL SL S S LS S SActual rooting depth (cm) 60 50 70 60 80 60 80 70 55 46Potential rooting depth (cm) 60 50 70 60 80 60 80 70 55 46Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* MMMMMWW I M IHumus form group* UR UR UR UR UR HR HR HR UR URSoil great group* DYB DYB DYB DYB DYB DYB DYB DYB DYB DYBStand age (years @ bh) 54515455555258525357Site index (m @ 50 yrs bh) 9 8 6.6 9.3 7.6 8.8 9.9 10.2 8.6 6.9Tree layer cover (%) 23 22 23 26 30 18 36 33 15 24Shrub layer cover (%) 62 55 60 54 51 40 33 48 58 65Herb layer cover (%) 7 7 6 11 15 22 30 26 13 8Moss layer cover (%) 21 16 27 34 17 8 3 18 22 21100APPENDICESAppendix 21Scientica Silvica Extension Series, Number 27, 2000Appendix 21. Selected environmental characteristics for plots of the 221 Populus tremuloides – Lathyrus ochroleucus: Hedysarum boreale subassociation.* Abbreviations defined in Appendix 17 on pag e96.Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on page112  for original plot codes.42 43 44 45 46 47 48 49 50 51 52Zone/subzone BWBSmwBWBSmwBWBSmwBWBSmwBWBSmwBWBSmwBWBSmwBWBSmwBWBSmwBWBSmwSBS dwSoil moisture regime* 3/SD 3/SD 3/SD 4/SD 3/SD 3/SD 3/SD 3/SD 3/SD 3/SD 5/MfSoil nutrient regime* MMMMMMMP P PMElevation (m) 710 710 710 710 710 710 710 750 750 750 790Slope gradient (%) 225230403540550Aspect* FFSFSSSSWWFForest floor thickness (cm) 4 4.5 6 6.5 5 5 7.5 3 4.5 3 32Textural cas* SSSSSLSSSSSSCLActual rooting depth (cm) 60 60 60 70 75 60 50 80 52 65 25Potential rooting depth (cm) 60 60 60 70 75 60 50 80 52 65 25Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 65Soil drainage* MMWM RWWWWW IHumus form group* RD RD RD RD RD RD RD RD HR RD YRSoil great group* DYB DYB EB DYB DYB DYB DYB EB DYB DYB GLStand age (yrs @ bh) >50 >50 >50 53 >50 52 53 52 56 56 154Site index (m 50 yr bh) N/D N/D N/D 15.5 N/D 15 13.1 10.8 13.1 12.4 12.2Tree layer cover (%) 38 35 30 27 28 28 28 30 35 33 86Shrub layer cover (%) 26 25 25 47 23 28 23 25 29 26 25Herb layer cover (%) 58 26 28 21 41 53 38 37 39 26 25Mos layer cover () 000100003250101APPENDICESAppendix 22Trembling Aspen EcosystemsAppendix 22. Selected environmental characteristics for plots of the 222 Populus tremuloides – Lathyrus ochroleucus: typic subassociation.Plot number 153 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68Subzone/Variant BWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwSoil moisture regime* 5/F 5/F 5/M 5/F 5/F 5/F 5/F 5/F 5/F 5/F 4/SD 4/SD 5/F 5/F 5/F 5/FSoil nutrient regime* MMMR P PMMR PRMMMMMElevation (m) 645 630 630 630 750 710 740 740 645 750 525 525 480 465 465 450Slope gradient (%) 0506461330210230Aspect* FSFESSFWEFFFFFSFForest flor thicknes (cm)967665.4.55.8745354.56Textural class* SL CL CL SiL CL LS SL CL CL LS SL LS CL SiL SiCL SActual rooting depth (cm) 40 50 20 50 25 80 60 50 50 30 85 70 40 40 40 35Potential rooting depth (cm) 30 20 15 50 25 80 35 20 50 30 85 70 40 25 20 55Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A 30 N/A N/A N/A N/A N/A N/Aoil drainage* MIIMIMIIIIMMMMM IHumus form group* RD TD RD RD HR RD RD RD RD HR HR HR HR HR HR RDSoil great group* GL GL GL EB EB DYB GL GL EB DYB DYB DYB GL GL GL DYBStand age (years @ bh) 70 >50 >50 55 52 53 64 65 69 67 >50 >50 >50 >50 >50 >50Site index (m @ 50 yrs bh) 17.6 N/D N/D 18.9 18.2 17.4 20.3 16.8 19.5 14.8 N/D N/D N/D N/D N/D N/DTree layer cover (%) 40 40 35 38 25 43 40 4 35 33 35 28 35 32 38 34Shrub layer cover (%) 27 21 18 36 65 20 15 18 38 83 50 30 31 30 38 65Herb layer cover (%) 35 27 22 42 18 51 32 29 46 24 40 36 22 20 18 45Mos layer cover (%) 1110101002011113102APPENDICESAppendix 22Scientica Silvica Extension Series, Number 27, 2000* Abbreviations defined in Appendix 17 on page96 .Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on pag e112 for original plot codes.69 70 71 72 73 74 75 76 77 78 79 80 81 82 83Subzone/Variant BWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwSoil moisture regime* 5/F 5/F 4/SD 4/SD 4/SD 5/F 4/SD 4/SD 5/F 5/F 5/F 5/F 5/F 4/SD 5/FSoil nutrient regime* PMMMMMMMMMMMMMMElevation (m) 450 465 525 525 525 750 750 750 750 720 720 720 700 700 750Slope gradient (%) 03222015475411594Aspect* FWFFFFEWWNWFWWWForest flor thicknes (cm)664.56.555756444764.5Textural class* S SL S S S CL SiCL SiCL SiL SiCL CL CL CL CL SiCLActual rooting depth (cm) 45 32 90 55 70 25 60 40 60 50 35 60 50 50 45Potential rooting depth (cm) 45 32 90 55 70 25 60 30 60 50 35 20 45 20 30Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* I I MMMMMM I I I I MM IHumus form group* RD RD HR RD RD HR RD RD RD RD RD HR HR HR RDSoil great group* DYB DYB GL DYB DYB GL EB GL GL GL GL GL GL GL GLStand age (years @ bh) >50 >50 >50 49 >50 66 >50 >50 >50 >50 >50 >50 >50 >50 50Site index (m @ 50 yrs bh) N/D N/D N/D 22.7 N/D 21.1 N/D N/D N/D N/D N/D N/D N/D N/D 18.6Tre layer cover (%) 252635404035373540364042364330Shrub layer cover (%) 59 60 37 27 42 44 38 38 9 21 14 4 34 55 23Herb layer cover (%) 325035363339483724322921581123Mos layer cover (%) 553112534004112103APPENDICESAppendix 23Trembling Aspen EcosystemsAppendix 23. Selected environmental characteristics for plots of the 223 Populus tremuloides – Latyrus ochrocleucus: Actaea rubra subassociation.* Abbreviations defined in Appendix 17 on page96 .Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on page 112 for original plot codes.84 85 86 87 88 89 90 91 92 93Zone/subzone BWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwBWBS mwSBS dwSoil moisture regime* 5/M 5/M 5/M 6/VM 5/M 6/VM 5/M 5/M 5/M 5/MSoil nutrient regime* RRRRRRRRRVRElevation (m) 630 750 750 750 450 450 450 700 700 1025Slope gradient (%) 3 2 8 4 10 12 12 8 4 2Aspect* S F S N S S S W N FForest floor thickness (cm) 11 12 6 8.5 9 13 10 12 14 4Textural class* CL SiL S SL S S SiL CL CL SCLActual rooting depth (cm) 70 40 45 35 60 60 60 50 30 50Potential rooting depth (cm) 70 40 45 35 60 60 60 26 30 70Seepage depth (cm) N/A N/A N/A 45 N/A 35 N/A N/A N/A 85Soil drainage* I M M I I I M I M IHumus form group* MD RD RD RD RD RD RD HR RD VLSoil great group* MB EB DYB DYB DYB DYB EB GL GL GBLStand age (years @ bh) 57 56 52 55 N/D N/D N/D 57 N/D 96Site index (m @ 50 yrs bh) 25.1 21.2 23.0 19.7 N/D N/D N/D 20.1 N/D 23.7Tree layer cover (%) 26 30 40 30 45 46 45 43 39 100Shrub layer cover (%) 28 14 26 24 27 27 40 67 45 7Herb layer cover (%) 256036574535443536 8Mos layer cover (%) 0000000101104APPENDICESAppendix 24Scientica Silvica Extension Series, Number 27, 2000Appendix 24. Selected environmental characteristics for plots of the 310 Populus tremuloides – Thalictrum occidentale  association.* Abbreviations defined in Appendix 17 on page96 .Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on page 112 for original plot codes.94 95 96 97 98 99 100 101 102 103Zone/subzone BWBS dk IDF xmIDF  dkSBPS dcSBPS dcSBS dwSBS dwSBS dwSBS dwSBS dwSoil moisture regime* 4/SD 5/SDf 5/SDf 5/Ff 5/Ff 4/F 5/Mf 4/F 5/Mf 4/FfSoil nutrient regime* MR PMMMMRRMElevation (m) 595 1115 960 900 870 880 880 885 900 920Slope gradient (%) 13 0 0 25 5 17 3 67 3 0Aspect* S F F W W E N E N FForest floor thickness (cm) 6.5 21 6 5 4 9 40 9 8 9Textural class* SL SCL CL CL L SL O L L SLActual rooting depth (cm) 100 70 30 80 90 35 70 60 120 50Potential rooting depth (cm) 100 70 90 80 90 35 70 60 120 50Seepage depth (cm) N/A 75 90 N/A N/A N/A 60 N/A N/A N/ASoil drainage* W M I M W W P W W WHumus form group* HR MD RD RD TD HR YR RD TD TDSoil great group* HFP GBL GL GL EB EB H EB EB EBStand age (years @ bh) 135 68 48 50 75 63 87 61 46 99Site index (m @ 50 yrs bh) 18.4 16.8 N/D 18.3 22.4 18.5 20 18.3 N/D 16.7Tree layer cover (%) 71 80 70 100 76 60 51 70 40 100Shrub layer cover (%) 19 85 32 5 23 47 53 20 19 31Herb layer cover (%) 2 9 8 11 15 8 8 20 84 4Mos layer cover (%) 40011046020105APPENDICESAppendix 25Trembling Aspen EcosystemsAppendix 25. Selected environmental characteristics for plots of the 411 Populus tremuloides – Viburnum edule: Spiraea betulifolia subassociation.* Abbreviations defined in Appendix 17 on pag e96.Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on pag e112 for original plot codes.104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120Zone/subzone SBS dwSBS dwSBS dwSBS dwSBS dwSBS dwSBS dwSBS dwSBS dkSBS dkICH mcSBS dwSBS dwSBS dwSBS dwSBS dwSBS dwSoil moisture regime* 3/SD 3/SD 3/SD 3/SD 3/SDf 4/Ff 4/F 4/F 4/F 3/SD 4/F 4/F 3/SD 3/SD 4/Ff 5/Mf 3/SDSoil nutrient regime* RRVRRRVRRRRRRRRRMRRElevation (m) 920 880 890 870 900 900 890 890 880 810 390 1025 855 850 885 880 900Slope gradient (%) 27700020041141160030Aspect* FNNFFFFFFWWNWWFFEForest floor thickness (cm) 5 5.5 12.5 10 10 19 10 13 6.5 9.5 8.5 6 5 4 7.5 7 8Textural clas* LLLLLLLLSLLSLSCLSLSLSSSCLActual rooting depth (cm) 30 60 60 50 50 50 60 60 60 60 60 30 30 90 70 80 60Potential rooting depth (cm) 30 60 70 60 60 60 70 70 70 70 70 30 30 90 70 80 60Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* WWWWWWWWWWWMWWRWWHumus form group* RD RD MD TD TD MD MD MD UR MD TD TD RD RD RD HR RDSoil great group* HFP HFP DYB EB DYB EB EB EB EB EB EB EB EB EB EB EB EBStand age (years @ bh) N/D 104 105 101 103 112 N/D N/D 81 103 72 116 85 65 83 81 48Site index (m @ 50 yrs bh) N/D 18.6 18.6 12.1 18.9 19.4 N/D N/D 16.7 15.2 13 17.3 15.2 18.1 13.6 15.6 N/DTre layer cover (%) 9610 7595958570857090309591865 10 85Shrub layer cover (%) 556585595248974854395018385967672Herb layer cover (%) 243521352 58212942352220Mos layer cover (%) 0127111000012003560106APPENDICESAppendix 26Scientica Silvica Extension Series, Number 27, 2000Appendix 26. Selected environmental characteristics for plots of the 412 Populus tremuloides – Viburnum edule: Paxistima myrsinites subassociation.* Abbreviations defined in Appendix 17 on pag e96.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on page 112 for original plot codes.121 122 123 124 125 126 127 128 129 130Zone/subzone ICH  mcICH  mcICH  mcICH  mcICH  mcICH  mcICH  mcICH  mcICH  mwICH  dwSoil moisture regime* 3/SD 3/SD 3/SD 3/SD 4/F 3/SD 3/SD 3/SD 4/F 3/SDSoil nutrient regime* RRRRRMMMMMElevation (m) 390 380 380 420 500 500 500 520 790 1020Slope gradient (%) 11 27 18 33 0 22 27 11 25 16Aspect* WSNWFWWSS EForest floor thickness (cm) 7.5 10 8 8.5 6 8.5 7 5 3.5 8Textural clas* L SLLSLSLSLSLSSL L SLActual rooting depth (cm) 40 60 70 70 70 70 40 50 50 35Potential rooting depth (cm) 50 70 70 70 70 70 40 60 50 35Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* W W M W M M M W W WHumus form group* TD RD TD TD TD HR TD TD RD RDSoil great group* DYBEBEBEBEBEBEBEBHFPEBStand age (years @ bh) 103 99 N/D N/D 63 71 71 N/D 47 96Site index (m @ 50 yrs bh) 16.9 14.8 N/D N/D 22.5 16.6 20.3 N/D N/D N/DTre layer cover (%) 204010 70525079717475Shrub layer cover (%) 54 63 95 37 41 50 54 31 15 18Herb layer cover (%) 861461026282Mos layer cover (%) 0010211901107APPENDICESAppendix 27Trembling Aspen EcosystemsAppendix 27. Selected environmental characteristics for plots of the 421 Populus tremuloides – Rosa nutkana: Aralia nudicaulis subassociation.* Abbreviations defined in Appendix 17 on page96 .Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on page112  for original plot codes.131 132 133 134 135 136 137 138 139 140 141 142 143 144Zone/subzone ICH mcMS   dkMS   dkMS   dkMS   dkMS   dkMS   dkMS   dkMS   dkICH   dwICH   dwICH   mwIDF   dmIDF   dmSoil moisture regime* 5/M 6/Mf 6/Mf 6/M 6/M 6/M 6/Mf 6/Mf 6/M 5/M 6/VM 6/VM 6/F 6/FSoil nutrient regime* R VR R R R M R R R R VR VR R MElevation (m) 520 815 980 990 1045 1035 1020 1040 1040 850 850 1025 1100 1115Slope gradient (%) 2 00313702800668Aspect* NFFEENFFWFFNEEForest floor thickness (cm) 7 10 2.5 7 4 8 2.5 3 3 5 30 17 6 10Textural class* SL SC S SL L S SCL SL SCL S L SCL SCL SLActual rooting depth (cm) 70 30 80 50 30 60 45 45 45 100 90 38 40 35Potential rooting depth (cm) 70 60 80 50 30 80 55 45 65 100 90 38 20 35Seepage depth (cm) 100 60 N/A N/A N/A N/A 55 N/A 65 70 45 45 20 N/ASoil drainage* M I MMMMPWP I I P PWHumus form group* TD TD VL TD MD TD VL VL VL RD YL YD VL RDSoil great group* EB GL HFP EB HFP R GL HFP GL HFP HR GL GL EBStand age (years @ bh) 95 N/D 58 56 59 58 75 73 74 80 80 81 63 62Site index (m @ 50 yrs bh) 28.3 N/D 29.6 26.4 26.6 26.8 26.6 24.8 24.5 29.3 30.7 24.1 20.6 22.3Tree layer cover (%) 54 100 60 78 100 91 80 97 85 79 100 100 75 45Shrub layer cover (%) 2744657121417932119235Herb layer cover (%) 15 26 44 11 25 78 80 49 70 3 3 0 15 32Mos layer cover (%) 1 0000001000001108APPENDICESAppendix 28Scientica Silvica Extension Series, Number 27, 2000Appendix 28. Selected environmental characteristics for plots of the 422 Populus tremuloides – Rosa nutkana: Arnica cordifolia subassociation.* Abbreviations defined in Appendix 17 on page 96.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.145 146 147 148 149 150 151 152 153Zone/subzone MS   dkMS   dkMS   dkMS   dkICH   dwICH   dwICH   dwMS   dkIDF   dmSoil moisture regime* 3/SD 2/MD 3/SD 2/MD 3/SD 3/SD 3/SD 2/MD 4/MDSoil nutrient regime* M M M M R R R M MElevation (m) 980 980 1020 1030 785 805 800 1285 1215Slope gradient (%) 40482127426565 0 16Aspect* NNNNWWWFEForest flor thicknes (cm)8737676410Textural class* LS LS S L LS SL LS LS SLActual rooting depth (cm) 80 60 35 45 70 90 30 45 40Potential rooting depth (cm) 80 60 35 45 70 90 30 45 40Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* W W M W R R R W WHumus form group* TD TD VL TD RD TD TD RD HRSoil great group* HFP HFP EB HFP HFP HFP R HFP EBStand age (years @ bh) 58 58 54 55 73 73 75 76 N/DSite index (m @ 50 yrs bh) 26.7 25.3 26.1 21.8 20 24.1 20.4 20.5 N/DTree layer cover (%) 95 70 80 100 85 75 93 90 100Shrub layer cover (%) 8 27 57 66 16 57 42 4 16Herb layer cover (%) 53 7 26 22 15 11 4 2 17Mos layer cover (%) 000000000109APPENDICESAppendix 29Trembling Aspen EcosystemsAppendix 29. Selected environmental characteristics for plots of the 423 Populus tremuloides – Rosa nutkana: Angelica genuflexa subassociation.* Abbreviations defined in Appendix 17 on pag e96.Plot number11 Plot numbers have been simplified in this report.  See Appendix 32 on page 112 for original plot codes.154 155 156 157 158 159 160 161 162Zone/subzone ICH   mwICH   mwICH   mwICH   mwICH   mwICH   mwIDF   dmIDF   dmIDF   dmSoil moisture regime* 4/F 4/F 4/F 4/F 4/F 4/F 6/F 5/SD 5/SDSoil nutrient regime* R R VR R R R M R MElevation (m) 795 795 800 800 805 805 1210 1210 1285Slope gradient (%) 48 18 32 27 30 21 4 0 0Aspect* SSSSSSEFFForest floor thickness (cm) 7 10 10 8 10 9.5 8 8 9Textural cas* SLLLLLSLLSSCLSActual rooting depth (cm) 50 50 70 70 70 60 65 45 50Potential rooting depth (cm) 50 50 70 70 70 60 65 55 50Seepage depth (cm) N/A N/A N/A N/A N/A N/A 65 55 60Soil drainage* W W W W W W P I IHumus form group* VL VL TD VL VL VL TD VL RDSoil great group* EB EB EB EB EB EB GL GL DYBStand age (years @ bh) 76 100 59 56 65 77 65 67 66Site index (m @ 50 yrs bh) 19.6 19.3 23.7 20.4 27 21 20.2 22.3 20Tree layer cover (%) 85 85 70 80 70 70 68 42 93Shrub layer cover (%) 48 72 58 23 70 28 27 84 13Herb layer cover (%) 16 28 19 45 27 48 30 35 13Mos layer cover (%) 000000000110APPENDICESAppendix 30Scientica Silvica Extension Series, Number 27, 2000Appendix 30. Selected environmental characteristics for plots of the 424 Populus tremuloides – Rosa nutkana: Senecio pseudoaureus subassociation.* Abbreviations defined in Appendix 17 on page 96.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.163 164 165 166 167 168 169 170 171Zone/subzone IDF   dmMS   dkMS   dkMS   dkMS   dxIDF   dwIDF   xmIDF   xmIDF   xmSoil moisture regime* 4/MD 3/SD 2/MD 2/MD 2/MD 4/MD 4/MD 4/MD 4/MDSoil nutrient regime* VRRRMRRRRMElevation (m) 1005 1025 1035 1040 1055 1010 1050 1215 1220Slope gradient (%) 0 8 45 5 59 48 5 12 15Aspect* FESWSWEEEForest floor thickness (cm) 7 3 2.5 9 3 9 4 13 9Textural class* SL SL SL SL LS LS S SCL SLActual rooting depth (cm) 100 90 100 40 40 80 80 70 40Potential rooting depth (cm) 100 90 100 40 40 80 80 70 40Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A 75 N/ASoil drainage* WWWWWWWMWHumus form group* VL VL VL VL VL TD VL TD HRSoil great group* EB HFP EB HFP EB EB EB GL EBStand age (years @ bh) 967461725789756986Site index (m @ 50 yrs bh) 20.2 24.9 20.7 17.9 15.2 24.6 20.6 23.8 19.1Tre layer cover (%) 706388754156419080Shrub layer cover (%) 9 23 3 6 28 59 77 55 69Herb layer cover (%) 13 19 78 16 18 10 5 22 18Mos layer cover (%) 010100000111APPENDICESAppendix 31Trembling Aspen EcosystemsAppendix 31. Selected environmental characteristics for plots of the 425 Populus tremuloides – Rosa nutkana: Shepherdia canadensis subassociation.* Abbreviations defined in Appendix 17 on page96.Plot number11 Plot numbers have been simplified in this report. See Appendix 32 on pag e112 for original plot codes.172 173 174 175 176 177 178 179 180 181 182 183 184 185 186zone/subzone IDF   xmIDF   xmIDF   xmIDF   xmIDF   xmSBPS   dcSBPS   dcSBPS   dcMS   dkMS   dkIDF   dmIDF   dmIDF   dmIDF   dmIDF   dmSoil moisture regime* 2/VD 2/VD 2/VD 3/VD 3/VD 4/MDf 4/MDf 2/VD 1/VD 1/VD 2/VD 2/VD 2/VD 2/VD 4/MDSoil nutrient regime* M M R M P M R R M P P M P P PElevation (m) 1095 1100 1040 965 980 960 960 970 1060 1060 1040 1080 1065 1285 1210Slope gradient (%) 0144800004358538386702Aspect* FEWFFFFWSSSSSFFForest flor thicknes (cm)5739593694510464Textural class* L SL SL L LS SCL SCL CL LS L SL SL S LS SLActual rooting depth (cm) 80 45 40 70 45 70 70 65 40 120 25 55 80 30 70Potential rooting depth (cm) 80 45 45 70 45 70 70 65 40 120 25 55 80 30 70Seepage depth (cm) N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/ASoil drainage* WRRWRWWMRRRRRRWHumus form group* TD RD VL TD HR VL TD TD TD TD TD TD TD TD HRSoil great group* EB EB EB EB EB SB EB GL DYB EB EB EB DYB DYB EBStand age (years @ bh) 70 63 63 122 113 95 65 117 61 62 86 95 75 68 74Site index (m @ 50 yrs bh) 12.6 13.1 8.7 10.2 9.8 10.2 11.2 10.3 14.1 12.7 14.6 10.2 14.8 N/D 16.2Tre layer cover (%) 603050824025258044257095256660Shrub layer cover (%) 62 1 0 1 4 53 51 18 15 69 42 33 5 13 37Herb layer cover (%) 4 51 12 1 2 16 7 14 35 9 22 74 0 4 25Mos layer cover (%) 000000000020000112APPENDICESAppendix 32Scientica Silvica Extension Series, Number 27, 2000Appendix 32. Conversion of the plot numbers used in this report to the plot codes used in the original data set (AtKK.MDB) on file with the British Columbia Ministry of Forests, Research Branch, in the VENUS data base.plot numberplot codeplot numberplot codeplot numberplot codeplot numberplot code1 97--040 48 95--115 95 98--007 142 98--2542 97--068 49 95--118 96 98--026 143 98--2773 97--107 50 95--124 97 98--095 144 98--2784 97--111 51 95--125 98 98--097 145 98--2175 97--015 52 98--114 99 98--099 146 98--2186 97--036 53 95--101 100 98--100 147 98--2217 97--037 54 95--102 101 98--102 148 98--2228 97--042 55 95--103 102 98--104 149 98--2359 97--047 56 95--104 103 98--111 150 98--23610 97--048 57 95--107 104 97--003 151 98--23711 97--051 58 95--109 105 97--005 152 98--28312 97--053 59 95--116 106 97--007 153 98--28613 97--059 60 95--117 107 97--009 154 98--20614 97--089 61 95--129 108 97--010 155 98--20715 97--102 62 95--131 109 97--011 156 98--20916 97--103 63 95--201 110 97--017 157 98--21017 97--109 64 95--202 111 97--018 158 98--21118 98--093 65 95--203 112 97--019 159 98--21319 97--008 66 95--204 113 97--020 160 98--27920 97--056 67 95--205 114 97--023 161 98--28021 97--063 68 95--206 115 98--063 162 98--28122 97--065 69 95--207 116 98--067 163 98--01023 97--066 70 95--208 117 98--068 164 98--22624 97--067 71 95--212 118 98--071 165 98--22725 97--069 72 95--213 119 98--073 166 98--22926 97--076 73 95--214 120 98--103 167 98--23227 97--082 74 95--215 121 97--024 168 98--26728 97--116 75 95--216 122 97--025 169 98--27529 97--117 76 95--217 123 97--026 170 98--28530 97--121 77 95--301 124 97--027 171 98--28731 98--096 78 95--302 125 97--028 172 98--00232 95--119 79 95--303 126 97--029 173 98--00333 95--120 80 95--304 127 97--031 174 98--00834 95--121 81 95--306 128 97--032 175 98--02335 95--122 82 95--307 129 98--203 176 98--02436 95--123 83 95--309 130 98--253 177 98--02537 95--126 84 95--105 131 97--034 178 98--02738 95--127 85 95--106 132 98--216 179 98--02839 95--132 86 95--128 133 98--219 180 98--23340 95--133 87 95--130 134 98--220 181 98--23441 95--134 88 95--209 135 98--223 182 98--26942 95--108 89 95--210 136 98--224 183 98--27043 95--110 90 95--211 137 98--225 184 98--27644 95--111 91 95--305 138 98--228 185 98--28245 95--112 92 95--308 139 98--230 186 98--28446 95--113 93 98--075 140 98--25147 95--114 94 97--120 141 98--252

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