Ecosystem units, their classification, interpretation and mapping in the University of British Columbia research forest

A synecological study was conducted at the University of British Columbia Research Forest, Haney, British Columbia. The objectives of the" study were to classify and map forest ecosystems occurring in the area and to provide interpretations as to their use for land and silvi-cultural management. One hundred and fifty eight sample plots were established, each plot representing a sample of an ecosystem individual—biogeocoenosis. Following an analysis of the vegetation and its environment by the phytosociological techniques of the Zürich-Montpellier School as applied by Krajina, and the associated soils, a synthesis of similar plots into abstract units was carried out. The ecosystems were classified according to the system of synecological classification developed by Krajina and his students. Biogeoclimatic and synsystematic units were floristically and environmentally described emphasizing environmental factors and processes which control their distribution and development. Lower synsystematic units were grouped to form management units for which relatively uniform management procedures and techniques could be proposed. By analyzing the properties of vegetation and soils, suitability of ecosystems for wood production was assessed along with suggested silvicultural systems for thirteen management units. The classification was verified by investigations to substantiate ecological significance of the differentiated units. These involved chemical analysis of seepage water, foliage samples of under-story vegetation, and humus layers in the Coastal western hemlock biogeoclimatic zone. Chemical concentrations in foliage of understory vegetation increased progressively along moisture and nutrient gradients. Characteristic species for the Pseudotsugetalia menziesii had the lowest concentrations, those for the Tsugetalia heterophyllae had the intermediate concentrations and finally those for the Thujetalia plicatae had the highest concentrations of metallic elements and nitrogen. The characteristic species for the ecosystem units appear to have a high indicative value in assessing their edatopes. Chemical concentrations in seepage water were found to vary with the season, forest stand type (based on age) and biogeocoenotic units. Seepage water, supplying the ecosystems with additional moisture and nutrients, affects soil development through increased decomposition and mineralization of organic matter. These habitats consequently support very productive ecosystems of the Thujetalia plicatae. Thus, seepage water can be considered as a part of the ecosystem which counteracts leaching. The results of these analyses supported the applied methods of synecological classification. The distinguished ecosystem units can be further characterized by specific indices of properties which were not used in the original classification procedure. On the basis of these synecological studies a synecological map of the 5,151 ha UBC Research Forest at the scale 1:12,000 was prepared by a combination of ground survey and aerial photographic interpretation. Ecosystem type was employed as a mapping unit. The mapping units were designated by selected colors and numerical symbols. In conclusion, it became apparent that the classification of ecosystems into the system of synecological classification, using the described methods, can provide not only a better understanding of forest ecosystems but also a basis on which to differentiate management practices.Forestry, Faculty ofGraduat

Scientia silvica extension series, no. 20

Ecosystem-specific forest management requires comprehension of tree species productivity in managed settings, and how this productivity varies with the ecological determinants of site quality, i.e., the environmental factors that directly affect the growth of plants: light, heat, soil moisture, soil nutrients, and soil aeration. A good understanding of this variation is necessary for making species- and site-specific silvicultural decisions to maximize productivity. Productivity of a given species is usually measured by site index (tree height at 50 years at breast height age). Quantitative relationships between site index and these measures of site quality provide predictive models for estimating site index. Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Forbes) is an important timber crop species in the coastal forests of British Columbia. In relation to climate, its range in southwestern British Columbia extends from sea level to almost timberline, and from the hypermaritime region on western Vancouver Island to the subcontinental region on the leeward side of the Coast Mountains. In relation to soils, its range extends from slightly dry to wet sites and from very poor to very rich sites. In view of this relatively wide climatic amplitude, a large variability in productivity can be expected. It is particularly important to consider the growth performance of Pacific silver fir when decisions are made regarding whether or not to cut stands on high-elevation sites. In the study summarized here, relationships between Pacific silver fir site index and selected ecological measures of site quality were examined, and site index models using these measures as predictors were developed.Forestry, Faculty ofForest Sciences, Department ofReviewedFacult

Scientia silvica extension series

Scientia Silvica extension series was started in 1997 by Karel Klinka, a silvics professor at the University of British Columbia. He saw the need for a friendly way of distributing current research results to the forestry community. Each extension pamphlet represents a 2-4 page summary of research findings in the field of forest ecology. Topics range from humus form and ecosystem classification to forest productivity, regeneration, stand structure, soil nutrient regimes, coarse woody debris, and plant diversity. Included in each summary is a reference to the more technical original report or scientific paper and contact information for those who wish further information. Also included in the series are several full colour comprehensive reports on ecosystem classification. All pamphlets and reports are in Adobe Acrobat (PDF) format for on-screen viewing or printing. Forest Renewal British Columbia provided the funding for this version of Scientia Silvica extension series.Forestry, Faculty ofForest Sciences, Department ofReviewedFacult

Seedfall, seed germination, and initial survival and growth of seedlings of Thuja plicata in southwestern British Columbia

Reasons for the relative absence of Thuja plicata regeneration in the old growth Thuja plicata - Tsuga heterophylla forests close to Vancouver, British Columbia, were assessed by measuring seedfall and applying Thuja seeds to small plots. All measurements were replicated in two different sites. The small (0.5 m2) plots were established in 2 canopy cover conditions (clearcut and forest). 3 seedbed conditions (mineral soil, burned forest floor, and undisturbed forest floor), and 2 mammal and bird seed predation conditions (with and without). Each canopy cover, seedbed, and seed predation combination was replicated 15 times in each study site. Large numbers of viable seeds (>200/m2) fell in 1990/91 and again in 1994/95. Seed germination decreased in the order burn > mineral soil > forest floor; forest > clearcut; and without predation > with predation. After 3 growing seasons, of the 100 seeds applied to each plot, an average of only 1-2 seedlings had survived. This number of surviving seedlings decreased in the order - burn > mineral soil > forest floor, and clearcut > forest, but was not influenced by predation. After 3 growing seasons. seedling growth tended to decrease in the order - burn > forest floor > mineral soil; clearcut > forest; and without predation > with predation. It was concluded that the relative lack of regenerating Thuja seedlings in the study area forests was not due to a lack of viable seeds. Although a lack of suitable seedbeds and the presence of the forest canopy reduce the number of seedlings in undisturbed forests, this number should still be substantial. The observed relative lack of regenerating Thuja seedlings must therefore result from other factors which were not considered in the present stud

Reconstructing temperature from tree rings of Pacific silver fir in Coastal British Columbia

We used ring-width (RW) and maximum latewood density (MLD) chronologies for high-elevation Pacific silver fir (Abies amabilis Dougl. ex Forbes) from the Coastal Western Hemlock zone near Vancouver, British Columbia to reconstruct April to September mean temperatures for the 1770 -1990 period. The reconstruction was based on a calibration and verification procedure. The best reconstruction result was achieved when both RW and MLD chronologies were utilized. The reconstruction agreed with that produced for interior British Columbia from densitometric data. We suggest that rings of Pacific silver fir, growing under the influence of a perhumid maritime cool mesothermal and subalpine boreal climates in the Pacific Northwest, can serve as proxy-climate indicator

Scientia silvica extension series, no. 28

This pamphlet provides a summary of a fuller report also issued under the title: The mountain hemlock zone of British Columbia. It describes both forested and non-forested ecosystems of the Mountain Hemlock (MH) zone of British Columbia (also referred to as the subalpine MH zone, coastal subalpine forest, or coastal mountain hemlock forest). It covers classification, reviews of vegetation regions and environmental relationships, as well as silvicultural and resource management implications.Forestry, Faculty ofForest Sciences, Department ofReviewedFacult

Scientia silvica extension series, no. 6

The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old. Understanding regeneration patterns in the MH zone has become increasingly important as logging continues towards higher elevations of the zone where snowpacks are deeper.Forestry, Faculty ofForest Sciences, Department ofReviewedFacult

The relationship of site index to synoptic estimates of soil moisture and nutrients for western redcedar (Thuja plicata) in southern coastal British Columbia

We described the pattern of mean site index and the associated variation in site index of western redcedar (Thuja plicata Donn. ex D. Don.) in relation to categorical variables of soil moisture and nutrients as identified by the field-procedures of the biogeoclimatic ecosystem classification. Additionally, we compared the site index of western redcedar to that of western hemlock (Tsuga heterophylla (Raf.) Sarg.). We sampled 105 plots from stands having western redcedar as the major tree species. The plots were distributed within each of two climates, a drier and a wetter cool mesothermal climate in south coastal British Columbia. Sixty-three plots had both western redcedar and western hemlock available for comparisons. Heights and ages were measured on five dominant trees on a 0.04 ha plot, and the height at a base age of 50 years was calculated to give site index. The highest western redcedar site index occurred on sites identified as having no moisture deficit or excess and high nitrogen availability. Site index decreased on sites identified by field procedures as being outside this optimum moisture and nutrient condition. The mean site index was significantly greater in the drier cool mesothermal climate than the wetter cool mesothermal climate on sites identified as having similar soil moisture and nutrient conditions. Climate appears to have a large effect on site index, therefore, on similar soil conditions the site index of western redcedar may be higher in the southern portion of its range in the United States; and lower in north coastal B.C. and southeastern Alaska. On sites where both western redcedar and western hemlock were sampled, the site index of western redcedar was consistently lower. Based on a northward trend. we may predict that in southeastern Alaska the site index values may be larger for western redcedar compared to western hemlock, while in Washington and Oregon there may be an even greater site index of western hemlock over western redcedar than reported her

Scientia silvica extension series, no. 23

Knowledge of ecological characteristics of sites and growth of trees on different sites is fundamental for silvicultural decision-making and planning. With the biogeoclimatic ecosystem classification in place in British Columbia, silvicultural management has been given an ecological foundation; however, relationships between growth and site quality have not yet been fully investigated, particularly for high-elevation tree species and sites. One of the contributing factors for this situation is limited knowledge of forest productivity in the high-elevation Mountain Hemlock (MH) and Engelmann Spruce - Subalpine Fir (ESSF) biogeoclimatic zones. Consequently, the management and planning in the high-elevation forest is fraught with difficulties and uncertainties. Current harvest rates of old-growth forest stands and the method and distribution of cuttings in these zones suggest that there needs to be more recognition of the uppermost elevation limit for harvesting. Subalpine fir (Bl), Engelmann spruce (Se), and lodgepole pine (Pl) are important timber crop species in the interior high-elevation forest which is represented predominantly by the subalpine boreal ESSF zone. This zone extends from 49° to approximately 57° N latitude and from approximately 900 to 1,700 m in the north, from 1,200 to 2,100 m in central BC, and from 1,500 to 2,300 m in the south. In view of this relatively wide climatic and edaphic amplitude, a large variability in productivity is expected. The objective of this study was to quantify relationships between site index (height @ 50 yrs @ bh) of Bl, Se, and Pl, and three ecological determinants of site quality: climate, soil moisture, and soil nutrients. Quantitative relationships between site index and these measures provide predictive models for estimating site index. Additionally, we compared the site indices of the three study species to each other to examine their early height growth performance on the same sites.Forestry, Faculty ofForest Sciences, Department ofReviewedFacult

Trembling aspen height-age models for British Columbia

Trembling aspen (Populus tremuloides), a common hardwood species in the interior of British Columbia, Canada is becoming an increasingly important timber crop species, especially in the northeast corner of the province. Better growth and yield information for aspen is required to manage this species properly. Height-age models for estimating site height and site index are provided in this paper. One-hundred and thirty-five stem analysis plots were established in six biogeoclimatic zones. Three trees in the 0.04 ha plots were selected and stem analysed, and ecological data were collected at each plot. The stem analysis data were split into a model calibration and test data set. Two models were fit to the calibration data: a base model and an extended model that is calibrated for the six biogeoclimatic zones. Both models adequately estimate the height of trembling aspen in British Columbia. The base model was compared to two models for aspen in Alberta, which showed that there were no large differences in the height growth of aspen, except on lower productivity sites