An ecological study of grassland communities separated by fence lines in the Southern Interior of British Columbia was conducted from spring 1968 to spring 1969. Measurements to compare plant species composition, herbage yield, growth habits and edaphic features on both sides of the fences were taken in the field. Soil organic matter was determined in the laboratory and moisture penetration patterns were demonstrated in the greenhouse. Heavy grazing resulted in the removal of the principal climax caespitose species and their replacement by shrubs, annuals and rhizomatous grasses. There were reductions in the composition, herbage yield and vigor of the caespitose species at all sites following heavy grazing. The success of the increasers under heavy grazing seemed to be favored by possession of rhizomes, presence of unpalatable flowering culms and inflorescences, shortness of tillers and an elaborate means of seed dispersal. The vegetational changes introduced by grazing on the heavily grazed side, resulted in a high level of organic matter in the top 25 cm. of soil, a high soil moisture content and high summer and low winter soil temperatures. The dense vegetation on the lightly grazed side modified both summer and winter soil temperatures. A technique was developed to determine the ability of caespitose grasses to redistribute moisture in the soil. It was demonstrated that aerial parts of Agropyron spicatum collect light rains and concentrate them in the rooting zone of the plant. This phenomenon is likely to be one of the adaptive features which enables caespitose species to dominate arid habitats. It is possible that the great susceptibility of Agropyron spicatum and other caespitose grasses to heavy grazing might be related to soil moisture disturbances introduced by the removal of aerial parts of the plants. / Land and Food Systems, Faculty of / Graduate

Patterns of in-stream summer transport of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) in a high gradient second order stream in southwestern British Columbia were described. Some biological, physical, and chemical processes were also identified and evaluated with respect to their role in regulating in-stream transport of TDN and TDP. Fifteen water sampling stations were established along an alternating series of open clearcut and densely forest covered drainage areas, each several hundred metres in length. These drainage sections represented young and midsuccessional ecosystems. The furthest upstream section (which was forest covered) and an adjacent downstream open clearcut section each had weirs which were used for comparisons of TDN and TDP export between the successionally different systems. Export of TDN was consistently lower from the clearcut section than from the upstream forested section. This indicated that there was consistent in-stream absorption of TDN within the clearcut section. Nitrate flux dominated the absorption of TDN. A pairing analysis of precutting nitrate export data from 1972 with post-treatment export data from 1979 indicated that the absorption of nitrate was due to increased solar radiation reaching the stream channel. It was proposed that the increased light inputs which provided an additional energy input to the stream ecosystem, increased nitrate spiralling rates. Without disruptive stormflow events the net effect was a retention of nitrate within the stream. Concentrations of TDP were often less than detectable limits so comparisons of P export could not be made. The TDN data suggested that if nutrient absorption in small watershed streams is widespread, nutrient retention on land may have been overestimated in past small watershed nutrient budget studies. A further analysis of downstream flux in element concentrations was conducted for all forms of TDN and TDP using three-dimensional images (distance downstream x time x element concentration) from data collected in summer 1979. Nitrate concentrations consistently declined in open sections but increased in densely forest covered sections. Trends in ammonium concentrations were difficult to detect. Orthophosphate levels were rarely greater than the detectable limit of 3 ug/1 in all sections. Dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) flux was highly variable with no apparent trend. Nutrient spiralling processes were proposed to explain the flux of each of these forms of TDN and TDP. An enrichment experiment conducted in a clearcut section of the study stream in mid-summer indicated that rates of disappearance of N0₃⁻-N, NH₄⁺-N, and HP0₄⁻²-P from solution were directly related to element concentrations in solution and that relationship could be expressed as fourth, first, and third degree polynomials respectively. Disappearance rates of the three ions were in the order NH₄⁺-N> HP0₄⁻²--P> N0₃⁻-N. Reasons for the differences in disappearance rates between elements and element forms were proposed. The first end-of-summer storm event produced a 20-fold increase in stream discharge at peak flow over summer base flow. This resulted in a 10-fold increase in N0₃⁻-N concentrations in all stream sections. The increased loading was attributed to flushing of N0₃⁻-N from land. Stream power was not destructive, however, and N0₃⁻-N removed from solution increased over that during summer base flow. The increased uptake rates were attributed to an increase in active nutrient processing areas of the stream substrate. DON and DOP concentrations and export increased during the storm but NH₄⁺-N and HPO₄⁻²-P concentrations did not change. Again, detailed explanations for this element behaviour were proposed. Results of an enrichment experiment designed to evaluate the role of periphyton in regulation of nutrient transport were insufficient to fully assess the quantitative role of periphyton. Hypotheses were proposed, however, to further evaluate the role of periphyton using alternative methods. Concluding hypotheses were presented to aid in the development of future research plans. / Forestry, Faculty of / Graduate

A study was carried out to ascertain the biogeochemical role of understory vegetation in three representative sites characteristic of the Mountain Hemlock Biogeoclimatic Zone. The three sites were selected to represent a typical topographic sequence of plant associations and were classified as members of the Vaccinio (membranacei) -Tsugetum mertensianae, Abieto (amabilis) - Tsugetum mertensianae and Streptopo (rosei) - Abietetum amabilis plant associations (xeric, mesic, and hygric site types, respectively). The overstory layer was found to be typical of old growth, high elevation forests of southwestern coastal British Columbia. Overstory biomass on the three sites was estimated to be 60.88, 55.68, and 34.05 kg•m⁻² for the hygric, mesic, and xeric site types, respectively. Understory aboveground biomass was found to be less than one percent of the aboveground overstory biomass. Average values for the three sites were: 44.1, 66.1, and 399.3 g•m⁻² for the hygric, mesic, and xeric site types, respectively. Understory aboveground production (UAP) was found to represent a greater proportion of overstory aboveground production, as indicated by the mean annual increment (MAI), than the biomass figures might suggest. UAP values of 25.95, 14.19, and 63.12 g•m⁻²•yr⁻¹ for the hygric, mesic, and xeric site types, respectively, were equivalent to 11.28 percent, 6.06 percent, and 48.55 percent of the estimated aboveground overstory production. Only a small percentage of the total aboveground nutrient standing crop was found in the understory. This is in agreement with comparable published values for old growth forest ecosystems. However, the understory was found to cycle a much greater proportion of its total standing crop annually compared to overstory. Approximately 80 percent of the macronutrients present in the understory standing crop are found in the understory annual production on the Streptopo - Abietetum amabilis site (hygric site type). Estimates of 17.6, 8.3, and 20.6 g•m⁻²•yr⁻¹ of understory aboveground litterfall (exclusive of the moss layer) were obtained for the hygric, mesic, and xeric sites, respectively. These values are substantially less than for overstory litterfall, but the biomass of different litterfall components (e.g. understory or overstory) was shown to be a poor indicator of the proportional contribution of the components to the quantity of nutrients in aboveground litterfall. Understory was shown to return a significant proportion of the litterfall nutrients on a yearly basis, the bulk of which was returned as a single pulse during the first autumn snowfall. Understory vegetation above the moss layer was shown to have a significant effect on the quantity of nutrients present in throughfall precipitation reaching the ground. The effect was seasonal in nature with PO₄-P, N0₃-N, and NH₄-N being removed in the spring and Ca, Mg, and K being added to overstory throughfall in the autumn. It was concluded that modifications of water chemistry previously attributed to the forest floor may in some cases reflect unmeasured influences of understory vegetation. The understory aboveground nutrient cycles follow two basic patterns. The first pattern, a conservative cycle, is exemplified by nitrogen and phosphorus and has the following characteristics: (1) removal of nitrogen and phosphorus from overstory throughfall by the non-bryophyte understory, (2) estimated annual nitrogen and phosphorus uptake up bryophyte production in excess of the remaining throughfall nitrogen and phosphorus content and (3) a large proportion of the annual requirement was accounted for by internal redistribution within the understory plants. The second cycling pattern, an open cycle, is characteristic of calcium and magnesium and displays characteristics opposite to those of the "conservative cycle". The potassium, manganese, zinc, and copper cycles are intermediate between the "conservative" and "open" nutrient cycles. The results are discussed with respect to a proposed model of ecosystem function and it is hypothesized that understory plays a major role in maintaining ecosystem stability by promoting nutrient cycling. / Forestry, Faculty of / Graduate

Ecosystematic methods were used to study synecological problems in the Alpine Zone of Garibaldi Park, British Columbia. The influence of snow pack and its effects upon soils and the distribution of vegetation are considered. The successional trend of plant communities in the subalpine alpine ecotone and alpine zone is presented. The plant succession is closely related to environmental changes, particularly to the duration of the snow pack and soil forming processes. The Phyllodoceto - Cassiopetum mertensianae can be regarded as the zonal community in the Alpine Zone above 5,500 feet. It is shown that alpine zone ranges from 5,500 feet to the highest summits over 8,000 feet. Environmental conditions are correlated with units of vegetation which allow the recognition of twelve plant associations. The associations are arranged in groups which tend to characterize the habitats in which they are found. The associations are grouped as follows:- A. Snow patch group i) Gymnomitrieto - Polytrichetum norvegici a. sub-assoc. gymnomitrieto - polytrichetum norvegici b. sub-assoc. polytrichetosum piliferi ii) Cariceturn nigricantis iii) Sibbaldietum procumbentis B. Chomophytic group i) Caricetum spectabilis ii) Luetkeetum pectinatae iii) Anaphaleto - Lupinetum arctici C. Alpine meadow group i) Mimuleto - Epilobietum latifolii ii) Valerianetum sitchensis D. Rupicolous group i) Junipereto - Penstemonetum menziesii ii) Silenetum acaulis E. Alpine heather group i) Phyllodoceto - Cassiopetum mertensianae F. Krummholz group i) Abieteto - Chamaecyparetum nootkatensis G. Peat bog group i) Sphagnum / Science, Faculty of / Botany, Department of / Graduate

Comparative ecology and interspecific competition were examined between two sympatric congeners, Sebastes caurinus Richardson 1845 (copper rockfish) and S. maliger (Jordan and Gilbert 1880) (quillback rockfish) in Saanich Inlet, British Columbia, Canada, from 1986-1990. Ecological profiles were constructed through analyses of depth distribution, habitat and species associations, activities, feeding habits, gut allometry, growth, and reproduction. Interspecific competition between copper and quillback rockfish was examined by experimentally manipulating the densities of one or the other species on rocky reefs in Saanich Inlet where they were sympatric. The Pisces IV submersible was used to survey the distribution of rockfish in relatively deep-water (21-140 m) in Saanich Inlet. Copper and quillback rockfish were sympatric in water depths of 21-65 m. They occurred in association with one another the majority of the time (>90%) and their densities were greatest over areas of complex substrate. Size of copper and quillback rockfish was positively correlated with increased depth, primarily due to the absence of small fish in deeper waters. Both species were observed most frequently perched on open substrate or hovering in the water column. Copper rockfish were observed swimming more frequently than quillback rockfish. Copper and quillback rockfish primarily consumed demersal crustaceans throughout the year. Copper rockfish consumed a greater proportion of pelagic fishes than quillback rockfish, whereas quillback rockfish had a greater proportion of pelagic crustaceans in their diet. Levins' (1968) measure of niche breadth of the diet (by mass), as standardized by Hurlbert (1978), was narrow (0.19-0.20) to moderate (0.32-0.51) for quillback and copper rockfish respectively, during spring, summer, and fall. In the winter it was extremely narrow (0.02) for both species due to their feeding predominantly on one prey type, juvenile herring (Clupea harengus) . The Simplified Morisita Index of niche overlap (Horn 1966) in feeding habits (by mass) was relatively high (>0.55) throughout the year, and particularly during the winter (0.99). This high niche overlap in the winter occurred when large schools of juvenile herring were available in the environment and were probably not a limited resource. Extensive niche overlap between copper and quillback rockfish may therefore indicate an abundance of a shared resource rather than competition for the resource. Copper and quillback rockfish consumed the greatest quantity of food during the winter when feeding on juvenile herring, although quillback rockfish consumed significantly less food mass than copper rockfish in the winter. A greater proportion of quillback rockfish were collected with food in their stomachs during the spring and summer, when the numerically dominant food items were pelagic crustaceans. The importance of fish prey in the diets of both copper and quillback rockfish increased with size. Copper rockfish had a shorter intestine and larger stomach relative to similar-sized quillback rockfish. This suggested that the gastrointestinal tract of copper rockfish was better suited to holding and digesting fish and larger crustaceans than quillback rockfish, an observation consistent with differences in their feeding habits. Copper and quillback rockfish had similar growth patterns with no readily identifiable species-specific and sex-specific differences. Both sexes of both species attained asymptotic lengths of 30-31 cm total length and had similar growth coefficients (0.141-0.187). Within each sex, copper rockfish had a smaller increase in mass per unit of body length than quillback rockfish, indicative of a more pelagic lifestyle for copper rockfish. Estimated lengths at first and 100% sexual maturity for female and male copper and quillback rockfish were similar. Male copper rockfish were ripe, and potentially inseminated females, in January and February. Female copper rockfish were found to be carrying fertilized eggs in April and May, and gave birth to their young primarily in June. The reproductive cycle of quillback rockfish preceded that of copper rockfish by approximately one month, with parturition for quillback rockfish occurring mainly in May. The fecundity of copper and quillback rockfish was similar, with a 30-cm fish giving birth to approximately 90,000 young. Visceral fat cycles of mature female copper and quillback rockfish were complementary to their cycles of gonad maturation and increases in gonad size, indicating that they use visceral fat stores as a source of energy for maturation of their eggs and nourishment of their developing young. Visceral fat cycles of mature males were mainly coincident with the maturation and size increase of their gonads, indicating that they did not use visceral fat reserves in the maturation of their gonads. Male rockfish secondarily may have used their fat reserves as an energy source during the period when they were ripe, perhaps for mating activities. Visceral fat accumulation and dissipation in immature males and females appeared to be primarily related to periods of feeding. Interspecific competition between copper and quillback rockfish was asymmetrical, seasonal, and transitory, based on experimental manipulations of the densities of the congeners in natural populations. Copper rockfish did not have a competitive effect on quillback rockfish, but quillback rockfish had a weak competitive effect on copper rockfish. This effect was apparent only during the fall, was strongest in the fall immediately following the density manipulations, and appeared to weaken in the subsequent fall season. The seasonal competitive effect may have been caused by copper rockfish moving onto the study reefs (18-31 m depth) from shallower waters (<20 m) during the fall and winter, creating a short-term 'ecological crunch' in which food or space resources were limited. Overall, comparative ecological profiles of copper and quillback rockfish exhibited a large degree of overlap. Differences observed between them were small but consistently indicated that copper rockfish had a more pelagic lifestyle than quillback rockfish. The otherwise high degree of similarity between the two congeners, however, did not translate into sustained interspecific competition. Ecological theory purporting a major role for interspecific competition in structuring fish communities was therefore not supported by experimental manipulations of population densities of deep-subtidal, temperate zone rockfishes. The asymmetrical, seasonal, and transitory occurrence of weak interspecific competition demonstrated that competition between these rockfish species is dynamic, and cannot account for the pattern of species association. Alternative hypotheses based on the importance of intraspecific competition, predation, or environmental variability must therefore be considered. / Graduate

Five plant associations and one Alluvial Complex are recognized for the Dry Subzone of the Interior Western Hemlock Zone of British Columbia. These include 22 phytocoenoses, here described as biogeocoenoses or forest types. Additionally 3 intrazonal Pinus ponderosa plant associations and 2 interzonal ecotones are discussed. In phytosociological analysis modified Zurich-Montpellier techniques are employed. For tree studies, dominance/ frequency/density (DFD) indices and standard forestry methods are applied. Phytocoenose descriptions are based on synthesis tables which include plant lists (total 538 species), habitat descriptions and tree growth data from 15.5 one-fifth acre plots. Forest types comprise: 1) Lichen association (Cladonietum) - open stands with Pseudotsuga menziesii as the edaphic climax dominant, occurring on xeric rock outcrops; 2) Moss association (Pachistimeto-Callier gonelletum) - closed stands with Tsuga heterophylla as the climatic climax dominant, occuring on me sic sites; this includes 6 forest types; 3) Aralia Oakfern association (Aralieto-Gymnocarpietum) - closed stands with Tsuga heterophylla, Thuja plicata as the edaphic climax codominants, occuring on moist sites; this includes 7 forest types; 4) Devil's Club association (Oplopanacetum) - closed stands with Thuja plicata as the edaphic climax dominant, occurring on wet sites; this includes 4 forest types; 5) Skunk Cabbage association (Lysichitetum) - open stands with Thuja plicata as the edaphic climax dominant, occurring on water-saturated ground; this includes 2 forest types; 6) Alluvial Complex - unstable riverside vegetation dominated by Populus trichocarpa. The Lichen, Skunk Cabbage and Alluvial Complex communities are floristically the most clearly defined, and are readily recognizable on the basis of lesser vegetation dominants alone. Recognition of mesic communities relies on a characteristic combination of species. The zonal (climatic climax) biogeocoenose is the Slope Normal Moss forest type of the Moss Association. The dynamic relationships of forest types are discussed. Secondary succession may go from the deforested stage directly to the climax, if edaphotope disturbance is minimal, but normally a pioneer-tree stage intervenes. This Subzone is unique in that, the pioneer stage of the zonal community may differ substantially from the climatic climax if humus is removed by fire. On mesic sites, proceeding from pioneer-conifer to climax stages, crown cover decreases and lesser vegetation increases. Tsuga heterophylla is the exclusive dominant of the climax forest„ In decreasing order of importance, as determined by DFD indices, Subzone trees are Tsuga heterophylla, Thuja plicata. Pinus monticola, Pseudotsuga menziesii, Betula papyrifera, Picea engelmannii, Larix occidentalis, Populus tremuloides, Pinus contorta, Populus trichocarpa. Abies lasiocarpa and Abies grandis. Most rapid tree height growth of Thuja plicata, Pseudotsuga menziesii, Pinus monticola and Picea engel-mannii occurs in Devil's Club communities; of Tsuga heterophylla, Larix occidentalis, Pinus contorta, Betula papyrifera, Populus tremuloides in Aralia Oakfern communities; and of Populus trichocarpa in Alluvial Complexes. Forest types are more productive in pioneer than in climax stages. Estimates of net primary productivity and standing crop of forest types for tree trunks of all tree species summed as one, showed that the greatest pioneer- conifer stand productivity (1251 kilogram/ hectare/year) and climax stand standing crop (180 x 10³ kg/ha) belong to the Devil's Club association, and the least productive (126 kg/ha/yr) and lowest standing crop (15 x 10³ kg/ha) to the Lichen association. It is concluded that biogeocoenotic classification provides a sound basis for land use planning in this region, and should be applicable to other areas. / Science, Faculty of / Botany, Department of / Graduate

Quantitative and qualitative vegetation and environmental data from one-hundred-fourteen sample plots were used to characterize and evaluate ecological relationships and dynamics previously little known for the Subalpine Mountain Hemlock Zone on the southwestern British Columbia mainland. Environmental analyses, presented in detail, include the description of thirty-six kinds of soil representing several major categories. From the analytical data, each sample plot consists of a single set of values representing local historically developed variations and patterns of vegetation, soil, microclimate and topography within the biogeoclimatic zonal concept of Krajina (1962). A combined vegetation-environment synthesis resulted in the characterization of ecosystematic units at several levels of generalization (zone, subzone, order, alliance, association, subassociation and variant) within the following classification scheme: (A) Parkland Subzone i) Chionophilous (Schneetalchen) units, with snow -duration of at least 9 months 1) Vegetation of unstable sheet-wash slopes or hamada-like surfaces 2) Sedge vegetation of semi-terrestrial basin habitats ii) Moderately chionophilous units with snow duration averaging between 8 and 9 months 1) Herbaceous vegetation of stream-edge, spring-line or semi-terrestrial habitats 2) Heath-like or low shrub vegetation of terrestrial mesic to hygric habitats iii) Chionophobous forested units with snow duration averaging about 8 months or less 1) Mesic habitats 2) Moderately dry habitats (B) Forest Subzone i) Forested units lacking a seepage influence or with only a temporary seepage influence 1) Moderately dry lithic habitats or habitats with shallow soils 2) Mesic habitats with shallow to deep soils 3) Hygric habitats with deep soils and a temporary seepage influence ii) Forested units of hygric habitats with a permanent seepage influence 1) Seepage fast-flowing in stream-edge or spring-line habitats 2) Seepage slow-moving or stagnating in depressions or spring-line habitats iii) Non-forested semi-terrestrial moor habitats As orders and alliances include units of lower rank with strong environmental and floristic similarities to those found in other biogeoclimatic zones and subzones and elsewhere, a new dimension is added to the organization of ecosystematic units. The Subalpine Mountain Hemlock Zone coincides with the main distributional area of Tsuga mertensiana -- an area with a cool, snowy forest climate (Dfc after Koppen), podzolization and gleization as the dominant soil-forming processes, and with the development of Humic and Humus Podzol soils with thick, acid accumulations of mycelial ecto-humus on mesic zonal habitats. Discontinuity in the forest cover coinciding with an increasing duration of snow provides a physiognomic, floristic and climatic basis for the recognition of the Parkland and Forest Subzones. Vegetation and soil patterns and relationships in the Parkland Subzone are evidently most influenced by snow duration, soil moisture regime, topography and microclimate, whereas soil moisture regime, land type and topography are important influences in the Forest Subzone. The interplay of compensatory influences may promote the development of similar floristic patterns on different topographic forms on an intra- and interzonal scale. The environmentally integrating influence of snow depth and duration in the Parkland Subzone results in sharp floristic and microclimatic patterns. Vegetation may have a strong autogenic influence on microenvironmental dynamics by hastening snow melt and extending length of the growing season over short distances. Dynamics within the zone favoring successional trends are proceeding at a very slow rate. Climatic changes shortening the duration of snow rather than cumulative autogenic influences would probably contribute most to vegetation changes at high elevations in the subalpine zone. / Science, Faculty of / Botany, Department of / Graduate

A field investigation was carried out over two seasonal periods on an oligotrophic coastal British Columbia lake to determine the role of sinking in the formation of the chlorophyll maximum as well as some aspects of phytoplankton seasonality. Sinking rates of two diatoms were measured and found to be highest in the epilimnion and lowest at the depth of the chlorophyll maximum. Light affected sinking rate as well as the position of the chlorophyll maximum. The chlorophyll maximum formed at 10-12 m following the onset of seasonal thermal stratification and descended to ca. 22 m for the summer. A major factor in the formation of the chlorophyll maximum is the decrease of phytoplankton sinking rate at depth. Rhizosolenia eriensis is one of the first phytoplankters to bloom in the spring. Small flagellates (3-15 um) and occasionally Dinobryon sp. were also important numerically. In the summer Cyclotella spp. displaced R. eriensis as the dominant diatom in the epilimnion. The relative timing of seasonal maxima of blooms of various species remained similar during the two years investigated. Lake fertilization affected the phytoplankton standing stock. R. eriensis did not greatly benefit from fertilization since it sank out of the epilimnion and became a major constituent of the chlorophyll maximum before fertilization. Because of its large size and low C : cell volume ratio due to a large vacuole, R. eriensis is probably not a good food source for zooplankton. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Juvenile coho, steelhead, and cutthroat trout commonly spend from one to three or more years in coastal streams before migrating to the sea. Much of this time is spent in streams during the winter, making a study of these fishes' winter habitat requirements, distribution, behavior, and the possible influences of stream habitat alteration on them a useful undertaking. Some physical characteristics of areas selected by juvenile coho and steelhead were observed by snorkeling in a small west coast of Vancouver Island stream between September 1972 and April 1973. Observations revealed that with lowering water temperatures from 9°C to 2°C coho and older steelhead tended to move into deeper water while most steelhead fry remained in shallow, marginal sections of the stream. As water temperatures dropped in the winter, juvenile fish fed less and moved closer to areas offering low water velocities and cover. Steelhead fry were most often found under rubble while coho and older steelhead were most often found within upturned roots and under logs. Results from fish traps located on the lower ends of two small tributary streams indicated that juvenile coho, steelhead and cutthroat trout moved upstream into these tributaries in the late fall. Overwinter survival of coho in one tributary was 3-6 times as great as the estimated survival of coho in the main stream. Together the two tributaries contributed between 15 and 25 per cent to the total coho smolt production of the larger system. A series of experiments comparing coho and cutthroat preference for alternative habitat types in sidepool areas as may occur before and after stream disturbance were carried out during the winter. Both coho and cutthroat demonstrated a strong preference for bay areas offering overhanging bank cover as opposed to bays without cover, and for bays offering clean rubble substrate as opposed to silted rubble substrate. The impacts of timber harvesting on overwintering fish as suggested by the results from the underwater observations, winter movements, and the sidepool experiments are discussed and management recommendations are made. / Forestry, Faculty of / Graduate

An ecosystem study, based on the concept and approach of biogeoclimatology (sensu the Krajina school of ecosystem classification), was conducted in the boreal forest of northeastern British Columbia in the Fort Nelson area. The prime purpose of this study was to produce an ecological classification of forested ecosystems of the area. The resulting classification was based on an analysis of as many environmental and vegetational characteristics as feasible. Interpretations of the environmental and vegetational analyses presented attempt to explain the factors which conspicuously contribute to ecosystem processes and development. The vegetation from 95 phytogeocoenotic plots was classified into 6 orders, 10 alliances and 15 associations and the soils were classified into 17 subgroups, some with their gleyed variations. Detailed soil analysis and descriptions are major components of the ecosystem descriptions. The ecosystems are summarized environmentally by their projection on an eda-topic grid of moisture and nutrient regimes. An elemental ash analysis was carried out on surface organic horizons. Ca and Mg content appear to be good indicators of the positions that ecosystems occupy on the edatopic grid. Additionally, mor humus of black spruce ecosystems was compared with moder humus of aspen ecosystems. It is confirmed that moder humus has properties which are more conducive to high biological activity than does mor humus. It is concluded that the cold boreal climate , flatness of the terrain, prevailingly fine textured soil parent material, and fairly frequent forest fires are the dominant environmental factors influencing ecosystem structure and dynamics in the study area. The fine texture of the parent material frequently causes very slow percolation of water through soils which produces semi-stagnant water conditions instead of the rich seepage sites of more easily drained materials in other areas. Sufficient moisture is retained in these fine textured soils to prevent xeric conditions from developing, even in shedding topographic positions. The cold temperatures reduce biological activity, of the area to the point where nutrient poor, mor humus conditions develop. Mor humus promotes degradation of soils. However, this process is greatly inhibited by frequent forest fires. These fires maintain aspen stands as a fire climax which retards the development of strong acidity, so characteristic in mor humus of black spruce stands (the theoretical climatic climax). The general flatness of the terrain results in poor drainage of the area and favours the development of bogs. In high moors, a permafrost layer consistently occurs. / Science, Faculty of / Botany, Department of / Graduate