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Boreal ecosystems of the Fort Nelson area of northeastern British Columbia Annas, Richard M.

Abstract

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.

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