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

Nitrogen deposition to adjacent grassland and forested areas in the vicinity of Sabie, Mpumalanga, South Africa was studied. Total deposition amounts to the forested area are calculated to be 7l.2 kg N ha-1 yr1 and to the grassland area, 25 kg N ha· 1 yr1. The average deposition amounts are similar to or at least approach nitrogen mineralisation amounts at nearby sites of 50-70 kg N ha-1 yr1. The deposition amounts are made up of 21.4 kg N ha-1 yr1 dry deposition, 7.8 kg N ha-1 yr1 wet deposition and 42 kg N ha-1 yr1 cloud droplet deposition for the forest. For the grassland, the amounts are 7 kg N ha-1 yr1 dry deposition, 7.8 kg N ha-1 yr1 wet deposition and 10.5 kg N ha-1 yr1 cloud droplet. deposition. For both wet and cloud droplet deposition, the amount attributable to nitrate was greater than that attributable to ammonium. For wet deposition, nitrate contributed 4.1 kg N ha-1 yr1 and ammonium contributed 3.7 kg N ha-1 yr1 to both forests and grasslands. For cloud droplet deposition to forests, the amounts were 28 kg N ha-1 yr1 attributable to nitrate and 14 kg N ha-1 yr1 attributable to ammonium. For grasslands the amounts were 7 and 3.5 kg N ha-1 yr1. In both forests and grasslands, the component of dry deposition contributing the most to deposition was ammonia gas, the amounts being 14.2 and 4.3 kg N ha-1 yr1 respectively. Nitric acid contributes 3.7 and 1.9 kg N ha-1 yr1 respectively and is followed by the nitrogen dioxide component that contributes 1.6 and 0.5 kg N ha- I yr1. Ammonium and nitrate particles contribute the least to deposition. For the forests the amounts are 1 and 0.9 kg N ha-1 yr1 and for the grasslands they are 0.2 and 0.1 kg N ha-1 yr1. A strong seasonal variance in deposition amounts is apparent with maximum deposition amounts occurring in Summer and minimum amounts in Winter. Intermediate amounts are deposited in Autumn and Spring, with the latter season having slightly larger deposition amounts. The seasonal variance is strongly linked to the seasonal rainfall and cloud droplet deposition patterns. Biomass burning is indicated as a possible important factor in influencing the chemical composition of rainfall during Spring. Of the deposition amounts obtained in this study, the deposition from cloud droplets is high compared to other studies and is probably overestimated. Further research into this area is needed.

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Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 148-172). Also available via the World Wide Web.