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Ecology of the alpine and timberline vegetation of Big White Mountain, British Columbia Eady, Karen

Abstract

During the summers of 1968 and 1969, a plant ecological study was carried out on Big White Mountain, in the Okanagan Highland of southern British Columbia. The main objectives of the research were to produce an ecosystematic classification of the vegetation, and to determine the environmental factors important in differentiating the plant communities. The vegetation was studied by the phytosociological methods of Braun-Blanquet, as modified by Krajina. A number of environmental features were noted for each plot, and soil samples were collected by horizon. Physical and chemical analyses of the soils were done in the laboratory. Fourteen plant associations, with nine variations, were distinguished in the study area. These communities were compared with one another, using an index of floristic similarity. In general, there is a very low degree of similarity among the communities, thus supporting the initial classification system. The communities were compared with those described in other alpine and subalpine areas. Trees occurring in the subalpine parkland were found to be much older than the krummholz forms found in the alpine area. It was suggested that there has been a recent migration of tree species into the alpine area. The occurrence^ of conifer seedlings in alpine and timberline communities was presented. No conifer seedlings were found in the tree island communities. The soils were classified according to the Canadian system of soil classification. Four orders are represented in the research area: Brunisolic, Regosolic, Podzolic and Gleysolic. The soils are generally shallow, with weak horizon development. Important chemical properties are the acidic pH, narrow carbon: nitrogen ratios, low cation exchange capacities, and very low amounts of exchangeable cations. In an analysis of environmental variables, the communities were grouped according to hygrotope. The environmental data were summarized for each group. From an analysis of variance, all the factors were significant either at the 1% or 5% level, except relief. Based on Duncan's New Multiple Range Test, each community was discussed, mentioning the environmental factors which were found to be significant in differentiating it. It was concluded that general environmental factors (with hygrotope the most important) are more significant in distinguishing the communities than the physical and chemical soil properties. Detailed soil moisture data were presented for a number of alpine and subalpine communities. Several of the communities were found to undergo soil moisture stress. In the zonation of the research area, the subalpine parkland area was placed in the Engelmann Spruce - Subalpine Fir Zone. The alpine and low alpine areas constitute the Alpine Zone. The timberline vegetation is composed of the subalpine parkland and parts of the low alpine area. The alpine zone of Big White Mountain is not as well developed as it is in the coastal area or the Rocky Mountains. It was concluded that much further work needs to be done in order to properly characterize the alpine zone in British Columbia.

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