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Epiphytic vegetation on Acer macrophyllum in south-western British Columbia

University of British Columbia

This dissertation is concerned with the analysis and description of epiphytic vegetation on the lower portion of the bole of Acer macrophyllum at 5 sites in south-western British Columbia.. At each site, trees were selected for intensive sampling. In addition, the vascular vegetation at each of the sites was characterized. Various aspects of the response of the vegetation to microenvironmental variation were examined using multivariate methods. Between-tree variation in the epiphytic vegetation appears to be partly correlated with microenvironmental and corresponding habitat variation within the forest. Between-site variation is relatively pronounced as sites are, in general, distinguishable on the basis of their epiphytic vegetation. This is likely a reflection of differences in forest structure, microenvironment, and climate between the sites. Environmental gradients related to changing height and inclination on the bole can be recognized. The response of the epiphytic vegetation to these gradients was analyzed by ordinating data on overall species performance at each of 24 height-inclination combinations at a site. The results indicate between-site differences in the response of the vegetation to these gradients. Patterns of variation in the epiphytic vegetation suggest that three major habitats exist on the lower bole: the tree base (to 1 m), the lower side of the bole, and the upper and mid sides of the bole. Species relationships and habitat preferences have also been examined using ordination methods. Patterns of association generally reflect habitat variation on the bole. This was further examined by analyzing the response of the individual species to the inclination and elevation gradients. Spatial niche differentiation is apparent for many of the species; however, there is often niche overlap, suggesting that species may, at least potentially, be competing for space on the bole. The phytosociological structure of the epiphytic vegetation was also examined. Cluster analysis of the quadrat data combined with field observations led to the recognition of 9 epiphytic community-types which show varying degrees of spatial distinctiveness on the bole. Analysis of the epiphytic vegetation on Acer macrophyllum has shown it to be structurally and ecologically complex. This is likely a reflection of the high degree of sensitivity bryophytes and lichens show to small-scale environmental changes. Despite this complexity, fairly marked trends in the vegetation are apparent which are believed to be related to a few dominant microenvironmental gradients operating on a given tree.

Text

2010-03-19

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http://hdl.handle.net/2429/22151

Botany

University of British Columbia

Graduate