Jones, Natalie , Baldwin, Lyn .
Isolated aspen stands: testing the Theory of Island Biogeography.
Given the increasing frequency of habitat fragmentation, naturally isolated habitats provide unique and important opportunities to examine the factors influencing patterns of native richness in plant communities. In this research, the species richness and abundance of native and exotic understorey vascular plants was examined in relation to the size and perimeter to area ratio of 24 naturally isolated aspen stands surrounded by a matrix of grassland within Lac du Bois Provincial Park, B.C. At the center of each stand and in the adjacent grassland matrix, vascular plants were sampled using a modified-Whittaker plot design (10 x 25 m) that includes nested subplots at three different spatial scales. Based on all species found in grassland and aspen plots, smaller stands are more compositionally similar to grasslands than large stands, indicating that species richness within stands is influenced by mass effects. Generalized linear models demonstrated that the species richness and abundance of native plants were positively associated with stand size and negatively associated with the perimeter to area ratio. Given that sampling effort was constant across patches, this suggests that small patches are able to support a lower density of native species either as a result of increased edge effects in small patches or higher stochastic extinctions coupled with immigration rates insufficient to replenish lost populations. While stand characteristics were important in determining species richness, we also found that exotic species abundance was negatively correlated with native species abundance. Interestingly, exotic species richness showed no association with aspen stand size or perimeter to area ratio.
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1 - Thompson Rivers University, Biological Sciences, 2860 Bellendean rd., Shawnigan Lake, B.C., V0R2W0, Canada
2 - Thompson Rivers University, Biological Science, 900 McGill Road, P.O. Box 3010, Kamloops, BC, V2C 5N3, Canada
isolated aspen stands
perimeter to area ratio
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 28th, 2008
Time: 4:45 PM