| Summary: | University of Minnesota M.S. thesis. May 2013. Major: Integrated Biosciences. Advisor: John Pastor. 1 computer file (PDF); iv, 541 pages, appendix p.52-541. The rocky shoreline of Lake Superior is home to disjunct arctic plant populations which are relicts from the Wisconsinan glaciation and survive in a cold lake-supported microclimate. Although these species are threatened by climate change, there have been few studies about their structure and diversity and relation to abiotic factors. We characterized the plant communities and abiotic environment of one of the largest expanses of arctic communities growing in cracks in the bedrock along a shoreline of Lake Superior in northern Minnesota. Two-way cluster analysis of species cover identified 4 communities, 3 with distinct species assemblages and 1 with an assemblage that was a combination of species in two of the other communities. A Bray-Curtis ordination also suggested four communities segregated according to crack volume, width, and length, as well as soil moisture, species diversity, and dominance-diversity curves. Species had their highest foliar nitrogen (N) and phosphorus (P) concentrations in the communities where they were most dominant. These correlations suggest that with a warmer and drier climate, the plants will experience increased moisture stress, especially in smaller cracks. This increased stress could lead to the disassembling of these communities, species by species.
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