Classification, vegetation-environment relationships, and distribution of plant communities on Southeast Farallon Island, California

摘要

We present the plant communities of Southeast Farallon Island and describe theirudrelationships to environmental variables and disturbance factors. We sampled a total ofud42 vegetation plots containing 26 taxa with a stratified design across the 29-hectare (72-udacre) island. To classify the herbaceous communities we applied agglomerativeudhierarchical clustering, while the influence of site parameters was obtained usingudNonmetric Multidimensional Scaling (NMDS) ordination. A total of five plantudcommunities were classified, including two native plant assemblages (Spergulariaudmacrotheca type and Lasthenia maritima type) and three invaded communitiesud(Tetragonia tetragonioides type, Plantago coronopus type, and Mixed vegetation type).udThe strongest gradients in vegetation composition can be explained by solar heat load,uddominance of substrate type, and edaphic factors (soil pH, salinity, depth). Physicaluddisturbance and proximity to anthropogenic land use also influence plant communityudcomposition. A map of the classified vegetation types and additional mapping units wereudcreated to better understand current patterns in vegetation and assist in long-termudmanagement of the island???s resources. Southeast Farallon Island is the largest seabirdudbreeding colony south of Alaska and the U.S. Fish & Wildlife Service is planning forudintensive habitat restoration, therefore, a clear understanding of native and invaded plantudcommunities and vegetation-environment relationships is required.