Conserving biological diversity in agrarian landscapes: A multiscale analysis of fen plant diversity patterns and investigation of livestock grazing in fen plant communities.

摘要

Understanding diversity patterns in the context of novel, human-influenced systems is necessary for successful conservation and management programs, and traditional land-use practices like livestock grazing are becoming common strategies for conservation of biological diversity in wetlands. The goals of this research were to describe patterns in fen plant species diversity at multiple scales in relation to environmental variables and surrounding land use, to investigate the influence of site grazing history and surrounding land use on plant diversity and composition in rich fens, and to investigate the actual and simulated short-term effects of livestock grazing on fen plant communities.;I used a multiscale approach to quantify variation in fen plant species richness and Shannon diversity measured at two spatial levels (i.e., 1 m 2 and whole fen). Species richness was negatively related to pore water pH and positively related to surrounding forest cover at both spatial levels. Microtopographic variation was positively correlated to species richness at the level of whole fen but negatively correlated to richness and diversity at the smallest spatial scale.;In an investigation of vegetation patterns in rich fens of New York State, species richness and Shannon diversity/1 m2 were found to be significantly higher in recently grazed fens. Ordinations revealed gradients of pore water pH, temperature, electrical conductivity and microtopographic relief, but no correlation with adjacent land use or fen grazing history was observed. However, hoof print density within grazed fens was associated with several rich fen plant species.;I established an exclosure study in nine rich fens actively grazed by livestock in New York State. I also conducted a field experiment to test the effect of simulated grazing disturbances (i.e. trampling and clipping) on fen plant communities. Species richness and Shannon diversity did not differ between grazed and ungrazed plots in the exclosure study. Grazed plots did have significantly lower aboveground biomass and litter, which may favor low-stature fen vegetation by reducing competition for light by taller species. In the simulated grazing study, the combined trampling and clipping treatment resulted in higher vascular plant species richness, and clipping increased Shannon diversity.