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Species richness, abundance and distribution in experimentally fragmented landscapes Perdue, Mark Edward

Abstract

Experimentally fragmented landscapes were created in prairie fields at the Konza Long Term Ecological Research Area in the Flint Hills of Kansas State. Landscapes (2m X 2m) were fragmented by isolating plots (0.1m X 0.1m) of open-habitat (bare ground) using Bromus inermis, an aggressive grass species, as a barrier. Elements of fragmentation, habitat area, dispersion, and isolation, were varied by altering the numbers of randomly located brome plots. From 1995 through 1998, species were recorded for each open-habitat plot and brome-occupied plot. The effects of fragmentation were considered in terms of species richness, abundance and spatial distribution, each correlated with the level of fragmentation. Fragmented landscapes had fewer species than contiguous landscapes. At intermediate levels of open-habitat, some species occupied alternate plot cover types more frequently, somewhat mitigating the effects of fragmentation. However, continued fragmentation resulted in the extirpation of most species. Fragmentation also reduced the abundance of satellite and core species. Core species abundance were dramatically reduced near 60% open-habitat, consistent with the changes in species richness. These changes coincided with the percolating threshold, suggesting that habitat dispersion did contribute to the effects of habitat loss. Changes in the spatial distribution of species, a fundamental expression of how species are affected by fragmentation, were characterized by spatial signature analysis. Changes in species' spatial signatures were compared to changes in available habitat. Spatial signature analysis was able to detect how each species responded to fragmentation spatially. Based on this analysis, successful species could be distinguished from those species imperiled by these experimentally fragmented landscapes.

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