[pp.31-40]

Can the Width of the Surrounding Area that Influences Within-Patch Species Richness in Urban Habitat Patches Be Estimate

Kazuhiro KATOH and Toshimori TAKAHASHI （The University of Tokyo / Utsunomiya University）

Abstract:
Recent studies have reported that attributes of the area surrounding a habitat patch may influence species richness within the patch. Some studies have used regression analysis to attempt to determine how the width of the surrounding area influences species richness within habitat patches. By this approach, an attribute of the surrounding area, such as the vegetation index, is calculated for various widths of surrounding area and used as the independent variable in regression models. A single model is constructed for each surrounding width. The width producing the best-fit model is then regarded as the optimal width of the surrounding area. However, in urban areas, landscape around a habitat patch is often homogenous for several kilometers. We confirmed this by testing the change in normalized difference vegetation index values around patchy urban woodlands with buffers 500 to 5000 m wide. Our numerical simulations demonstrate the inappropriateness of the above-mentioned approach. Comparing regression models using various widths of surrounding areas, we found that when landscape matrices around habitat patches are substantially homogenous regardless of the distance from the patch, determining the width of the surrounding area that influences the habitat ecology of the patch is difficult.

Key Word:
biological homogenization, buffer width, habitat patch, landscape matrix, species richness, urban landscape

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