Much of California's biodiversity is found in oak (Quercus spp.) woodland vegetation. Residential development is expanding in northwestern California, resulting in a larger number of houses and roads in wooded areas. To examine the effects of this type of habitat fragmentation on biodiversity, 12 low-elevation oak woodland sites with gentle slopes were identified using remote sensing and a geographic information system. These sites were stratified across a gradient of differing lot sizes including large continuous parcels of relatively undisturbed hardwood rangeland in private parcels greater than 122 hectares; ranchettes on 4 to 16 hectare lots; and suburban areas with single-family homes on 0.20 to 1.0 hectare lots. Level of development was shown to have a significant effect on plant and bird species composition, and to be independent of stand structure and tree cover in the surrounding landscape.
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