An historical analysis of landscape structure change at Birch Creek State Park, Lake Somerville, Texas

Abstract

Changes in land-use subsequently affect the landscape's spatial patterning and ecological processes. This thesis applies concepts of landscape ecology in order to assess the degree of landscape structural change which has taken place due to the impoundment of Lake Somerville and recreational development within Birch Creek State Park, a unit of Lake Somerville State Recreation Area managed by Texas Parks and Wildlife Department. Mapping is a fundamental tool necessary in recording and quantifying patterns of landscape change. This research employs the landscape ecological mapping scheme developed by Karen Lynch (1996) in order to monitor and detect landscape change in Birch Creek State Park from 1958 to 1988. Geographic information system (GIS) software was used to create land-use maps from aerial photographs. Maps were classified with level III Anderson et at. (1975) land-use and land cover classification, and then reclassified using Lynch's patch-corridor-matrix landscape ecological mapping scheme. These maps provide a temporal summary of spatial change at Birch Creek State Park. Comparing these maps from four different time periods, addresses changing landscape patterns. From 1958 to 1988, Birch Creek State Park experienced a change in its land-use/land cover as well as its landscape ecology. The data indicates that as human modification of the landscape increased so did the measured heterogeneity. Not only has there been an increase in the number of patches, but there has been an increase in the types of patches present. The increase of urban land-use has dissected, perforated, and fragmented the landscape. This increase in urban land-use has changed the shape of forest patches, resulting in a decrease in area-to-perimeter ratio. Analyses of avian communities provide valuable information about the effects of landscape change on wildlife. While the introduction of the lake provides new habitat for some avian species, fragmentation of the landscape due to recreational development reduces habitat for species requiring large interior habitat. Local diversity can increase as a result of fragmentation coupled with ecotonal expansion, meaning the colonization of patches by opportunistic species.