2000 BES Abstracts

Patch delimitation in the gauged catchments of the Gwynns Falls Watershed

Mary L. Cadenasso, Steward T. A. Pickett, and Wayne C. Zipperer

A guiding question of the Baltimore Ecosystem Study is: "How do the spatial structure of socio-economic, ecological, and physical factors in an urban area relate to one another and how do they change through time." A first step to address this question is to define socio-economic, ecological, and physical patches within the study area. This presentation will provide an update on an approach we are using to describe, delimit, and quantify ecological patches in four regions of the Gwynns Falls Watershed that include the gauged catchments. Specifically, we have focused on 1) how can structural patches, based on ecological factors, be described, delimited, and quantified? and 2) how does patchiness of ecological factors differ among the four catchments? Digital air photos, taken during the leaf on season of 1999 and of submeter resolution, are used in an ArcView system to create a data layer on top of the digital images. The ecological patches are of three broad categories: forest, open areas, and built structures. The specific patches types within these three categories are based on tree canopy size, elements that make up the non-forest and non-built areas, and a matrix of the type and density of built structures and the types and densities of vegetation, respectively. We will compare the frequency distributions of patch types in two of the catchments as well as the degree of heterogeneity that is found in both of these catchments. How this approach can be integrated with patch delimitation by other disciplines and by other methods used to evaluate spatial heterogeneity will be briefly discussed.