James Runkle (Advisor)
Master of Science (MS)
Gap analysis is a method to identify insufficiency in biodiversity protection. In degraded agricultural landscapes, it requires information on the past, present, and the potential natural distribution of forest vegetation to construct a comprehensive nature reserve network. Using Geographic Information Systems (GIS), I conducted a biodiversity gap analysis to assess the representation of ecological land units (ELUs) supporting forest vegetation both within and external to the current reserve network in the Lower Twin Creek Watershed (LTCW), southwestern Ohio. I used this analysis to make conservation planning recommendations to the local park district. ELUs are based on relatively stable associations of soils, physiography, and potential natural vegetation. In heavily deforested landscapes, such as the LTCW, ELUs model a more intact functioning landscape by predicting the distribution of potential natural forest vegetation. ELUs were classified using multivariate and cluster analyses on forest canopy tree species and seven physiographic and soil variables derived from digital elevation models and a soil series map in GIS. A cluster analysis of the five most significant variables (landform, drainage, hillshade, curvature, and percent slope) influencing vegetation distribution resulted in nine discrete ELUs. They included uplands dominated by Fagus grandifolia – Acer saccharum, dry slopes dominated by Quercus spp. - Carya ovata, mesic slopes dominated by a mixed mesophytic community, and wet floodplains dominated by Platanus occidentalis – Populus deltoides. A reference ecosystem map was constructed using ArcView GIS Spatial Analyst with the five environmental variables identified in the multivariate analysis. To determine the area of forest cover in each ELU within the reserve network and the watershed as a whole, the reference ecosystem map was overlaid with a 1990 land cover type map and the reserve boundaries. The area of forest in each ELU in the reserve network was then compared to the area of forest in each ELU in the watershed as a whole and the potential natural distribution of forest cover as predicted by the reference ecosystem map to determine the percent of forest protected in each condition. The gap analysis, using the current forest distribution, indicated that the well and poorly drained upland ecosystems were underrepresented in the reserve network. A similar pattern emerged using the reference ecosystem map; however, reflecting the degree to which these upland ecosystems are deforested, to meet a 25% representation target would require three to four times more forest than existed in these ELUs in 1990. The results of the gap analysis based on the current vegetation distribution were influenced by the pattern of deforestation in the LTCW. The reference ecosystems map provided a model of an intact functioning landscape from which to establish conservation planning targets. Although the upland matrix forest ecosystems may have lower species richness per land unit area and are relatively common, restoring portions of the matrix forest may be the key to the long-term maintenance of biological diversity in the LTCW.
Department or Program
Department of Biological Sciences
Year Degree Awarded
Copyright 2002, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.