A vegetation monitoring program was initiated at Big Oaks National Wildlife Refuge (Big Oaks NWR) to help understand the effects of fire management on critical wildlife habitat. The objectives of this study were to produce a baseline description of plant community structure and composition and to describe the landscape-level impacts of fire management within the refuge. These grassland communities are important for managing rare grassland wildlife species, especially Henslow's sparrows. Permanent plots were established in three managed grassland communities. Information on plant community species composition and structure was collected during 2000-2001. Andropogon viginiana and Solidago juncea were the dominant plant species in the permanent plots. Rhus copallinum and Liquidamber styraciflua were the dominant woody species. Changes in landscape structure were determined using aerial photographs and a geographic information system (GIS). Vegetation data layers were created for 1995 and 1998 with vegetation patches classified using the National Vegetation Classification System (NVCS). Field data was collected during 2000 and 2001 to validate the data layers. Changes in composition and structure of nine vegetation classes were compared between burned and unburned areas. Percent cover of grassland area increased while sparse woodland and shrubland decreased during the study period. The amount of total patches and total edge declined in the burn areas. Mean grassland patch size increased while the number of grassland patches and grassland edge decreased in the burn areas. Therefore, the grassland areas within the burn units were more homogeneous in 1998. The results of this study were related to Henslow's sparrow population estimates in the fire management units.

During autumn 1993, the U. S. Forest Service began implementing a program of prescribed surface fire in the Fork Ridge region of Hoosier National Forest. To determine the effects of the prescribed surface fire on ground- and shrub-nesting nearctic migrants, I conducted vegetation structure sampling, bird abundance surveys, and nest searches during the 1996 and 1997 breeding seasons. The prescribed surface fire drastically reduced understory vegetative cover from 0.0 to 2.5 m above ground and the density of live stems < 5.0 cm dbh. Herbaceous cover < 0.5 m tall in the burned site returned to levels similar to the unburned site within 2 years of the burn.Prescribed burning had little effect on overall avian species diversity, but altered the community composition. In 1996, there were 12 species present in the unburned site which were absent in the burned site and 9 species present in the burned site which were absent in the unburned site. In 1997, there were 9 species present in the unburned site which were absent in the burned site and 7 species present in the burned site which were absent in the unburned site. As a guild, ground- and shrub-nesting nearctic migrants and residents were less abundant in the burned site compared to the unburned site. Conversely, species such as Indigo Buntings (Passerina cyanea) and White-breasted Nuthatches (Sitter carolinensis) were more abundant in the burned site.Nests in the burned site had a 25% success rate, whereas nests in the unburned site had a 44% success rate. Nest parasitism did not differ between the burned site (1.2 cowbird eggs/nest) and unburned site (0.9 cowbird eggs/nest). Worm-eating Warblers (Helmitheros vermivorus) were the only ground- and shrunb-nesting nearctic migrant found in the burned site. Worm-eating Warbler nests in the burned site were characterized as having greater understory cover than surrounding burned areas. My results suggest that prescribed surface fires in Fork Ridge may be negatively impacting some ground- and shrub-nesting migrants by altering nesting habitat. / Department of Biology