These natural areas are all habitat islands surrounded by pavement, but they are large enough to support a wide variety of native plants and wildlife. We have observed wild turkeys, pileated woodpeckers, and ruffed grouse in campus forests, and numerous fish species in Indian Lake. The outer boundaries of these natural habitats are diffuse zones, with both abrupt and gradual differences in environmental variables. For example, a forest island bordered by a parking lot will most likely experience higher average temperatures than a forest surrounded by agricultural fields. Relative Humidity increases with lower temperatures, increased shading, and decreased wind, as well as increased evaporation from soils and plants.
Light decreases from forest perimeters into the interior.
Species composition changes often accompany light gradients. In older forests, such as the wooded ravines around Indian Lake, this effect is complicated by light gaps created when large trees die. Wind speed decreases as the complex structures in forests absorb wind energy. Water runoff decreases as tree leaves and forest soils intercept and absorb rain. Soil Compaction decreases due to the cushioning effect of rain interception and the high carbon content of forest soils.