| I examined avian community composition and vegetation structure in the pine barrens of Wisconsin and how they are affected by disturbance type, patch size, soil quality, and habitat heterogeneity.; Density and species richness of grassland/savanna birds differed little between habitat patches created by fire and clearcutting. Patch species richness is highly correlated with area, and species-area regressions do not differ for fire-created/maintained versus clearcut patches. Presence of grassland/savanna bird species in habitat patches is strongly hierarchical, with some species found only in the largest patches. Species richness and density of birds along transects is positively correlated with Shannon-Wiener diversity of woody vegetation, indices of soil quality, and height range of woody vegetation. Species richness along transects is slightly lower in clearcuts than in sites created and maintained by fire.; I modelled timber harvest in the pine barrens using dispersed and aggregated clearcuts in a simulated landscape. Timber harvest was equal in all simulations. Bird species presence and richness in the simulation landscape were modelled using empirical data. In simulations, landscape fragmentation was lowest and grassland/savanna bird species richness was greatest when clearcuts were aggregated.; I tested the hypothesis that predation of artificial nests is greater along edges than in the interior of savanna patches. Predation of artificial nests increased significantly with proximity to edge. In addition, densities of blue jays (Cyanocitta cristata) and brown-headed cowbirds (Molothrus ater) were significantly greater along edges than in the interior of early successional habitat patches.; Structure of woody vegetation differed among wildfire, repeated prescribed fire, and clearcut disturbance types. Patches created by wildfire had greatest Shannon-Wiener diversity of woody vegetation; highest densities of snags, blueberries, and jack pine; and greatest variation in height of woody vegetation. Clearcuts had greatest coverage by slash and raspberries, and lowest Shannon-Wiener diversity and height variation of woody vegetation. Sites maintained through repeated prescribed burns had lowest densities of trees, slash, jack pine, and blueberries. |
