The Interaction of Habitat Fragmentation, Plant, and Small Mammal Succession in an Old Field

We compared the density and spatial distribution of four small mammal species (Microtus ochrogaster, Peromyscus maniculatus, Sigmodon hispidus, and P. leucopus) along with general measures of an old field plant community across two successional phases (1984–1986 and 1994–1996) of an experimental study of fragmentation in eastern Kansas. During the early phase the plant community was characterized by little spatial or temporal variance across patch size, consistent with spatially neutral models of succession. In contrast, there was a strong, species-specific effect of patch size on small mammal species distribution and abundance. The lack of variance in vegetation structure across patch size during the early seres suggests that small mammal distributions were responding in large part to features of the system other than variance in vegetation structure and composition across patch size. As succession proceeded, the colonization of the system by woody plant species precipitated a series of patch size effects on plant community composition. Differential habitat selection by small mammals at the patch scale tracked these changes in plant distribution. For example, M. ochrogaster and S. hispidus shifted their distributions away from less fragmented patches toward smaller patches, where retarded plant succession had maintained an earlier sere. P. leucopus successfully colonized and maintained high densities only on large patches, where plant succession had progressed most rapidly toward a woody-speciesdominated community. Our results highlight the role of landscape structure in long-term community dynamics and indicate that some of the complexity observed in successional systems may result from the structure and composition of the landscape mosaic. In general, our results suggest that to fully understand long-term change within communities, the influence of landscape structure on patterns of heterogeneity in both vegetation and consumer dynamics must be understood. Moreover, the long-term and landscape-scale perspectives afforded by our study provide insight into community dynamics that might otherwise be missed.