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 speci es (Microtus ochrogaster, Peromyscus maniculatus, Sigmodon hispidus, and P. leucopus) along with general measures of an old field plant community acro ss two successional phases (1984-1986 and 1994-1996) of an experimental stu dy of fragmentation in eastern Kansas. During the early phase the plant com munity was characterized by little spatial or temporal variance across patc h 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 str ucture 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 spec ies precipitated a series of patch size effects on plant community composit ion. Differential habitat selection by small mammals at the patch scale tra cked these changes in plant distribution. For example, M. ochrogaster and S . hispidus shifted their distributions away from less fragmented patches to ward smaller patches, where retarded plant succession had maintained an ear lier sere. P. leucopus successfully colonized and maintained high densities only on large patches, where plant succession had progressed most rapidly toward a woody-species-dominated community. Our results highlight the role of landscape structure in long-term communit y dynamics and indicate that some of the complexity observed in successiona l systems may result from the structure and composition of the landscape mo saic. In general, our results suggest that to fully understand long-term ch ange within communities, influence of landscape structure on patterns of he terogeneity in both vegetation and consumer dynamics must be understood. Mo reover, the long-term and landscape-scale perspectives afforded by our stud y provide insight into community dynamics that might otherwise be missed.