Though succession is typically thought of as a temporal process, it is also an inherently spatial one as abandoned agricultural land is often bounded by remnant woodlands. Adjacent forests not only serve as sources of colonists for succession, but also generate environmental gradients which may alter plant growth. The primary objective of this study was to examine the effect of an old growth forest edge on plant population dynamics within abandoned agricultural land. We used long term data collected from the Buell-Small Succession Study (BSS) in the piedmont region of New Jersey to analyze population dynamics in relation to the forest edge during the first 50 years of succession. By looking at individual species’ edge responses, the role the forest edge plays in regulating successional processes may be determined. We hypothesized that individual edge responses would be driven by differential dispersal (plot colonization), differential performance (increase within plots), or a combination of both.
Results/Conclusions
Large amounts of variation were found among species in both the direction and magnitude of edge responses. Of the species analyzed, approximately 39% were more abundant closer to the forest edge, 33% were more abundant farther from the edge, and 28% had no discernable edge response. In general, the variation in edge responses seemed idiosyncratic, leading to little ability to generalize across species. Edge responses were not directly associated with plant life form or the presence of clonal growth, but were correlated with dispersal mode. For vertebrate dispersed species, abundance increased with distance from the forest edge, while wind dispersed species decreased slightly. The increase in the abundance of vertebrate dispersed species with distance from the forest edge suggested that dispersal from the edge was not limiting to regeneration, but that shading from the adjacent forest may have reduced growth in some species. Factors that contributed to the individualistic variation in edge responses among species appear to include, dispersal, water stress, and shade tolerance. Through understanding the population growth patterns and the dynamics generated by the forest edge, we can integrate spatial constraints to project the spatio-temporal dynamics of successional plant communities and ultimately generate management recommendations.
