Spatial heterogeneity in white-tailed deer activity increases seed dispersal of shade-intolerant plants near forest edges in fragmented forests

Abstract

Seed dispersal structures plant populations and communities but may be affected by forest fragmentation. Recent work demonstrates that white-tailed deer (Odocoileus virginianus Zimmerman) can be important seed dispersers in North American forests, potentially moving seeds over long distances. However, little is known about the role of deer as seed dispersal agents in landscapes characterized by small, isolated forest patches. The objectives of this study were to (a) determine how habitat structure influenced the spatial distribution of deer activity, and (b) describe which plant species and traits were dispersed by deer in a highly fragmented, agricultural matrix. I collected deer fecal pellet groups from 10 forest patches in plots that ranged from 10 to 100 m from forest edge. Pellet groups were cold-stratified and planted in a greenhouse to quantify seeds dispersed by deer. The number of pellet groups collected was highest near forest edges but was not influenced by patch size or isolation; 258 seedlings from 15 species emerged from collected pellets, with three species contributing 80% of seedlings. Most seedlings emerging from deer pellets were herbaceous, nonnative plants with a foliage-as-fruit dispersal mode. Plants with these traits typically perform well in high-light habitats, such as forest edges, where deer are most active. These results suggest that while seed dispersal by deer is common in highly fragmented forest patches, it is most likely to benefit shade-intolerant herbaceous species, maintaining populations of those plants along forest edges.