Student Honors Theses

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Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

Document Type


Publication Date

Spring 2008


With continued forest fragmentation, edge effects play an important role in shaping the structure and composition of plant communities. Some forest plant species exhibit increased abundance at forest edges, while other species have a negative edge response. Despite welldocumented edge effects, there are few studies that document the underlying effects on population dynamics of individual species that result in edge responses. Two mechanisms may generate differential distribution of a species across an edge. Edges may 1) alter population demographics by influencing the plant’s uptake and allocation of resources, or may 2) influence the spatial pattern of seed dispersal. Coral berry (Symphoricarpos orbiculatus) is a fleshy-fruited native shrub present at both forest edge and interior habitats. In order to assess spatial demographic responses of S. orbiculatus, reproductive success was determined for individuals occurring along transects perpendicular to the forest edge. Following light gradients, population density of S. orbiculatus declined with distance into the forest, with few individuals occurring eight meters into the forest. Similarly, total fruit production by each individual was positively correlated with light intensity and negatively correlated with distance from the edge. The quality of offspring produced was unaffected by the edge as the weight of individual seeds and fruits did not change significantly with distance from the edge. Seeds produced were ~99% viable across the entire population with no edge effects. For this species, increased growth and reproductive 3 performance at forest edges appears sufficient to generate the observed spatial pattern of the species. With increasing forest fragmentation, these data suggest that populations of this understory shrub could see rapid growth at edges and that the high seed production of edge plants may increase seed availability even beyond edges.

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