Thursday, August 6, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Background/Question/Methods The effects of forest fragmentation on neotropical forest regeneration are poorly understood. We hypothesized that forest fragmentation negatively affects the diversity of regenerating neotropical forests and alters species composition of forest regeneration through changes in seed predation and seedling herbivory. We tested these hypotheses at the Biological Dynamics of Forest Fragments Project site, located in the Brazilian Amazon. In 120, 10 m2 experimental plots we measured seed predation and herbivory in continuous forest controls and forest fragments of different sizes (1, 10, and 100 ha) to determine the effect of fragment area on seed predation and seedling herbivory. To measure seed predation, we placed seeds of 5 species of tropical forest trees of varying seed sizes in these plots and recorded percent seed removal after one month. To quantify seedling herbivory, we placed two seedlings of four local tree species at each of our experimental plots. On each seedling we marked three leaves and evaluated percentage herbivory after one month and six months on these marked leaves. We determined the effect of seed predation and herbivory on forest regeneration dynamics by simultaneously measuring tree and shrub seedling species richness and composition in each of our experimental plots.
Results/Conclusions Seed predation was significantly (P < 0.0001 ) higher in forest fragments compared to continuous forest for all species and percentage herbivory was significantly different (P = 0.002) in forest fragments compared to continuous forest. Species richness of tree and shrub seedlings was significantly lower (P = 0.011) and species community composition significantly different (P = 0.011) in forest fragments compared to continuous forest. Multiple regression analysis and canonical multivariate analysis results show a significant relationship between percentage seed removal (seed predation) and both seedling species richness and species composition respectively, with seed removal of large and medium-sized seeds explaining over 19% of the variation in seedling species richness. We conclude that forest fragmentation significantly affects both seed predation and seedling herbivory; our results suggest that high seed removal rates in forest fragments may be an important factor contributing to lower species richness and altered species composition in forest fragments in the Brazilian Amazon.
Results/Conclusions Seed predation was significantly (P < 0.0001 ) higher in forest fragments compared to continuous forest for all species and percentage herbivory was significantly different (P = 0.002) in forest fragments compared to continuous forest. Species richness of tree and shrub seedlings was significantly lower (P = 0.011) and species community composition significantly different (P = 0.011) in forest fragments compared to continuous forest. Multiple regression analysis and canonical multivariate analysis results show a significant relationship between percentage seed removal (seed predation) and both seedling species richness and species composition respectively, with seed removal of large and medium-sized seeds explaining over 19% of the variation in seedling species richness. We conclude that forest fragmentation significantly affects both seed predation and seedling herbivory; our results suggest that high seed removal rates in forest fragments may be an important factor contributing to lower species richness and altered species composition in forest fragments in the Brazilian Amazon.
