PARENT SESSION
Contributed Oral Session 168: Invertebrate Ecology: Food Webs, Physiology, and Communities
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 524 B, Level 5, Palais des congrès de Montréal
Contrasting arthropod biomasses between temperate and tropical sites.
Richards, Lora1, Coley, Phyllis1, 1 Dept. of Biology, Salt Lake City, UT
ABSTRACT- Globally, primary productivity decreases with increasing distance from the equator. This latitudinal gradient has implications for interactions between plants, their herbivores and predators. One challenge is to quantify the relative differences in factors affecting herbivores along this gradient. By examining how trophic level biomass differs in high productive patches and the understory in tropic and temperate forests we can begin to quantify differences in trophic interactions along a latitudinal gradient. To address this question we compared arthropod biomass and predation on artificial caterpillars in productive treefall gaps and neighboring understory. Our field sites are in natural gaps in Panama and man-made gaps in North Carolina. We found that gaps in both forests have five times the young leaf density and twice the plant density than the understory. We also found five times herbivore biomass and about 3.5 times the predator biomass in gaps than the understory. However, predation on artifical clay caterpillars indicates a potential higher per capita predation rate in gaps of tropical forest, but in the understory of temperate forest. In addition, a multiple regression model suggests that predator in tropical gaps have a significant positive effect on young leaf density, even more than light, suggesting potentially top-down effect. In the tropical understory we found that young leaf density accounted for the majority of herbivore variance. We found the opposite pattern in temperate forests, with young leaf density having a greater effect on herbivore biomass in gaps. The results are consistent with the hypothesis that natural enemies have a stronger influence on herbivores in the tropics and that food resources have a stronger influence in temperate forest.
Key words: Treefall gap, Productivity, Arthropod Predation, trophic interactions