Monday, December 11, 2006
D0103

Spinning the forest food web: Using stable isotopes (δ13C and δ15N) to quantify trophic connections between ecosystem components

Erin E. Hladilek, hladilek@uky.edu and David H. Wise, dhwise@uky.edu. University of Kentucky, Entomology, S-225 Agricultural Science Center North, Lexington, KY

Elucidating the reticulate connections and pathways of energy flow within complex terrestrial food webs can improve our understanding of ecosystem-level processes such as decomposition and nutrient cycling. The aboveground portion of a temperate forest food web is composed of two relatively distinct subwebs, the grazing (plant-based) web and the leaf-litter (detritus-based) web. Litter-dwelling generalist predators, such as spiders, may constitute potentially important links between the grazing and leaf-litter webs via consumption of herbivorous prey in addition to detritivores. We tested the hypothesis that large, litter-dwelling predatory arthropods can mediate energy flow between the grazing and leaf-litter subwebs of a temperate deciduous forest using stable isotope analysis. Generalist predators, microbi-detritivores and herbivores were collected from undisturbed areas of the forest floor and understory vegetation in an Appalachian oak-hickory forest. Stable isotope analysis (δ13C and δ15N) was used to examine the strength of connections between predators and prey derived from the grazing vs. detrital webs, and to establish relative trophic positions of all fauna. Species-specific differences in predator δ13C values indicated variation in utilization of resources from the grazing web amongst the ground predator community.


Species 1: Araneae Lycosidae Schizocosa ocreata