Institute of Ecosystem Studies

2007 BES Annual Meeting Presentation and Poster Abstracts

Resource quality and diversity implications for detritivore inter- and intra-specific interactions
Burgess, Jerry
Co-Authors: Swan, Christopher M, Szlavecz, Katalin, and Poudel, Amir
Abstract: A driving question in ecology is whether communities are composed of random species assemblages or if there are processes that influence the composition of species within communities. Detritivores strongly influence soil community structure and ecosystem processes. Earthworms are known to have an important impact on soil fertility and leaf litter decomposition. In this study we asked, how does resource quality affect interspecific and intraspecific interactions among soil fauna (earthworms), and what were the subsequent effects on organic matter decomposition? Inter- and intraspecific interactions of two naturally coexisting earthworm species, Lumbricus rubellus and Octolasion lacteum, were examined in a 3 x 3 factorial design, with covariance of density treatments: 0, 1, 2, 4, 8 earthworms in single and mixed species combinations. The experiment lasted six weeks, while L. rubellus and (or) O. lacteum fed on single or mixed leaf litter species of Liriodendron tulipfera and Quercus rubra. Feeding rates ranged from .002 to .025 g/g/day. Biomass increased in low-density chambers of both earthworm species with L.tulipfera as the leaf resource. However overall biomass and feeding rates decreased in mixed-litter interspecific and high-density intraspecific competition assays. Slopes of the mean mass loss per capita were calculated for each combination to derive an Interaction Strength. Accordingly, when the two earthworm species were mixed in L.tulipfera the interaction was comparatively relaxed, thus intraspecific interactions were more intense than interspecific interactions. This work highlights the complexity of biotic interactions between and among species at two trophic levels, and the implications for decomposition and community structure in soils.