PARENT SESSION
Oral Session 3: Biogeochemistry I: Litter and Decomposition.
Presiding: J Dilustro
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 107.

Impacts of altered precipitation on leaf-litter decomposition and forest-floor arthropods.

Lensing, Janet^*,1, Wise, David¹, ¹ University of Kentucky, Lexington, KY

ABSTRACT- Because the microflora and arthropods in the leaf-litter community are sensitive to moisture levels, changes in rainfall predicted to occur with global climate change (both increased rainfall and drought) will likely affect rates of litter decay. We constructed rainout shelters to cover eight 14-sq. m fenced plots assigned to either a high- or low-rainfall treatment (irrigated with sprinklers at rates +/- 30% long-term mean). We have been manipulating rainfall 6-7 months/yr since June 2002. Litterbags of three mesh sizes, which excluded different faunal categories, were placed in each plot in autumn 2002. The rate of disappearance of oak and maple leaves was 20% higher in the high-rainfall treatment during the first year. Arthropods were periodically sampled by sifting and litter extraction. Both sampling techniques revealed that small and large spiders, ubiquitous predators in this system, have been 2x more abundant in high-rainfall than low-rainfall plots since the first post-manipulation census 5 months into the experiment. Litter extraction revealed that densities of Collembola, important microbivores in this system, were 2x greater in high-rainfall plots after 5 months, but densities in the two treatments had converged after 13 months. Larger Collembola, sampled by sifting litter, were 5x more abundant in the high-rainfall plots 17 months into the experiment. Litter extraction was used to sample mites, which include both microbivores and predators. Mites were 2x more abundant in high-rainfall plots after 5 and 13 months. Despite clear effects of the rainfall perturbation on both rates of litter decay and the arthropod community, there was no interaction between rainfall and litterbag mesh size on rates of litter disappearance. Surprisingly, the rate of litter decay was similar in all three types of litterbag. The experiment is continuing for an additional year to determine whether or not these patterns will persist.

Key words: litter decomposition, spiders, Collembola, climate change