Monday, December 10, 2007 - 9:53 AM

Influence of decomposing logs on the spatial distribution of oribatid mite assemblages in the eastern Canadian boreal forest

Andrea D. Déchêne, and Christopher M. Buddle, McGill University, Natural Resource Sciences, 21, 111 Lakeshore Road, Ste. Anne de Bellevue, QC, Canada

The removal of timber during harvesting substantially reduces potential sources of carbon and nutrient input and important invertebrate habitat, most noticeably microhabitats associated with fallen trees. Oribatid mites represent much of the biodiversity on the forest floor and are essential to decomposition and nutrient cycling processes. We investigated the influence of decaying logs on the spatial distribution of oribatids on the forest floor at the SAFE (sylviculture et aménagement forestiers écosystémique) research station in the Abitibi region in NW Quebec. In June 2006, six logs were classified as decay class III-IV (ellipsoid shape, moss coverage 50-80%, <50% bark) and were sampled at three distances each: directly on top of the log (ON), directly beside the log (ADJACENT) and at least one meter away from the log and other fallen wood (AWAY). Samples ON logs consisted of a litter layer sample, an upper wood sample (i.e. upper portion of log) and an inner wood sample (i.e. loose woody material not connected to outer wall of log). Samples at the ADJ and AWAY distances consisted of litter and soil samples. Oribatid species richness is higher and composition is significantly different directly ON logs in litter and inner wood layers; total abundance is not different, although there are considerable species-specific changes in abundance with distance from logs in all layers. In order to better understand decomposer assemblages on the forest floor, it is imperative to investigate habitats other than litter and soil; fallen dead wood is one such habitat.