Canopy Oribatida: Tree specific or microhabitat specific?

A diverse assemblage of oribatid mites inhabits the canopy of coniferous trees in western North America. We tested the hypothesis that oribatid mites are microhabitat specific in old-growth Douglas fir, Western hemlock and western redcedar at the Wind River Crane Canopy Research Facility, Washington, USA. The upper 3 in of canopy of the three tree species were accessed using the canopy crane. Oribatida were extracted from 4 to 12 g dwt samples of alecterioid and foliose lichens using the twig-washing technique. Overall species richness was low, 16 species representing 11 families, with no species unique to this site. Species were absent from samples taken contemporaneously from the forest floor. All oribatid species were found in foliose lichens, whereas only nine species, in seven families, were recovered from alecterioid lichens. Oribatid species richness was lichen specific depending on the tree species. On Western hemlock both lichens supported similarly rich communities, but on Douglas fir and western redcedar foliose lichens supported the richer community. (c) 2007 Elsevier Masson SAS. All rights reserved.