Arboreal Arthropods: Diversity and Rates of Colonization in a Temperate Montane Forest

Abstract

To investigate the micro-arthropod species inhabiting the montane forest canopy from three elevational sites (800 m, 1000 m, 1200 m) at Mt. Cain on Vancouver Island, British Columbia, Canada, we placed sterile litter bags filled with fir needles in the canopy and on the ground beside nine randomly chosen amabilis fir (Abies amabilis) trees. Our objectives were 1) to determine the faunal composition and diversity of micro-arthropods that colonize the needle litter microhabitat; 2) to determine the colonization rates of canopy micro-arthropod groups, specifically oribatid mites (Acari: Oribatida); and 3) to compare the rates of needle litter decomposition between the ground and canopy at different elevations, relating these results to patterns of micro-arthropod abundance. Arthropods were collected after three colonization periods (60, 120, 360 days), extracted from litter bags using a modified Lussenhop method, counted, and identified to order. Acari, Collembola, and Psocoptera were the dominant arthropods colonizing the needle litter. Two-way analysis of covariance showed ground and canopy colonization rates significantly different but with similar patterns of colonization occurring over time for all groups. Colonization rates were lower for most taxa at high elevations compared to low elevations, and most micro-arthropod taxa showed significantly different patterns of colonization across elevations. Colonization and decomposition rates were lower in the canopy than on the ground, and no differences in decomposition rates were found to occur across elevations. Our study of the colonization and decomposition of these experimental substrates will enable further assessment of the micro-arthropod diversity and decomposition processes in the montane forest. It also will contribute to our understanding of the biology of soil organisms inhabiting the lichenrich canopy of montane amabilis fir trees.