Functional role of Collembola in successional coastal temperate forests on Vancouver Island, Canada

The interrelationships among collembolan feeding groups (FG), decomposition rates, microbial biomass, and forest successional stage were studied at three sites in Douglas-fir dominated stands on the dry leeward side of Vancouver Island, BC, Canada. Each site contained a basic suite (or chronosequence) of four stages of stand development: old-growth (>248 years), regeneration (7-9 years), immature (35-46 years), and mature (80-102 years). Principal component analysis (PCA) was used to identify four collembolan feeding groups on the basis of gut contents. Three of the feeding groups (FG 1-3) were fungal-feeders, but differed from one another in the types of fungal material consumed. The last group (FG 4) comprised species that ingested particulate organic matter (POM). Significant positive correlations between microbial biomass and collembolan abundance were obtained for the fungal-feeding Collembola (FG 1-3), but not for the detritivorous FG 4. The proportional representation of collembolan species feeding on darkly pigmented fungi (FG 1) was reduced in the regeneration stands, where species feeding on particulate organic matter predominated. Over the 4 years of this study, the mass loss of decomposing wood chips in litterbags was not significantly influenced by the age of the forest in which the bags were placed. In contrast, the mass loss of needle litter was significantly reduced in regeneration stands. Multiple regressions based on the abundance of the different feeding groups of Collembola provided better estimates of the mass loss of decomposing litter or wood chips than did regressions based on total collembolan numbers. (C) 2003 Elsevier B.V. All rights reserved.