Influence of micro- and macro-habitat factors on collembolan communities in Douglas-fir stumps during forest succession

Abstract

We studied the relative importance of micro- and macro-habitat factors on collembolan communities in decaying stumps in three Douglas-fir ecosystems. Each ecosystem contained four seres: regeneration (3–8 years old), immature (25–45 years old), mature (65–85 years old), and old-growth stands (over 200 years old). Stumps were classified, depending on stage of wood decay as: sound, moderate decay, and advanced decay. The relationship between collembolan communities and habitat factors was determined by canonical correspondence analysis (CCA) and detrended correspondence analysis (DCA). Macrohabitat factors (stand age and study site) were the most important ones affecting species distribution. When data were pooled for season and stump decay stages, collembolan communities were characteristically grouped by seres, particularly for the regeneration and old growth. However, only a few species were characteristic of a particular sere, notably Vertagopus alpa, Hymenaphorura cocklei, and Folsomia stella in old-growth forests, and Anurophorus septentrionalis and Ballistura libra in regeneration seres. In contrast to collembolan species, microhabitat factors in the stump were influenced more by season than by stand age or site. DCA-ordination indicated that within an individual season, microhabitat factors, especially %C, %P and microbial biomass, were important determinants of collembolan distribution. Common and abundant collembolan species tended to be positively correlated with %C, but negatively correlated with %N, %P, numbers of nematodes and microbial biomass. We suggest that collembolan numbers were not directly related to the first four factors and that the negative correlation with microbial biomass was caused by excessive grazing on fungi by the Collembola.