Oribatid mites (Acari: Oribatida) in boreal forest floor and decaying wood

SummaryWe studied the oribatid mite communities in forest floor and in decaying wood in pine (Pinus sylvestris), spruce (Picea abies) and deciduous (mainly Betula pendula and B. pubescens) forests at different latitudes in Finland. The study sites were either in mature managed forests or in old-growth forests in nature reserves. Altogether 78 sites were sampled in 2004 and 2005, yielding a total of 38,145 oribatid mites belonging to 133 species, of which four were new to Finland. Oribatid mite communities differed in terms of total number and community structure between forest types and latitudes within the boreal forest zone. The most abundant and diverse communities were in spruce forests and at central and southern latitudes. Total oribatid number in deciduous forests was three-fold lower compared to that in coniferous forests; still the number of species was roughly equal in all forests. The greatest differences in communities were observed between forest floor and decaying wood microhabitats. Total densities in decaying wood were three-fold lower than in coniferous forest floor. Strong differences were also observed in community structure (indicated by non-metric multidimensional scaling (NMDS)), although the majority of the species encountered were shared. Our results suggest that decaying wood maintains diverse sub-communities of mites which vary little between different forests and latitudes. Coarse woody debris (CWD) provides favorable habitat for many forest floor species and arboreal habitat species.