Associations between corticolous microarthropod communities and epiphytic cover on bark

The discontinuous bark cover formed by epiphytic lichens and algae provides a mosaic of microhabitats for the fauna. Multivariate analyses applied to 1800 samples collected in Belgian Lorraine (southern Belgium) during each of the four seasons has made it possible to distinguish five major classes of arthropod microcommunities. Two of them are confined to special habitats or places at certain seasons, viz. a Pseudochermes fraxini (Homoptera) community found on Fraxinus during the summer, and “trophically” different from others; a Vertagopus arborea (Collembola) community observed in foliose lichens in St. Mard mainly in winter. The three other classes are directly related to the epiphytic cover, viz. a Dometorina plantivaga (Oribatida) community found in crustose epiphytes; an Eueremaeus oblongus/Trichoribates trimaculatus (Oribatida) community sheltered by foliose lichens; an Entomobrya nivalis (Collembola)/Cerobasis guestfalicus (Psocoptera) community observed in fruticose lichens. The ecological meaning of those microcommunities (mosaic and stratification patterns, seasonal variation, succession) is discussed. The results support the hypothesis that corticolous microcoenoses are associated with the epiphyte type and that their composition is greatly affected by the vegetation stratification pattern on bark.