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ABSTRACT
The distribution patterns of isopods were studied in old-growth beech forests in a mountainous area in central Germany (Nature Park “Habichtswald” near Kassel). Two spatial scales were considered: Small-scale variation within a forest on limestone, and large-scale variation between forests on different substrates (basalt, limestone, sandstone).
Small-scale distribution was studied by sieving 100 litter samples from a 25 × 25 m2 grid. Small aggregations with a range of <5 m with relatively few specimens (8 · m−2) were found for Oniscus asellus, while Porcellium conspersum was aggregated in higher numbers (>12· m−2) and in larger areas (range >5 m).
Large-scale distribution was studied by means of a standardized field sampling technique of 36 study sites. Of 8 isopod species, Trichoniscus pusillus and Oniscus asellus were the most abundant and frequent. Abundance patterns and community organization varied between biotopes. Trichoniscus pusillus was most abundant on limestone sites, and Ligidium hypnorum on limestone sites with a northern aspect.
Within biotopes, microhabitat distribution was analyzed by differentiating leaf litter, tree feet, tree trunks, and lying dead wood. Species differed in their association with these microhabitats: Relatively high numbers of Trichoniscus pusillus were sampled from leaf litter, while the highest proportion of Ligidium hypnorum, Trachelipus ratzeburgii, and Oniscus asellus was sampled from dead wood.