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We studied the leaf litter-dwelling fauna of managed deciduous forests and primeval reference sites in Western and Central Europe and addressed the questions if the higher overall species richness close to downed coarse woody debris (CWD) is related to intra-specific or inter-specific aggregation, if the aggregation pattern changes with the amount of CWD on the forest floor, and how much CWD is needed for different taxa. The analysis is based on shelled Gastropoda, Diplopoda/Isopoda, Chilopoda and Coleoptera. Among-sample heterogeneity was lower close to CWD than distant from CWD. This was most pronounced in Diplopoda/Isopoda and Gastropoda. Diplopoda/Isopoda are comparatively mobile and assemblages were already quite homogenous close to CWD at levels above 5 m3 downed deadwood ha−1. Gastropoda have a low mobility, and more than 20 m3 downed deadwood ha−1 is needed for assemblage homogeneity. We further focused on the Gastropoda as sensitive indicators. Enhanced densities and species richness close to CWD were not a simple function of leaf litter weight, thus effects of densities on heterogeneity are not solely driven by leaf litter accumulation close to CWD. In contrast to euryecious litter-dwellers such as the Punctidae, stenecious slow active dispersers such as the Clausiliidae clearly require more than 20 m3 CWD ha−1 for an even distribution. Specialists depending on CWD even seem to have gone extinct in some managed forests. For conserving the litter-dwelling fauna, we propose a target of at least 20 m3 downed CWD ha−1 in already managed forests and rigorous restrictions for deadwood removal from still (almost) pristine systems.

The degradation–deforestation–afforestation-enrichment cycle many west European forests have undergone during the last centuries equals a large-scale disturbance experiment. The aim of this study is to analyze effects of past disturbances and recent management on forest-floor slugs, i.e. a group with comparatively low mobility and presumably low recolonizing ability. To account for spatial variability within forests, slugs were collected from moist leaf litter from sites close to and distant from coarse woody debris (CWD). In total, 68 different forests were sampled, and 1736 slugs from 15 species were found. The species response curves illustrated that most slugs have defined habitat preferences and thus may be suitable indicators. A canonical correspondence analysis with 10 environmental factors revealed that the slug assemblages were predominantly structured by anthropogenic disturbance. Rarefaction diversity was higher in disturbed forests, but the proportion of stenoecious forest species ( Arion silvaticus , A. subfuscus , Limax cinereoniger , Lehmannia marginata , Malacolimax tenellus ) within the assemblages was higher in comparatively undisturbed forests than in forests with high anthropogenic disturbance. The proportion of these species increased with forest age and the amount of woody debris on the forest floor. Soil acidity did not influence densities, but species richness was highest on soils with pH values between 4 and 5. The proportion of stenoecious forest species within the assemblages increased with decreasing pH. Slug densities and species richness were higher close to CWD than distant from CWD. The proportion of Limacoidea (Limacidae, Agriolimacidae, and Boettgerillidae) increased close to CWD whereas that of the Helicoidea (Arionidae) decreased. The results show that the slug assemblages are relatively resilient. However, stenoecious forest slugs profit from nature-oriented forestry, whereas exotic species such as Arion “ lusitanicus ” profit from high anthropogenic disturbance.

In a 2-year study we investigated soil macro-arthropods (Opilionida, Araneida, Pseudoscorpionida, Isopoda, Diplopoda, Chilopoda, Coleoptera) in a forest where forestry management is nature oriented and includes the accumulation of about 10 m 3 deadwood per ha. We focused on soil arthropod density close to (c-CWD) or distant from coarse woody debris (d-CWD) in different locations of the forest stand (interior location versus edge zone) and in different seasons (summer versus winter). We found twice as many individuals of almost all taxa at c-CWD sites compared to d-CWD sites. The influence of CWD on most taxa of soil arthropods was more pronounced in the edge zone than in the interior location. In the edge zone c-CWD sites yielded significantly higher numbers of all taxa in both seasons. In the interior location seasonal effects occurred. For example, Pseudoscorpionida and Coleoptera-Larvae preferred c-CWD sites only in summer, whereas Araneida preferred c-CWD sites only in winter. A three-way ANOVA, regarding site, location and season as the main factors, emphasised the dominant influence of CWD on the density of all taxa. Consequently, CWD is an important structural component that serves as a habitat for many saprophagous species and thus locally improves the nutritional situation of a forest stand. CWD also may reduce the pest species problem because it harbours many zoophagous soil macro-arthropods as well. # 2004 Elsevier B.V. All rights reserved.