Comprehensive analyses of the α-diversity of deciduous forest soil fauna: Idiosyncratic effects of climate and environmental variables lead to independent patterns

The aims of the study were (1) to identify possible indicator groups for the α-diversity of soil animals in undisturbed deciduous forests and (2) to investigate the main environmental variables responsible for the patterns of soil animal α-diversity on a regional spatial scale. Therefore, field data of nine taxonomic groups of soil associated animals from 55 permanent sampling plots in unmanaged deciduous forests in the federal state Baden-Württemberg were analysed comprehensively applying a macroecologic approach.

There were no definite significant correlations between the species richnesses, abundances or the values of Shannon-Index of the local communities between any two animal groups. Hence, no animal group was capable to indicate biodiversity patterns of another. This can be explained by the idiosyncratic relationships of the different animal groups to environmental variables. The tightness of relationships between environmental variables and soil animal diversity differed remarkably between animal groups, ranging from more than 50 % explained variance for earthworms to no significant effect of any of the explanatory variables (e.g. Chilopoda, Opiliones). Generally, species richness of soil animal groups was not coupled with the aboveground species richness of plants, while climatic conditions had a strong independent effect on the species richness of soil animal taxa.

We conclude that the diversity patterns of soil animal groups in undisturbed deciduous forests cannot be adressed by a correlative indication approach due to the very case specific relationships of species with their surrounding environment.