Spatial analysis of earthworm biodiversity at the regional scale

Abstract

Abstract Information about the spatial patterns of soil biodiversity at the regional scale is limited though required, e.g. for understanding regional scale effects of biodiversity on ecosystem processes. This study was conducted to determine whether earthworm biodiversity parameters display spatial patterns at the regional scale and whether they are related to soil properties. A transect study was carried out in 1996, 1997 and 1998 on tilled, sandy to loamy soils in the morainal landscape of northeast Germany. One soil block (50 cm × 50 cm × 20 cm) was sampled at 50 sites for earthworm number, biomass and species composition. Total earthworm abundance and biomass fluctuated randomly along the transect in all years studied. However, reproducible spatial patterns of earthworm biodiversity were found along the transect, in respect to the occurrence of single earthworm species and in respect to species number and species composition. Species number and species composition displayed increasing trends from south to north, in all years studied. This pattern corresponded to increasing trends of soil properties like pH, soil organic carbon, total nitrogen (Nt) and clay content. By applying state-space analysis to the 1996 data set, the number of earthworm species along the transect could be estimated with parameters pH and total nitrogen. The results show that spatial patterns of earthworm biodiversity may be identified at the regional scale. State-space analysis was shown to be an effective tool for detecting relationships between earthworm biodiversity and soil properties at this scale.