Der Regenwurm Proctodrilus tuberculatus (Černosvitov, 1935) auf Hangschultern der mitteldeutschen Lössrandstufe (Oligochaeta: Lumbricidae)

Abstract

. The earthworm Proctodrilus tuberculatus (Černosvitov, 1935) on the crest of slopes in the central-German loess-edge ramp (Oligochaeta: Lumbricidae). – The distribution of Proctodrilus tuberculatus (Černosvitov) along the line of gradient (fall line) on the slopes of the central-German loess-edge ramp (Lössrandstufe) was investigated. The highest density on loess-edge ramps reached by the species (max. 47 adults/0.25 m²) was on the crest of slopes where the fall line of the slope merges with the plateau of the culmination area. In these locations the occurrence of surface runoff along the fall line of the slope is at its lowest and percolation into the soil profile at its highest. The soil depth in the luvisol preferred by P. tuberculatus lies in the transition zone of the A1/Bt horizons, which are influenced by soil leaching (lessivage) and conspicuously marked by the presence of many argillans. The dietary strategy of P. tuberculatus is apparently a specialisation in that the species extracts its nutrition principally from the mineral part of the soil profile in luvisols. It seems that the channels in the luvisol, which are filled with muddy sediment, are advantageous to the endogeic P. tuberculatus as it moves through the soil and feeds. In the A1/Bt layer this species probably takes up pluviolessivate, which contains microorganisms and finely dispersed or unstable organic and mineral components. This means that the ecological niche of the species is determined by the movements of nutritional material in the soil. Aporrectodea caliginosa (Sav.) and Ap. rosea (Sav.), which were always found in association with the species in the loess slopes studied, can contribute to the flow of nutrients in the mineral part of the profile by their finely dispersed particles of excrement.