SPATIAL-DISTRIBUTION OF EARTHWORMS AND SOIL PROPERTIES IN AN ARABLE LOESS SOIL

The spatial distribution of earthworms and soil properties under sugar beet and winter-barley was investigated in 1987 and 1989, respectively, in an arable loess soil near Hannover, Germany. In a pattern of a 10 x 10 square grid on an area of 1 ha earthworms were collected with the formalin expulsion method. Three species were determined: Lumbricus terrestris, Allolobophora caliginosa and Allolobophora rosea. Different stages of development, biomass and abundance were recorded. At all 100 points of the square grid, soil samples were taken at three depths. Carbon content, bulk and aggregate density, hydraulic conductivity and gas diffusion coefficients were measured. Maps of the distribution of all properties were computed with geostatistical interpolation methods. Earthworms showed a spatial dependence in a range of 20-50 m. The larger the average size of the respective species, the more the spatial distribution of biomass and abundance of a population differed. Earthworm abundance and biomass in 1987 and 1989 were correlated. For the tilled Ap-horizon only the carbon content showed a spatial dependence and a significant correlation between both years. Further correlations between soil properties and earthworms are: L. terrestris and carbon content in the Ap; L. terrestris and aggregate density in the Al-horizon; and a negative correlation of Allolobophora species and the aggregate density in the Al.