A GEOSTATISTICAL APPROACH TO THE STUDY OF EARTHWORM DISTRIBUTION IN GRASSLAND

This study characterises the spatial variability of the earthworm spec ies in a conventional grassland system in Le Rheu (Brittany, France) u sing a geostatistical approach. The first experiment was carried out i n autumn 1995 using a systematic grid sampling pattern. Preliminary re sults describe the spatial variability of Lumbricus terrestris and Apo rrectodea caliginosa in relation to soil hydromorphy, at the field sca le. The distributions of L. terrestris adults and A. caliginosa adults were correlated positively (Pearson correlation coefficient p = 0.56) . These distributions were also correlated with soil hydromorphy: a hi gh-biomass patch corresponded to a well drained area and a low-biomass patch corresponded to a highly hydromorphic area. The distribution of L. terrestris juveniles was very different from the adult distributio n and was not correlated to soil hydromorphy. (C) 1998 Elsevier Scienc e B.V.