7th international symposium on earthworm ecology

Populations of soil organisms and especially earthworms are spatially dependent at various scales. The present study was designed to assess the short-range spatial variability of different tropical earthworm populations in a savanna protected from fire for 15 years in the station d'Ecologie Tropicale of Lamto (Cote d'lvoire). Earthworms were sampled in 1995 and 1996 using 75 and 98 25 x 25 x 10 cm soil monoliths respectively. Sampling points were distributed along a transect with minimum inter-sample distance of 50 cm. The earthworms displayed clear spatial structures either when density or biomass were analysed. Some variograms displayed two plateaux thus indicating the presence of two distinct scales of spatial autocorrelation. However small the minimum sample spacing, the nugget variance remained high, which indicated the high value of residual, small-scale variability. SADIE analyses were used to test for statistical significance of the spatial aggregation and clusters description.