Earthworm distribution and humus forms in the development of a semi-natural alpine spruce forest

The relationship between earthworm population, soil humus and forest develo pment were studied along a 200-m transect of an alpine Norway spruce (Picea abies Karst.) forest in the Sixt-Fer-a-Cheval nature reserve near Samoens in Haute-Savoie in the North Alps. Four developmental stages in the spruce forest were included in this transect ranging from early colonization by tr ees to degradation. Observations were made both at the scale of these devel opmental stages and at the scale of individual trees. Fifteen plots were sa mpled along the transect and the humus profile in each plot was described. Earthworms were collected by spraying formaldehyde onto 1-m(2) plots for th ree repetitions. Earthworm distribution was strongly correlated with the ag e of individual trees, but not with the developmental stages of the forest. The greatest density and biomass of earthworms were associated with mull a nd dysmull humus. (C) 2000 Editions scientifiques et medicales Elsevier SAS .