RELATIONSHIPS BETWEEN EARTHWORMS ASSOCIAT IONS AND VEGETATION IN FORESTED SOILS IN ARGENTINA

Earthworms species associations were studied troughout two years in a forested soil with homgeneous stands of several tree species. The domi nant and more frequent species were Aporrectodea caliginosa, A. rosea, A. trapezoides (Lumbricidae), and Pheretima hawayana (Megascolecidae) ; all of them are nonindigenous species in Buenos Aires (Argentina), w here the sampling was carried out. Aporrectodea caliginosa and A. rose a showed positive spatial and spatio-temporal association values. For several cases, our data suggest that species with great niche overlape coexist, and there is not evidence of competitive exclusion. Some spe cies use the same patch at different periods along the year. Trees whi ch give poliphenols to soil depress earthworm numbers while those whic h incorporate nitrogen to soil improve its quality and increase earthw orm numbers.