Lumbricids and soil types in prealpine and alpine woods

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Abstract
Lumbricid population densities and their relationships to certain environmental factors were studied in the Venetian pre-Alps and in coniferous woods of Cadore. Sixteen species of earthworms, of which one quarter endemic, were sampled in areas of the pre-Alps. L. rubellus and O. lacteum were the dominant species. The relationships between the relative abundance of the six species D. octaedra, L. rubellus, O. lacteum, O. lissaense, A. rosea, A. jassyensis and some pedological parameters were investigated. Throughout the year the rainfall was uniform and all the soils examined had sufficient moisture for lumbricids. D. octaedra, together with the surface-living species, was favoured by the leaf litter and the tree cover. In all biotopes modest changes in pH or in soil texture were recorded which did not affect the relative proportions of the various species. A well aerated soil, with high values in gravitational water, appeared to increase O. lissaense, whereas a compact soil appeared to increase A. jassyensis. The water retention capacity of the soil (assimilable capillary water) clearly discriminated O. lissaense from L. rubellus and O. lacteum. In Cadore the number of species was reduced to eight; most of the endemic and all of the deep-burrowing species were absent. L. rubellus and O. lacteum remained the dominant species. The importance of the historical factors in earthworm populating is stressed.