VERTICAL-DISTRIBUTION OF COLLEMBOLA IN A PINUS-NIGRA ORGANIC SOIL

The vertical distribution of some abundant Collembola species in a con iferous forest soil was studied for 2.5 years, with summer and winter sampling. Enclosures were used to manipulate the presence of live tree roots and other soil fauna, in order to study their effects on the de pth stratification of these species. Mean depths and depth deviations (Usher 1970) were expressed as relative measures, related to rank numb ered subsamples of the soil core by fresh litter, fragmented litter an d humus layers. The various Collembola species, viz. Isotoma notabilis , Neanura muscorum, Neelus minimus, Lepidocyrtus cyaneus, L. lignorum, Orchesella cincta and Tomocerus minor showed specific mean relative d epths with partial overlap between species. The mean relative depths o f these species varied between 1.29-1.67 cm, which is equivalent to an average of 2.2-2.8 cm actual depth. Mean relative depths and relative depth deviations varied with body size. Litter moisture content, leac hate acidity, and the presence of other soil fauna and live tree roots affected depth distributions of Collembola species in a species-speci fic way. The method used to measure relative vertical distributions is discussed.