Abstract
Soil-zoological studies were carried out in ten old-growth forests of the northern taiga subzone of the Murmansk region and species composition, density, and the biomass of earthworms were assessed. Four species of earthworms were identified in pine and spruce forests, and among them dominant were the litter species Dendrobaena octaedra and the soil-litter species Lumbricus rubellus. It has been concluded that earthworm species composition, density, and bio-mass reach maximum values in forest litters characterized by increased ash content, reduced acidity, and containing organic matter of the humate type. Bioindicators of litters having such properties are L. rubellus and Aporrectodea caliginosa while the former is predominant. Body sizes and weight, seasonal and long-term dynamics of population are described for L. rubellus. Based on the peculiarities of intra-biotope distribution of earthworms, optima for main soil factors were determined.