Population structure and topical preferendum of earthworms (Oligochaeta, Lumbricidae) in the soils of normal forest formations of the Teberda and Bolshoi Zelenchuk river basins (Teberda nature reserve, North-Western Caucasus)

The species composition and abundance rates of earthworms in normal forest biogeocenoses of Teberda nature reserve and adjacent territories have been investigated. The greatest species number is marked in pine forests. The most “caucasian” image distinguishes the fauna of fir and hornbeam forests in addition to stable cosmopolitan block, and is formed by two crimean-caucasian endemics - D. tellermanica, Caucasian by its origin and the species representing ancient Mediterranean fauna of the Caucasus. Hornbeam forest earthworms are characterized by general high population, maximum biotopiс species diversity and earthworm abundance evenness which is the closest to the maximum value. Debris epigeic and cosmopolites are less represented in fir forests than in other biogeocenoses. The soil population of maple, alder and birch formations have similar ecological structure. However, the minimum representation of endogenic earthworms and frequent occurrence of boreal species is marked in birch forests, a wide spectrum of dominants - in maple forests, and evenness of Lumbricidae abundance is maximum in alder forests. In soil samples of beech forests only two species are registered, the other Lumbricidae are stratified under the bark of brushwood, in green moss synusia and hygrophitic areas. Dominance index of earthworms represents the largest extremum of the researched communities, biomass, indexes of biodiversity and abundance evenness of earthworms are minimal. The fauna of deciduous and mixed forests and communities including motley grasses in the herbaceous layer differs from coniferous biogeocenoses (of dead soil coverings or gramineous) by the most total representation of morpho-ecological forms. Podzol occurrence or hydromorphic character of soils confines distribution of anecic and endogenic species. The substitution of epigeic D. octaedra by Mediterranean debris epigeic D. attemsi is registered in croocked birch, pine and spruce forests.