Fauna, population and peculiarities of landscape distribution in earthworms (Oligochaeta, Lumbricidae) of the steppe meadow belt in the Central Caucasus

The species composition, population structure and landscape distribution of earthworms in the steppe meadow belt from the elbrusskiy variant of vertical zonation, are studied. It is shown that the character of moisture distribution accumulating in negative landforms and on gentle shady slopes where maximum parameters of earthworm abundance are registered, is a prevailing factor for developing the population structure of Lumbricidae. The number of species from the steppe meadow belt is less than in the belts of meadow steppes and broad-leaved forests, but it exceeds the species abundance of the subalpine belt. The species distribution in their stations depends on landscape location of the biogeocenosis and gorge orientation relative to basic moisture transfer flows. The steppe meadow belt differs from subjacent belts by the more “caucasian” type of the earthworm population. Proper soil Lumbricidae dominate in most communities. Prevalence of proper soil species which are more adapted to survive under adverse climatic conditions is associated with total xerophytization of landscapes in the elbrusskiy variant of vertical zonation. In mountain steppes at altitude from 1000 m a.s.l. cosmopolitan A. rosea is substituted by autochthonous vicarious D. tellermanica, and by proper soil D. schmidti in steppe meadows.