Investigations of soil biological processes and biota were carried out in 1993–2006 in a relatively natural minimally disturbed ecosystem – pine forest soil of the old Ažvinčiai forest, Aukštaitija National Park. The obtained dynamic data for 14 years allow analysing the influence of climate changes on the density and species diversity of soil microarthropods and determining the trends of changes. In order to find out seasonal fluctuations in the abundance of zoocoenoses and to determine their dependence on climate conditions, the investigation of 1998 was carried out on a monthly basis.

It was determined that coniferous forests (Pinetum myrtillosa vacciniosum) of the moderate climate zone, growing in carbonaceous arenosols, are characterized by a rich complex of microarthropods predominated by oribatid mites. The microarthropod density reaches 228.1 thou ind. m^–2. Their species composition includes 157 species. The high density of microarthropods persists throughout a year, reaching its maximum (548.6 thou ind. m^–2) in late autumn.

Though generally soil moisture in this kind of forests is sufficient and soil temperature is optimal, soil moisture reduction in different years may entail fluctuations of the density of most sensitive (having the shortest life cycle) pedobionts (microorganisms, collembolans, etc.). This may destabilize the settled relationships among the organisms and entail functional changes in the prime biological processes of soil, i.e. mineralization and humification of organic matter.

Keywords: temperature, precipitation, microarthropods, coniferous forest