Distribution of microorganisms in the Al-Fe-humus podzols of natural and anthropogenically impacted boreal spruce forests

Natural and anthropogenically induced seasonal variations in the abundance and biomass of various groups of microorganisms in the Al-Fe-humus podzols of boreal spruce forests were analyzed. The fungal biomass in these soils w as found to be considerably higher than the bacterial biomass. The microbia l population was mainly concentrated in a thin surface layer (10-15 cm in t hickness), which included the forest litter and the upper mineral root-inha bited soil horizon and greatly differed from other soil horizons in morphol ogy and other properties. This layer was found to be optimal with respect t o hydrothermal and nutritional conditions and is characterized by profound seasonal variations in the abundance and biomass of microbiota. The high ac idity, typical of the Al-Fe-humus podzols, resulted from the metabolism of their microbial communities. In the polluted podzols, the population of pro karyotes increased and that of eukaryotes decreased.