Microbial Biomass and Its Structure in Karst Peats of Tula Oblast

Resumo

Microbial biomass and its structure in karst peats (Eutric Fibric Histosols), Dystric Fibric Histosols) in Tula oblast were studied by luminescent microscopy. The microbial biomass varied from 11 to 37 mg/g in the upper 0.5-m layer and reached its maximum in a young thin peat layer. In thick peat layers, microbial biomass amounted to 15 to 21 mg/g as calculated for the whole thickness. Upper layers contributed significantly (78–86%) to microbial biomass and fungi represented by mycelium predominated there. Bacteria were dominants in lower layers and their fraction in microbial biomass accounted for 54 to 85%. Thick karst peats are rare objects dominated by prokaryotic component in their microbial spectra. Deep karst peats represented an evolutionary sequence of floating mats with decreasing microbial pool from the younger thin peats to the deep ancient ones. This trend was attributed to the substitution of eutrophic plant communities by mesotrophic ones or it could be explained by the increase in thickness of a floating mat.