SOIL DEVELOPMENT AND PROPERTIES OF MICROBIAL BIOMASS SUCCESSION IN RECLAIMED SITES IN BULGARIA

One of the most important preconditions of ecosystem rehabilitation in post mining landscapes is the process of soil development. In this context, the microbial activity in soil plays an important role. Microbial activity was studied in several reclaimed post mining sites resulted from the mining activity in Bulgaria. The studied soils are characterized by different biogenicity. The development of the total microflora in soils is higher in the surface layers but in depth, their number decreases due to the inhibiting effect of pollutants (heavy metals) and a change in the physico-chemical conditions. The dominant microorganisms are non-spore bacteria and all studied soils showed the development of pigment types of bacteria resulting from the high content of heavy metals. The composition of the microorganisms is poor, which can be taken as an indicator that the microbicenosis is still in the process of formation. In depth, their number is reduced by applying the effect of contamination. The mineralization coefficient values are the highest in the field with the greatest age of re-cultivation, where humidification is the most advanced. The study shows that vegetation type and litter quality seem to be more important for soil microbial activity than the substrate quality on the reclaimed sites.