C - Lublin

STATE OF MICROBIAL COMMUNITIES IN MODERN AND BURIED
SOILS AS INDICATOR OF CHANGING SOIL-FORMING CONDITIONS
Demkina T.S., Borisov A.V., Demkin V.A.
Soil microbial community is an important part of soil. Practically all soil
processes are going on with the participation of soil microorganisms. Therefore the
state of microbial community is one of the most important indicators of
pedogenesis conditions. Paleosols buried under kurgans retain their properties from
the time of kurgan building and, consequently, the environmental conditions of that
time should be reflected in the properties of microbial community. The earliest our
investigations have demonstrated the existence of active microorganisms in the
buried soils. This microorganism grown well after the soil-water suspense was
sowed on the nutrient medium. Using various nutrient mediums it is possible to
appreciate the trophic groups, quantity, and biomass of microorganisms. These data
allowed us to reconstruct the pedogenesis conditions in the past.
At present there is little evidence of these microorganism’s ages and of the
diagenesis changes of microbial communities in paleosols. Not numerous data
show that 14 C age of bacteria from marine sediments varies from 985±85 to
7480±80 years (1). Studying microbial properties of ancient paleosols buried under
sediments dated back 1-4 million years it was shown that on the depth of 50-60 m
the paleosols enriched by organic carbon had a higher population of culturable
heterotrophs, a greater glucose mineralization potential, a higher microbial
diversity, and a more than 20-fold higher concentration of ATP than the weakly
developed paleosols (2). To the author’s opinion, the survival of microorganisms
over geologic time periods would be dependent on their ability to prevent cell
death imposed by desiccation contaminant nutrient limitation. A second adaptive
strategy for long term survival is the ability to enter a resting state characterized by
a lack of metabolism or very slow utilization of endogenous energy reserves at low
matric water potential. The complex of fungi in cultural layers of medieval
archaeological sites was shown to be similar to that of modern city soils (3).
Dispersion analysis of microbiological data of buried and modern soils allowed
us to establish intensity of diagenetic changes of microbial parameters and to
appreciate whether the characteristics of microbial community of the paleosols can
be used to reconstruct soil-forming conditions in the past. It was established that
during 3000-4000 years the diagenetic changes of microbial community in the
horizon B2 of the paleosols were not going on. Hence the state of microbial
community in this horizon reflects the soil-forming conditions in the past.
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