Microbiological investigations of paleosols of archeological monuments in the steppe zone

Microbiological studies of the paleosols of archeological monuments (burial mounds) of the Neolithic, Bronze, Early Iron, and Middle Ages (the fourth millennium BC to the fourteenth century AD) located in the dry and desert steppe of the Lower Volga River basin were conducted. The microbial communities that existed at the time of creating the burial mounds were shown to be preserved up to the present time. This fact was confirmed by the regularities of the distribution of the microorganisms in the “mound-buried soil” system and by the data on the determination of the age for the microbial fraction of the paleosols using the method of ¹⁴C atomic mass spectrometry. The total biomass of the microbial communities in the paleosols amounted to 20–40% of the microbial biomass in their background analogues. In all the paleosols, a special pool of viable microorganisms was present. In the microbial community of the paleosols, the biomass of the active microorganisms corresponded to 0.30–41.0% of the biomass in the present-day soil; the content of mycelium of microscopic fungi composed 43–50% of that in the recent soil. In the mycelium structure in the paleosols, the share of the dark-colored mycelium increased to 98–100%. The microbiological parameters that give a contrasting characterization of the state of the microbial communities in the soils during the arid and humid climatic periods were revealed. The changes of the arid and humid climatic epochs were reflected in the structure of the microbial communities in the paleosols at the ecological-trophic, metabolic, and genetic levels.