Contribution of Soil Microbiota and Soil Carbonates to CO2 Emission from Steppe and Dry-Steppe Soils of Western Transbaikalia

Carbon reservoirs were identified, and the quantitative contribution of soil carbonates and microbial biomass carbon to CO emissions from soils was revealed. The objects of the study were dispersed carbonate chemozems (Haptic Chernozems Hypocalcic) and chestnut soils (Haptic Kastanazems) of Western Transbaikalia. The data from the assessment of carbon reservoirs, as well as the contribution of carbonates and carbon from microbial biomass to the transformational carbon dioxide emission stream, will be used to calculate the carbon balance of terrestrial ecosystems and model its response to climatic and anthropogenic environmental changes. The total carbon reserves in chemozems and chestnut soils were compared. It has been revealed that there are different ratios of organic and inorganic forms within carbon pools. In chestnut soils, carbon is mostly accumulated in the form of carbonates (61–67%), while the organic component dominates in chemozems (52–78%). The contribution of carbonates to C-CO emissions has been determined, the indicator is significant and amounts to 1–3% of the total in chemozems and 3% in chestnut soils, which should be taken into account in balance calculations. The contribution of Ctotal to carbon dioxide emissions is significant and amounted to 1.1–2.5 in virgin soils, 0.8–3.1% in agrogenic soils. The participation of microbial biomass carbon in the total organic carbon reserve was insignificant and amounted to 1.4–2.5% of chemozems and 1.8–3.3% of Corg of chestnut soils. It was revealed that microbial respiration of soils decreased in the series: dispersed-carbonate chemozem → chestnut soil.