This study presents the result of topsoil (010 cm) soil organic carbon (SOC) mapping in two areas of Moscow Region (2007 status): 1096 km2 Podolsky District, and 1101 km2 Serpukhovsky District. Based on 2007 legacy soil sampling data (n= 282) within these areas, we have created astatistical model between the target variable (SOC stocks, kg/m2) and numerous covariates (legacy maps and remote sensing data). GBM model has explained 56% of soil organic carbon stocks variability. Differences in stocks within different land use types were shown quantitatively. At the same time, the spectral reflectance in the near infrared band (B5) of Landsat‑5 TM made the greatest contribution in explaining the differences within individual types (among fallow lands and urbanized areas), and the spectral index NDVI has explained the spatial variability of soil organic carbon among forest ecosystems. The root mean square error of cross-validation (RMSEcv = 0.67 kg/m2) was chosen to describe the uncertainty of soil organic carbon stock prediction. According to the model, the total soil organic carbon stocks in the upper 10 cm soil layer of the Podolsky District were 2.65 0.72 Tg, for the Serpukhovsky District 2.77 0.73 Tg.

Adapting agriculture to long-term accrual of organic carbon (С) is beneficial both for ensuring food security and for mitigating climate change. This study quantified the responses of total soil C content and its constituent pools to implementing no-tillage (NT) versus conventional tillage (CT) on farms with contrasting water regimes. The farms were chosen at two sites in the Russian steppe zone: Rostov with non-waterlogged Calcic Chernozem (CCH; sunflower-wheat rotation) and Krasnodar with periodic waterlogged Stagnic Chernozem (SCH; maize-wheat rotation). At each site, we surveyed the 0–10 cm and 10–30 cm soil layers in one continuous CT field and two short-term NT fields (8–14 years). The average C content in CCH was higher than in SCH (22.5 vs 17.7 g kg^–1). For both sites, NT showed the potential for an increase in C content (by 12–16%) relative to CT only in the 0–10 cm topsoil. Microbial-available C pool (mineralized for 180 days of soil incubation) was most sensitive to tillage systems, unlike unchanged particle-size pools. Specifically, it increased from CT to NT for CCH (by 7–16%), but it showed a decreased trend for SCH (by 11–29%), possibly due to the worsening of soil aeration in the periodically flooded regime. Gradient boosting machine models accurately predicted the spatial distribution of topsoil C content (R² = 0.99) and its microbial-available pool (R² = 0.78%) across the farmland area. The mutual drivers of both parameters were topography (elevation) and vegetation distribution (near-infrared surface reflectance). These outcomes are useful for developing site-specific management strategies to effectively restore C stocks in Chernozem soils.

Across eleven administrative districts of the Moscow region and the Moscow metropolitan area, 559 survey sites were studied from 2001 to 2020. These sites were grouped by land use types (forest, meadow and fallow land, arable land, and urban soil) and the main soil groups: Albic Podzols, Folic Retisols, Greyzemic Phaeozems, and Luvic Chernozems. At all survey sites, the dominant vegetation and geographic coordinates were recorded, and soil samples were collected from the upper 10 cm of the humus-accumulative layer. Forest soils were represented by 204 sites, meadows and fallow lands by 120, arable land by 43, soils of small towns (8 in total) by 108 sites, and those of the Moscow metropolitan area, by 84. In towns and cities, survey sites were selected in recreational, residential, and industrial land uses. The soil samples were analyzed for organic carbon (C_org), microbial biomass carbon (C_mic), basal (microbial) respiration (BR), and pH. The C_mic/C_org and BR/C_org ratios were calculated. It has been shown that the microbial parameters of soils for different land uses in small towns did not differ significantly, but in the megalopolis they did. In forest soils, the C_mic, BR, C_mic/C_org, and BR/C_org values were the highest and amounted, on average, to 589 μg C/g, 1.07 μg C–CO₂/(g h), 1.99%, and 36.0 μg C–CO₂/(g C_org h), respectively; in meadows they were lower, and in arable lands and in small towns they were the lowest (on average, 249 and 328 μg C_mic/g, 0.41 and 0.60 μg C–CO₂/(g h), 1.14 and 0.82%, 18.3 and 15.1 μg C–CO₂/(g C_org h), respectively). The spatial distribution of microbial indicators of soils in the region is visualized using the spatial interpolation method, separately for natural (forest, meadow, and fallow lands) and anthropogenically transformed (arable land, small towns) ecosystems.