Estimation of Carbon Stocks in Soils of Forest Ecosystems as a Basis for Monitoring the Climatically Active Substances

Abstract

—The eluvozems and soddy eluvozems on two-layered deposits dominating in the soil cover of the Zvenigorod Biostation of Moscow State University, contain, on average, 65–83 t/ha of organic carbon in the organic layer and the upper meter of mineral strata. Carbon stock is minimal (59–68 t/ha) in the coarser-textured soddy eluvozem of the spruce forest and reaches 76–92 t/ha in soils of birch–spruce and pine–spruce forests. Organic layers store 3.3–5.8 t C/ha or 4–9% of the total soil organic carbon stock; the upper mineral layer (0–20 cm) stores 64–69%. Different levels and profile distribution of organic carbon in soils are determined by lithological and textural features of the soil profiles and by the nature of vegetation. The contribution of water-extractable organic carbon to the total organic carbon content in the upper mineral horizons does not exceed 1.3–1.8%; the contribution of microbial carbon is 1.7–2.4%. In acidic loamy soils, the enrichment in calcium and potassium, the cation exchange capacity, the content of exchangeable bases, and the degree of base saturation can serve as indicators of the content and stocks of organic carbon at the ecosystem level. The relationship with the content of clay fractions and oxalate-extractable Al and Fe is manifested to a lesser extent due to the similar origin and properties of soils. The variability of organic carbon stocks in soils is largely determined by its content, the influence of which decreases with depth. Accounting for spatial heterogeneity, field measurements of the soil bulk density and proportion of fine earth, and correct analytical determinations are essential components of the assessment of carbon stocks in soils of forest ecosystems as a part of the national monitoring system for carbon pools and greenhouse gas fluxes.