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

Abstract

The eluvozems and soddy eluvozems on two-layer 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 litter and a meter-deep layer of mineral strata. Carbon stocks are minimal in the soddy eluvozem of the complex spruce forest (59–68 t/ha), which is characterized by a lighter granulometric composition, and reach 76–92 t/ha in the soils of the birch–spruce and complex pine–spruce forests. At the same time, 3.3–5.8 t C/ha or 4–9% of the total organic carbon reserves are concentrated in the litter, and 64–69% in the upper mineral layer (0–20 cm). Different levels and profile distribution of organic carbon reserves in soils are determined by lithological and granulometric features and the nature of vegetation. The contribution of water-extractable organic carbon compounds to their total content in the upper mineral horizons of soils does not exceed 1.3–1.8%, microbial carbon, 1.7–2.4%. In acidic light loamy soils, the enrichment in calcium and potassium, the cation exchange capacity, the content of exchangeable bases, and the degree of saturation can serve as indicators of the content and reserves of organic carbon at the ecosystem level. The relationship with the content of finely dispersed 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 determined to the greatest extent by its content, the influence of which decreases with depth. Accounting for spatial heterogeneity, field measurements of the 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 part of a national monitoring system for carbon pools and greenhouse gas fluxes under development.