Model Estimates of Changes in Soil Organic Matter Stocks in Forested Areas of European Russia under Different Forest Management Regimes

The results of the dynamic simulation of organic matter stocks in forest soils are discussed from the point of a predictive assessment of carbon sink depending on forest site types and forest management regimes. The biological cycle in the “soil–forest stand” system was simulated with FORRUS-S, Romul_Hum, and SCLISS simulation models. Computational experiments were carried out for three forest enterprises and a nature reserve located in the Republic of Karelia and in Nizhni Novgorod, Moscow, and Bryansk oblasts, which corresponds to a gradient of zonal conditions from the middle taiga to the broadleaved forest subzone. Forest survey data available for all study objects were used to simulate the long-term (100 years) forest dynamics. Calculations of soil Corg pools were carried out separately for each forest taxation area using the corresponding characteristics of the forest stand (mean height, diameter, basal area, growing stock) and soil (Corg and Ntot contents in the forest floor and mineral soil) as initial data, which made it possible to take into account the spatial variability of forest conditions and successional change of species in the resulting area-based estimates of soil carbon sink. Under the nature reserve regime, the mean increase in soil stock of organic matter by 35–80 t C/ha compared to the initial values is predicted for all territories over 100 years. Felling practices of varying intensity reduce the possible Corg sink into forest soils by an average of 30–50 t/ha compared to the reserve regime. Regional features of the dynamics of organic matter are manifested in different ratios of carbon accumulation in organic and organomineral soil horizons.