Application of Mathematical Models ROMUL and Romul_Hum for Estimating CO2 Emission and Dynamics of Organic Matter in Albic Luvisol under Deciduous Forest in the South of Moscow Oblast

Abstract

The aim of this study was to validate the ROMUL and Romul_Hum simulation models based on the data of long-term measurements of soil respiration performed by the Institute of Physicochemical and Biological Problems in Soil Sciences of the Russian Academy of Sciences in the south of Moscow oblast (54°50′ N, 37°34′ E). We estimated the dynamics of carbon stocks and soil CO2 emission for three scenarios of plant litterfall compiled with the account of experimental data on the composition and mass of litterfall entering the gray forest soil (Albic Luvisol) under secondary deciduous forest. The calculations of long-term series of temperature and moisture content in the forest litter and upper organo-mineral soil horizons in simulation experiments are based on the real data on air temperature and precipitation for 1973–2016. The correspondence of simulation results to the data of field measurements was better for the Romul_Hum model, which comprises a description of the effects related to the vital activity of soil fauna, leading to the formation of different fractions of soil organic matter. The best correspondence of simulated values of CO2 emission, carbon stocks, and the C : N ratios in gray forest soil horizons to field data was for the litter scenarios, which excluded the fraction of small branches. The revealed differences between the simulated and real values of soil parameters are explained by specific features of the input and transformation of different litterfall fractions, which are not always taken into account during soil sampling. The results of the study attract the attention to the uncertainties of estimates of carbon budget in forest ecosystems due to the difficulties of accounting both large wood residues (dead tree and coarse branches debris) and smaller wood fractions in the litterfall.