Application Of The Denitrification-Decomposition (DNDC) Model To Retrospective Analysis Of The Carbon Cycle Components In Agrolandscapes Of The Central Forest Zone Of European Russia

Abstract

The retrospective dynamics of major components of the carbon cycle under land use changes in the Central Forest zone of European Russia was investigated. This area is known as one of the most important agricultural and economical regions of the country. We applied the process-based simulation model DNDC (DeNitrification-DeComposition) recommended by UNCCC and world widely used. In this study the DNDC model was parameterized for Russian arable soils using official statistical information and data taken from published sources. Three main carbon variables in agrolandscapes were modelled: soil organic carbon, soil respiration, and net ecosystem exchange over the period of 1990-2017. For the analysis six administrative regions were selected: three with unchanged (permanent) arable land structure (Kaluga, Moscow, and Yaroslavl), and other three with changed crop rotation (Kostroma, Smolensk, and Tver). All regions in the study are characterized by homogeneous soil cover and similar cultivated crops. The results of the modelling were verified using the data from field CO 2 fluxes observations in the European part of Russia. In growing season, the agrolandscapes function as a net carbon sink and accumulate C from the atmosphere into plant biomass. The dynamics of organic carbon in soil under growing crops depends on organic fertilizers in cultivation technologies, and if they aren’t inputted, soil loses carbon. During the last 30 years the cumulative rates of net ecosystem exchange and soil respiration had decreased mostly due to reduction of arable land area. CO 2 emission and soil organic carbon losses are the most important controls of land degradation. Based on the dynamic patterns of CO 2 fluxes, the regions of the Central Forest zone could be separated into two groups. The group with central location characterized by intensive soil respiration and high rate of accumulation of organic carbon in soil, whereas peripheral group characterized by losses of soil organic carbon and low rates of soil respiration. According to the modelling, within the period of observations the inter-annual changes of carbon fluxes are mainly controlled by rising air temperature and heat supply, variable precipitation, and increasing concentration of CO 2 in the atmosphere. Among human activity the most important are change of arable land area and decreasing amount of fertilizers.