Dynamics of carbon balance components in fallow arable lands on the Valdai Upland

The dynamics of carbon pools in the live phytomass, necromass, and soil reservoirs have been analyzed in fallow arable lands of Novgorod oblast. The results show that the amounts of above- and belowground necromass increase with the age of fallows, while the dynamics of live phytomass have no distinct trend. Comparisons with archival data show that the stocks of soil organic carbon in the studied ecosystems have decreased by 1.39 t C/ha since 1983, which is equivalent to an annual loss of 0.03 t C/ha. The main factors accounting for changes in the carbon stocks of fallow soils are the initial organic carbon contents in topsoil, the intensity of agromeliorative measures taken during the period of agricultural land use, and carbon contents in soils of meadow communities typical for a given region (zone).