Аннотация:Until recently, a lot of arable lands were abandoned in many countries of the world. About 25% of such abandonments were found in Russia. More than 50% of the total abandoned area is now located in the Taiga zone оf European part of Russia. Land‐use changes affect soil organic carbon stocks and can either lead to sequestration or emission of CO2. Character of changes depends on climatic zones, soil geneses, previous land use history and other factors. We have studied the dynamics and structure of carbon stocks in post‐agrogenic ecosystems during the natural reforestation of abandoned arable land. A chronosequence of post‐ agrogenic ecosystems on soddy‐podzolic loamy soils was investigated (Kostroma region, 58.670° N, 43.310° E). The sequence includes croplands, meadow (7 years), young forest (20 years), forest (45 years) and spruce forest (80‐100 years). It was shown, that a self‐restoration of forests leads to the sequestration of carbon. Total ecosystem carbon stocks increase from 5.2 kg C/m2 in the agroecosystem to 27.6 kg C/m2 in the spruce forest (80‐100 years). It may be explained, first of all, by the increase of phytomass and, in the less extent, carbon accumulation in the soil. The phytomass carbon storage increases in 48 times, while in the soil – only in 1.4 times. The maximal rate of carbon accumulation in the post‐agrogenic ecosystems is equal to 0.24 kg C/m2 per year. In the process of postagrogenic succession there are structure changes in carbon stocks in ecosystems. In agroecosystems, 93% of the total stock of carbon is a soil carbon. During the reforestation, proportion of this pool is reduced to 57% in the young forest (20 years), further decreasing to 30% and to 22% in spruce forests aged 45 and 80‐100 years, correspondently. Soil carbon stocks dynamics was also investigated, during self‐reforestation, in the framework of computer simulations based on the carbon cycle models NAMSOM, as a function of soil texture and land use history.