Land-use change in the Soviet Union between 1850 and 1980: causes of a net release of CO2 to the atmosphere

A detailed analysis of the history of land-use change in the Soviet Union that included tree cutting and regrowth, oxidation of woody debris, decay of wood products, and clearing of lands for agricultural expansion showed that the net carbon flux between the USSR and the atmosphere resulting from these activities was approximately zero in 1980; that is, there was only a small net flux of 0.037 × 10¹⁵ g carbon from the land to the atmosphere in that year. These results are in contrast with previous analyses that found the USSR to be a net carbon sink. In our analysis, we found that regrowth of forest vegetation following harvest, when considered alone, was responsible for an annual net storage in the USSR of about 0.136 × 10¹⁵ g C for the period 1955-1975. a value intermediate between estimates derived from a previous analysis. This storage was balanced by a net release to the atmosphere of about the same amount of carbon from a variety of processes, including the oxidation of woody debris and decay of wood products. In 1980, the carbon flux between the land and the atmosphere due to land-use change throughout the entire northern hemisphere’s temperate and boreal systems was also small, as these systems accumulated only 0.025 × 10¹⁵ g C that year.