A synthesis of the impact of Russian forests on the global carbon budget for 19611998

An attempt is made to synthesize the current understanding of the impact of Russian forests on the global carbon (C) budget for the period 1961–1998 (37 years), based on a detailed inventory of pools and fluxes in 1988–1992, and a historical reconstruction of a full forest carbon budget for 1961–1998. All major intermediate indicators of the budget (phytomass, net primary production, impact of disturbances, soil respiration, etc.) were independently estimated and compared with earlier reported results. During the entire period, the C pools of Russian forest land (FL, 882.0 × 106 ha in 1998) increased by 433 Tg C yr−1, of which 153 Tg C yr−1 are accumulated in live biomass, 57 Tg C yr−1 in aboveand belowground dead wood, and 223 Tg C yr−1 are sequestered in soil. A significant part of this increase deals with land-cover changes. The annual average C uptake by the FL from the atmosphere, defined by a flux-based method, is estimated to be −322 Tg C yr−1 for 1961–1998. The lateral transport to the lithosphere and hydrosphere comprised 47 Tg C yr−1 (including charcoal), which is considered part of the “missing C sink.” The uncertainties (excluding unrecognized biases) of averages for the entire period are estimated to be in the range of ±5–8% and ±24% for major fluxes out/into the atmosphere and for net ecosystem exchange, respectively (a priori confidential probability of 0.9). If the impact of land-cover change is excluded, the average annual sink in 1961–1998, estimated by both pooland flux-based methods, was 268 ± 94 and 272 ± 68 Tg C yr−1, respectively. The reported results are in line with recent estimates for Northern Eurasia made by inverse modeling at the continental scale, if land classes other than forests contribute to the total sink of terrestrial vegetation.