The carbon sequestration potential of China's grasslands

With the consequences of anthropogenic activities such as overgrazing and cropland expansion, grasslands in China suffer severe degradation since the 1980s. The national grassland restoration policy enacted at the beginning of the 21th century has the potential to increase plant growth and productivity and hence regional carbon (C) sequestration. Here, we assessed plant and soil organic C (SOC) stocks for both degraded and restored/non-degraded plots at 802 sites in Northern and Northwest China using pairwise field sampling and quantified the C sequestration potential (CSP) of China's grasslands. A geostatistical model was performed to upscale the field measurements to national scale. Averaged across the 802 paired grassland sites, the mean plant biomass C and SOC density in the top 1 m depth were 0.44 +/- 0.17 and 8.82 +/- 1.78 kg C/m(2), respectively. Compared to the degraded grasslands, the restored grasslands had an average of 0.11 +/- 0.17 (29.2%) and 1.02 +/- 1.28 kg C/m(2) (12.3%) greater plant biomass C and SOC density, respectively. The geostatistical model produced a total CSP of 17.3 +/- 2.3 Pg C in China's grasslands, with 94% in soils. If the CSP estimated in this study could be achieved, the current grassland SOC stock would increase by 61%, offsetting 11 yr (2000-2010) of national fossil CO2 emissions.