The magnitude, spatial and temporal patterns of terrestrial carbon sink and the underlying mechanisms remain uncertain and need to be investigated. China is important in determining the global carbon balance in terms of both carbon emission and carbon uptake. Of particular importance to climate-change policy and carbon management is the ability to attribute the relative contributions of multiple environmental factors to net carbon source/sink in China’s terrestrial ecosystems. Here the effects of multiple environmental factors (climate, atmospheric CO₂, ozone pollution, nitrogen deposition, nitrogen fertilizer application, and land use/land cover change) on net carbon storage in terrestrial ecosystems of China for the period 1961-2005, were modeled with newly developed, detailed historical information on these changes.

Results/Conclusions

For this period, results from two models indicated a mean land sink of 0.21 Pg C per year, with a range of 0.18 to 0.24 Pg C per year. The models’ results are consistent with field observations and national inventory data and provide insights into the biogeochemical mechanisms responsible for the carbon sink in China’s land ecosystems.  In the simulations, nitrogen deposition and fertilizer applications accounted for 61 percent of the net carbon storage in China’s land ecosystems in recent decades, with atmospheric CO₂ increases and land use also functioning to stimulate carbon storage. The size of the modeled carbon sink over the period 1961-2005 was reduced by both ozone pollution and climate change. The modeled carbon sink in response to per unit nitrogen deposition shows a leveling off or a decline in some areas in recent years, although the nitrogen input levels have continued to increase.