Potential effect of land-use changes on China’s terrestrial carbon uptake in 21st century
The intensified land-use changes are known to cause a large proportion of China’s carbon emission and a series of environmental problems, and are likely to impact on China’s carbon cycle in the coming decades. In this study, we analyzed the potential impact of land-use changes on China’s carbon uptake in the 21st century under two Representative Concentration Pathway scenarios (RCP4.5 and RCP8.5) based on a highly integrated process-based ecosystem model (the Dynamic Land Ecosystem Model, DLEM). To reduce uncertainty from the projection of future climate, we used the estimated climate conditions from three models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) as the input for DLEM. We conducted two experiments, considering full impacts from climate, land-use change, increasing atmosphere CO2 concentration and N deposition, and impact from land-use changes alone, respectively, to investigate the effect of land-use change on China’s carbon sequestration and carbon storage.
The human appropriation flux (land conversion related carbon emission and C loss from agricultural harvest and wood production) will compensate more than half of China’s natural carbon sink (NEP) in the 21st century, and in the decades with severe cropland expansion the anthropogenic fluxes will outnumber the natural sink and cause China to be a carbon source. Throughout the 21st century, land-use change in China contributes about 44% and 55% to the change of accumulated NCE in RCP4.5 and RPC8.5 scenarios, respectively. Land-use changes also affect the carbon storage in vegetation and soil. Before 2050 in the RCP4.5 scenario, severe cropland expansion will cause carbon loss from biomass and soil; while during 2050-2099, the decrease of cropland area and afforestation reduce the biomass carbon loss and result in an increasing storage of in soil.