Estimates of Nitrous Oxide Emission Fluxes from Different Land Uses/Covers in China

Based on more than 260 direct N₂O emission fluxes in 93 published Chinese and English journal papers from 31 studying sites (including data from our own study), N₂O emission fluxes from various land uses/covers (arable lands, forests, grasslands, swamps and marshes, riparian areas and freshwaters) were compiled and analyzed. Results showed that the annual N2O emissions fluxes ranged from 0.14 to 54.66 kg N·ha^-1·yr^-1, with a mean of 3.54 kg N·ha^-1·yr^-1. Emissions from arable lands were the actual largest contributor with a mean of 4.66 kg N·ha^-1·yr^-1, followed by freshwaters. Grassland emission flux was the lowest. A negative correlation between annual N₂O emission fluxes and latitudes was observed in China, suggesting that northern China may contribute less N₂O than the South. A new calculation using the method of Intergovernmental Panel on Climate Change (IPCC) indicated the method is acceptable for arable lands with high fertilization levels and might overestimate N₂O emissions in areas with low fertilizations. The significant decrease in areas of arable land recently resulted in a remarkable reduction in annual N₂O emissions from agriculture. Therefore, the current IPCC method needs to be paid additional attentions on more environmental factors other than the single fertilization.