摘要：

There is increasing concern that agricultural intensification in China has greatly increased N2O emissions due to rapidly increased fertilizer use. By linking a spatial database of precipitation, synthetic fertilizer N input, cropping rotation and area via GIS, a precipitation-rectified emission factor of N2O for upland croplands and water regime-specific emission factors for irrigated rice paddies were adopted to estimate annual synthetic fertilizer N-induced direct N2O emissions (FIE-N2O) from Chinese croplands during 1980–2000. Annual FIE-N2O was estimated to be 115.7 Gg N2O-N year-1 in the 1980s and 210.5 Gg N2O-N year-1 in the 1990s, with an annual increasing rate of 9.14 Gg N2O-N year-1 over the period 1980–2000. Upland croplands contributed most to the national total of FIE-N2O, accounting for 79% in 1980 and 92% in 2000. Approximately 65% of the FIE-N2O emitted in eastern and southern central China.