川渝地区农业生态系统氧化亚氮排放

N_2O Emissions from Agricultural Ecosystem in Sichuan-Chongqing Region

基于县级农业活动水平数据及区域氮循环模型IAP-N方法,并根据地理特征、环境气候条件及地区行政区划将川渝地区划分成4个亚区,详细估算了1990-2004年川渝地区农业生态系统氧化亚氮（N2O）的排放及其时空分布状况.结果表明,川渝地区1990-1994、1995-1999、2000-2004年农业生态系统N2O年平均排放量（以纯氮量计）分别为52.3、58.2、62.0 Gg/a,其中55%来自农田直接排放.3个时期农田直接排放量分别为29.6（7.6-63.3）、33.0（8.4-71.8）、34.0（8.5-75.8）Gg/a,农田直接排放通量分别为4.73、5.39、6.11 kg/（hm2.a）.农田旱作是农田N2O直接排放的主要源,水旱轮作对农田N2O直接排放的贡献也很大.川渝地区农业生态系统N2O排放量以及农田N2O排放通量,1995-1999年期间比1990-1994年期间增长幅度较大;2000-2004年期间,农田N2O排放通量增长速度未呈现减缓趋势,但由于耕地面积减少,农田N2O排放量增长呈现停滞状态.川渝地区农业生态系统N2O主要排放地区分布在成都平原和重庆地区,各区域的N2O排放源贡献各不相同,重庆地区和成都平原农田N2O直接排放处于主导地位,而川西北地区则是放牧N2O排放处于主导地位.研究结果为决策者合理利用肥料,制定川渝地区农业生态系统温室气体减排措施提供科学依据.

A regional nitrogen cycling model IAP-N was adopted to estimate nitrous oxide （N20） emission from the agro-ecosystem in the Sichuan-Chongqing Region during 1990-2004. The county level agricultural activities data were used, and Sichuan-Chongqing Region was divided into four sub-areas by the geographical characteristics, environment and local climatic conditions and administrative division. The results showed that annual averaged N20 emissions （in nitrogen gauge） in 1990-1994, 1995-1999, 2000-2004, respectively, were 52.3, 58.2,62.0 Gg/a, of which 55% came from the N20 direct emission of the fertilized croplands. They were 29.6（7.6-63.3）, 33.0（8.4- 71.8）, 34.0（8.5-75.8） Gg/a, equals to 4.73,5.39,6.11 kg/（hm^2·a）, respectively. Upland/glebe was the primary source of the N20 direct emission. Meanwhile, paddy-upland rotation system also played an important contribution to it. The increasing rates of N20 emission from agro-ecosystem and N20 emission flux in cropland were much higher in 1995-1999 than in 1990-1994. The N20 emission flux in the cropland showed a continuous increasing trend in 2000-2004, but the increasing rates of total N20 emission from agro-eeosystem were stagnant due to the decrease of arable land area. The N20 emission of agro-eeosystem mainly came from Chengdu Plain and Chongqing. The contributions of different sources to the total N20 emission of agro-eeosystem were variable in the region. For instance, the primary source of N20 emission was the direct emission from croplands in Chengdu Plain and Chongqing, whereas, in northwest region of Siehuan province was the N20 emission induced by grazing. The results will provide a scientific basis for policy maker to make fertilizer effectively applied and mitigate GHG emission from agro-eeosystem of Sichuan-Chongqing Region.