江苏沿海地区农田生态系统碳源/汇时空变化及公平性研究

目的 开展区域农田生态系统碳源/汇及其时空格局研究，对农田生态系统管理与农业可持续发展具有重要意义。方法 文章采用碳排放系数法、农作物经济产量法分别估算农田生态系统碳排放量、碳吸收量，并构建生态承载效率指数、经济贡献效率指数对2007—2016年江苏沿海地区农田生态系统碳源/汇的时空变化以及公平性进行研究。结果 （1）江苏沿海地区农田生态系统碳排放先上升后下降，并呈中间高，南北低的分布格局。化肥、农药使用是碳排放的主要因素，农膜、柴油使用对碳排放影响逐渐增加。（2）江苏沿海地区农田生态系统碳吸收总体呈上升趋势，呈中西部高，南北低的分布格局。稻谷和小麦碳吸收占比高达75%，蔬菜碳吸收年平均增长率高达6.84%，逐渐成为江苏沿海碳吸收重要来源。（3）江苏沿海地区10个县（市、区）农业发展的生态、经济效率较好，启东市、海门市、赣榆区、盐城市区、大丰区、射阳县等6个县（市、区）碳汇和农业总产值的比例低于碳排放比例，是影响江苏沿海地区农业低碳发展的关键地区。结论 江苏沿海地区农田生态系统碳源/汇动态区域差异较大，需要针对不同区域情况制定和完善差异化减排策略。

SPATIAL AND TEMPORAL DYNAMICS IN CARBON SOURCE/SINK AND EQUITY OF THE FARMLAND ECOSYSTEM IN JIANGSU COASTAL AREA, CHINA

To study the spatiotemporal dynamics of carbon sources/sinks of farmland ecosystems is of great significance to farmland ecosystem management and sustainable agricultural development. We used carbon emission coefficients and crop economic yield methods to estimate the carbon emissions and absorption of a farmland ecosystem. We also developed indices of ecological carrying efficiency and economic contribution efficiency to evaluate the spatiotemporal dynamics and fairness of the farmland ecosystem in the Jiangsu coastal area from 2007 to 2016. Our study had three main results. (1) Carbon emissions from the farmland ecosystem showed an increasing and then decreased pattern from 2007 to 2016, with higher emissions in the central part than in the northern and southern parts. Excessive use of chemical fertilizers and pesticides were the main factors influencing carbon emissions, although the influence of plastic film use and diesel fumes was increasing. (2) Carbon absorption in the farmland ecosystem showed a generally increasing trend, with higher values in the central and western parts than in the northern and southern parts. Carbon absorption by rice and wheat accounted for 75% of total carbon absorption. The average annual growth in rate of carbon absorption by vegetables reached 6.84%, and this had become an important source of carbon absorption in the area. (3) The ecological and economic efficiencies of agricultural development of 10 counties (cities, districts) in the Jiangsu coastal area were relatively better than in other counties. The proportions of carbon sink and total output value of agriculture were lower than carbon emissions in Qidong, Haimen, Ganyu, Yancheng city, Dafeng, and Sheyang counties, which were the key areas influencing low-carbon agricultural development in the Jiangsu coastal area. To conclude, large regional differences in carbon sources/sink dynamics in farmland ecosystems are found in the Jiangsu coastal area, and so differentiated emission reduction strategies need to be established and perfected for different regions.