1990~2018年长江经济带农田氮素平衡转变特征

利用"氮素平衡模型"评估了1990~2018年长江经济带农业生态系统的氮素平衡情况，并利用去势分析、相关分析、莫兰指数等方法探索了长江经济带农田氮素平衡的时空演变特征.结果表明：农田氮素输入总量呈上升趋势，氮输出总量变化趋势微弱，氮剩余总量呈逐年递增趋势.时间上，去趋势后的氮剩余量变化以2004年为转折点呈现先增加后减小的特征；1990~2018年东部、中部、西部氮剩余量变化趋势与研究区域整体变化基本一致，但地域性差异显著，东部氮剩余增长速度最快，其次为中部、西部.空间上，东部和中部地区由氮负荷状态转变为氮剩余状态，西部地区氮剩余情况加重；氮剩余在空间上出现较为显著的空间集聚现象，主要发生在四川省和江苏省.氮剩余量空间分布集聚性现象呈较显著的方向性特征，由东北向西南方向转变，并且随着离散程度趋于缩小，沿着长江流域方向的积聚程度逐渐增大.

Characteristics of nitrogen balance transformation in farmland of Yangtze River Economic Belt from 1990 to 2018

The "Nitrogen Balance Model" was used to evaluate the nitrogen balance of the agroecosystem of the Yangtze River Economic Belt (YREB) from 1990 to 2018. The methods of castration analysis, correlation analysis and Moran index were used to explore the spatiotemporal characteristics of farmland nitrogen balance in the YREB and found results as follows:the total amount of nitrogen input increased yet the total amount of nitrogen output changed slightly, leading to the rise of the total amount of nitrogen surplus year by year. Temporally, the total amount of nitrogen surplus increased firstly and then decreased at 2004. from 1990 to 2018, the overall dynamics of nitrogen surplus, including the eastern, central and western parts, was basically consistent. However, the regional difference was obvious i.e., the eastern part exhibited the higher increasing rate for nitrogen surplus than the middle and western ones. Spatially, there was an obvious transition from nitrogen load to nitrogen surplus in the eastern and central parts, and the nitrogen surplus was aggravated in the western part. In addition, clear spatial agglomeration of nitrogen surplus was detected especially in Sichuan and Jiangsu Provinces. The spatial agglomeration showed evident directional feature, mainly from northeast to the southwest; with the reduction in spatial dispersion, the agglomeration would be reinforced.