长江水系氮磷生态化学计量学空间变化特征及影响因素

氮（N）与磷（P）的化学计量学特征反映了N、P在生态系统过程中的耦合关系。当前对于长江水系中全流域N与P摩尔质量比（N:P）的时空衍化规律及其对人类活动的响应机制仍然缺乏科学认知，难以满足长江流域生态保护的治理理论和管理实践需求。根据长江水系水质监测数据和河流水沙数据，从全流域尺度上阐述长江水系N:P的时空分布特征，识别关键控制因素。结果表明：长江干流的N:P从上游到下游呈下降趋势，均值为92±78，大通站N:P输出为47±16；影响长江水系N:P空间变化的主要因素包括支流汇入、沿途面源输入、城市污水输入、磷矿开采活动以及水库拦截；颗粒态P和溶解态N的输入和截留控制着长江干流N:P的季节性差异。从生态化学计量学的角度，揭示人类活动对长江水系营养盐迁移转化的影响，可为未来长江流域生态修复和治理保护工作提供理论参考。

Spatial variation characteristics and influencing factors of nitrogen and phosphorus ecological stoichiometry in the Yangtze River system

The nitrogen (N) and phosphorous (P) ecological stoichiometry characteristics reflected the coupling relationship between N and P in ecosystem process. However, there was a short of the insights in the spatial and temporal evolution law of the mole ratio of N and P (N:P) in the Yangtze River watershed, as well as its response mechanism to anthropogenic activities, which was difficult to satisfy the demands in the governance theory and management practice. Based on the water quality monitoring data and river water and sediment data of the Yangtze River system, the spatial-temporal distribution characteristics of N:P in the Yangtze River system were illustrated from the whole basin scale, and the critical impact factors on N:P variations were identified. The results showed that there was a decreased tendency of N:P in the mainstream from upstream to downstream with the average of 92±78. The N:P ratio of the export of Datong station was 47±16. The spatial variations of N:P in the Yangtze River system were influenced by inputs from tributaries, non-point sources input along the way, urban sewage input, phosphate mining activities, and reservoirs interception. Temporal patterns of N:P depended on the inputs and retention of particulate P and dissolved N in the river system. The impacts from human activities on the nutrient transportation and transformation in the Yangtze River system were preliminarily revealed on the view of ecological stoichiometry and a certain theoretical support was offered for future ecological restoration, management and protection of the Yangtze River watershed.