农业源头流域景观异质性与溪流水质耦合关系

以丹江口库区胡家山流域为研究区域，分析了溪流枯、丰水期的水质变化特征，结合流域和河岸缓冲带景观类型及其格局，运用Spearman秩相关分析筛选了影响溪流水质的景观指数，利用逐步回归和冗余排序法定量描述景观格局与溪流水质的耦合关系.结果表明：溪流水质指标中氨氮和总磷浓度时空变化较大，其标准变异系数范围分别为69.8%~207.6%和52.0%~146.1%.景观类型中耕地和居民地是溪流水体污染的重要来源，两者在100m河岸缓冲带尺度上对氨氮的解释程度为58.6%，高于流域尺度；景观格局指数中蔓延度、林地和居民地斑块密度、林地和居民地最大斑块指数以及林地和耕地聚集度指数等显著影响溪流水质（P<0.05），流域尺度上各景观类型的景观指数对总氮和总磷的解释程度分别介于71.1%~81.6%和74.5%~83.8%，均高于100m河岸缓冲带尺度，其中蔓延度对总氮和总磷均有显著影响（P<0.05）.无显著因子进入高锰酸盐指数模型中，其浓度变化是各景观指数共同作用的结果.此外，景观格局季节变化也显著影响溪流水质.枯水期景观指数能够更好的解释总氮和总磷变化，而丰水期对氨氮的解释程度要好于枯水期.

The coupling relationship between landscape heterogeneity and stream water quality in an agricultural catchment

This study was conducted in the Hujiashan catchment close to the Danjiangkou Reservoir. In consideration of landscape patterns at the catchment and 100m buffer scale, the relationships between landscape characteristics and spatiotemporal variations of stream water quality were explored by combining Spearman's rank correlation analysis, stepwise regression analysis and redundancy analysis. The results showed that the ranges of standardized coefficients of variation for ammonia nitrogen and total phosphorus were 69.8%~207.6% and 52.0%~146.1%, indicating the significant spatiotemporal variations. Cropland and residential land were the primary sources of stream water pollution, which explained 58.6% of variations of NH₃-N at 100m buffer scale. Landscape metrics including contagion, patch densities of forest and residential land, largest patch index of forest and residential land, and aggregation intensities of forest and cropland had significant effects on stream water quality (P<0.05). Landscape metrics in the whole catchment accounted for 71.1%~81.6% of total nitrogen and 74.5%~83.8% of total phosphorus, which performed better than those at the 100m buffer scale. All landscape metrics had the combined effects on the concentration of COD_Mn. Furthermore, stream water quality was significantly influenced by seasonal variations of landscape pattern. The variations of total nitrogen and total phosphorus in the dry season and ammonia nitrogen in the wet season could be better explained by landscape metrics.