研究不同尺度景观背景对地表水水质的影响对流域生态系统的管理及水质提升具有重要意义。以丹江口库区石板河小流域为研究区,研究了子流域、100 m圆形缓冲区、200 m圆形缓冲区、100 m河流缓冲区和200 m河流缓冲区尺度下景观背景对河流水质的影响,探讨了景观背景对地表水水质的作用机制。结果表明,石板河小流域地表水的总氮(TN)和硝态氮( ${NO}_{3}^{-}-N$)浓度较高。耕地和林地占比对河流水质具有重要的影响,在子流域、100 m和200 m河流缓冲区尺度上,其相关性更为显著。在子流域尺度上,斑块密度与TN、 ${NO}_{3}^{-}-N$浓度呈极显著相关关系;蔓延度指数、斑块结合度、香浓多样性指数和香浓均匀度指数是影响水质的重要指标,且在子流域和100 m河流缓冲区尺度作用力更大。景观背景对河流水质的影响具有明显的尺度效应,子流域和采样点100 m河流缓冲区是影响河流水质的关键尺度。研究结果是对丹江口库区景观格局指数在不同尺度上对水质的差异化影响的有效补充,可为制定科学合理的水质保护与提升措施提供重要参考依据。

[Objective] Soil erosion and non-point source pollution have become increasingly prominent in the Danjiangkou Reservoir area, affecting the water quality of inflow rivers and posing a threat to the water security of the Danjiangkou Reservoir area. Existing studies have not thoroughly analyzed the influence of landscape patterns at different scales on water quality. This study aims to supplement research on the differentiated effects of landscape pattern indices at different scales on water quality in the Danjiangkou Reservoir area, thereby providing a reference for developing scientifically sound water quality protection and improvement measures. [Methods] We took the Shibanhe small watershed in the Danjiangkou Reservoir area as the research object. Based on the spatial pattern characteristics of land use, we adopted spatial analysis, mathematical statistics and Mantel test to reveal the spatial differentiation characteristics of different water quality indicators, investigate the main landscape pattern indices affecting water quality at scales such as subwatershed, river buffer zone, and circular buffer zone, and explore the mechanisms of landscape background on surface water quality. [Results] (1) The concentrations of total nitrogen (TN) and nitrate nitrogen ( ${NO}_{3}^{-}-N$) in the surface water of the Shibanhe small watershed were relatively high, mainly distributed in the central and southeastern parts of the watershed where cultivated land and residential areas were concentrated. Orchards near the river also served as important potential sources of river water pollution. (2) At different scales, the proportions of cultivated land and forest land had a significant impact on river water quality, and their correlation was more significant at scales of subwatershed, 100 m river buffer zone, and 200 m river buffer zone. At the subwatershed scale, patch density (PD) had a highly significant correlation with TN and ${NO}_{3}^{-}-N$. Landscape pattern indices, such as contagion index (CONTAG), cohesion index (COHESION), Shannon’s diversity index (SHDI), and Shannon’s evenness index (SHEI), had certain effects on water quality at all scales, and their effects were greater at subwatershed and 100 m rive buffer zone scales. (3) The effects of landscape background on river water quality had a significant scale effect. The subwatershed and 100 m river buffer zone scales were the key scales affecting river water quality, where landscape structure and landscape pattern exerted the greatest influence. [Conclusion] Management and regulation of landscape structure and landscape patterns at scales of subwatershed and 100 m river buffer zone—especially strengthening the monitoring and management of landscape fragmentation—are of great significance for improving river water quality in the Danjiangkou Reservoir area. Future research should strengthen long-term water quality monitoring to reveal dynamic change patterns of regional water quality and seasonal differences in their driving factors.