スケール効果と景観閾値が水質と溶存有機物に及ぼす影響

Evaluating the effect of landscape patterns on river water quality and dissolved organic matter (DOM) is vital for informing water management. The aims of this study were to quantify the crucial spatial scales and landscape pattern metrics that affect seasonal variations in water quality and DOM in the Dan River Basin, and to establish the threshold relationships between landscape pattern metrics and water quality fluctuations. The 100 m riparian buffer zone was the key scale affecting water quality and DOM changes. The total explanatory degree of the landscape pattern metrics for water quality and DOM changes was the highest during the normal season (70.93%). Key indicators affecting water quality and DOM changes were land use intensity (L), contagion index (CONTAG), shape index (SHAPE), Shannon's diversity index (SHDI), and forest. The DOM components were most strongly influenced by fluorescence spectral indices and least affected by landscape pattern metrics. The contribution rate of non-point source inputs was 55.4%, which was the main anthropogenic source of protein-like DOM. Landscape threshold results showed that maintaining land use intensity and CONTAG below 365 and 61, respectively, and increasing SHAPE, SHDI, and forest coverage proportion to 1.59, 1.225, and 52.5%, respectively, in the 100 m riparian buffer zone helped protect the water environment. This study underscores the importance of integrating scale-specific landscape planning with the targeted control of pollution sources for effectively protecting aquatic environments.