Coupled analysis on land use, landscape pattern and nonpoint source pollution loads in Shitoukoumen Reservoir watershed, China

Landscape pattern is a major factor affecting nonpoint source pollution (NPS) of watercourse, and understanding the impact of landscape pattern on NPS is critical for sustainable land management. This study undertook a comprehensive analysis, at sub-basin scales, of the interactions among land use, landscape pattern and NPS load in Shitoukoumen Reservoir watershed in the time period between 1980 and 2005. FRAGSTAT was used to quantitatively analyze the temporal and spatial change of landscape metrics, whilst the responses of streamflow, NPS TN and TP load to land uses were simulated by SWAT model. Redundancy analysis (RDA) was used to analyze the interactions between NPS load and landscape pattern dynamics at sub-basin scales. It was found that cropland and forest were the main forms of land use, increased by 38.0 km(2) and 8.5 km(2) between 1980 and 2005. Thirteen landscape metrics were chosen by factor analysis (FA) method. The magnitudes of changes in streamflow and NPS TN, TP load were found to vary significantly in the sub-basins, decelerated by forest patterns that are unfragmented, have a high value for the largest patch proportion. These analyses provided scientific support for preparing NPS control strategies from the perspective of landscape ecology.