Abstract:Soil erosion in Hekou-Longmen section of the middle reaches of Yellow river in the loess hilly and gully region of the Loess Plateau in China is serious. In this study, the watersheds from Hekou to Longmen (Helong section) in awhere 42 hydrological stations located were selceted to investigate the relationship between landscape pattern and soil and water loss by using Geographic Information System (GIS) and Revised Universal Soil Loss Equation (RUSLE). Specially, the landscape pattern index analysis, canonical correspondence analysis and path analysis were used to analyze the effects of landscape pattern on soil and water loss in different scales. The results showed that the spatial variation and relative differences of landscape pattern versus soil erosion/sediment delivery processes in the watersheds changed significantly with scales. At patch-class level, the cohesion (CONHESION3) and the coefficient of variation of fractal dimension index (FRAC_CV3) of grassland, the chumpy of cropland (CLUMPY1), the chumpy of residential construction land (CLUMPY5) and the edge density of residential land (ED5) were the main landscape pattern indices t controlling the variation of soil and water loss processes. Furthermore, the cohesion of grassland was closely related to soil and water loss processes. At landscape level, the cohesion (COHESION), mean patch area (AREA_MN), aggregation index (AI) and patch richness of landscape (PR) were the main pattern indices effectively affecting the variation of soil and water loss processes of a watershed. Landscpe metrics on patch-class level had more indicative ability than that on landscape-level. With comprehensive analysis of the impacts of land use patterns on the soil and water loss processes at the class-level and landscape-level, we found that land-use patterns show signifcant "landscape nesting" characteristics, in influencing the soil and water loss. At the "nested landscape" level, the cohesion of grassland (the path coefficient is -0.867) and the chumpy of cropland (the path coefficient is -0.367) were the main landscape pattern factors dominating watershed sediment yield, and the coefficient of variation of fractal dimension index (FRAC_CV3) (the path coefficient -0.49)could contribute positively to suppression of sediment delivery. Resluts of this study indicated that the landscape pattern has significantly influences on watershed soil erosion and sediment delivery, however, the statistical relationship between landscape indices and response variables of soil and water loss varies with landscape scale. Landscape is a mixture of natural and human-managed patches of different sizes and shapes, and the multiple-level mosaic structure of landscape is one of the important factors affecting the relationship between landscape pattern and ecological process. Selecting suitable spatial and temporal scales and analytical perspectives may improve our understanding of the interactions between pattern and process in the landscape.