中文摘要：

利用长江上游DEM、降雨、土地利用、土壤类型数据库，计算出通用土壤流失方程中代表影响侵蚀产沙的各因子，建立这些因子以及流域面积与长江上游268个水文站以上流域输沙模数回归关系，探讨上游侵蚀输沙的尺度效应。结果显示长江上游输沙模数与流域面积之间呈负幂函数单元回归关系，而且这一关系主要产生于降雨侵蚀力因子和土壤可蚀性因子随流域面积的变化。长江上游输沙模数随流域面积增大而降低主要发生在大约1×10^4～1．58×10^5km2之间。在考虑了影响侵蚀产沙因子对输沙模数的作用后，输沙模数与流域面积之间呈正幂函数相关，反映出上游输沙近源沉积的特征。分析还发现长江上游各主要支流输沙模数变化与流域尺度大小的关系和原因有明显不同。

英文摘要：

Scaling effects on sediment yield in the upper Yangtze River are investigated through constructing relationships between the specific sediment yield （SSY） and drainage area and factors influencing soil erosion based on data of drainage basins upstream of 268 hydrological stations. The factors influencing soil erosion used in the study are those in the Revised Universal Soil Loss Equation （RUSLE） and are calculated from DEM, rainfall, landuse, soil type data banks for the upper Yangtze River. Results show that there is a negative power relationship between SSY and the drainage area of all the gauged drainage basins in the upper Yangtze River and this relationship can be ascribed to the changes in rainfall erosivity factor R and soil erodibility factor K in RUSLE with the drainage area. Between the drainage area of 10^4-1.58 × 10^5 km2 exists an abrupt decline of SSY with the increase of drainage area and it is a main component of the overall decreasing trend of SSY with the drainage area. In the regression relationship of SSY with the drainage area and all RUSLE factors, SSY is positively and exponentially related with the drainage area, revea- ling that deposition of eroded sediment occurs in a short distance in the upper Yangtze River. The relationships of SSY with the drainage area and RUSLE factors of the drainage basins of the main first-order tributaries of the upper Yangtze River are also constructed and analyzed. The results show different relationships for different tributaries because of different reasons. The scaling effects on sediment yield and causes for changes in SSY with the drainage area in the Jingsha basin are similar to those in the whole upper Yangtze River. The causes for changes in SSY with the drainage area in the Min-Tuo （Minjiang-Tuojiang） basin are also associated to the changes in factors R and K with the drainage area, but SSY is negatively related with the drainage area in the multiple regression relationship between SSY and the drainage area and factors in RUSLE due to