[Relationships between soil and water loss and landscape pattern on Loess Plateau]

Based on the theories of detrended canonical correspondence analysis (DCCA), 12 soil and water loss indices ("species") and 7 landscape indices ("environmental factors") were adopted to quantitatively analyze the effects of landscape pattern on the soil and water loss in Jinghe River basin on Loess Plateau. The results showed that the first four DCCA axes were significantly correlated to agricultural land ratio, landscape diversity index, forest land ratio, and landscape contagion index. The characteristics of soil and water loss changed obviously with landscape pattern gradient, e. g., Sanshuihe watershed with a forest cover larger than 65% and low landscape diversity had a big and stable runoff, but small sediment and low river sand content. The runoff generation coefficient and runoff depth as well as the sediment transport and river sand content increased with the increasing agricultural land ratio and landscape diversity and the decreasing forest land ratio. As for Honghe watershed with a very low forest cover but high agricultural land ratio (53.41%), and with a relatively high landscape diversity and complex landscape pattern, it had the highest river sand content and the biggest sediment transport, and its monthly runoff and sediment transport varied markedly. The soil and water loss in the Upper-Huan, Down-Huan and Dongchuan watersheds with smaller forest and agricultural land ratio and relatively simple landscape pattern was smaller than that of the watersheds with dominated agricultural land.