Effects of Precipitation and Vegetation Cover on Annual Runoff and Sediment Yield in Northeast China: A Preliminary Analysis

Northeast China is an important food producing area because it contains large areas of organic soil. However, land degradation caused by soil erosion poses a serious threat to the soil conditions in this region. It is therefore crucial to explore the mechanisms behind the soil erosion and transport processes. This study assessed the effects of precipitation and vegetation cover variations on runoff and sediment yield within nine major watersheds in Northeast China, using Pearson correlation and multiple linear regression models. There were significantly positive correlations between annual precipitation, runoff and sediment yield within all watersheds between the 1960s and 2011. In addition, the vegetation index was negatively related to differences within annual water-sediment variables within most of the watersheds from 1982 to the 2010s. Within Songhua River basin, the runoff depth and runoff coefficient had significant positive correlations with NDVI and the proportion of forest. In contrast, the vegetation had negative effects on the runoff within Liao River basin. Spatial analysis of sediment showed that area-specific sediment yield decreased with increasing drainage watershed area, and the correlations between sediment variables and NDVI were stronger within watersheds of the upper reaches and tributaries than large basins in general. The combined effects of precipitation and vegetation influence the erosion and sediment transport processes, and various human activities can influence the routing of sediment to the watershed outlet. If anthropogenic activities such as reservoir and dam construction do not decrease, the protective benefits of vegetation cover may not be realized for a long time, especially along the river mainstream due to the more complex drainage network.