关键词: 黄土坡面, 植被空间配置, 坡型, 土壤侵蚀, “源、汇”效应

Abstract:

Land use/land cover and slope configuration are important factors affecting soil erosion in the gully and hilly area of the Loess Plateau. However, most work conducted in China against soil erosion in the loess plateau mainly focused on vegetation restoration, and few of them is concerned with the influences of slope configuration and vegetation combination along the slope transacts. The combination of the slope forms and vegetation patterns in the hill-slopes may give rise to different results to the soil erosion process, to be a source or a sink. It is, to great extent, determined by the slope configuration, the position of vegetation on the hill slope, as well as their combination. In this study, the effects of slope configuration and vegetation pattern on soil erosion in the loess hill-slope were explored by using ¹³⁷Cs isotope method and extensively field sampling in Yangquangou catchment of the Northern Shaanxi Province. In total, 118 sampling sites in 25 slope profiles are selected, and these slopes are classified into 6 types according to the configuration and 8 groups based on the vegetation patterns. The results show that: 1) Slope configuration will have significant impacts on soil erosion. In general, the slope configuration with straight form in the upper hill-slope and concave form in the lower hill-slope may have the lowest soil erosion modus, which will become a sink in term of soil erosion as a whole. However, the slope configuration with concave form in the upper hill-slope and straight/convex form in the lower hill-slope has the highest soil erosion modus. This slope may function as a source in term of soil erosion. The soil erosion effects of the other slope configurations fall in between the above two slope configurations. 2) Much difference exists on soil erosion regarding to different vegetation patterns on the loess hill-slope. It was found that the loess hill-slope with wild grassland or woodland in the upper hill-slope and orchard or other vegetation types in the lower hill-slope may have the lowest erosion modus, which plays as a sink in terms of soil erosion from the whole slope. However, the slope with strong human disturbance, for example the sloping farmland, will have the highest soil erosion modus, which plays as the source of soil erosion as a whole. 3) For controlling soil erosion, planting mature forests and grasses in the upper and middle position of loess hill-slope may remarkably reduce the overall soil erosion and sediment yields in the entire watershed. The results are valuable for land-use pattern optimization in the loess hill-slope by identifying the potential risky area of soil erosion in both slope configurations and vegetation patterns. And also, it is helpful for sustainable land use planning and ecosystem management at catchment in the loess plateau.

Key words: Loess hill-slope, vegetation pattern, slope configuration, soil erosion, source-sink effects