玛曲县高寒草甸沙化是青藏高原地区发生沙化的典型案例,其成因、趋势和治理一直受到极大关注。利用三维激光扫描仪,结合野外监测和室内分析等方法,揭示了区域风沙环境,结合区域沉积物粒度与形态特征,依据沙物质来源复杂程度将沙化类型划分为风蚀坑沙化类型和复杂沙化类型。结果表明:区域全年输沙势为164.34 VU,合成输沙势为91.57 VU,合成输沙方向132.37°,风向变率0.56,属于中比率低风能环境。综合风蚀坑沙化类型周边风蚀坑与积沙区的长度比、体积比、长轴线、与区域主风向吻合程度及沉积物粒度特征,可知风蚀坑是该沙化类型区域积沙的主要贡献者。在现代沙化过程中,复杂沙化类型除周边风蚀区、活化沙丘以及沙化草地等为区域积沙贡献沙物质外,黄河河道也为区域积沙提供一定量的沙物质。

Alpine meadow desertification in Maqu County is a typical case of desertification in the alpine and humid regions of China. The causes, trends, and management of desertification have received considerable attention; however, due to the limitations of research methods and other factors, the precise positioning of sand sources is still unclear. Here, we combined a three-dimensional laser scanner with traditional methods, such as field surveys and indoor analysis, to locate sand sources accurately from a morphological perspective. The results showed that the regional annual sand drift potential was 164.34 VU, synthetic sand transport potential was 91.57 VU, synthetic sand transport direction was 132.37°, and wind direction variability was 0.56, which belonged to a medium-ratio low wind energy environment. According to the complexity of the contribution of regional sand material, this paper further subdivides the sandy zone along the Yellow River into two types: blowout desertification and complex desertification. The blowout desertification was characterized by isolated sand dunes with a slightly smaller area and wind erosion blowout in the upwind direction. The long axis direction was highly consistent with the regional main wind direction, the length ratio of the wind erosion area and sand accumulation area, volume and other morphological parameters, and the special diagnosis of sand material particle size. The desertification process was relatively simple. Also, the sand material mainly came from wind erosion blowout. The complex desertification area was larger than the blowout desertification area. The causes of desertification include dune activation, regional wind erosion, thermal melt slump. The sources of dune material include surrounding activated dunes, wind erosion land, desertified grassland. Compared with the former, the sand source of complex desertification was relatively wide, and the desertification process was complex and diverse. In modern desertification, the wind-eroded depressions around the region were still the main contributors of sand accumulation in the complex desertification type. At the same time, the Yellow River also provides some amount of sand material for regional desertification.