黄河流域沙漠化空间格局与成因

黄河流域地势西高东低，自西向东有青藏高原、内蒙古高原、黄土高原和黄淮海平原4个地貌单元，总面积为79.6万km²。黄河流域是中国重要的生态屏障和重要经济带，黄河流域生态保护和高质量发展已上升为国家战略。沙漠化是中国北方干旱、半干旱以及部分半湿润地区主要的土地退化形式，沙漠化对黄河流域，尤其是流域中、上游地区的影响较大。为了全面掌握黄河流域的沙漠化土地空间分布特征，本研究以Landsat遥感影像为数据源，通过地理信息系统（GIS）技术，获得了黄河流域2010年的沙漠化土地分布数据。结果表明：黄河流域内沙漠化土地面积为128 667 km²，占流域总面积的16.2%；黄河上游的沙漠化土地面积最大，然后依次是黄河中游、黄河源区、黄河下游，沙漠化土地面积分别为89 341、21 426、17 894、7 km²，分别占全流域沙漠化土地总面积的69.4%、16.7%、13.9%、0.01%。黄河流域的沙漠化土地绝大部分分布于内蒙古，其沙漠化土地面积为91 398 km²，占全流域沙漠化土地面积的71.0%；其次是青海，沙漠化土地面积为17 432 km²，占全流域沙漠化土地面积的13.5%；陕西和宁夏的沙漠化土地面积分别占全流域沙漠化土地面积的8.3%和6.5%。黄河流域的沙漠化空间格局主要是降水量与沙源空间耦合的结果，流域92.6%（119 114 km²）的沙漠化土地分布于干旱、半干旱地区。从20世纪70年代以来，黄河流域的沙漠化总体上经历了快速发展—发展放缓—明显逆转的过程，沙漠化大幅度的变化主要受人类活动影响所致，在过去几十年间风速持续减小对沙漠化逆转的积极作用也应引起重视。

Spatial pattern of aeolian desertification and its causes in the Yellow River catchment

The Yellow River catchment is high in the west and low in the east， spanning four geomorphic units， namely Tibetan Plateau， Inner Mongolia Plateau， Loess Plateau and Huang-Huai-Hai Plain from west to east， with a total area of 79.6×10⁴ km². The Yellow River catchment is an important ecological barrier and economic belt in China. Today， ecological protection and high-quality development in the Yellow River catchment has become a national strategy of China. Aeolian desertification is the main form of land degradation in arid， semi-arid and partly humid areas of northern China， and it has a great impact on the Yellow River catchment， especially in the middle and upper reaches of the catchment. To obtain the spatial distribution characteristics of aeolian desertified land in the Yellow River catchment， the Landsat remote sensing image was taken as the data source to monitor the aeolian desertified land distribution in the Yellow River catchment in 2010 based on geographic information system （GIS） technology. The monitoring result shows that the area of aeolian desertification land in the Yellow River catchment is 128 667 km²， accounting for 16.2% of the total area. The area of aeolian desertification land in the upper reaches of the Yellow River was the largest， followed by the middle reaches of the Yellow River， the source region of the Yellow River， and the lower reaches of the Yellow River， and the area is 89 341 km²， 21 426 km²， 17 894 km²， and 7 km²， respectively， accounting for 69.4%， 16.7%， 13.9%， and 0.01% of the total area of aeolian desertification land in the whole catchment. The result also shows that most of the aeolian desertification land in the Yellow River catchment is distributed in Inner Mongolia， with an area of 91 398 km²， accounting for 71.0% of the total area of aeolian desertification land in the catchment， and it was followed by Qinghai， Shaanxi and Ningxia， accounting for 13.5%， 8.3% and 6.5%， respectively. It is concluded that the spatial pattern of aeolian desertification land in the Yellow River catchment is mainly controlled by precipitation， because 92.6% （119 114 km²） of desertification land in the region is distributed in arid and semi-arid regions. Since the 1970s， the aeolian desertification in the Yellow River catchment has experienced a process of rapid development-slow development-obvious reversal， and the significant change trend of aeolian desertification is mainly caused by human activities. Nevertheless， the positive effect of the continuous decline in wind speed over the past few decades on aeolian desertification reversal should be emphasized.