中文摘要：

土地沙漠化成因机制的研究具有非常重要的理论与实践意义。根据黄河源区的自然环境条件、社会经济发展状况，在GIS的支持下对沙漠化发生发展的物质条件、气候条件以及人类活动等影响因子的空间格局特征、规律和变化趋势进行了定量分析。在此基础上，结合沙漠化遥感监测的时空数据，就黄河源区沙漠化成因机制进行了探讨。研究表明，黄河源区高寒干旱的气候条件，决定了该区域生态环境的脆弱性，沙漠化内在危险性高。同时气候作为本区最为活跃的生态环境因素，20世纪80年代以来气候干暖化加剧了风沙活动，使自然沙漠化过程得以增强。黄河源区以超载过牧为主的土地资源的过度利用以及由此造成的鼠害泛滥，人为造成了广大范围草地退化、风沙活动强度的增强，从而导致人为沙漠化过程的发生与发展。黄河源区自然因素与人为因素共同作用，互相激发，最终导致沙漠化的不断扩展及其程度的日益加重。在本区沙漠化的治理、生态环境恢复中，既要认识到生态环境的脆弱性，更要重视人为因素的负面影响。

英文摘要：

The cause of desertification is one of important parts in desertification research. Based on spatial pattern of physical environment and socioeconomic status, the causes of desertification in the headwater area of the Yellow River are discussed using geographical information system and remote sensing. The result indicates that the fragile ecological environment makes the region to have higher risk of desertification, the drier and warmer climatic changes since 1980s intensify the wind erosion and makes desertified land expansion, the human activities such as overgrazing and grassland rodent make the grassland degradation and result in the desertification intension. As a result, the desertification intensification in the headwater area of the Yellow River is resulted from physical and socioeconomic factors. Therefore, in order to control desertification effectively, we should not only deeply understand the physical environment factors, but also pay more attention to human activities resulting in desertification in the headwater area of the Yellow River.