【摘要】 [目的]探究西藏“一江两河”(雅鲁藏布江、年楚河和拉萨河)地区人类活动对植被覆盖变化的影响机制，为该区开展山水林田湖草沙冰一体化保护与修复工程实施提供理论依据和科学指导。[方法]基于2000—2020年归一化植被指数、土地利用数据、生态工程数据和气象数据，利用GIS技术、残差分析、slope趋势分析和M-K检验等方法，研究“一江两河”地区人类活动对植被覆盖时空变化的影响机制。[结果](1)2000—2020年研究区植被NDVI总体呈增加趋势，但表现出显著的空间差异性，NDVI增加区主要集中在河谷两岸。(2)2000—2020年人类活动对NDVI正向影响区主要集中在雅鲁藏布江和拉萨河等河谷地带，负向影响主要分布在拉萨市区及其周边地区，分布较少，以正向影响为主导。(3)不同土地利用类型对植被覆盖变化的影响程度不同，草地和灌丛对NDVI变化的贡献率最大，两者共达到92.8%,其中城镇和森林面积急剧增加，城镇生态系统增加面积主要由农田和草地生态系统转入，森林和灌丛生态系统主要由草地和荒漠生态系统转入。(4)生态工程林是研究区NDVI增加主要原因之一，生态工程林面积变化与NDVI变化率、残差变化率均呈极显著正相关关系，同时生态工程林能够较好地解释残差变化。[结论]人类活动是西藏“一江两河”地区地表植被覆盖变化的重要促进因素，适度的生态工程对植被恢复有重要作用。更多还原

【Abstract】 [Objective] The mechanism of human activities affecting vegetation cover change in the Yarlung Zangbo River, Nyangqu River and Lhasa River(referred as “YNL rivers”) area of Xizang Autonomous Region was analyzed in order to provide an important theoretical basis and scientific guidance for the implementation of integrated protection and restoration projects of mountain, water, forest, farmland, lake, grass, sand, and ice in the area. [Methods] Normalized vegetation index(NDVI), land use data, ecological engineering data, and meteorological data from 2000 to 2020 were used with GIS technology, residual analysis, slope trend analysis, and the M-K test to determine the influence mechanism of human activities on temporal and spatial changes of vegetation cover in YNL rivers area. [Results](1) From 2000 to 2020, NDVI of vegetation in the study area showed an overall increasing trend, but showed a significant spatial difference. The increased area of NDVI was mainly concentrated on both sides of the river valley.(2) From 2000 to 2020, the positive impact of human activities on NDVI was mainly concentrated in the valley areas of the YNL rivers, while the negative impact was mainly located in Lhasa and its surrounding areas, the distribution was less, and the positive influences was dominant.(3) Different land use types had different degrees of influence on vegetation cover change. Grassland and scrub ecosystems contributed the most to NDVI changes, reaching 92.8% in total. The urban and forest ecosystem areas increased sharply, and the increase in area of the urban ecosystem was mainly transferred from farmland and grassland ecosystems, while the forest and scrub ecosystems were mainly transferred from grassland and desert ecosystems.(4) Ecologically engineered forest was one of the main reasons for the increase in NDVI in the study area. The area change of ecologically engineered forest was positively correlated with the rate of change of NDVI and the residual change rate. The ecologically engineered forest can better explain the residual change rate. [Conclusion] Human activity is an important contributing factor to vegetation cover change in YNL rivers area of Xizang, and appropriate ecological engineering plays an important role in vegetation restoration.更多还原