黄河流域内蒙古段植被时空变化特征及条带状分布成因

监测干旱、半干旱地区植被覆盖度的动态变化，评估大尺度区域地质背景，尤其是活动构造在植被变化过程中发挥的作用对植被时空格局的认识具有重要意义。黄河流域内蒙古段地处干旱半干旱区，植被多依赖于地下水；且该地区活动构造较发育，是认识植被非地带性特征的理想区域。基于中分辨率成像光谱仪（MODIS）、归一化植被指数（NDVI）、气象与土地利用数据，对2000-2018年黄河流域内蒙古段植被覆盖度（FVC）的时空变化及稳定性进行分析，在此基础上针对河套段植被条带状特征及其成因进行讨论。结果表明，近20年研究区的FVC总体表现为增加趋势。降雨增加是大黑河流域、浑河流域及十大孔兑区域FVC增加的主要原因，沙漠地区FVC的增加得益于三北防护林工程建设。大黑河与浑河流域水分条件较好，物种多样性丰富，植被覆盖度高，能较好的抵御气候变化；而十大孔兑区域和沙漠地区FVC较低，生态系统脆弱，对气候波动的响应较大。河套灌区受人类活动主导，对气候变化的敏感性较低。河套段山前植被赋存环境为条带状地下水溢出带，在地下水储量增多条件下呈条带状增加趋势；而在山前过渡带，新构造运动及其造成的较大地表高差使得土壤层薄且储水能力较差，表现为FVC的高波动。现今黄河干流沿岸植被受土地利用转变影响整体减少；且在河流摆动、河道变迁扰动下，稳定性较差。河套盆地与鄂尔多斯台地边界处，受隐伏断裂和地震活动影响，地下水易沿带状透水断裂下渗，难以维持浅表水分和稳定的补给条件，使得FVC呈线状显著降低，且稳定性较差。研究从宏观水文地质条件和地表过程的角度，更加深入认识了植被空间分布的非地带性特征，为相似地区的研究提供了较好的科学依据。

Spatio-temporal variations and strip patterns of vegetation in the Inner Mongolia of Yellow River Basin

It is of great significance to monitor the variations of fractional vegetation cover (FVC) and assess the impact of large-scale geological sets, especially the active tectonics on vegetation variability for a deep understanding of the spatio-temporal pattern of ecosystem. The Inner Mongolia section of the Yellow River Basin belongs to arid and semi-arid areas, where the vegetation is mostly dependent on groundwater and the active tectonics are frequent, so it is an ideal area for understanding the azonal characteristics of vegetation. Based on MODIS NDVI (Normalized Difference Vegetation Index), meteorological and land-use data, this paper analyzed the spatio-temporal variation and stability of FVC in the Yellow River Basin (Inner Mongolia section) from 2000 to 2018 and further explored the reasons for strip distribution of vegetation. The results showed an increasing trend of FVC in the past 20 years. The increase in rainfall was the main reason for the increased FVC in the Dahei River Basin, Hun River Basin, and Ten Kongdui Basin. The Three-North Shelterbelt Project contributed to increased FVC in the desert regions. Dahei River Basin and Hun River Basin had better water conditions and rich biodiversity with high FVC, helping to resist external disturbances. In contrast, the Ten Kongdui areas and deserts with lower FVC and fragile ecosystems were more sensitive to climate fluctuations. Hetao irrigation area is dominated by human activities, characterized by weak sensitivity of FVC to climate change. The vegetation grows along the groundwater overflow belt in the piedmont zone of Hetao. It increases as the groundwater storage increases. Over the piedmont transition zone, the soil layer is thin and its water storage capacity is poor due to large surface height difference caused by neotectonic movement, manifested as the high fluctuation of FVC. The vegetation along the mainstream of the Yellow River reduced due to land-use change and its stability was poor under the disturbance of river oscillation and channel migration. At the boundary between the Hetao Basin and the Ordos platform, groundwater tends to infiltrate along the permeable faults forced by seismic activities, which makes it difficult to maintain shallow water and stable recharge conditions, thus resulting in a significant linear decrease of FVC and poor stability. This study highlights the role of macroscopic geological background (i.e., hydrogeological conditions and surface processes) on vegetation pattern and has a deep insight into the azonal characteristics of vegetation, which provides a better scientific basis for similar studies.