格尔木河流域植被指数时空分布及其影响因素研究

格尔木河流域气候干旱少雨,生态环境较脆弱,植被动态对其生态环境保护具有重要意义。基于连续序列的MODIS NDVI数据,分析了格尔木河流域植被指数时空分布及其影响因素。结果表明:研究区NDVI平均值总体较小,主要在0.10～0.12间波动,但呈增大趋势。区内植被改善区分布在格尔木市东、西两侧,基本不变区为荒漠地区,植被退化区分布在北部盐湖区。区内裸土的面积逐渐减小,低覆盖率和高覆盖率植被的面积逐渐增加。研究区植被生长与气象、土壤水分和地下水位埋深都有关系。气温与植被指数相关关系较好,相关系数为0.822,而降水对植被的生长也有一定的作用。植被指数与表观热惯量是正相关关系,相关系数为0.979。区内植被的地下水位埋深范围为0～12 m,在水位埋深约为6.5 m的地方,植被长势最好。

Spatial-temporal Characteristics of Vegetation Index and Its Impact Factors in the Golmud River Basin

Located in the south-central part of Qaidam Basin in Qinghai Province, the Golmud River Basin is arid and its ecology is fragile. Vegetation dynamics are of great significance to ecological conservation in arid regions. Based on continuous record of MODIS NDVI data, the spatial-temporal characteristics of vegetation index in the Golmud River Basin were analyzed via remote sensing, and the influencing factors were discussed. The results show that the annual average NDVI value is generally small, but increased from 0.10 to 0.12 during 2001 to 2016. Areas of increasing NDVI trend are distributed to the east and west of Golmud City, while constant and decreasing trends of NDVI occur in the desert and the northern salt pond area, respectively. Both areas of low-density and high-density vegetation show an increasing rate, whereas the bare soil shows a decreasing trend in the vegetation coverage. Generally, the vegetation variation depends on various attributes such as climate change, soil moisture and groundwater depth. The correlation between NDVI and temperature is good (correlation coefficieis=0.822), and precipitation also has a certain impact on the growth of vegetation. There is a strong correlation between NDVI value and the apparent thermal inertia (correlation coefficieis=0.979). The corresponding range of groundwater depth to vegetation in the study area is from 0 to 12 m, and the vegetation growth is the best when the groundwater depth is about 6.5 m.