以黄河源区植被为研究对象, 应用 MODIS13Q1 遥感数据、DEM 数据、气象数据以及土地利用类型图, 采用基于高程分段的研究方法对研究区 NDVI( 归一化植被指数) 与水热条件空间分布特征进行深入探究。根据 NDVI 随 高程分布特征, 将研究区划分为高程段? ( < 3 400 m) , 高程段ò ( 3 400~ 4 200 m) 和高程段ó ( > 4 200 m) 。在各 高程段内分析植被分布格局、NDVI 与水热条件分布特征、NDVI 与水热因子响应关系。结果表明: 黄河源区内主要 植被类型为草地, 其面积占源区总面积 75% , 林地面积占比为 7% , 农田面积仅占 1% 。高程段? 内主要植被类型 为农田和草地, 高程段ò内主要植被类型为林地和草地, 高程段ó 内基本只有草地。3 种不同类型植被 NDVI 平均值 大小为林地> 草地> 农田。气温表现为梯度递减的空间分布格局, 降水量呈现从东南向西北递减的趋势。高程段 ? 属干旱区域, 高程段ò 属湿热区域, 高程段ó 属干冷区域。3 个高程段内水热组合条件最好的是高程段 ò , 高程 段ó 水热条件较差。植被 NDVI 在不同高程段内受水热因子的驱动作用不同。高程段 ? 和高程段 ó 内降水量较 低, NDVI主要驱动因子是降水量, 高程段ò 的降水量丰沛, 影响 NDVI 的主要因子是气温。

Different datasets ( MODIS13Q1 NDVI, DEM, LULC, and meteorological data) were used to study the regional differences of the spatial distribution pattern of NDVI and hydrothermal conditions in the Yellow River Headwaters. The distribution pattern of vegetation and hydrothermal conditions and the correlation between NDVI and hydro thermal fact ors were analyzed and investig ated based on three elevation sections ( section I< 3 400 m, section II 3 400 m~ 4 200 m, section III> 4 200 m) , respectively. The results showed that the maintype of vegetation in the Yellow River Headwaters was grassland, which accounted for 75% of the to tal area. However, forest and farmland areas accounted for 7% and 1% , respectively. Farmland was mainly distributed in sect ion ? and the forest was mainly distributed in section ò , while grass grows in all three sections. The average NDVI of different vegetation types ranks in this order: forest, grassland, and farm land. Moreover, the temperature displayed a spatial distribution pattern of decline gradient, and the precipitation represented a declining trend from southeast to northwest. The three partitions have different hydrothermal conditions. Section I belonged to the arid region, section II belonged to the moistheat region, and section ó belonged to the dry region, respectively. Section ò had the relatively best hydrot hermal combination conditions, which was followed by section ? , while section ó had the worst of three partitions. The results also revealed that NDVI was driven by different hydrothermal factors indifferent sections. The main factor that affected the growth of vegetation in section I and ó was precipitation, while in section II, the temper ature is the main factor while the rainfall was abundant .

国家重点研发计划( 2016YFC0402405) ; 国家自然科学基金( 51779270 ) ; 流域水循环模拟与调控国家重点实验室课题 (SKL2018TS04)