基于高程分段的黄河源区NDVI和水热条件空间分布格局

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Ⅰ(3 400m),高程段Ⅱ(3 400～4 200m)和高程段Ⅲ(4 200m)。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Ⅰ内主要植被类型为农田和草地,高程段Ⅱ内主要植被类型为林地和草地,高程段Ⅲ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Ⅰ属干旱区域,高程段Ⅱ属湿热区域,高程段Ⅲ属干冷区域。3个高程段内水热组合条件最好的是高程段Ⅱ,高程段Ⅲ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Ⅰ和高程段Ⅲ内降水量较低,NDVI主要驱动因子是降水量,高程段Ⅱ的降水量丰沛,影响NDVI的主要因子是气温。

Distribution pattern of NDVI and hydrothermal conditions in the Yellow River Headwaters based on elevation section

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 .