黄河源区高寒草地NDVI格局与梯度变化

黄河源区是我国重要的生态屏障,该区高寒草地生态系统随气候环境因子梯度变化值得重视,本研究利用气象台站观测数据和遥感归一化植被指数(NDVI)研究黄河源区高寒草地生态系统随水热梯度的变化过程。结果表明,近12年来黄河源区草地NDVI平均值为0.557 8。NDVI最高的地区为久治和甘德县,其次为达日和玛沁县,玛多、称多和曲麻莱县NDVI最低。扎陵湖和鄂陵湖以北的高寒草原地区为研究区内NDVI低值区。近12年来,草地NDVI年变化速率均值为0.002 4,变异系数均值为0.076 7,变化幅度较小。该区从东南至西北NDVI变化速率和变异系数上升,该格局是气候变化、草地现实载畜量下降和生态建设工程实施三方面因素叠加的结果。黄河源区气候环境因子自西北向东南存在梯度变化,形成水热梯度,从而导致草地NDVI、NDVI变化率和NDVI变异系数存在梯度变化。年平均气温与NDVI具有极显著相关关系,与NDVI变化率和NDVI变异系数具有极显著负相关关系。年降水量和湿润指数与NDVI具有极显著相关关系,与NDVI变化率和NDVI变异系数具有极显著负相关关系。海拔与NDVI具有极显著负相关关系,与NDVI变化率和NDVI变异系数具有极显著相关关系。

Spatial pattern and change gradient of alpine grassland in the Source Region of Yellow River

The Yellow River Source Region is China’s important ecological barrier, and variation of alpine grassland ecosystem in this region with the climatic environment factors changing was worth to pay more attention. In this research, we used meteorological observation data and remote sensing normalized vegetation index (NDVI) to study the variation process of alpine grassland ecological system with the hydrothermal changing gradient in the source region of Yellow River The results showed that, during the past 12 years, the average of grassland NDVI was 0.557 8. The highest NDVI were in Jiuzhi and Gande County, followed by Dari and Maqin County. The lowest NDVI were in Maduo, Chengduo and Qumalai County. Alpine grassland NDVI was lower in north of Zhaling and Eling Lake than in other regions. During the last 12 years, change rate of the grassland NDVI was 0.002 4·a-1, and the coefficient of variation is 0.076 7, which showed litter change of NDVI. Climatic environment factors of the source region of Yellow River changed with gradient from northwest to southeast and formed hydrothermal gradient, which led to the grassland gradient change of NDVI, NDVI change rate and NDVI coefficient of variation. With the annual average temperature rose, NDVI increased significantly, and NDVI change rate and variation coefficient decreased significantly. With the annual precipitation and moisture index rose, NDVI increased significantly, while NDVI change rate and variation coefficient decreased significantly. With the elevation rose, NDVI decreased significantly, while NDVI change rate and variation coefficient increased significantly.