2000—2016年三江源区植被生长季NDVI变化及其对气候因子的响应

NDVI changes and its correlation with climate factors of the Three River-Headwater region in growing seasons during 2000—2016

植被与气候因子的相关性分析不仅反映气候变化背景下植被的长势,还可以预测未来植被的变化趋势。基于2000—2016年间研究区MODIS13A1 C6归一化植被指数(normalized difference vegetation index,NDVI)数据,结合研究区1∶100万植被类型图和气象站观测数据,采用相关分析研究方法,分别就三江源区17 a间植被时空分布特征、植被NDVI变化及气象站点缓冲区内植被生长季NDVI均值与逐月气候因子的相关性进行了研究。结果表明:①三江源区生长季植被NDVI值在2000—2016年间整体上呈增加趋势,全区生长季NDVI增速为0. 8%/10 a,在空间上具有显著的区域差异,整体表现为由西北向东南逐渐增加的趋势;②气候因子在生长季初期和中期对植被生长影响较大,而在后期相关性则不明显;③研究区植被生长季初期,当月气温对高寒草甸草原、高寒草原NDVI变化的影响大于降水量对其的影响,但在植被生长季中期,当月降水量对高寒草甸草原、高寒草原和高寒草甸3种不同类型植被的生长影响均较大。

The correlation analysis between climatic factors and vegetation indexes can not only reflect the impact of climate change on vegetation but also predict the trend of vegetation in the future.Based on the data of MODIS13A1 C6 NDVI of the Three River headwater region and combined with 1∶1000000 map of vegetation types and meteorological data,the authors analyzed spatial-temporal characteristics of NDVI and the relationship between vegetation indexes and climatic factors by using correlation analysis from 2000 to 2016.The results are as follows:①NDVI increased with a rate of 0.8%/10a in Three River headwater region during 2000—2016,whereas vegetation cover increased from the northwest to southeast.②Climate factors had a greater influence on vegetation growth in the early and middle growing season,but the correlation between NDVI and climate factors was not obvious in the later growing season.③The partial correlation between NDVI and climate factors in the vegetation growing season of the study area showed that the influence of the air temperature on NDVI of the alpine meadow grasslands and alpine grasslands was greater than that of precipitation in the early growing season.However,during the middle of the growing season,the precipitation had a greater impact on the growth of three different types of vegetation.