NDVI-based vegetation dynamics and their response to recent climate change: a case study in the Tianshan Mountains, China

Mountains form distinct geographical units with complex topographic and climatic features. Mountain ecosystems, especially those in arid and semi-arid regions, are likely to be strongly influenced by climate change. The NDVI-based vegetation response to climate change was analyzed in the Tianshan Mountains in China, one of the largest mountain systems of central Asia. Datasets, including the Normalized Difference Vegetation Index (NDVI), precipitation, soil moisture, and snow cover, were used to analyze spatial patterns of NDVI during 2001-2013. A trend test and correlation analysis were used to verify the results. Results showed that: (1) Spatial patterns of NDVI in the Tianshan Mountains revealed significant differences during 2001-2013. A decreasing trend appeared mainly in the Ili River Valley (<-0.005 NDVI/year), the Kaidu River (-0.01 to -0.005 NDVI/year), and Bogda Shan (-0.005 to 0 NDVI/year). NDVI in the western Tianshan Mountains, eastern and western Bogda Shan showed an increasing trend. (2) Spring NDVI in the Tianshan Mountains decreased, while summer NDVI increased during 2001-2013. (3) Spatial variations in vegetation dynamics were attributed to the interaction of the four spheres of the earth's system, hydrosphere-pedosphere-atmosphere-biosphere. The main contributors including temperature, precipitation, and soil moisture had a notable effect on variations in vegetation. (4) The snow cover in the mountains was crucial for vegetation growth, especially in the winter half of the year. Understanding the spatial characteristics of NDVI in mountains under the effects of climate change will underpin further study in this ecological environment.