remote sensing Article Interannual and Seasonal Vegetation Changes and Influencing Factors in the Extra-High Mountainous Areas of Southern Tibet Zu-Xin Ye 1,2,3, Wei-Ming Cheng 2 , Zhi-Qi Zhao 1,4,* , Jian-Yang Guo 1, Hu Ding 1 and Nan Wang 2,3 1 State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
[email protected] (Z.-X.Y.);
[email protected] (J.-Y.G.);
[email protected] (H.D.) 2 State Key Laboratory of Resources and Environmental Information System, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;
[email protected] (W.-M.C.);
[email protected] (N.W.) 3 University of Chinese Academy of Sciences, Beijing 100049, China 4 School of Earth Science and Resources, Chang’an Univeristy, Xi’an 710054, China * Correspondence:
[email protected] Received: 11 April 2019; Accepted: 8 June 2019; Published: 11 June 2019 Abstract: The ecosystem of extra-high mountain areas is very fragile. Understanding local vegetation changes is crucial for projecting ecosystem dynamics. In this paper, we make a case for Himalayan mountain areas to explore vegetation dynamics and their influencing factors. Firstly, the interannual trends of the normalized difference vegetation index (NDVI) were extracted by the Ensemble Empirical Mode Decomposition (EEMD) algorithm and linear regression method. Moreover, the influence of environmental factors on interannual NDVI trends was assessed using the Random Forests algorithm and partial dependence plots. Subsequently, the time-lag effects of seasonal NDVI on different climatic factors were discussed and the effects of these factors on seasonal NDVI changes were determined by partial correlation analysis.