Journal of Ecology and Rural Environment ›› 2017, Vol. 33 ›› Issue (12): 1102-1108.doi: 10.11934/j.issn.1673-4831.2017.12.006

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Changes in Vegetation Phenology and Its Elevation-Dependent Effects in the Yarlung Zangbo River Valley of Tibet, China

LI Hai-dong1, CHEN Bin1,2, YERNAER·Humaerhan2, CAO Xue-zhang1   

  1. 1. Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing 210042, China;
    2. School of Remote Sensing, Nanjing University of Information Science & Technology, Nanjing 210044, China
  • Received:2017-06-12 Online:2017-12-25 Published:2017-12-19


The Yarlung Zangbo River Valley (YZR), stretching across the southern part of the Tibetan Plateau from west to east over a wide range of elevation from 147 m to over 7 000 m above sea level (a.s.l.) with an average elevation of 4 600 m, has been regarded as one of the ideal regions for the study on ecological response to climate change in alpine watershed. Based on the datasets of SPOT-VGT normalized difference vegetation index (NDVI) and SRTM digital elevation model (DEM), phonological features of the valley were extracted and elevation-dependent phenological change of the vegetation of the YZR during 1999-2013 was analyzed. The SPOT-VGT NDVI was first preprocessed with the non-symmetrical Gaussian function (AG) fitting method, and then the start date of growing season (SOG), the end date of the growing season (EOG) and the length of the growing season (LOG) of the vegetation was extracted, separately, through the threshold value method. Results show:(1) The SOG exhibited an advancing trend in 61.3% of the YZR, and a delaying trend in 38.8%, while the EOG did an advancing trend in 45.3% and a delaying trend in 54.7%. As a consequence, the LOG in the YZR was shortening, with the annual changing rate per pixel being -0.47 d·a-1; (2) The SOG was gradually delaying, the EOG gradually advancing and the LOG gradually shortening along the river from the downstream up to the upstream. Besides, LOG and its annual changing rate is generally on a declining trend with rising elevation.

Key words: vegetation phenology, elevation-dependent effects, remote sensing technology, alpine regions, Tibetan Plateau

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