Acta Geographica Sinica ›› 2005, Vol. 60 ›› Issue (3): 467-478.doi: 10.11821/xb200503013

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NDVI Reflection of Alpine Vegetation Changes in the Source Regions of the Yangtze and Yellow Rivers

YANG Jianping, DING Yongjian, CHEN Rensheng   

  1. Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou 730000, China
  • Received:2005-02-23 Revised:2005-04-11 Online:2005-05-25 Published:2010-09-09
  • Supported by:

    National Natural Science Foundation of China, No.40301010; No.40401012; No.40371026;Knowledge Innovation Project of CAREERI, CAS, No.KZCX2004112

Abstract:

The spatial distribution and dynamic change of vegetation cover in the source regions of the Yangtze and Yellow rivers of the Tibetan Plateau are analyzed in recent 20 years based on 8 km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 2001. The data are from NASA Pathfinder AVHRR Land datasets. On the basis of simple correlation analysis of air temperature, precipitation, shallow ground temperature and NDVI, which is 3×3 pixel at the center of Wudaoliang, Tuotuohe, Qumalai, Maduo, and Dari meteorological stations, the statistical models of air temperature, precipitation, shallow ground temperature and NDVI are constructed in this paper under two conditions—considering ground temperature action and not considering ground temperature effect. The results show that as a whole vegetation cover keeps original conditions basically in recent 20 years, vegetation continues to degrade in local areas of the source regions of the Yangtze and Yellow rivers. Remarkable decrease regions in NDVI are Zhaling Lake and Eling Lake edges, areas to the east and the north of the lakes, the headwater area of Duoqu river in the northern foot of Bayan Har Mountain in the source region of the Yellow River, part areas in Geladandong region, some regions along the Qinghai-Xizang Highway between Tuotuohe and Wudaoliang, Qumalai and Zhiduo belts in the source region of the Yangtze River. Decrease range of NDVI is 0% to 20%. Vegetation degraded very severely in the above-mentioned regions. In the source regions of the Yangtze and Yellow rivers annual NDVI changes, namely good or bad vegetation cover is influenced mainly by temperature, especially near 40 cm ground temperature below the earth surface. NDVI is very sensitive to near 40 cm ground temperature change. Permafrost is widely distributed in the source regions of the Yangtze and Yellow rivers. Its freezing-thawing processes are not only associated with ground temperature change, but also affect soil water content. Permafrost degradation will influence directly alpine vegetation growth in the source regions of the Yangtze and Yellow rivers.

Key words: Qinghai, the Yangtze River, the Yellow River, alpine vegetation, vegetation index, NDVI