Acta Geographica Sinica ›› 2005, Vol. 60 ›› Issue (6): 965-973.doi: 10.11821/xb200506009

Previous Articles     Next Articles

Temporal and Spatial Distribution of Grassland Degradation in Northern Tibet

GAO Qingzhu1, LI Yu'e1, LIN Erda1, Jiangcun Wangzha2, WAN Yunfan1, XIONG Wei1, WANG Baoshan2, LI Wenfu2   

  1. 1. Institute of Agricultural Environment and Sustainable Development, Chinese Academy of Agricultural Sciences, Beijing 100081, China;
    2. Naqu Bureau of Agriculture and Husbandry Management Department, Tibet Autonomous Region, Naqu 852100, China
  • Received:2005-05-10 Revised:2005-09-20 Online:2005-11-25 Published:2010-09-09
  • Supported by:

    The National Basic Research Program of China, No.2002CB412508;Cooperation Project with Naqu Bureau of Agriculture and Husbandry Management Department and Institute of Agricultural Environment and Sustainable Development "Remote sensing monitoring of grassland degradation of Naqu region in Tibet autonomous region"

Abstract:

Ranging from 83o41' to 95o11'E and from 30o27' to 35o39'N, northern Tibet in the highest of Tibet is known as the ridge of the roof of world with a mean elevation of 4500 m. Northern Tibet is the headstream of the Yangtze River, Nujiang River and Lancang River. It is both the "sensitive area" of climate system and the "water tower" of China. The environmental condition of this area has significant effect on the main rivers, climate and eco-environment of Tibet and the whole country, even on the globe for its rigorous natural condition and fragile ecosystem. This study selected vegetation cover as the main evaluation index, calculated the grassland degradation index (GDI) and established the remote sense monitoring and evaluation system for grassland degradation in northern Tibet, according to the national standard (GB19377-2003), based on the remote sensing data such as NDVI data derived from NOAA/AVHRR with a spatial resolution of 8 km of 1981-2000 and from SPOT/VGT with a spatial resolution of 1 km of 2001 and from MODIS with a spatial resolution of 0.25 km of 2002-2004 respectively in this area, in combination with the actual condition of grassland degradation. The grassland degradation processes and their response to climate change during 1981-2004 were discussed and analyzed systematically in the study. The result indicated that grassland degradation in northern Tibet is very severe, and mean value of the GDI in recent 20 years is 2.54 which belongs to the severe degradation grade. From 1981 to 2004, the grassland degradation fluctuated evidently with great interannual variations in proportion of degradation degree and GDI but the total tendency turned to severe during this period with the grassland degradation grade changed from light to severe in northern Tibet. The extremely seriously degraded and seriously degraded respectively occupied 1.7% and 8.0% of the study area, the moderately and lightly degraded grassland accounted for 13.2% and 27.9% respectively and un-degraded grassland occupied 49.2% of the total grassland area in 2004. The grassland degradation was severe especially in the conjunctive area of Naqu, Biru and Jiali counties, the headstream of the Yangtze River that is Galadandong snow mountain, the areas along the Qinghai-Tibet railway and highway, and areas around the Tanggula and Nyainqentanglha snow mountains and glaciers. So the snow mountains and glaciers as well as their adjacent areas in northern Tibet which were sensitive to climate change and the areas along the vital communication line with frequent human activities experienced relatively severe grassland degradation.

Key words: grassland degradation, remote sensing monitoring, temporal and spatial distribution, northern Tibet