摘要
THE Tibet Autonomous Regionis situated on Chine’s south-westem border southwest fo theQinghai-Tibet Plateau.It has a vastterritory and high and steep topogra-phy,and has long been known as the"Roof of the World."Depending onthe topography,Tibet can be dividedinto three different natural geographi-cal regions:the westem Tibetan Pla-teau,the southem Tibet valley and theeastem Tibetan gorge.Tibet is China’s least populous re-gion.According to the fourth nation-wide census of 1990,Tibet had a
