Abstract: The climate and vegetation change in the north of Shaanxi Province during the past 1.28 million years was analyzed in this paper.The results showed that the climate in the north of Shaanxi had changed periodically with the succession of cold,warm,dry and wet.During the early geological and historic stage,it was the climate that mainly influenced the change of the vegetation in the north of Shaanxi.Along with the development of human activity,the climate was no longer the only element influencing the vegetation,while the human activity had played a more and more important role in the vegetation change.During the Ming and Qing dynasties,the ecological environment in the north of Shaanxi became vulnerable due to the dry and cold climate.The vegetation reduced sharply because the excessive reclamation and burning and the ecosystem in the north of Shaanxi was destroyed seriously.Since 1950s,protective measures had been implemented in this area.Though there still existed some deforestation phenomena,the ecological environment in the north of Shaanxi has been gradually improved since the 1980s.

Key words: Middle reaches of Tarim River, Niche breadth, Niche overlap, Species, Xinjiang