中文摘要：

潜在植被是指在没有人为干扰、在现有的环境条件下,植被的全部演替系列完成时立地应该存在的植被状况。西北干旱区生态环境问题突出,以潜在植被为研究对象来探究西北干旱区植被背景及其变化规律,成为西部生态环境恢复重建的基础性工作。本研究以IOCSG（integrated orderly classification system of grassland）模型为潜在植被评定模型,在GIS研究方法的支持下,对西北干旱区潜在植被进行了模拟,并对其动态变化进行了分析,得出以下结论：1）采用IOCSG评定模型对中国西北干旱区潜在植被分布进行了模拟,通过检验得出,IOCSG评定模型对研究区植被模拟精度达到了78%,较好的重现了研究区潜在植被分布格局。2）分布在研究区的潜在植被类型有21类,不同区域植被的多样性差异较大。天山、阿尔泰山一带及大兴安岭地区植被分布较为丰富。相比之下,准噶尔盆地、塔里木盆地、巴丹吉林沙漠地区分布比较单一,主要以荒漠、半荒漠为主。3）由于立地气候环境的改变,区域植被系统表现出不稳定性,主要表现为4个特点：扩展变化、缩减变化、波动性变化以及消亡变化。4）气候环境适应性的改变使潜在植被发生了演替过程,从2个周期的变化来看,天山、阿尔泰山、大兴安岭及以西地区以及呼伦贝尔高原地区成为植被演替的敏感区。

英文摘要：

The potential vegetation,as a final state of succession which achieves the balance with its site,is the most stable and mature climax vegetation type at the site without human interference.The ecological and environmental problems of the northwest arid area are very serious.Taking the potential vegetation as the reference for showing backgrounds of vegetation and rules of change has become the preliminary and infrastructural work towards ecological construction in arid areas of Northwest China.Based on the integrated sequence classification（IOCSG） and the support of GIS,this paper simulates distribution of vegetation,and analyzes dynamic changes in the study area.1） Using the IOCSG model in arid areas of Northwest China,the accuracy of potential vegetation simulated reached 78%.2） There were 21 potential vegetation types distributed in the study area.The diversity of vegetation in different regions was quite different.Vegetation was abundant in Tianshan,Altai,Daxinganling.In contrast,in the Junggar Basin,Tarim Basin,and Badain Jaran desert,the distribution of vegetation was relatively simple,mainly in desert and semi-desert.3） As climate and environment change at a site,the regional vegetation system shows instability.There are four typical variation patterns,i.e.increasing change,reducing change and disappearing and fluctuating vegetation.4） Complicated processes of succession of the potential vegetation happened because of changes in climatic and environmental adaptability at the site.In Tianshan,Altai,Daxinganling,to the west of Daxinganling and Hulunbeier,successions of the potential vegetation are more significant.