Review of Study on Vegetation Cover Change in the Lower Reaches of Heihe River in Nor thwest Ar id Ar ea
西北干旱区黑河下游植被覆盖变化研究综述

In arid areas, vegetation can reflect the status of environment directly as a sensitive element of environment; and the vegetation cover changes can represent evolvement and variance of the environment. So, the study of vegetation cover changes becomes an important instrument to open out the changes of environment and their laws in arid area. This paper is aimed at a special region of the lower reaches of Heihe River and the problems with its ecosystem of vegetation, discussing synthetically the vegetation cover changes and the elements related, such as the groundwater, the balance of soil water-salt, global climatic changes and human activities. The aim is to analyze the mechanism of vegetation cover changes exactly by analyzing correlative factors with vegetation cover changes extensively, and to provide supports for the study of environmental evolvement of the lower reaches of Heihe River. Finally, this paper summarizes existent questions in the study of vegetation cover changes, and puts forward relevant strategy to resolve them, providing references for the study of vegetation cover changes in the lower reaches of Heihe River.