Degradation Characteristics and Causes of Desert Grassland in the Northern Tianshan Mountains

In this paper,the typical desert grassland in Northern Tianshan Mountains was studied for analyzing pattern dynamic changes of desert grassland between 1990 and 2008 by means of point-line-surface methods.Human activity areas(city and agriculture) of typical grassland were used as study sites for discussing dynamic changes according to landscape ecologic method.In addition,the causes for grassland degradation were discussed from natural factors to social factors.The result showed that the areas of grassland decreased and those of agricultural and other land use types increased during the last 19 years.At the same time,grassland vegetation coverage also declined from 1990 to 2008,especially middle and high coverage grassland vegetation.In order to gain a clear cause of grassland changes,natural and social factors were discussed.The main factors of grassland area decreased and grassland degradation was caused due to human activities and unreasonable use of grassland resource.Therefore,these results implied that grassland resource reasonable and scientific utilization was the theoretical basis for grassland sustainable development.