Study On The Characteristics Of Land Use Change And Its Ecological Effect In Tailan River Watershed Of XinJiang In The Recent 15 Years

Land use structure and quality of land resources are changed by the influences of natural factor and social factor of humanity. This may induce the change of regional ecology and global environment. Therefore, the investigation of the process, discipline and ecological effect of regional land use change were the basis of the investigation of ecological environmental change and were the scientific base for making decision of the regulation of human activities. In this study, based on GIS, the land use change, landscape pattern and ecological effect of Tailan river from 1990 to 2005 were investigated. Moreover, according to the existing problems of land use, the countermeasures and suggestions were proposed. The results indicate that:From 1990 to 2005, the areas of cropland and sandy land increased by 35027.11 hm2 and 10443.46 hm2, respectively. The areas of woodland, waters and bare land also increased, while the areas of saline land, construction land, particularly grassland decreased by 14326 hm2. This suggests that large-scale reclamation occurred in this area. The grassland, woodland and unutilized land were mainly transformed into farmland, while the woodland and grassland were mainly degenerated into unutilized land.The decrease in the number of landscape patches and patch density indicate that the landscape fragmentation, the complexity of patch shape, and the landscape stability were decreased. The assimilation of farmland patch increases the risk of crop pests. The increase in the diversity index and evenness index of landscape suggest that the landscape heterogeneity was increased.The results indicate that the soil organic matter (SOM) and total salt decreased sharply with soil depth, and the land use effects on them occurred mainly within top 25 cm soils. The total salt of croped glycyrrhiza land and saline-alkali land were greatly higher than those of the other land use types. SOM content in topsoils of the land use types followed the order: economic forest > farmland > croped glycyrrhiza land > ameliorated sandy land > saline-alkali land. In addition, total salt decreased with the years of farming, while SOM increased.The remarkable increasing of cropland resulted in the damage of natural vegetation and the decrease of biodiversity, and the conflict between agricultural water and ecological water. The area of soil salinization in the old oasis was decreased, while the area of soil salinization in some regions of the new oasis periphery presented an aggravation tendency.The rapidly increase of the woodland area result in the decrease of ecological water at downstream. Therefore, the area of sandy land was increased by 11370.69 hm2. Moreover, biodiversity was reduced for the damage of natural vegetation.