塔里木河中下游地区湿地景观格局变化

Changes of wetland landscape pattern in the middle and lower reaches of the Tarim River

在RS和GIS技术的支持下,结合塔里木河中下游的区域特点,确定了塔里木河中下游湿地景观分类系统.通过采用景观多样性指数、优势度、景观破碎化指数、分布质心和平均斑块形状指数等景观的空间格局指数,较系统地分析了1980～2000年塔里木河中下游湿地景观空间格局变化.结果表明：塔里木河中下游湿地的分布面积呈显著下降趋势.1980～1990年湿地面积减少,斑块数量和密度增加.1990～2000年湿地面积有所增加,斑块数量和密度持续增加;随着人类干扰强度增加,景观多样性增加,优势度降低,湿地的破碎化程度越来越大;湿地景观要素中,河渠湿地、水库坑塘湿地面积有所增加,而湖泊、滩地、沼泽面积均在不断减少,其中沼泽湿地面积减少幅度最大.

Spatial pattern of landscape mainly refers to the distribution of patches that are different in sizes and shapes in space owing to the interaction of various ecological activities. The study on spatial pattern of landscape can provide significant information for rational management to the environmental resources and has been one of the important research fields in landscape ecology as a whole. This article, based on the diversity index, dominance index and fragmentation index of the landscape, distribution centroid and average patch-shaped index, presents the dynamic changes of the wetland spatial pattern in the middle and lower reaches of the Tarim River during the last 2-decades. Our study focused on the section of the middle and lower reaches in the Tarim River between the Taklimakan and the Kuruke deserts （38°47′52″～41°38′30″N, 85°33′38″～88°40′30″E）. The length of the section is 413 km, the width 87 km and the area 3.45 × 10^4km^2. Satellite images, Landsat TM/EM in 1980, 1990 and 2000 were respectively used to analyze the dynamic change of the wetland spatial pattern in the study area. Since the images were approximately captured in the same seasons, the change detection error introduced by mere seasonal difference was minimized. Following an interactive interpretation procedure, the distribution map of the wetland in 1980, 1990 and 2000 were obtained, which were geometrically registered to a common map projection. The data were obtained by software Arcgis 9.0, PCI 9.0, Fragstats 3.0 and Excel 2003 .The results show that from 1980 to 1990 the total area of the wetlands was reduced by 45.7 % ; the number of the patches increased from 49 to 151 ; and the density of the patches increased fourfold. During 1990 and 2000 the total area of the wetlands was slightly increased; the numbers of the patches increased from 151 to 511; and the density of the patches was doubled. The results also indicate that due to the disturbance of human activities, landscape diversity index increased while landscape dominance index decreased, and landscape fragmentation index increased gradually. In 1980, 1990 and 2000, the above-mentioned indices were respectively 0.6340, 0.7523 and 0.0018; 0.9247, 0.6667 and 0.0103; 1.0545, 0.5549 and 0.0321. Among the wetland types, the areas of the river-channel, reservoir and pond wetlands increased, while the areas of the lake, bottomland and marsh wetlands reduced constantly. The decrease of the areas for the marsh wetlands was most marked. In short, under the impact of the natural factors and human activities, the areas of the wetlands and the average areas of the patches in the middle and lower reaches of the Tarim River reduced as a whole, but the fragmentation increased. Comparision with in 1999, the area of the wetlands in 2000 increased. At the beginning of 21th century, the ecological water conveyance to the Tarim River led to the increase of the wetland area.