塔里木河下游植被覆盖变化遥感定量分析

在RS与GIS技术支持下,采用空间模型分析法,以2 a为一研究时段,定量分析塔里木河下游输水后植被覆盖变化。结果表明:输水11 a来,Ⅳ级低覆盖植被、Ⅴ级裸地及沙地仍是研究区主要地类。与2000年相比,2010年Ⅰ级极高覆盖植被、Ⅱ级高覆盖植被、Ⅲ级中覆盖植被、Ⅳ级低覆盖植被均呈现逐级增加的趋势,分别增加了986.76、 681.84、 1 091.88、 8 641.89 hm²;Ⅴ级裸地、沙地减少了11 420.37 hm²。整个研究时段,Ⅲ级与Ⅳ级间、Ⅳ级与Ⅴ级间的转化为研究区主要转化类型。随着输水次数和年输水量的稳步增加,研究区植被覆盖类型将向覆盖度、面积稳步增长的平衡态发展,而随着输水量的减少,植被覆盖又转向类型变化频繁的非平衡态。植被覆盖度的增减变化客观反映了输水状况(输水量、输水持续时间),持续、稳定的输水是植被覆盖(覆盖度、面积)稳步增长的前提。

Remote Sensing Quantitative Analysis on Vegetation Coverage Change in Lower Reaches of the Tarim River

Based on the technology of RS and GIS, vegetation coverage changes were analyzed quantitatively every two years with spatial models after water delivery in lower reaches of the Tarim River. The result indicates that low coverage vegetation, bare land and sandy land were the key land categories in the study area. The area of vegetation coverage (Ⅰ-Ⅳ) increased 986.76, 681.84, 1091.88 and 8641.89 hm² in 2010 compared with that in 2000, while the bare land and sandy land (Ⅴ) decreased 11420.37 hm², indicating that the water delivery was effective. The conversion between Ⅲ and Ⅳ as well as between Ⅳ and Ⅴ was the major transformation type of vegetation coverage throughout the study period in the study area. The development of vegetation coverage turned to be an equilibrium state characterized by steady increase with increasing frequency and volume accumulation of water supply, while it turned to be a non-equilibrium state characterized by frequent changes with decrease of water supply. Changes in vegetation cover can reflect the water situation objectively, and the continuous and stable water supply was the premise of steady growth of vegetation coverage.