黑河流域酒泉绿洲景观生态安全格局分析

以1986年和2000年的酒泉市遥感数据为基础资料，利用GIS软件生成研究区的景观类型图，计算各景观斑块的面积、数目、形状等空间特征和基于景观空间邻接的绿洲生态安全指标，进而在空间格局方面对绿洲的生态安全进行评价，以了解在人类活动影响下酒泉绿洲的生态安全状况，为该地区生态环境保护提供科学依据。结果表明：（1）从1986年到2000年，绿洲不断扩张，各绿洲斑块类型面积呈增加趋势，同时强烈的人类活动也造成了沙地和裸土面积的增加；（2）从1986年到2000年，受沙化威胁程度最大的斑块类型由耕地变成了草地，而城乡居民用地始终是受胁程度最小的斑块类型；除了城乡居民用地，各绿洲斑块类型受沙化的潜在威胁程度是增加的，人类有目的性的干扰活动改变了干旱区有限水资源的分布与分配，社会经济发展的同时导致了生态环境的退化；（3）与1986年相比，2000年各绿洲斑块类型受盐碱化威胁呈减弱趋势，表明注水洗盐改良土壤使得局部地区生态系统向良性方向演替。干旱区绿洲生态环境有脆弱性和易变性的特点，加强区域景观生态建设和生态安全控制有利于将景观演化导入良性循环。

Changes of landscape pattern bteween 1986 and 2000 in Jiuquan oasis, Heihe River basin

We reported changes of landscape patterns affected by human activities in the Jiuquan oasis, Heihe River basin. Remote sensing products of the Landsat 5 TM in 1986 and the Landsat 7 ETM image in 2000 were used to perform the analysis on a digital elevation model (DEM) within a geographic information system (GIS), including patch number, area, shape, and the spatial neighboring characteristics between the oasis patch and the sandy land/Salinized land patches. We found that: (1) the oasis expansion was embodied with an increase in the area of each oasis patch type between 1986 and 2000, while intensive human activities led to an increase in the sandy and barren lands; (2) the desertification threat on farm lands was the most significant in 1986, while the threat on the grasslands was the most severe in 2000. The threats on residential areas were minor both in 1986 and 2000 and remained the same during the 15-year study period, but the threats on other oasis patch types had greatly intensified; and (3) the salinization threats on all oasis patch types decreased in 2000, which was likely a consequence of water diversion effort throughout the region. Clearly, human activities have significantly changed the distribution and allocation of the limited water resources in Heihe River basin, leading to a conflict between the two dominant processes: desertification and oasis expansion. Our results further confirmed the vulnerability and high-dynamic nature of the arid ecosystems.