黑河下游额济纳盆地景观空间格局动态变化分析

Dynamics of Landscape Pattern in Ejina Basin,the Lower Reaches of Heihe River

基于1977、1993、2001和2005年4期Landsat遥感影像资料,选用面积、斑块数量、斑块平均大小、斑块面积标准差和面积加权平均斑块形状指数,对额济纳盆地景观空间格局的动态变化进行了分析。结果表明:乔木林面积持续减少,表现为绿洲外部及边缘的小斑块大量消失;灌木林在早期以斑块的萎缩和破碎化为主,随后因建群种演替为旱生生态型而趋于稳定,2001年后部分小斑块消失;草地在1977～1993年以小斑块的消失为主,1993～2001年以斑块的破碎化为主,2001年后斑块的团聚性增强,草地扩张;戈壁在1977～2001年斑块的破碎化程度增大,2001年后受草地恢复和巴丹吉林沙漠入侵的影响,总面积和斑块数量减少;沙地在研究期间持续扩张,1977～1993年表现为向植被的分散入侵,1993～2001年斑块的扩张和新小斑块的形成同步进行,2001年后以斑块的扩展和相互连通为主,团聚性增强。黑河输水量的变化是研究区景观空间格局动态变化的主要驱动力,在生态输水工程实施后,生态环境的恶化趋势得到了一定的扼制,但仍需采取措施提高输水的生态效果。

Based on Landsat RS images obtained in 1977, 1993, 2001 and 2005, the dynamics of landscape pattern in Ejina Basin is studied using five common landscape indices. It is found that arbor woods degenerated continuously in the study period and presented spatially the disappearance of little parches in Gobi and the edge of oasis. Shrub woods showed resistance to water change due to high shrub species diversity, and kept relatively stable until 2001 after shrinkage and fragmentation of patches in the period of 1977-1993. The total area and spatial distribution of grassland changed successively with Heihe River flow, with the disappearance of little patches from 1977 to 1993, fragmentation of patches from 1993 to 2001, and aggreation of patches from 2001 to 2005. While the fragmentation degree of Gobi landscape increased trom 1977 to 2001. However, the total area and patch numbers of Gobi declined since 2001 due to restoration of grassland and expansion of Badain Jaran Desert. The total area of sand land and size of individual dune increased continuously, presenting spatially the intrusion of dunes to vegetation dispersedly from 1977 to 1993, expanding to the existing patches and formation of new patches from 1993 to 2001, and connecting and aggregating the patches since 2001. The changes of Heihe River water transport to the basin is the major driving force of landscape pattern dynamics. Though deterioration of ecologic environment in Ejina Basin is taken under control owing to the establishment of water transport for ecologic usage, more measures should be adopted to improve the effect of water transport.