土地利用/覆被变化对张掖黑河湿地国家级自然保护区景观破碎化的影响

Effect of Land Use/Cover Change on Landscape Fragmentation of Zhangye Heihe National Wetland Nature Reserve

在遥感和GIS技术支持下,基于1975—2010年长时间序列遥感影像,结合转移矩阵模型等方法,阐述了张掖黑河湿地国家级自然保护区及其周边区域的土地利用/覆被变化状况。选取斑块密度指数、聚合度、斑块平均面积指数、斑块形状破碎化指数等指标,系统分析了保护区内湿地景观破碎化过程,据此探讨了保护区及其周边区域土地利用/覆被变化对保护区内湿地景观破碎化过程的影响。结果表明:①保护区内及其周边地区的耕地比重分别增加了7.67%和5.5%,湿地比重分别减少了6.91%和0.4%;②保护区内湿地逐渐由研究初期大面积斑块体占主导、空间上连续分布的格局趋于景观破碎化;③区域土地利用/覆被变化直接导致了保护区内湿地平均斑块面积的缩减,间接降低了湿地斑块间的聚合度等;④保护区内湿地景观破碎化对土地利用/覆被变化的响应主要表现为各景观破碎化指数对大规模的耕地开垦等开发活动的响应上。

Land use and land cover change have been greatly affecting the function and structure of wetlands landscape ecosystem. It can make so many changes on wetlands from multiple aspects, such as to initiate the wetlands fragmentation process. Wetlands within the Zhangye Heihe National Wetland Nature Reserve is of a great significance to keep the eco-environment safety of northwestern China. Besides that, it also plays a key role in preventing the Tengger Desert and Badain Jaran Desert to be a whole. However, its landscape begins to be fragmented with the change of land use and land cover in recent years. Based on multi-temporal remotely sensed TM and ETM images from1975, 1987, 1992 and 2010, changes of land use and land cover in the nature reserve during 1975 -2010 were quantitatively analyzed using transition matrix in this paper. At the same time, the landscape fragmentation indices contained patch density, aggregation in- dex, mean patch size, mean shape fragmengted index and area-wegihted mean shape fragmengted index were calculated to study the effects of land use and land cover change on landscape frag- mentation process of the wetlands in the nature reserve and its surrounding areas. The results show that the land use structure in the nature reserve and its surrounding areas has undergone great changes and its wetland landscape fragmentation became more and more serious from 1975 to 2010. The proportions of farmlands in the nature reserve and its surrounding areas have increased 7.67% and 5.5% respectively. On the contrary, the wetlands declined 6.91% and 0. 4%. In terms of wetland landscape, the wetland patches tend to be fragmented, especially for the river and bottomland wetlands. The mean shape fragmengted indices and area-wegihted mean shape fragmengted indices have raised from 0.48 and 0.88 to 0.52 and 0.91 in 1992 -2010. However, its aggregation index decreased 9.19%. All of those indicated that the wetlands in the nature reserve has been fragmented under the effects of land use and land cover change. As for how land use and land cover change functioned on the wetland fragmentation, it can be expressed with the effect of land use and land cover change on the mean patch size, aggregation indices, shape frag- mentation indices and so on. Because land use and land cover change play a key role in shifting material cycle and energy transportation mode of wetland at basin scale, it can alter the ecological processes of landscape elements and influence the wetlands landscape pattern and function in the nature reserve. Therefore, it is strongly suggested land use and land cover can affect the tation process of the wetlands.