黑河中游湿地景观破碎化过程及其驱动力分析

在遥感和GIS技术支持下,基于1975-2010年长时间序列遥感影像,选取斑块密度指数(PD)、景观内部生境面积指数(IA)、斑块平均面积指数(MPS)、斑块形状破碎化指数(FS1、FS2)等具有典型生态意义的景观指数模型,系统分析了黑河中游湿地景观的破碎化过程,并结合灰色关联分析、主成分分析等方法,探讨了影响研究区湿地景观破碎化过程的各驱动因子.结果表明:近35年来,研究区湿地景观破碎化主要表现为斑块平均面积的萎缩,斑块密度的上升以及斑块形状破碎化指数的增大.整个研究时段内,研究区湿地斑块平均面积减少了48.95hm2,斑块密度的上升0.006个/hm2;导致黑河中游湿地景观破碎化发生和发展的驱动力包含自然和人文两个方面.自然因子对湿地景观破碎化进程的影响则主要体现在气温和降水上,而且气温对湿地景观破碎化进程的影响程度明显大于降水.但在1975-2010年间的这一较小时间尺度上,人类活动对湿地景观破碎化的贡献率明显高于自然因子,人类活动能力的增强以及影响范围的不断扩大是引发黑河中游湿地景观破碎化的主因.

Fragmentation process of wetlands landscape in the middle reaches of the Heihe River and its driving forces analysis

Heihe River is one of the most important inland rivers in the northwest arid district of our country. Wetlands that distributed along the middle Heihe River Basin has a great significance to the eco-environment safety of northwestern regions in our country. It plays a key role in preventing the Tengger Desert and Badain Jaran Desert to be a whole. However, it had been destructed by human activities and climate change deeply in recent years. So the research of the wetlands in Heihe River is urgently needed. Based on satellite images of 1975, 1987, 1992, 2001 and 2010, the paper chose some typical landscape index models, such as patch density, landscape internal habitat area index, mean patch size, FS and so on, to analyze the wetland landscape fragmentation process and its drivers of the middle Heihe River Basin between 1975 and 2010, combining with grey relational analysis, principal component analysis and other analytical methods. The results indicated that fragmentation process of wetland landscape in the middle reaches of the Heihe River mainly expressed as the shrinkage of internal habitat area and mean patch size, the increase of fragmentation index and the enlargement of FS in the past 35 years. In the entire period of study, the mean patch size of the wetlands in middle Heihe River Basin decreased 48.95 hm² corresponding to the patch density raised 0.006 Ind/hm². In terms of patch shape fragmentation index, it mainly expressed as the increasing of mean patch shape fragmentation index and area-weighted mean shape fragmentation index. Especially the values of the mean patch shape fragmentation index and area-weighted mean shape fragmentation index increased from 0.524, 0.269 to 0.556 and 0.276 between 1992 and 2010. So it can draw a conclusion that wetland landscape fragmentation has been the main manifestations of wetland degradation in the study area throughout the study period. The dominant driving force which led to the middle reach of the Heihe River wetland landscape fragmentation and development is human factors. Natural factors on the process of wetland landscape fragmentation have a certain influence. Yet the contribution of human activities on the wetland landscape fragmentation was significantly higher than the natural factors in a smaller time scale. The increased capacities as well as the expanding influence sphere of human activities act as the main cause of the middle reach of the Heihe River wetland landscape fragmentation. In addition, natural factors also have some influence on the process of wetland landscape fragmentation. Furthermore, the impact of natural factors on the process of wetland landscape fragmentation is mainly reflected in the temperature and precipitation. Comparing with precipitation, in the natural context of arid environments just like the study area, the temperature plays a significantly greater actor in the process of wetland landscape fragmentation.