基于水文平衡的湿地退化驱动因子定量研究

作为地球上最为重要的生态系统类型之一,湿地与森林、海洋并称为地球三大生态系统。但是,近年来湿地生态系统退化速度远大于其他类型生态系统,开展湿地退化的定量评估分析研究对于湿地生态系统的保护和恢复具有重要意义。选择北京城市湿地为研究对象,利用卫星遥感数据分别提取得到1991年和2007年的湿地面积,基于湿地水量平衡理论和湿地水文方程方法,定量评估分析了导致湿地退化的原因和不同驱动因子的贡献率。结果表明:(1)与1991年相比,2007年北京湿地减少约6275.31 hm2,约占1991年北京湿地总面积的24.46%。显著退化区域主要发生在野鸭湖湿地和密云水库湿地,分别减少了约1377.69 hm2和4654.50 hm2。(2)引起湿地退化的自然驱动因子中,以降水减少、入境地表水减少和蒸发量增加为主,驱动湿地退化的贡献率分别为39.22%、14.05%和11.85%。引起湿地退化的人为驱动因子中,以城市扩展为主,驱动湿地退化的贡献率为3.42%,而技术进步所采取的节水措施等有利于湿地保护,贡献率为25.55%。

Quantitative analysis of driving factors for wetland degradation based on hydrology balance

Wetlands are among the most important ecosystems on Earth, which provide plenty of ecological services, and supporting the sustained development of the human being. However, with the development of our society and the change of natural conditions, lots of wetlands is degrading and disappearing. According to the conclusion from Millennium Ecosystem Assessment, the degradation speed of wetlands is faster than any other ecosystems. In order to protect wetlands, it is very important to monitoring degradation of wetland and analysis the driving factors resulting in degrading, then recognize the contribution of these factors by turns. Firstly, extracting exactly wetlands from satellite images is the key in this paper. In the hill region, with the help of spatial analyses function in geographical information system software and DEM simulation method, the simulated images of hill shade is gained according to the solar radiation conditions of remote sensing image, then the mixture of hill shade and wetlands in satellite images can be recognized, and influence of hill shade on wetland can be removed successfully. In the flat urban region, because there is the similar digital number scope of old residential areas and wetlands in urban region, the digital number is replaced with surface reflectance to extract urban wetland information, and old residential area influences on the wetland is wiped off. Urban wetland is exactly extracted with normalized difference water index and its change is accurately detected with Landsat TM images acquired at 1991 and 2007. According to the wetland water budget theory, taking hydrology factors in wetland water budget equation as the main index, together with the society, hydrology and meteorology statistic data, this research quantitatively analyzes the contribution of natural and human driving factors to wetland change. Natural factors are the main reasons for wetland change, the decrease of precipitation, surface water inflows and the increase of evaporation are negative contribution to wetland maintenance, about 39.22%, 14.05% and 11.85% respectively, the decrease of surface water outflows is positive contribution, about 12.75%. To the human factors, urban sprawl is negative contribution, about 3.42%, however, technology progress is positive contribution, about 25.55%, and helpful to protect wetland and reduce the negative contribution of urban sprawl.