基于RS和GIS的乌江流域(重庆段)湿地景观动态分析

摘要

为了探究三峡库区的建立对乌江流域(重庆段)即重庆东南地区湿地环境产生的影响,以landsat-5 TM和landsat 8OLI遥感影像为主要数据源,基于eCognition和ArcGIS平台,采用面向对象分类的方法,建立重庆地区乌江流域1995、2005和2015年湿地景观数据库,利用景观动态变化度、景观破碎度及土地利用转移矩阵等方法,分析重庆地区乌江流域内湿地景观近20年的时空变化特征.结果表明:1)重庆地区乌江流域整体湿地景观面积近20年处于增长趋势,动态变化指数最高为水库,最低为水田;2)湿地景观转移以湿地景观内部转移为主,湿地景观与非湿地景观转移为辅,人工湿地增加比重高于天然湿地;3)研究区内景观破碎度呈现先增加后减少的趋势,说明该区域湿地环境先恶化后得到改善;4)1995、2005和2015年,天然湿地景观分维数均低于1.6,人工湿地均高于1.7,说明人工湿地景观格局比天然湿地复杂.天然湿地的稳定性指数远低于人工湿地,且接近于0,说明自然湿地内部空间结构更加脆弱.通过三峡工程及其他水利工程的建设,导致乌江流域(重庆段)湿地景观格局发生变化,对该地区的湿地环境总体改善起到明显的促进作用.随着三峡工程建设、库区蓄水,以及龙潭水利工程、江口电站等水利设施修建,乌江流域内湿地总体面积增加,人工湿地变化较天然湿地更为明显,但天然湿地相比人工湿地更易受外界干扰,应加强相对应的保护措施.研究为保护该地区湿地景观,建立乌江流域湿地生态系统动态监测体系,以及为武陵山区精准扶贫提供技术支持.%[Background] As one of the most important natural ecosystems,wetland impacts significantly the improvement of regional environmental quality and economic development.The decrease of wetland area will directly affect the survival of wetland,leading to the decline of wetland function,and resulting in the deterioration of soil and water loss and ecological environment.The establishment of the Three Gorges Reservoir caused the impact on the surrounding wetland landscape pattern.[Methods] Using object-oriented classification method,Landsat-5 TM and Landsat 8OLI remote sensing image as the main data source,the wetland landscape database of Chongqing section of Wujiang River basin in 1995,2005 and 2015 was established based on eCognition and ArcGIS platform.We used the dynamic change of landscape,landscape fragmentation and land use transfer matrix method to analyze the temporal and spatial changes in nearly 20 years of wetland landscape in Wujiang River Basin and to explore the reasons.[Results] 1)The overall wetland landscape area of Wujiang River Basin (Chongqing section) is in the growth trend in recent 20 years,and the overall dynamic change of natural wetland is higher than that of constructed wetland.The highest index of dynamic change occurs in reservoir,and the lowest in paddy field.2) The transfer of wetland landscape is dominated by the internal transfer of wetland landscape,and the transfer of wetland landscape and non-wetland landscape is as supplement.The proportion of constructed wetland is higher than that of natural wetland.3)In the study area,landscape fragmentation shows a decreasing trend after the increase at first,indicating that the wetland environment tends to be improved after the deterioration at first.4) In 1995,2005 and 2015,the landscape fractal dimensions of natural wetland are lower than 1.6,and that of artificial wetlands is higher than 1.7,indicating that the artificial wetland landscape is more complex than natural wetland.The stability index of natural wetland is lower than that of constructed wetland,which is close to 0,indicating that the inner space structure of natural wetland is more fragile.[Couclusions] The construction of the Three Gorges Dam and other water conservancy projects lead to the change of wetland landscape pattern in Wujiang River Basin (Chongqing section),which played a significant role in promoting the overall improvement of the wetland environment in the area.With the construction of the Three Gorges project,reservoir sluicing,and water conservancy project such as Longtan hydro project,Jiangkou hydro-power station and other water conservancy facilities constructed,the total area of wetland in Wujiang River Basin increased,and the change of constructed wetland is more obvious than that of natural wetland.Compared with constructed wetland,natural wetland is more vulnerable to the external disturbance so that we should strengthen the corresponding protection measures.