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    近20年来英罗湾红树林景观过程及周边土地利用/覆盖变化

    Mangrove landscape changing process and land use coverage change of its surrounding areas in Yingluo Bay, southern China during the past 20 years

    • 摘要: 全球红树林正以惊人的速度消失,红树林遥感监测对于资源保育至关重要。在GIS和遥感技术支持下,基于1991—2010年的5期Landsat TM遥感影像及相关专题图,结合立地调查,研究了英罗湾红树林空间变化的过程并对其周边的土地利用/覆盖动态和驱动力进行分析。结果表明:研究时段内人为和自然因素均对研究区红树林动态变化产生影响,表现为红树林近陆的内边界缩减而近海的外边界向海扩展;红树林总面积表现为先减少后增加的趋势,净损失量约7%。变化轨迹分析表明:1991—2000年间围垦养殖引起靠近陆地的红树林面积快速减少;红树林在滩涂上不断向海扩展以及2000年以来的生态恢复工程使研究区红树林边界向海推移,且主要发生于靠近河流和海洋的外缘。近20年来,红树林周边的土地利用/覆盖变化显著,城镇化和工业化使研究区林地、耕地减少且主要转化为建设用地,建设用地规模迅速增加且在湛江一侧沿交通干线呈多点分散格局,广西一侧则在原有城镇建设用地基础上向外扩张;靠近河流和红树林周边的水产养殖塘的面积持续增加,前期主要是对红树林的直接围垦,后期则主要来自于政策鼓励下在水田上的筑塘养殖。

       

      Abstract: Based on GIS and RS technology, the Landsat TM images from 1991 to 2010, associated with the ground truth data in 2011 and the thematic maps on mangrove forests, were hierarchically extracted to identity mangrove and other land use coverage surrounding Yingluo Bay, southern China. Together with the local expert knowledge, 7 land use types were identified, namely farmland, forestland, construction area, water, unused area, aquiculture pond and mangrove forests respectively. The spatial process of mangrove forests landscape change and the dynamics of land use coverage as well as the rate and cause of the changes nearby the Yingluo Bay were analyzed in this paper. The results indicated that both anthropogenic and natural factors had influenced mangrove forests in the study area. During the period of 1991-2010, the area of mangrove forests decreased at first and then increased, the net loss reached about 7%. The mangrove forests had been extending seaward and the vegetation coverage had increased continuously since 1991. The changing trajectories of mangrove forests were analyzed to retrieve the spatial and temporal features of mangrove change. The loss speed had been much faster significantly than that of natural expansion and afforestation during the period of 1991-2000. The loss of mangrove distributed mainly on the landward, the mangrove forests outside the forest boundary had decreased and the reclamation from mangrove forests for aquaculture was the major reason. Mangrove forest area had increased due to the ecological restoration and natural expansion during the period of 2000-2010, the increased mangrove area distributed mainly on seaward of mangrove and nearby the rivers mouth. In addition, the extent of mangrove forests also changed as a result of the erosion and accretion near the river. In the past 20 years, the significant changes on land use coverage occurred in the coastal areas nearby the Yingluo Bay. Forestland and farmland had decreased because of the rapid rural urbanization and industrialization; the construction area had increased significantly, particularly in the period of 2000-2010. The area of aquiculture pond had increased continuously and was distributed along the rivers and adjacent to mangrove forests. In the former phase, the increased area of aquiculture pond was converted mainly from the mangrove deforestation, while in the later phase those mainly from the paddy rice under the related policy support.

       

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