东江河岸缓冲带景观格局变化对水体恢复的影响

Influence of landscape pattern changes on the restoration of stream in Dongjiang River riparian buffer

以1998年,2006年的TM遥感影像数据为基础,利用地理系统软件Arc GIS对东江主干边缘做10km的缓冲区。以Fragstats为工具,利用景观指数从类型水平和景观水平上,分析河岸带景观格局变化。重点分析了各景观相关要素及景观整体对水体恢复的影响。结果表明:经过8a的变迁,东江水体斑块面积占河岸带景观面积的比例增加,水体连通性加强,破碎化程度有所下降,体现了在景观格局上流域水体有一定的恢复成效。河岸带区域中植被斑块面积增加,表明植被覆盖率增大,会有助于流域的水土保持;区域中耕地斑块面积在整个河岸带中的比例降低,对水体水质的污染会有减缓作用;整个河岸带景观破碎化程度有所下降,空间连通性相对增加。以上3种因素都会对水体的恢复起到促进作用。河岸带地区城市化水平加剧,这可以从建成地斑块面积增加,形状更加规则等景观格局特征看出,反映了人类干扰还在增强,无疑会对水体恢复造成不利影响。综合分析东江河岸缓冲带景观格局变化可以看出,东江河岸带水体恢复有一定成效,但是恢复的力度还有待加强,特别要注重植被质量的优化,改善植被的空间配置结构和种类搭配。城市规划中对建成地的选择要考虑河岸带的特殊性。水体的恢复要在景观水平上采取恢复措施,注重多因子的协调整合,改善流域尺度的景观格局配置。

Rivers are increasingly investigated from a landscape perspective.Recognition and understanding of landscape dynamics as a historical legacy of disturbances are necessary for sustainable management of stream ecosystems.This study analyzed temporal changes in land use and cover patterns in a riparian buffer area in Dongjiang River.To analyze the riverine landscape pattern,we created a buffer zone along the stream of the Dongjiang River with width of 10 km.Based on Thematic Mapper remote sensing data of 1998 and 2006,we identified 6 land use and land cover types using supervised classification techniques,a selected group of landscape metrics at the class and landscape level was used to quantify the changing pattern of land use and land cover in the study region.All of the analyses were performed using a geographic information system and the landscape pattern analysis software Fragstats.The quantitative evidences showed that there was a net increase of 8.57% in total water patch areas as an overall change between 1998 and 2006.The fragmentation of the water decreased as indicated by the larger areas and smaller numbers of patches.Analysis of the metrics revealed that water structure in study area had changed better over the past 8 years in terms of spatial configuration.The coverage of forest becomes larger indicated by the increases of woodland areas.The revegetations of the riparian would be helpful to the soil and water conservation.The proportion of agricultural land patch decreased by 35.72%,which would be responsible for the mitigation of water quality deterioration.The fragmentation of riparian decreased in landscape level,and the structural connectivity improved.The changes of woodland,farmland and the connectivity would place positive effects to the restoration of stream.The increasing urbanization indicated by a series of indices＇ changes such as the increases of PLAND and LSI and so on,which would bring new challenges to water quality.Dramatic changes of the landscapes,which due to the spread of urban land use around the riparian,may hold a negative influence over the restoration of stream.On all accounts,the restoration of Dongjiang River riparian gained effects to some extent,but some aspects should be enhanced.The optimization of vegetation is especially emphasized,and the spatial allocation of vegetation and plant species composition should be improved.The ecological particularity of riparian should be considered in the urban planning.Where water restoration is the goal,integrative measures at the landscape scale are supposed to be adopted.It is suggested that the distributing configuration of landscape pattern was ought to be optimized,and reinforcing the integration of multiple factors,so as to draw appropriate lessons for water ecosystem management.