流域尺度湿地可恢复性评价——以永定河上游流域为例

Wetland Restoration Potential Estimation at the Watershed Scale——A Case Study in Upstream of the Yongdinghe River

湿地具有独特的生态服务功能和很高的生态效益,因此恢复或重建退化湿地非常重要。针对目前湿地恢复的相关研究主要集中在恢复举措等宏观方面,缺乏在整体上考虑湿地之间的连通性及其空间结构的影响因素等问题,在流域为尺度上,对湿地的可恢复性进行评价,综合考虑湿地结构、湿地景观特征等自然因素以及人类建设活动干扰下流域下垫面等因素对整个流域内湿地恢复的影响,以永定河上游流域为例,建立一个基于GIS的多指标综合评价模型,对湿地的可恢复性进行评价。具体研究步骤包括指标信息提取、指标赋值及归一化和多指标综合。首先,选择河流等级、坡面流长、河流水质、饱和指数、水成土、土地利用/覆盖类型作为评价指标;然后,针对指标参量对湿地恢复的贡献度进行赋值,并做归一化处理以消除不同指标量纲对结果的影响;最后,利用层次分析法分析指标权重,计算加权值,根据加权值的正态分布对流域内湿地的可恢复性进行等级划分,并使用优序图法对评价结果进行佐证。研究结果表明,永定河上游流域研究区内可恢复湿地面积约979km2,占流域总面积的2.18%;其中,阳原县的可恢复湿地面积最大,约为131.6km2,其次为怀来县,为129.1km2;可恢复的湿地类型以水库/坝区型湿地和河流为主,分别占可恢复区域总面积的11.75%和11.33%。研究成果为湿地的管理和恢复工程选址的合理性提供了科学的理论参考,避免了依据单一生态环境要素或局部区域特征进行恢复对象选择的片面性。

It＇ s important to make the recovery and reconstruction of the degraded wetlands because of their high ecological benefits and ecosystem services. However, most related strategies have focused on certain sin- gle familiar objectives, such as water quality improvement of the wetlands, or watershed flood utilization, without considering the interaction among the wetlands. Thus the special effects on the restoration perfor- mance and management implications are not fully evaluated. This paper proposes a GIS-based multi-criteria comprehensive evaluation methodology for potential estimation of wetland restoration, by taking upstream of the Yongdinghe River as the example. The research includes three steps： criteria information extraction, crite- ria value assignment and normalization, and integrated evaluation. For the first step, the stream order, over- land flow length, stream water quality, saturation index, hydric soil and land use were selected as the evalua- tion criteria. In the second step, unique value was assigned to each criterion according to their potential contri- bution to the restoration. And all the criteria were normalized in order to eliminate errors that may result from different dimensions. In the final step, the weight of each criterion was calculated and the integrated criterion was deduced by using the analytic hierarchy process method. The restoration suitability prioritization of the wetlands was classified into 5 levels： lowest, low, middle, high and highest by using the histogram segmenta- tion method. And the evaluation accuracy was verified with the precedence chart method. The result showed that about the wetlands of 979 km2 in the overall study area has the highest suitability for restoration, account- ing for 2.18% of the total area. And most of them were located in Yangyuan country, with an area of about 131.6 km~. The main types of the wetlands were reservoir and river. They were accounting for 11.75% and 11.33% of the total area, respectively. The results provided scientific theory and exemplary role to decisions of wetland management and restoration, avoiding the unilateralism of the site chosen on the basis of single eco- logical factor or region features.