三江平原湿地区域生态风险评价研究

采用“点轴体系”及“中心地理论”来描述和表征区域人类活动的空间集聚特征,以此反映湿地区域人类活动直接风险来源,通过土壤侵蚀与非点源污染途径,区域非湿地部分(森林、水田、旱地等)通过物质联系(泥沙、氮磷、水等的输出与输入)方式也会对湿地健康造成影响,反映湿地区域人类活动间接风险来源。基于对人类活动影响湿地直接途径和间接途径的区分以及相应部分风险指标的选择,论文最终完成三江平原湿地区域生态风险评价研究工作。结果表明：DMSP/OLS(Defense Meteorological Program Operational Line-Scan System)夜间灯光及多等级道路数据可以用于区域点轴体系描述,从而表征出湿地区域人类活动直接风险来源的空间分布特征,其中高和极高风险源强度等级与区域高等级中心地和高等级道路拟合程度较好;由于较高的生态资产及脆弱性水平,湿地有最高的生态风险水平;三江平原低、中、高和很高风险等级所占比例分别为64.00%、24.28%、10.38%、1.34%,大部分为低和中等风险水平,但有关风险防范任务仍不可掉以轻心,特别是在相应的高等级风险分布区域;南部地区有较高的风险水平,因此需要着重加以保护。从生态系统服务功能来看,一般认为水田、旱地为生产功能区,森林、湿地为生态功能区。过分关注水田、旱地的生产服务功能会造成下游湿地过量的物质输入从而加剧其风险水平;相反,注重森林保育能够减少泥沙、氮磷等大量输出风险,增加流域产流,从而可为下游湿地健康维持作出贡献。因此,水田、旱地与湿地间是一种生态服务权衡关系,森林与湿地间是一种生态服务协同关系,因此,风险管理方面,应强调区域”点轴体系“与湿地间的空间邻接关系,注重湿地重点生态风险来源（地点与方位）的防范以及湿地与非湿地类型间基于生态系统服务功能的权衡及协同管理问题。可为从区域整体水平上削减湿地健康风险水平提供指导和帮助。

Regional ecological risk assessment of wetlands in the Sanjiang Plain

Characterizing the regional intensity of human activities is an important scientific issue. In this study, the pole-axis spatial system (central places and roads of multiple grades, such as city, county, farm, and village and railway, highway, national road, provincial road, municipal road, county road, and town road) and central place theory were adopted to represent the spatial agglomeration characteristics of regional human activities as direct risk source of wetlands. Soil erosion and non-point source (NPS) pollution indicating indirect effects of human activities on wetlands at the regional scale were also considered. Based on these results, the regional ecological risk assessment (RERA) framework of wetlands was established. Using this wetland RERA framework, the spatial heterogeneity of risk grades in the Sanjiang Plain area was analyzed. The results show that: 1) The Defense Meteorological Program Operational Line-Scan System (DMSP/OLS) nighttime light intensity data and multiple level roads data could be used to delineate the regional "pole-axis" system and characterize the direct risk source of wetlands stemming from human activities at the regional scale. High and very high risk source intensity areas matched well with the regional pole-axis system, especially with the central places and roads of high grades. 2) Owing to its high ecological capital value per unit area and vulnerability, wetlands had highest risk. 3) The low, medium, high, and very high risk areas accounted for 64.00%, 24.28%, 10.38%, and 1.34% of the study area, respectively. 4) Overall, the southern parts of the Sanjiang Plain had higher risk levels than the northern parts. With regard to the management of regional ecological risk of wetlands, our recommendations include emphasizing the spatial relationship (location, direction, and so on) between wetlands and the regional pole-axis system in order to control direct risks of wetlands from human activities, and tradeoff and synergy between wetlands and other ecosystems (rainfed cropland, rice field, and forest land) through prevention and control of soil erosion and NPS pollution stemming from non-wetland areas in order to reduce the risk level of wetlands at the regional scale.