综合模型法评估黄河三角洲湿地景观连通性

景观连通性是区域生态系统功能完整的重要表征。连通性的评估对生态系统管理和保护规划有重要意义。综合常用的景观连通性评估模型，即最小耗费距离模型与电路理论模型，根据生态网络构建的一般范式，采取两种不同阻力面赋值方案，对黄河三角洲的湿地景观连通性进行评估，并对比分析了两种模型的基本原理、工作性能、分析尺度等。结果表明：最小耗费距离模型能够识别最优生态廊道，为景观连通性评估提供基本模式。电路理论则能扩展到潜在生态廊道和关键生态点的量化识别，能确定具有生态功能的“夹点”和障碍区的空间位置。综合两种模型，可以量化评估黄河三角洲湿地景观连通性，空间化三角洲湿地保护恢复的管理目标，即潜在廊道和关键生态节点，为区域生态系统功能评估和管理提供精准的数据支持。

Application of the least cost distance model and the circuit theory model in the evaluation of wetland landscape connectivity in the Yellow River Delta

Landscape connectivity is important for maintaining the integrity of ecosystem structure and function, but usually ignored in practical ecosystem management and conservation planning. Graph theory and circuit theory were commonly considered as useful methods to quantify landscape connectivity through identifying potential corridors and key ecological nodes and thus contributed greatly to policy-making at both regional and global scales. The Yellow River Delta (YRD) has typical coastal wetland ecosystems and provided unique ecosystem services, such as high bird diversity. However, natural wetlands in this delta have been greatly fragmented due to global climate changes and human activities, especially after 1980''s. How to efficiently evaluate wetland landscape and to identify those hotspots for maintaining wetland connectivity is a primary task for regional wetland conservation and management. Using wetland classification and land cover data in the YRD, 56 wetland patches without human disturbances and with larger areas were selected as source patches. We designed two resistance surface schemes, considering the characteristics of coastal wetlands and rivers in this delta. The principles, processing procedures and analysis scales of models from graph theory (the Least Cost Distance model, LCD) and circuit theory (Circuitscape), respectively, based on source patches and resistance surface designation, were compared. Finally, we assessed the wetland connectivity of the YRD using the two models and provide specific suggestions for wetland protection in this delta. The results showed that, (1) the Least Cost Path (LCP) generated by the LCD model is consistent with the high current density area obtained by Circuitscape, (2) different resistance values schemes for rivers and water bodies have clear impacts on outputs of LCP, (3) the key ecological nodes, such as pinch points generated on the two resistance surface are mainly concentrated in the central area of the YRD, (4) according to the improvement score of the obstacle area, three major improvement areas of this delta are extracted:industrial and mining areas, aquaculture ponds in the east, aquaculture ponds in the west and the current estuary of the Yellow River. The results indicated that the LCD model could identify the optimal ecological corridors and Circuitscape model could identify potential corridors, obstacle areas and pinch points. Combination of the two models can not only quantify the spatial patterns of potential corridors and key ecological notes, but also identify the objects of wetland protection and restoration for the YRD and thus provide a scientific and feasible research scheme for landscape protection and wetland management in the other coastal zone.