湿地功能评价的尺度效应——以盐城滨海湿地为例

湿地功能与空间尺度大小有着密切的联系,研究湿地功能的空间尺度效应对从功能上指导湿地系统的空间保护与管理工作有着重要意义。文章借助生态位理论构建了湿地功能的生态经济位评价模型,并以四个不同空间尺度为评价单元,探讨盐城滨海湿地功能评价的空间尺度响应特征。结果表明：随着评价尺度变大,高生态功能和高经济功能湿地面积表现为减少且减幅不断加大,较低和较高功能级别的湿地面积则随着尺度的变大而成倍增加;各功能级别湿地的空间形态也随之变化,且较低和较高功能级别的湿地空间扩展形态变化尤为突出;其原因是评价单元的变化,改变了单元内的地类结构,从而使其对应的某个湿地功能的主导优势地位发生了变化。研究结论表明大尺度评价结果更符合盐城滨海湿地“滚动开发”模式的特点,在湿地功能区划和湿地资源利用规划与管理方面更具有指导意义。

The effect of spatial scales on wetland functions evaluation: a case study for coastal wetlands in Yancheng, Jiangshu Province

Wetland functions are closely related to the spatial scales. Research on the effect of spatial scales on wetland functions is therefore of great importance for guiding the spatial protection and management of wetland ecological system. The paper takes Yancheng wetland as a case study to explore wetland function evaluation methodology based on ecological niche theory.The related study of Niche Theory were focused on species or communities surviving conditions in a certain habitat,as well as their playing roles. The development and conservation for wetlands also can be considered by integrating the ecological and economic factors together. Based on the ecological niche theory, the Ecological-Economic Units (EEU) in wetlands was defined according to their ecological and economic functions. The function position for each EEU is determined by its available resources condition and the requirement of its products for social and economy. Among which, the "ecostate" in EEU was referred to the potential functions, and the "ecorole" referred to the ability of function changes. In addition, the Ecological-Economic Niche (EEN) is also defined as the situation of EEU be in possession of available resources or the function position of EEU. Namely, the EEN is the position and function of EEU in the wetland system. We also defined the most adaptive niche in the paper which refered to the highest ecological value or can provide highest net-economic benefits. Involving the most adaptive niche and the reality niche of wetland functions, the ecostate and ecorole of the EEN for wetland functions is formulated. The ecostate of ecological functions, for example, is the nearness degree between the most adaptive ecological niche and reality ecological niche. While the ecorole represents the trend of reality ecological niche to the most adaptive ecological niche. The EEN of wetland functions is formulated by the ecostate and the ecorole. The value of EEN is greater, the more efforts for protecting the EEU are necessary; otherwise the development will go ahead.Based on the above information, an ecological-economic niche model was developed to evaluate the wetland functions in Yancheng coastal wetland. We explored the wetland functions at four different spatial scales including 1km 1km, 2km 2km, 4km 4km and 8km 8km. The results indicated that: (1) With the increase of the spatial scale for evaluation, the wetland area with the highest ecological and economic functions is decreasing, and the reductions are gradually increasing; the wetland area with the lower functions is increasing, and the increased areas is multiplied with the scale enlarged. (2) With the increase of the spatial scale for evaluation, the spatial forms of wetland at different function levels were changed accordingly. Especially, the spatial forms of wetland at relatively lower or higher functions levels showed a significant change. (3) Reasons for the above mentioned results are that the variation of estimated units in spatial scale would make the structure of land use types also changed, which lead the dominant wetland functions to be changed. (4) The results of large spatial scale evaluation are more in line with the characteristics of "Rolling Development" model of the Yancheng Coastal Wetlands, and therefore of great significance in guiding the wetland functions zoning, wetland use planning and wetland management.