土地利用变化对生境网络的影响——以苏锡常地区白鹭为例

生境网络对于物种更具有生态意义。研究土地利用变化对生境网络的影响,对破碎景观中种群的扩散和迁徙至关重要。研究结果有助于区域生境网络的恢复和完善,从物种的角度而非景观结构的角度优化生态网络。以城市化快速发展、土地利用变化明显的苏锡常地区为研究区域,优势湿地鸟类白鹭为代表物种,构建物种生境斑块约束条件概念模型,提出按照物种生活习性特征划分、选择生境斑块的方法,并从斑块和网络结构两个视角分析了土地利用变化对生境网络的影响。结果表明:(1)2000—2010年研究区白鹭生境的适宜地类总面积虽有所增加,但主要由于大量新增线性人为干扰致使白鹭生境网络质量下降;(2)白鹭生境网络在研究区不是全区覆盖的回路,基本由宜兴—溧阳片、无锡滨湖片、苏州吴中片和苏州阳澄湖片4个小片网构成,其完整程度按照宜溧片、滨湖片、吴中片、阳澄湖片降次排列;至2010年,宜溧片破坏最为严重,滨湖片和吴中片次之,阳澄湖片受破坏程度相对最弱。总体上,白鹭生境境况在10年间恶化明显,土地利用变化朝着不利于白鹭持续生存的方向发展。

The impact of land use change on habitat network: a case study of Egretta garzetta in Su-Xi-Chang Area

Habitat network as part of ecological networks is very important for species. Consequently, it is necessary to find out the impacts of land use change on habitat network as well as the dispersal and migration of species, especially in current rapid urbanizing condition. The research results will be a great contribution to rebuilding and optimizing regional ecological network from the perspective of species conservation and ecological process, but not only the landscape structure as most previous research did. The aim of the paper is to find out: (1) how to map out the habitat network of a certain species from TM images in a grid pattern? (2) How land use change affected the habitat network of the species, especially from the views of habitat patch and network structure? The Su-Xi-Chang Area of the Yangtze River Delta Area was selected as case study due to its rapid urban development and land use changes. In this research, the Egretta garzetta was selected as a regional representative species for the following three reasons: (1) marshland birds are the superior species among wild animals of the study area; (2) Egretta garzetta is the superior species among marshland birds which is on the list of Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES); (3) the data related to living and hunting habitats of Egretta garzetta in the study area are easy to get. Based on the study of the Egretta garzetta habitat, we developed a Conceptual Constraint Model of Species Habitat Patch (CCMSHP) and a method to select habitat patch properly from different land types. In CCMSHP, factors which affect the forming of species habitat were classified into three categories coarsely, which are physical, biological, and human disturbances. In each category, main specific constraints were obtained from previous results and transferred suitably from the calculation supported by the ArcGIS software. Based on the identified Egretta garzetta habitats, their habitat networks were accordingly developed. Then, landscape metrics and network structure indicators were applied to analyze the effect of land use change on the mapped-out habitat network. The results showed that: (1) the total area of patches suitable for Egretta garzetta''s living and hunting was increased during the period from 2000 to 2010; however, the quality of the habitat network was decreased seriously due to the strong negative effect of newly-built constructions, such as expressways and high-speed railways. (2) The habitat network of Egretta garzetta is only a small part of the whole area which consists of four separate fractions. They were Yixing-Liyang Part, Binhu Part, Wuzhong Part, and Yangchenghu Part and ranked down respectively, according to their conditions of 2000. During the recent ten years, these fractions have been seriously destroyed. Among of them, Yixing-Liyang Part was in the worst condition and then following by Binhu, Wuzhong and Yangchenghu Part. In a summary, during the past ten years, the condition of Egretta garzetta habitat environment was becoming worse; and the land use change has affected the survival of Egretta garzetta badly. We suggest that the protection both of high and low-level patches in hierarchy is important and it is necessary to identify and rebuilt those disappeared low-level patches to improve the quality of habitat network.