基于CL-PIOP方法的青岛市生态网络结构要素评价

景观生态学中的生态网络概念,已被国内外越来越多机构与学者所接受。生态网络结构要素的量化评价成为生态网络能否真正发挥在空间上调和自然生态保护与社会发展作用的关键。图形理论中相关评价指数为量化评价提供了方法。探讨如何基于图形理论中相关评价结果数据,发现对一个地区生态网络连通性有重要影响的斑块与廊道等生态网络结构要素。以青岛作为研究案例区域,使用最小成本路径模型构建了湿地和林地两种生态网络,并以一定阈值为标准对生态网络做等级划分,采用图形理论中的CL-PIOP评价方法作为基础方法,提出两种生态网络结构要素评价标准对结果数据作深入分析。分析结果表明:基于不同等级生态网络斑块的CL-PIOP重要性频次统计可以有效的识别对网络连通性有重要作用的斑块,既涵盖了几乎所有大面积的斑块,同时也包括一定数量的小面积斑块;CL-PIOP评价方法可在众多廊道中快速识别具有不可替代作用的廊道,且根据CL-PIOP值大小以及在各等级网络中非零CL-PIOP值的频率统计进一步确定廊道的重要程度。此外,不同等级网络中CL-PIOP值存在异常增大的斑块及其相关廊道对于网络构建与连通性增强有关键作用,这些斑块通常与面积等自身的属性无关,而与其在网络所处的位置相关。生态网络模型与图形理论相关方法结合可以快速有效的识别区域重要的生态用地,为相关规划中生态用地的保护、恢复提供量化依据。

Evaluation of the structural elements of Qingdao ecological network based on the CL-PIOP method

The analysis of ecological networks in landscape ecology has been accepted increasingly by a growing number of institutions and scholars worldwide. The network connections of structural landscape elements, such as patches and corridors, enhance the effective flow of matter, energy, and information. Furthermore, the network structure can guarantee stability of the ecological network when certain ecological patches or corridors disappear. The ecological network therefore has some flexibility in the layout and adjustment of its spatial structure. This makes it possible to provide compromises for the spatial contradiction between protection of ecosystems and the socio-economic development that accompanies the current rapid urbanization in China. Quantitative evaluations of the structure elements of ecological networks play a key role in the protection, restoration, and adjustment of the regional environment. The related evaluation indexes from graph theory provide methods for such a quantitative evaluation. We intended to identify the patches and corridors that have a large influence on the connectivity of an ecological network, based on data evaluated by indexes from graph theory. Taking Qingdao City as an example, our study constructed wetland and woodland ecological networks, and classified these ecological networks by a certain threshold. This created a series of ecological networks of these two ecosystems with different connection strengths. We proposed two standards (Standard I and Standard II) to analyze the data produced by the evaluation index CL-PIOP (Correlation Length-Percentage of Importance of Omitted Patches). Our results show that:Standard I can determine the importance of patches and corridors in ecological networks of a certain connection strength. Standard I can also subdivide the important patches and corridors by the statistics of the importance of each connection strength. The most important patches based on standard I overlapped with almost all the larger patches when they were ranked by size. This shows that patch area or other properties cannot be used as the sole criterion for evaluating the maintenance of regional ecosystems. It also indicates some patches with a smaller area should receive more attention, because they may play a fundamental role in the overall connectivity of the ecological network. In addition, standard II can identify the critical patches and corridors that can connect two sub-networks of a certain connection strength by analyzing the patches and corridors with abnormal large CL-PIOP values at a set connection strength. Furthermore, the critical patches recognized by standard II are not prominent in their own properties (e.g., their areas are not large), and the corridors may not stand out from the numerous corridors that differ little, so are therefor hard to identify with other conventional methods. Overall, our study explored the application of evaluation indexes from graph theory to evaluate an ecosystem within the framework of ecological networks. Furthermore, our study proposed two standards to determine the important patches and corridors rapidly, which can provide a quantitative database for regional ecological land evaluation, planning, protection, and restoration.