山东科技大学 土木工程与建筑学院,清华大学 建筑学院,青岛市城市规划设计研究院,环境保护部卫星环境应用中心
School of civil engineering and architecture Shandong University of Science and Technology,,,
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.