KMS Chongqing Institute of Green and Intelligent Technology, CAS
| Identifying and evaluating functional connectivity for building urban ecological networks | |
Chen, Chun Di1,3 ; Colin, Meurk D.2; Maria, Ignatieva E.3; Glenn, Stewart H.3; Wu, Sheng Jun1
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| 2015 | |
| 摘要 | With rapid urbanization and industrialization, habitat fragmentation and loss are inevitable. Under these circumstances, landscape connectivity and ecological networks have become a focus of applied landscape ecology. A well-connected ecological network is believed to facilitate energy and resource fluxes, species dispersal, genetic exchange and multiple other ecological processes, and to contribute to the maintenance of ecosystem stability and integrity. Identifying and evaluating functional connectivity between habitat patches is the key step in designing and building well-connected ecological networks. Based on a review of literature on linkage identification approaches, our study combined least-cost path modeling with graph-theory based network analysis to simulate, identify, evaluate, and prioritize functional linkages. We made some modifications to conventional least-cost model and network analysis in order to reduce subjectivity and to better suit the specific conditions of urban environments. Least-cost models are commonly used to determine the movement routes of wildlife to optimize conservation of meta-populations in wild environments. Ideally, least-cost models should be parameterized with field data for a specific organism (usually a small animal); however, these data are difficult and time-consuming to collect, and this has resulted in a large number of studies relying entirely or in large part on collective expert opinion. Different experts may assign different values and therefore affect the reliability of network simulation. Therefore, we adopted the Landscape Development Intensity (LDI) index, which is a measure of human disturbance of ecosystems, to quantify the relative costs of land use/cover types. In addition, we chose not to use small mammals as the individual surrogate for designing our urban ecological network. Most studies of animal movement patterns have been conducted in continuous forest landscapes, which are very different from patchy urban environments. These are characterized by much smaller and fragmented habitat patches, surrounded by a non-living concrete matrix with various threats hostile to life. Instead, we used native trees as individual surrogates and their seed dispersal pattern, based on a field survey, for devising and simulating a functional urban ecological network. Taking Christchurch, New Zealand, as an example, our study used a climax native forest tree, Dacrycarpus dacrydioides as a surrogate in establishing our urban ecological network. We used the LDI index to build the cost surface for a least-cost model in ArcGIS 10.0, and the observed maximum seed dispersal distance of D. dacrydioides (1200 m) as the threshold distance for network analysis in Conefor 2.6. Under the 1200 m threshold distance, a total of 408 links were simulated in the study area. These were grouped into 10 importance grades using Hierarchical Cluster Analysis in SPSS 21.0 combined with input from decision-makers. Among these, the three most important links were between Richmond Park and Petrie Park, Hansons Reserve and Auburn Reserve, and between Centaurus Park and King George Reserve. They were identified as the cut-links in a landscape graph, i.e. removal would disconnect critical components in the landscape. Indeed, if these links were absent, the Integral Index of Connectivity (IIC) of the whole landscape would be reduced by 31.73%. Additionally, our study found that there was no linear relationship (Pearson’s r =0.078, P =0.118) between link importance value and total area of habitat connected. That is, the links between larger habitats are not necessarily more important to the network. Further studies are needed to support this finding. Overall, our case study suggests that the combination of least-cost pathway analysis and graph-theoretical algorithms is an efficient approach for simulating and prioritizing functional connectivity in urban landscapes, and might be valuable for Chinese urban ecological network planning. Furthermore, the energy-consumption based LDI index was shown to be a reliable measurement of relative cost values of land use/cover types. However, it should be pointed out that the LDI index was calculated based on western land use/cover types, which are different from those used in China. It is recommended that when being applied in China, the LDI index should be adjusted to China’s land use/cover types. © 2015, Ecological Society of China. All rights reserved. |
| DOI | 10.5846/stxb201402160263 |
| 发表期刊 | Shengtai Xuebao/ Acta Ecologica Sinica
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| ISSN | 10000933 |
| 卷号 | 35期号:19页码:6414-6424 |
| 语种 | 中文 |
| EISSN | 18722032 |
