Thornhill Ian, Batty Lesley, Hewitt Matthew, Friberg Nikolai R, Ledger Mark E
1School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, West Midlands B15 2TT UK.
2CoLA - Culture and Environment, Bath Spa University, Newton Saint Loe, Bath, BA2 9BN UK.
Urban Ecosyst. 2018;21(2):213-225. doi: 10.1007/s11252-017-0724-8. Epub 2017 Dec 18.
Pond networks support high levels of biodiversity when compared to other freshwater ecosystems such as rivers, lakes and streams. The persistence of species in these small, sometimes ephemeral, aquatic habitats depends on the dispersal of individuals among ponds in the landscape. However, the number of ponds across the landscape is at a historical low as urbanisation and intensified agricultural practices have led to a substantial loss of ponds (nodes in the pond network) over more than a century. Here, we examine the extent and drivers of pond loss in a heavily urbanised landscape (Birmingham, UK) over 105 years and determine how pond loss influences key structural properties of the pond network using graph theoretic approaches. Specifically, we calculated minimum spanning trees (MST) and performed percolation analyses to determine changes in both the spatial configuration and resilience of the pond network through time. Pond numbers declined by 82% between 1904 and 2009, such that pond density decreased from 7.1 km to 1.3 km. The MST analyses revealed increased distance between ponds in the network (i.e. edge length increased) by up to 49% over the 105-year period, indicating that ponds in the modern landscape (2009) were considerably more isolated, with fewer neighbours. This study demonstrates that graph theory has an excellent potential to inform the management of pond networks in order to support ecological communities that are less vulnerable to environmental change.
与河流、湖泊和溪流等其他淡水生态系统相比，池塘网络支持着高水平的生物多样性。这些小型、有时短暂的水生栖息地中物种的存续取决于个体在景观中各池塘之间的扩散。然而，由于城市化和集约化农业活动导致在一个多世纪的时间里池塘（池塘网络中的节点）大量流失，景观中池塘的数量处于历史低位。在此，我们研究了105年间一个高度城市化地区（英国伯明翰）池塘流失的程度和驱动因素，并使用图论方法确定池塘流失如何影响池塘网络的关键结构特性。具体而言，我们计算了最小生成树（MST）并进行了渗流分析，以确定池塘网络的空间配置和恢复力随时间的变化。1904年至2009年间，池塘数量减少了82%，池塘密度从每平方公里7.1个降至每平方公里1.3个。MST分析显示，在这105年期间，网络中池塘之间的距离增加（即边长增加）了49%，这表明现代景观（2009年）中的池塘彼此隔离得多，邻居更少。这项研究表明，图论在为池塘网络管理提供信息方面具有巨大潜力，以便支持对环境变化不太敏感的生态群落。
