Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, Scotland, UK.
Scottish Natural Heritage, Great Glen House, Inverness IV3 9NW, Scotland, UK.
Sci Total Environ. 2017 Dec 15;605-606:1021-1030. doi: 10.1016/j.scitotenv.2017.06.173. Epub 2017 Jul 12.
Potential for habitat restoration is increasingly used as an argument for reintroducing ecosystem engineers. Beaver have well known effects on hydromorphology through dam construction, but their scope to restore wetland biodiversity in areas degraded by agriculture is largely inferred. Our study presents the first formal monitoring of a planned beaver-assisted restoration, focussing on changes in vegetation over 12years within an agriculturally-degraded fen following beaver release, based on repeated sampling of fixed plots. Effects are compared to ungrazed exclosures which allowed the wider influence of waterlogging to be separated from disturbance through tree felling and herbivory. After 12years of beaver presence mean plant species richness had increased on average by 46% per plot, whilst the cumulative number of species recorded increased on average by 148%. Heterogeneity, measured by dissimilarity of plot composition, increased on average by 71%. Plants associated with high moisture and light conditions increased significantly in coverage, whereas species indicative of high nitrogen decreased. Areas exposed to both grazing and waterlogging generally showed the most pronounced change in composition, with effects of grazing seemingly additive, but secondary, to those of waterlogging. Our study illustrates that a well-known ecosystem engineer, the beaver, can with time transform agricultural land into a comparatively species-rich and heterogeneous wetland environment, thus meeting common restoration objectives. This offers a passive but innovative solution to the problems of wetland habitat loss that complements the value of beavers for water or sediment storage and flow attenuation. The role of larger herbivores has been significantly overlooked in our understanding of freshwater ecosystem function; the use of such species may yet emerge as the missing ingredient in successful restoration.
栖息地恢复的潜力越来越多地被用作重新引入生态工程师的论据。通过筑坝，海狸对水生态形态学有着众所周知的影响，但它们在多大程度上能够恢复因农业而退化的湿地生物多样性，在很大程度上是推断出来的。我们的研究首次对计划中的海狸辅助恢复进行了正式监测，重点关注在农业退化湿地释放海狸后 12 年内，通过对固定样地的重复采样，植被的变化。将这些影响与未放牧的围栏进行了比较，围栏允许将水浸的广泛影响与树木砍伐和食草动物的干扰分开。在海狸存在的 12 年内，每个样地的平均植物物种丰富度平均增加了 46%，而记录的物种总数平均增加了 148%。通过样地组成的不相似性来衡量的异质性平均增加了 71%。与高湿度和光照条件相关的植物覆盖率显著增加，而指示高氮的物种则减少。暴露在放牧和水浸两种环境下的区域，其组成变化最为明显，放牧的影响似乎是水浸的附加和次要影响。我们的研究表明，一种众所周知的生态工程师——海狸——可以随着时间的推移将农业土地转变为一个相对物种丰富和异质的湿地环境，从而达到常见的恢复目标。这为湿地栖息地丧失的问题提供了一种被动但具有创新性的解决方案，补充了海狸在水或沉积物储存和水流减缓方面的价值。在我们对淡水生态系统功能的理解中，大型食草动物的作用被严重忽视；这些物种的利用可能会成为成功恢复的缺失因素。
