Centre for Conservation Ecology and Environmental Sciences, Faculty of Science and Technology, Bournemouth University, Poole, BH12 5BB, UK.
Botanical Survey and Assessment, 3 Green Close, Woodlands, Southampton, Hampshire, SO40 7HU, UK.
Sci Rep. 2017 Jul 28;7(1):6775. doi: 10.1038/s41598-017-06082-6.
Ecological thresholds, which represent points of rapid change in ecological properties, are of major scientific and societal concern. However, very little research has focused on empirically testing the occurrence of thresholds in temperate terrestrial ecosystems. To address this knowledge gap, we tested whether a number of biodiversity, ecosystem functions and ecosystem condition metrics exhibited thresholds in response to a gradient of forest dieback, measured as changes in basal area of living trees relative to areas that lacked recent dieback. The gradient of dieback was sampled using 12 replicate study areas in a temperate forest ecosystem. Our results provide novel evidence of several thresholds in biodiversity (namely species richness of ectomycorrhizal fungi, epiphytic lichen and ground flora); for ecological condition (e.g. sward height, palatable seedling abundance) and a single threshold for ecosystem function (i.e. soil respiration rate). Mechanisms for these thresholds are explored. As climate-induced forest dieback is increasing worldwide, both in scale and speed, these results imply that threshold responses may become increasingly widespread.
生态阈值是生态属性快速变化的临界点，是科学界和社会关注的主要问题。然而，很少有研究关注实证检验温带陆地生态系统中阈值的发生。为了弥补这一知识空白，我们检验了在森林枯损梯度下，一些生物多样性、生态系统功能和生态系统状况指标是否存在响应阈值的现象，该梯度通过相对无近期枯损的区域来衡量活树基面积的变化来进行测量。枯损梯度通过在温带森林生态系统中的 12 个重复研究区域进行采样。我们的研究结果提供了关于生物多样性（即外生菌根真菌、附生地衣和地被物的物种丰富度）、生态状况（如草层高度、可食用幼苗丰度）和生态系统功能（即土壤呼吸速率）的几个阈值的新证据，同时也证明了只有一个阈值与生态系统功能相关。我们还探讨了这些阈值的机制。由于气候引起的森林枯损在全球范围内无论是在规模还是速度上都在增加，这一结果表明，阈值响应可能会越来越普遍。
