Disparities between plant community responses to nitrogen deposition and critical loads in UK semi-natural habitats
Disparities between plant community responses to nitrogen deposition and critical loads in UK semi-natural habitats
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DOI：
10.1016/j.atmosenv.2020.117478
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发表时间：
2020-10
影响因子：
5
通讯作者：
R. Payne;C. Campbell;C. Stevens;R. Pakeman;L. Ross;A. Britton;R. Mitchell;L. Jones;C. Field;S. Caporn;J. Carroll;J. Edmondson;E. Carnell;S. Tomlinson;A. Dore;U. Dragosits;N. Dise
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文献类型：
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作者：
R. Payne;C. Campbell;C. Stevens;R. Pakeman;L. Ross;A. Britton;R. Mitchell;L. Jones;C. Field;S. Caporn;J. Carroll;J. Edmondson;E. Carnell;S. Tomlinson;A. Dore;U. Dragosits;N. Dise
经验临界负荷被广泛用于量化和管理活性氮（N）沉降的生态影响。临界负荷值的目的是确定一个水平的氮沉积低于显着的有害影响不会发生根据目前的知识。临界载荷主要是基于实验，但数量很少，并且具有众所周知的局限性，因此迫切需要用其他形式的证据来测试和验证值。我们收集了在英国的植被群落的空间变异性的数据，并使用阈值指标类群分析（TITAN），调查物种变化和模拟电流和累积N沉积之间的联系。我们的分析集中在五个数据集：酸性草原，高山栖息地，沿海固定沙丘，沙丘松弛和潮湿的草地。在四个这些栖息地有证据表明，至少有一个物种（“物种损失变点”）的覆盖率显着下降发生在临界负荷以下，并往往在非常低的N沉积水平。在所有的栖息地有证据表明，许多个别物种的损失变点的聚类，这意味着一个社区的变点类似于一个生态阈值。其中三个社区变化点发生在临界负荷以下，其余两个与临界负荷范围重叠。使用类似方法的研究现在越来越普遍，结果也相似。在19个类似的分析中，有证据表明，18个分析中的植物物种损失变点低于临界负荷，13个分析中的群落物种损失变点低于临界负荷。这些分析都没有显示社区变化点高于临界负荷。实地数据越来越多地表明，许多欧洲的临界负荷太高，不能自信地防止敏感物种的损失。
Empirical critical loads are widely used to quantify and manage the ecological impacts of reactive nitrogen (N) deposition. Critical load values aim to identify a level of N deposition below which significant harmful effects do not occur according to present knowledge. Critical loads have been primarily based on experiments, but these are few in number and have well-known limitations, so there is a strong imperative to test and validate values with other forms of evidence. We assembled data on the spatial variability in vegetation communities in the United Kingdom and used Threshold Indicator Taxa Analyses (TITAN) to investigate linkages between species changes and modelled current and cumulative N deposition. Our analyses focused on five datasets: acid grasslands, alpine habitats, coastal fixed dunes, dune slacks and wet grasslands. In four of these habitats there was evidence for a significant decline in the cover of at least one species (a ‘species-loss change-point’) occurring below the critical load, and often at very low levels of N deposition. In all of the habitats there was evidence for clustering of many individual species-loss change-points, implying a community change-point analogous to an ecological threshold. Three of these community change-points occurred below the critical load and the remaining two overlapped with the critical load range. Studies using similar approaches are now increasingly common, with similar results. Across 19 similar analyses there has been evidence for plant species loss change-points below the critical load in 18 analyses, and community-level species loss change-points below the critical load in 13 analyses. None of these analyses has shown community change-points above the critical load. Field data increasingly suggest that many European critical loads are too high to confidently prevent loss of sensitive species.