Species distribution models are key to evaluate how climate change threatens European forests and tree species distributions. However, current models struggle to integrate ecophysiological processes. Mechanistic models are complex and have high parameter requirements. Some correlative species distribution models have tried to include traits but so far have struggled to directly connect to ecophysiological processes. Here, we propose a new strategy in which species distributions are based on safety margins which represent species' proximity to their physiological thresholds. We derived frost and drought safety margins for 38 European tree species as the difference between physiological tolerance traits and local maximum stress. We used LT50 and Ψ50 as tolerance traits for frost and drought, respectively, and local minimum temperature and minimum soil water potential as maximum stress. We integrated these safety margins into a species distribution model, which tests if the probability of species presence declines rapidly when the safety margin reaches zero, when physiological stress exceeds the species' tolerance traits. Our results showed thaet 35 of the 38 studied species had their distribution explained by one or both safety margins. We demonstrated that safety‐margins‐based model can be efficiently transferred to species for which occurrence data are not available. The probability of presence dropped dramatically when the frost safety margin reached zero, whereas it was less sensitive to the drought safety margin. This differential sensitivity may be due to the more complex regulation of drought stress, especially as water is a shared resource, whereas frost is not. Our analysis provides a new approach to link species distributions to their physiological limits and shows that, in Europe, frost and drought safety margins are important determinants of species distributions.

中文翻译：

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生活在边缘 – 对霜冻和干旱的生理耐受性解释了 35 种欧洲树种的分布范围限制


物种分布模型是评估气候变化如何威胁欧洲森林和树种分布的关键。然而，目前的模型难以整合生态生理过程。机理模型复杂且参数要求高。一些相关物种分布模型试图包括性状，但到目前为止，一直难以直接与生态生理过程联系起来。在这里，我们提出了一种新的策略，其中物种分布基于安全边际，该边际代表物种接近其生理阈值。我们得出了 38 种欧洲树种的霜冻和干旱安全边际，作为生理耐受性状和局部最大压力之间的差异。我们分别使用 LT50 和 Ψ50 作为霜冻和干旱的耐受性状，局部最低温度和最小土壤水势作为最大应力。我们将这些安全边际整合到物种分布模型中，该模型测试当安全边际达到零时，当生理压力超过物种的耐受性特征时，物种存在的可能性是否迅速下降。我们的结果表明，在研究的 38 个物种中，有 35 个物种的分布由一个或两个安全边际解释。我们证明，基于安全边际的模型可以有效地转移到没有发生数据的物种。当霜冻安全边际达到零时，存在的可能性急剧下降，而对干旱安全边际的敏感性较低。这种差异敏感性可能是由于干旱胁迫的调节更加复杂，特别是因为水是一种共享资源，而霜冻则不是。 我们的分析提供了一种将物种分布与其生理极限联系起来的新方法，并表明在欧洲，霜冻和干旱安全边际是物种分布的重要决定因素。