Multi‐year lags in tree drought recovery, termed ‘drought legacy effects’, are important for understanding the impacts of drought on forest ecosystems, including carbon (C) cycle feedbacks to climate change. Despite the ubiquity of lags in drought recovery, large uncertainties remain regarding the mechanistic basis of legacy effects and their importance for the C cycle. In this review, we identify the approaches used to study legacy effects, from tree rings to whole forests. We then discuss key knowledge gaps pertaining to the causes of legacy effects, and how the various mechanisms that may contribute these lags in drought recovery could have contrasting implications for the C cycle. Furthermore, we conduct a novel data synthesis and find that legacy effects differ drastically in both size and length across the US depending on if they are identified in tree rings versus gross primary productivity. Finally, we highlight promising approaches for future research to improve our capacity to model legacy effects and predict their impact on forest health. We emphasise that a holistic view of legacy effects – from tissues to whole forests – will advance our understanding of legacy effects and stimulate efforts to investigate drought recovery via experimental, observational and modelling approaches.

中文翻译：

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过去的鬼魂：干旱遗留如何影响森林功能和碳循环

树木干旱恢复的多年滞后，被称为“干旱遗留效应”，对于理解干旱对森林生态系统的影响（包括对气候变化的碳（C）循环反馈）的影响非常重要。尽管干旱恢复普遍存在滞后性，但遗留效应的机理基础及其对碳循环的重要性仍存在很大的不确定性。在本文中，我们确定了用于研究从树木年轮到整个森林的遗留效应的方法。然后，我们讨论与遗留效应原因有关的关键知识缺口，以及可能导致干旱恢复滞后的各种机制如何对碳循环产生相反的影响。此外，我们进行了新颖的数据综合，发现遗留效应在美国各地的规模和长度都大不相同，这取决于它们是否在年轮中被识别出来，而不是总初级生产力。最后，我们重点介绍了有前途的研究方法，以提高我们对遗留效应进行建模并预测其对森林健康影响的能力。我们强调，从遗迹影响（从组织到整个森林）的整体观点，将增进我们对遗迹影响的理解，并通过实验，观察和建模方法激发人们调查干旱恢复的努力。