As the climate warms, drought will increasingly occur under elevated temperatures, placing forest ecosystems at growing risk of extensive dieback and mortality. In some cases, increases in tree density following early 20th‐century fire suppression may exacerbate this risk. Treatments designed to restore historical stand structure and enhance resistance to high‐severity fire might also alleviate drought stress by reducing competition, but the duration of these effects and the underlying mechanisms remain poorly understood. To elucidate these mechanisms, we evaluate tree growth, mortality, and tree‐ring stable‐carbon isotope responses to stand‐density reduction treatments with and without prescribed fire in a ponderosa pine forest of western Montana. Moderate and heavier cutting experiments (basal area reductions of 35% and 56%, respectively) were initiated in 1992, followed by prescribed burning in a subset of the thinned units. All treatments led to a growth release that persisted to the time of resampling. The treatments had little effect on climate–growth relationships, but they markedly altered seasonal carbon isotope signals and their relationship to climate. In burned and unburned treatments, carbon isotope discrimination (Δ¹³C) increased in the earlywood (EW) and decreased in the latewood (LW) relative to the control. The sensitivity of LW Δ¹³C to late‐summer climate also increased in all treatments, but not in the control. Such increased sensitivity indicates that the reduction in competition enabled trees to continue to fix carbon for new stem growth, even when the climate became sufficiently stressful to stop new assimilation in slower‐growing trees in untreated units. These findings would have been masked had we not separated EW and LW. The importance of faster growth and enhanced carbon assimilation under late‐summer climatic stress became evident in the second decade post‐treatment, when mountain pine beetle activity increased locally, and tree mortality rates in the controls of both experiments increased to more than twice those in their respective treatments. These findings highlight that, when thinning is used to restore historical forest structure or increase resistance to high‐severity fire, there will likely be additional benefits of enhanced growth and physiological activity under climatic stress, and the effects may persist for more than two decades.

中文翻译：

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在美国黄松森林中进行森林恢复治疗可增强生理活性并在气候胁迫下生长。

随着气候变暖，干旱将在升高的温度下越来越多地发生，使森林生态系统面临更大的死亡和死亡风险。在某些情况下，20世纪初的火灾扑灭后树木密度的增加可能加剧这种风险。旨在恢复历史林分结构并增强对高强度火势的抵抗力的处理方法还可以通过减少竞争来缓解干旱压力，但对这些影响的持续时间和潜在机制仍知之甚少。为了阐明这些机制，我们评估了蒙大拿州西部的美国黄松林中树木生长，死亡率和树木密度稳定碳同位素对有无明火下的林分密度降低处理的反应。中度和较重的切割实验（基本面积减少了35％和56％，分别于1992年开始，然后在一部分变薄的单元中进行规定的燃烧。所有处理均导致生长释放，并持续到重新采样的时间。这些处理对气候与生长的关系影响不大，但是它们显着改变了季节性碳同位素信号及其与气候的关系。在燃烧和未燃烧的处理中，碳同位素判别（Δ相对于对照而言，早木（EW）中的¹³ C）增加，而晚木（LW）中的¹³ C）减少。LWΔ的敏感性¹³在所有处理中，C到夏末的气候也有所增加，但在对照中却没有。这种提高的敏感性表明，竞争的减少使树木能够继续为新茎的生长固定碳，即使气候变得压力很大，也可以阻止未经处理的生长较慢的树木中新的同化。如果不将电子战和轻武器分开，这些发现将被掩盖。在处理后的第二个十年中，夏末气候胁迫下更快的生长和增强碳同化的重要性变得很明显，当时山松甲虫的活性在局部增加，并且两个实验的对照中的树木死亡率都增加了两倍。他们各自的待遇。这些发现突出表明，