Minimizing forest vulnerability to more frequent and severe droughts, as climate models predict, has emerged as a primary goal of forest management. One potential strategy to moderate drought‐induced stress is reducing basal area through the repeat application of prescribed fire. However, use of prescribed fire as a management tool to reduce drought vulnerability has been largely untested. Here, we report the long‐term effects of repeat fires on the climate‐growth response of adult oaks (Quercus spp.) in the Missouri Ozarks, USA. We measured the annual radial growth of trees that experienced either no fire, periodic (every 4 yr), or annual prescribed fires from 1950 to 2015. To assess whether increased fire frequency interacts with climate to determine long‐term forest productivity, we modeled annual growth as a function of potential evapotranspiration, fire treatment, and their interaction. We also quantified the effect of fire‐driven reductions in tree density on carbon and oxygen isotope composition of tree rings and drought resistance (growth during drought) and resilience (growth recovery after drought) during past drought events. Annual radial growth and isotopic composition data indicated trees experienced reduced growth due to moisture stress, but drought vulnerability did not vary between frequently burned forests and unburned controls. In contrast, periodic, but not annual, fires reduced annual growth by 9.6% during wet periods favorable to growth with the effect consistent over time. Fire had minimal effects on total and inorganic soil nitrogen after 65 yr of treatment, regardless of frequency, suggesting other underlying causes of the observed growth declines under periodic burning (e.g., crown, bole, or root injury). Our results suggest that long‐term, increased fire frequency can have negative effects on long‐term tree growth, but effects are contingent upon the fire return interval. These findings highlight important differences in how fire and thinning influence density‐dependent competition and the response of tree growth to climate. Although additional studies are needed from other forest ecosystems, this study provides early evidence that increased fire frequency will not alleviate drought stress and instead, may reduce long‐term, aboveground carbon storage in forests.

中文翻译：

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六十五年的火源处理揭示了气候和火源的相互作用，从而决定了栎属的生长速率。

如气候模型所预测的那样，使森林对更频繁和严重干旱的脆弱性最小化已成为森林管理的主要目标。缓解干旱引起的压力的一种潜在策略是通过重复使用规定的火源来减少基础面积。但是，使用明火作为减轻干旱脆弱性的管理工具在很大程度上尚未得到测试。在这里，我们报告了多次生火对成年橡树（栎属）的气候增长响应的长期影响spp。）在美国密苏里州的奥扎克斯市。我们测量了1950年至2015年间无火，无周期性（每4年）或每年有指定林火的树木的年径向生长。为评估火灾频率的增加是否与气候相互影响以确定长期森林生产力，我们对年度森林进行了建模潜在蒸散量，火灾处理及其相互作用的函数关系。我们还量化了火灾导致的树木密度降低对树木碳环和氧同位素组成以及过去干旱事件期间的抗旱性（干旱期间的生长）和恢复力（干旱后的生长恢复）的影响。年度径向生长和同位素组成数据表明，由于水分胁迫，树木生长减少，但是在经常烧毁的森林和未烧制的森林之间，干旱的脆弱性没有变化。相反，在潮湿时期，定期而非每年的火灾使年增长率降低了9.6％，有利于增长，且随时间变化的效果一致。在65年的处理后，火对总氮和无机土壤的氮影响微乎其微，无论频率如何，这表明在定期燃烧下观察到的生长下降的其他根本原因（例如冠，胆或根部损伤）。我们的结果表明，长期增加的火灾频率可能会对长期树木生长产生负面影响，但影响取决于回火间隔。这些发现突显了火与间伐如何影响密度依赖性竞争以及树木生长对气候的响应方面的重要差异。