Droughts influenced the effects of increasing intrinsic water use efficiency (iWUE) on tree growth. Yet, litter is known on stand density- and age-related relationship among droughts, iWUE, and tree growth in plantations. We used tree-ring growth and δ¹³C data from three dominated species (larch, spruce, and pine) to evaluate the density- and age-dependent relationship between droughts and iWUE, and their linkage to tree growth in temperate plantations. The results showed that low-density old-age stands were more sensitive to drought stress than high-density young-age stands. Drought-induced increased iWUE had translated into growth loss for low-density old-age stands. Whereas droughts showed weak influences on iWUE, and thus had no clear effects on tree growth in high-density young-age stands. High-density young-age trees had a more balance carbon uptake per water loss compared to low-density old-age trees, suggesting that competition to grow fast was of utmost important for high-density trees. Droughts reinforced stomatal closure to reduce carbon uptake in low-density old-age stands, while stomata were not sensitive to droughts in high-density stands. High-density young-age trees had higher resistance to drought, but lower recovery than low-density old-age trees. Our results suggested that maintaining high-density forests could reduce drought-induced growth loss if drought frequency is continuous increasing in the future. Considering the beneficial effects of thinning on growth could last for several years, proper thinning frequency and rotation period should be implemented in forest management to enhance trees’ adaptation to droughts.

干旱影响了提高内在水分利用效率 (iWUE) 对树木生长的影响。然而，枯枝落叶在干旱、iWUE 和人工林树木生长之间的林分密度和年龄相关关系上是众所周知的。我们使用了年轮生长和 δ ¹³来自三个主要物种（落叶松、云杉和松树）的 C 数据，用于评估干旱和 iWUE 之间的密度和年龄依赖性关系，以及它们与温带人工林树木生长的联系。结果表明，与高密度幼龄林相比，低密度老年林对干旱胁迫更为敏感。干旱引起的 iWUE 增加已转化为低密度老年林分的生长损失。而干旱对 iWUE 的影响较弱，因此对高密度幼龄林的树木生长没有明显影响。与低密度的老树相比，高密度的幼树每次水分流失的碳吸收更加平衡，这表明快速生长的竞争对于高密度的树木至关重要。干旱加强了气孔关闭，以减少低密度老年林分的碳吸收，而气孔对高密度林分的干旱不敏感。高密度的幼龄树比低密度的老树具有更高的抗旱性，但恢复率较低。我们的研究结果表明，如果未来干旱频率持续增加，维持高密度森林可以减少干旱引起的生长损失。考虑到间伐对生长的有益影响可持续数年，在森林管理中应实施适当的间伐频率和轮作周期，以增强树木对干旱的适应能力。我们的研究结果表明，如果未来干旱频率持续增加，维持高密度森林可以减少干旱引起的生长损失。考虑到间伐对生长的有益影响可持续数年，在森林管理中应实施适当的间伐频率和轮作周期，以增强树木对干旱的适应能力。我们的研究结果表明，如果未来干旱频率持续增加，维持高密度森林可以减少干旱引起的生长损失。考虑到间伐对生长的有益影响可持续数年，在森林管理中应实施适当的间伐频率和轮作周期，以增强树木对干旱的适应能力。