Abstract

Climate models project warmer summer temperatures will increase the frequency and heat severity of droughts in temperate forests of Eastern North America. Hotter droughts are increasingly documented to affect tree growth and forest dynamics, with critical impacts on tree mortality, carbon sequestration, and timber provision. The growing acknowledgement of the dominant role of drought timing on tree vulnerability to water deficit raises the issue of our limited understanding of radial growth phenology for most temperate tree species. Here, we use well-replicated dendrometer band data sampled frequently during the growing season to assess the growth phenology of 610 trees from 15 temperate species over six years. Patterns of diameter growth follow a typical logistic shape, with growth rates reaching a maximum in June, and then decreasing until process termination. On average, we find that diffuse-porous species take 16–18 days less than other wood-structure types to put on 50% of their annual diameter growth. However, their peak growth rate occurs almost a full month later than ring-porous and conifer species (ca. 24 ± 4 days; mean ± 95% credible interval). Unlike other species, the growth phenology of diffuse-porous species in our dataset is highly correlated with their spring foliar phenology. We also find that the later window of growth in diffuse-porous species, coinciding with peak evapotranspiration and lower water availability, exposes them to a higher water deficit of 88 ± 19 mm (mean ± SE) during their peak growth than ring-porous and coniferous species (15 ± 35 mm and 30 ± 30 mm, respectively). Given the high climatic sensitivity of wood formation, our findings highlight the importance of wood porosity as one predictor of species climatic sensitivity to the projected intensification of the drought regime in the coming decades.

中文翻译：

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与环孔树和针叶树相比，散孔树种的径向生长峰值发生在可用水量较低的时期

摘要

气候模型预测，夏季气温升高将增加北美东部温带森林干旱的频率和严重程度。越来越多的证据表明，更炎热的干旱会影响树木生长和森林动态，对树木死亡率、碳固存和木材供应产生重大影响。人们越来越认识到干旱时间对树木缺水脆弱性的主导作用，这提出了我们对大多数温带树种的径向生长物候学了解有限的问题。在这里，我们使用在生长季节频繁采样的良好复制的树木测量仪带数据来评估六年来来自 15 个温带物种的 610 棵树的生长物候。直径增长模式遵循典型的逻辑形状，增长率在六月达到最大值，然后下降，直到过程终止。平均而言，我们发现散孔树种比其他木结构类型要少 16-18 天，年直径增长 50%。然而，它们的峰值生长率比环孔树和针叶树种晚了几乎整整一个月（约 24 ± 4 天；平均 ± 95% 可信区间）。与其他物种不同，我们数据集中的散孔物种的生长物候与其春季叶物候高度相关。我们还发现，散孔物种的后期生长窗口，与蒸散量峰值和较低的可用水量同时发生，使它们在生长高峰期间比环孔物种和环孔物种面临更高的水分亏缺，为 88 ± 19 mm（平均值 ± SE）。针叶树种（分别为 15 ± 35 毫米和 30 ± 30 毫米）。鉴于木材形成对气候的高度敏感性，我们的研究结果强调了木材孔隙度作为物种气候敏感性对未来几十年干旱状况预计加剧的预测因素之一的重要性。