Although wood anatomical features can provide yearly resolved climatic information at sub-seasonal resolution, the occurrence of intra-annual density fluctuations (IADFs) might be triggered by several abiotic factors under different ecological settings. Here, we use information on cambial age and tree-ring width to standardize the frequency of IADFs in European black pines from three different mountain slopes in the central Apennines (Italy). At each site, we sampled isolated 15–30-year pioneer pines above the forest limit, as well as close-grown 40–60-year planted pines at the forest limit. Mainly restricted to the latewood of both pioneer and planted trees, the occurrence of IADFs reveals a significant positive relationship with cambial age and ring width. Although the standardized IADFs are well synchronized between the planted and pioneer pines, the frequency of IADFs in narrow rings was higher in the pioneer pines. Drought conditions in July and August are responsible for the highest IADFs frequency in planted and pioneer pines, respectively. Our study underlines the value of IADFs to obtain a more nuanced understanding of the climatic drivers of wood formation at the intra-annual scale.

中文翻译：

---

在亚平宁山脉中部（意大利）高海拔的黑松（JF阿诺德）中的年内密度波动（IADF）

尽管木材解剖特征可以在亚季节分辨率下提供逐年解析的气候信息，但年内密度波动（IADF）的发生可能是由不同生态环境下的几种非生物因素触发的。在这里，我们使用有关冈比亚年龄和年轮宽度的信息来标准化来自亚平宁山脉（意大利）中三个不同山坡的欧洲黑松中IADF的频率。在每个站点，我们都采样了高于森林极限的孤立的15–30年先锋树以及在森林极限处的密植的40–60年种植松树。IADF的出现主要限于先锋树和人工林的晚材，这表明它们与冈比亚年龄和年轮宽度呈显着正相关。尽管标准化的IADF在种植的松树和先锋松之间很好地同步，但先锋松中窄环中IADF的频率更高。七月和八月的干旱情况分别是造成人工林和先锋松IADF发生频率最高的原因。我们的研究强调了IADF的价值，以便在年度范围内更深入地了解木材形成的气候驱动因素。