Key message

In Abies alba Mill. (silver fir), the frequency of intra-annual density fluctuations (IADFs) increases along the latitudinal transect, from North to South, is higher in pure than in mixed stands, and their formation is linked to spring and/or summer drought conditions.

Abstract

Trees respond to climate, recording information in tree rings and their anatomical features, such as IADFs. The IADFs are regions within the tree ring where density changes in response to tree physiological processes and environmental conditions. The objective of this study was to assess the effect of different forest-stand structures and of climate on IADF formation and frequency in populations of silver fir along a latitudinal gradient in Italy (Trentino, Molise and Calabria regions). In doing so, we aimed to compare the frequency of IADFs in pure or mixed stands and to understand the ability of silver fir to cope with environmental fluctuations. Results showed higher frequency of IADFs in pure than mixed stands (in Trentino and Calabria) and in younger trees (namely in the pure stand in Calabria), because of the higher sensitivity to environmental variability. The formation of IADFs in silver fir emerged as a response to cope with drought. Summer precipitation (both pure and mixed stands in Trentino) and early spring/summer (both pure and mixed stands in Calabria) played a key role in the formation of IADF-type E⁺. The formation of IADF-type L⁺, on the other hand, was related to temperature/precipitation in late summer and early autumn (both pure and mixed stands in Molise) and to precipitation in summer (pure stand in Calabria). Our findings support the theory that IADFs are an important structural/functional mechanism for responding to climate fluctuations.

中文翻译：

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干旱条件引发银杉的年内密度波动

关键信息

在冷杉阿尔巴磨坊。（银杉），年内密度波动 (IADF) 的频率沿纬度横断面增加，从北到南，纯林高于混合林，其形成与春季和/或夏季干旱条件有关。

抽象的

树木对气候做出反应，在树轮中记录信息及其解剖特征，例如 IADF。IADF 是树木年轮内密度随树木生理过程和环境条件而变化的区域。本研究的目的是评估不同林分结构和气候对意大利（特伦蒂诺、莫利塞和卡拉布里亚地区）沿纬度梯度的银杉种群的 IADF 形成和频率的影响。这样做的目的是比较纯林或混林中 IADF 的频率，并了解银杉应对环境波动的能力。结果表明，纯林比混合林（特伦蒂诺和卡拉布里亚）和年轻树木（即卡拉布里亚的纯林）中 IADF 的频率更高，因为对环境变化的敏感性更高。银杉中 IADF 的形成是应对干旱的一种反应。夏季降水（特伦蒂诺的纯林和混合林）和早春/夏季（卡拉布里亚的纯林和混林）在 IADF E 型的形成中发挥了关键作用⁺。另一方面，IADF 型 L ⁺的形成与夏末秋初的温度/降水（莫利塞的纯林和混合林）以及夏季的降水（卡拉布里亚纯林）有关。我们的研究结果支持以下理论，即 IADF 是应对气候波动的重要结构/功能机制。