Understanding the influence of the current climate on the distribution, composition, and carbon storage capacity of Mediterranean tree species is key to determining future pathways under a warmer and drier climate scenario. Here, we evaluated the influence of biotic and environmental factors on earlywood (EW) and latewood (LW) growth in Aleppo pine (Pinus halepensis Mill.). Our investigation was based on a dense dendrochronological network (71 sites), which covered the entire distribution area of the species in the Iberian Peninsula (around 119.652 km²), and a high-resolution climate dataset of the Western Mediterranean area. We used generalized linear-mixed models to determine the spatial and temporal variations of EW and LW across the species distribution. Our results showed an intense but differentiated climatic influence on both EW and LW growth components. The climatic influence explained significant variations across the environmental gradients in the study area, which suggested an important adaptation through phenotypic plasticity and local adaptation to varying climatic conditions. In addition, we detected a clear spatial trade-off between efficiency and safety strategy in the growth patterns across the species distribution. Additionally, in more productive areas, the trees presented a higher proportion of EW (more efficient to water transport), while, in more xeric conditions, the LW proportion increased (more safety to avoid embolisms), implying an adaptation to more frequent drought episodes and a higher capacity of carbon depletion. We therefore concluded that Mediterranean forests adapted to dryer conditions might be more efficient as carbon reservoirs than forests growing in wetter areas. Finally, we advocated for the need to consider wood density (EW/LW proportion) when modeling current and future forest carbon sequestrations.

中文翻译：

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当密度很重要时：早材和晚材之间的空间平衡

了解当前气候对地中海树种的分布、组成和碳储存能力的影响是确定在更暖和更干燥气候情景下未来路径的关键。在这里，我们评估了生物和环境因素对阿勒颇松 ( Pinus halepensis Mill.)早材 (EW) 和晚材 (LW) 生长的影响。我们的调查基于密集的树木年代学网络（71 个地点），该网络覆盖了该物种在伊比利亚半岛的整个分布区域（约 119.652 km ²)，以及西地中海地区的高分辨率气候数据集。我们使用广义线性混合模型来确定 EW 和 LW 跨物种分布的空间和时间变化。我们的研究结果表明，气候对 EW 和 LW 生长成分都有强烈但有差异的影响。气候影响解释了研究区环境梯度的显着变化，这表明通过表型可塑性和局部适应不同的气候条件进行了重要的适应。此外，我们在整个物种分布的生长模式中发现了效率和安全策略之间明显的空间权衡。此外，在生产力更高的地区，树木的 EW 比例更高（对水的运输效率更高），而在更干旱的条件下，LW 比例增加（更安全以避免栓塞），意味着适应更频繁的干旱事件和更高的碳消耗能力。因此，我们得出结论，适应干燥条件的地中海森林作为碳库可能比生长在潮湿地区的森林更有效。最后，我们主张在模拟当前和未来的森林碳固存时需要考虑木材密度（EW/LW 比例）。