Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.
Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, Switzerland.
Glob Chang Biol. 2024 Mar;30(3):e17237. doi: 10.1111/gcb.17237.
Scots pine (Pinus sylvestris L.) is a common European tree species, and understanding its acclimation to the rapidly changing climate through physiological, biochemical or structural adjustments is vital for predicting future growth. We investigated a long-term irrigation experiment at a naturally dry forest in Switzerland, comparing Scots pine trees that have been continuously irrigated for 17 years (irrigated) with those for which irrigation was interrupted after 10 years (stop) and non-irrigated trees (control), using tree growth, xylogenesis, wood anatomy, and carbon, oxygen and hydrogen stable isotope measurements in the water, sugars and cellulose of plant tissues. The dendrochronological analyses highlighted three distinct acclimation phases to the treatments: irrigated trees experienced (i) a significant growth increase in the first 4 years of treatment, (ii) high growth rates but with a declining trend in the following 8 years and finally (iii) a regression to pre-irrigation growth rates, suggesting the development of a new growth limitation (i.e. acclimation). The introduction of the stop treatment resulted in further growth reductions to below-control levels during the third phase. Irrigated trees showed longer growth periods and lower tree-ring δ C values, reflecting lower stomatal restrictions than control trees. Their strong tree-ring δ O and δ H (O-H) relationship reflected the hydrological signature similarly to the control. On the contrary, the stop trees had lower growth rates, conservative wood anatomical traits, and a weak O-H relationship, indicating a physiological imbalance. Tree vitality (identified by crown transparency) significantly modulated growth, wood anatomical traits and tree-ring δ C, with low-vitality trees of all treatments performing similarly regardless of water availability. We thus provide quantitative indicators for assessing physiological imbalance and tree acclimation after environmental stresses. We also show that tree vitality is crucial in shaping such responses. These findings are fundamental for the early assessment of ecosystem imbalances and decline under climate change.
欧洲赤松（Pinus sylvestris L.）是一种常见的欧洲树种，了解其通过生理、生化或结构调整来适应快速变化的气候对于预测未来的生长至关重要。我们研究了瑞士一个自然干燥森林中的长期灌溉实验，该实验比较了连续灌溉 17 年的欧洲赤松（灌溉）、灌溉 10 年后中断灌溉的树木（停止）和未灌溉的树木（对照），利用树木生长、木质部形成、木材解剖学以及水中的碳、氧和氢稳定同位素测量、植物组织中的糖和纤维素。树木年代学分析突出了对处理的三个明显的适应阶段：灌溉树木经历了（i）在处理的前 4 年中显著的生长增加，（ii）在接下来的 8 年中高生长速率但呈下降趋势，最后（iii）回归到灌溉前的生长速率，表明出现了新的生长限制（即适应）。引入停止处理导致第三阶段的生长进一步降低到低于对照水平。灌溉树木表现出更长的生长周期和较低的树木年轮 δ C 值，反映出比对照树木更低的气孔限制。它们强烈的树木年轮 δ O 和 δ H（O-H）关系反映了与对照相似的水文特征。相反，停止树木的生长速度较低，木质部解剖特征保守，O-H 关系较弱，表明存在生理失衡。树冠透明度确定的树木活力显著调节了生长、木材解剖学特征和树木年轮 δ C，所有处理的低活力树木无论水分供应情况如何，表现都相似。因此，我们提供了评估生理失衡和树木适应环境胁迫的定量指标。我们还表明，树木活力对于塑造这些反应至关重要。这些发现对于气候变化下生态系统失衡和衰退的早期评估具有基础性意义。
