At leaf level, elevated atmospheric CO₂ concentration (eCO₂) results in stimulation of carbon net assimilation and reduction of stomatal conductance. However, a comprehensive understanding of the impact of eCO₂ at larger temporal (seasonal and annual) and spatial (from leaf to whole‐tree) scales is still lacking. Here, we review overall trends, magnitude and drivers of dynamic tree responses to eCO₂, including carbon and water relations at the leaf and the whole‐tree level. Spring and early season leaf responses are most susceptible to eCO₂ and are followed by a down‐regulation towards the onset of autumn. At the whole‐tree level, CO₂ fertilization causes consistent biomass increments in young seedlings only, whereas mature trees show a variable response. Elevated CO₂‐induced reductions in leaf stomatal conductance do not systematically translate into limitation of whole‐tree transpiration due to the unpredictable response of canopy area. Reduction in the end‐of‐season carbon sink demand and water‐limiting strategies are considered the main drivers of seasonal tree responses to eCO₂. These large temporal and spatial variabilities in tree responses to eCO₂ highlight the risk of predicting tree behavior to eCO₂ based on single leaf–level point measurements as they only reveal snapshots of the dynamic responses to eCO₂.

中文翻译：

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树木对大气 CO2 升高响应的时间变化

在叶片水平，大气 CO ₂浓度 (eCO ₂ )升高会刺激碳净同化并降低气孔导度。然而，仍然缺乏对 eCO ₂在更大的时间（季节性和年度）和空间（从叶子到整棵树）尺度上的影响的全面了解。在这里，我们回顾了动态树木对 eCO ₂响应的总体趋势、幅度和驱动因素，包括叶子和整棵树水平上的碳和水关系。春季和早季叶片反应最容易受到 eCO _{2 的影响}，然后在秋季开始时下调。在整棵树水平上，CO ₂施肥只会在幼苗中引起一致的生物量增量，而成熟的树木则表现出不同的反应。由于冠层面积的不可预测的响应，CO ₂升高引起的叶片气孔导度的降低不会系统地转化为全树蒸腾作用的限制。季末碳汇需求的减少和限水策略被认为是季节性树木对 eCO ₂响应的主要驱动因素。树木对 eCO _{2 的}响应的这些大的时间和空间变异突出了基于单叶水平点测量预测树木对 eCO ₂行为的风险，因为它们仅揭示对 eCO ₂的动态响应的快照。