Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
Department of Natural Resources and Systems, Universidad Politécnica de Madrid (UPM), Madrid, Spain.
Plant Cell Environ. 2021 May;44(5):1292-1310. doi: 10.1111/pce.13986. Epub 2021 Jan 9.
At leaf level, elevated atmospheric CO concentration (eCO ) results in stimulation of carbon net assimilation and reduction of stomatal conductance. However, a comprehensive understanding of the impact of eCO 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 eCO , including carbon and water relations at the leaf and the whole-tree level. Spring and early season leaf responses are most susceptible to eCO and are followed by a down-regulation towards the onset of autumn. At the whole-tree level, CO fertilization causes consistent biomass increments in young seedlings only, whereas mature trees show a variable response. Elevated CO -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 eCO . These large temporal and spatial variabilities in tree responses to eCO highlight the risk of predicting tree behavior to eCO based on single leaf-level point measurements as they only reveal snapshots of the dynamic responses to eCO .
在叶片水平上，大气中 CO 浓度的升高（eCO）会刺激碳的净同化，并降低气孔导度。然而，我们仍然缺乏对 eCO 在更大时间（季节和年度）和空间（从叶片到整树）尺度上的影响的全面理解。在这里，我们综述了动态树木对 eCO 的整体响应趋势、幅度和驱动因素，包括叶片和整树水平的碳和水分关系。春季和早期叶片对 eCO 最为敏感，随后在秋季开始时下调。在整树水平上，CO 施肥只会导致幼苗的生物量持续增加，而成熟的树木则表现出不同的响应。由于树冠面积的不可预测响应，eCO 诱导的叶片气孔导度降低不会系统地转化为整树蒸腾的限制。由于对季节间碳汇需求的减少和限水策略的考虑，eCO 是树木对季节性响应的主要驱动因素。树木对 eCO 的这些大时间和空间的变异性突出了基于单个叶片水平点测量来预测树木对 eCO 的行为的风险，因为它们仅揭示了对 eCO 动态响应的快照。
