CNR-ISAFOM, via Patacca 2, 80056, Ercolano, Italy.
CNR-IRET, via Marconi 2, 05010, Porano, Italy.
New Phytol. 2019 Oct;224(2):625-631. doi: 10.1111/nph.16047. Epub 2019 Aug 27.
Late frost can destroy the photosynthetic apparatus of trees. We hypothesized that this can alter the normal cyclic dynamics of C-reserves in the wood. We measured soluble sugar concentrations and radiocarbon signatures (Δ C) of soluble nonstructural carbon (NSC) in woody tissues sampled from a Mediterranean beech forest that was completely defoliated by an exceptional late frost in 2016. We used the bomb radiocarbon approach to estimate the time elapsed since fixation of mobilized soluble sugars. During the leafless period after the frost event, soluble sugar concentrations declined sharply while Δ C of NSC increased. This can be explained by the lack of fresh assimilate supply and a mobilization of C from reserve pools. Soluble NSC became increasingly older during the leafless period, with a maximum average age of 5 yr from samples collected 27 d before canopy recovery. Following leaf re-growth, soluble sugar concentrations increased and Δ C of soluble NSC decreased, indicating the allocation of new assimilates to the stem soluble sugars pool. These data highlight that beech trees rapidly mobilize reserve C to survive strong source-sink imbalances, for example due to late frost, and show that NSC is a key trait for tree resilience under global change.
晚霜会破坏树木的光合作用器官。我们假设这会改变木材中 C 储备的正常循环动态。我们测量了可溶性糖浓度和放射性碳特征（Δ C）在 2016 年一次异常晚霜导致完全落叶的地中海山毛榉森林中采集的木质组织中的非结构性碳（NSC）。我们使用了炸弹放射性碳方法来估计从固定可移动可溶性糖到现在的时间。在霜灾后无叶期，可溶性糖浓度急剧下降，而 NSC 的 Δ C 增加。这可以解释为缺乏新鲜同化产物的供应以及从储备库中动员 C。在无叶期，可溶性 NSC 变得越来越老，从树冠恢复前 27 天采集的样本中，最大平均年龄为 5 年。随着叶片重新生长，可溶性糖浓度增加，可溶性 NSC 的 Δ C 降低，这表明新的同化产物被分配到茎可溶性糖库中。这些数据表明，山毛榉树会迅速动员储备 C 来应对强烈的源库失衡，例如由于晚霜，并表明 NSC 是树木在全球变化下恢复力的关键特征。
