Data from: Environmental conditions and vascular cambium regulate carbon allocation to xylem growth in deciduous oaks

Environmental conditions and the structure of the dormant cambium are assumed to affect seasonal patterns of cambial activity, hence controlling allocation of non-structural carbohydrates (NSC) to growth. However, seasonal dynamics of xylogenesis, and their connections with NSC content and dormant cambium size, have been rarely assessed along an environmental gradient. We monitored xylogenesis and leaf phenology during 2012 and 2013, and NSC in 2012, for the drought-sensitive Quercus robur and the drought-tolerant Quercus pyrenaica along a water-availability gradient in the north-western Iberian Peninsula, and analysed dependencies of xylem production and phenology on the number of cells in dormant cambium. Study oak species showed comparable seasonal fluctuations in cambial activity and NSC content, despite Q. pyrenaica had a shorter growing season and a lower wood production than Q. robur. A sharp drop in spring NSC levels at all study sites evidenced that stored carbohydrates were crucial for earlywood formation. Under drier conditions, both species extended the growing period in spring and autumn, but reduced and even stopped xylogenesis in summer, showing an enhanced NSC accumulation before dormancy. A higher number of cells in dormant cambium of large dominant oaks accounted for their wider xylem increments and longer active periods. Our study demonstrates that xylogenesis is modulated by predisposing effects of dormant cambium size on xylem production and growing season length. Moreover, the high plasticity of cambial activity in deciduous oaks would confer resistance against recurrent summer drought through the improvement of the NSC status.普遍认为，环境条件与休眠形成层的结构会影响形成层活动的季节节律，进而调控非结构性碳水化合物（non-structural carbohydrates, NSC）向生长过程的分配。然而，现有研究极少沿环境梯度开展木质发生（xylogenesis）的季节动态及其与NSC含量、休眠形成层规模之间关联的评估。 本研究于2012至2013年间，针对伊比利亚半岛西北部沿水分可用性梯度分布的耐旱敏感型夏栎（Quercus robur）与耐旱型比利牛斯栎（Quercus pyrenaica），开展了木质发生与叶片物候的监测，并于2012年测定了其NSC含量；同时分析了木质部生产量与物候对休眠形成层细胞数量的依赖关系。 供试栎属物种的形成层活动与NSC含量均呈现相似的季节波动特征，尽管比利牛斯栎的生长季较夏栎更短，木材生产量也更低。所有研究样地春季NSC水平的急剧下降表明，储存的碳水化合物对早材形成至关重要。在更为干旱的生境中，两个物种均会延长春季与秋季的生长周期，但夏季的木质发生过程会受到抑制甚至完全停止，且休眠前的NSC积累量有所提升。高大优势木的休眠形成层细胞数量更多，这使得其木质部增量更大、活动周期更长。 本研究证实，休眠形成层规模对木质部生产量与生长季长度的前置调控效应，会对木质发生过程产生调节作用。此外，落叶栎类形成层活动的高度可塑性，可通过改善NSC状态，增强其应对周期性夏季干旱的抗性。