Laboratoire sur les écosystèmes terrestres boréaux, Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 boulevard de l'Université, Chicoutimi (QC) G7H2B1, Canada.
Direction de la recherche forestière Ministère des Forêts, de la Faune et des Parcs, Québec, QC G1P3W8, Canada.
Ann Bot. 2022 Dec 16;130(6):811-824. doi: 10.1093/aob/mcac110.
Upscaling carbon allocation requires knowledge of the variability at the scales at which data are collected and applied. Trees exhibit different growth rates and timings of wood formation. However, the factors explaining these differences remain undetermined, making samplings and estimations of the growth dynamics a complicated task, habitually based on technical rather than statistical reasons. This study explored the variability in xylem phenology among 159 balsam firs [Abies balsamea (L.) Mill.].
Wood microcores were collected weekly from April to October 2018 in a natural stand in Quebec, Canada, to detect cambial activity and wood formation timings. We tested spatial autocorrelation, tree size and cell production rates as explanatory variables of xylem phenology. We assessed sample size and margin of error for wood phenology assessment at different confidence levels.
Xylem formation lasted between 40 and 110 d, producing between 12 and 93 cells. No effect of spatial proximity or size of individuals was detected on the timings of xylem phenology. Trees with larger cell production rates showed a longer growing season, starting xylem differentiation earlier and ending later. A sample size of 23 trees produced estimates of xylem phenology at a confidence level of 95 % with a margin of error of 1 week.
This study highlighted the high variability in the timings of wood formation among trees within an area of 1 km2. The correlation between the number of new xylem cells and the growing season length suggests a close connection between the processes of wood formation and carbon sequestration. However, the causes of the observed differences in xylem phenology remain partially unresolved. We point out the need to carefully consider sample size when assessing xylem phenology to explore the reasons underlying this variability and to allow reliable upscaling of carbon allocation in forests.
扩大碳分配需要了解在收集和应用数据的尺度上的可变性。树木表现出不同的生长速度和木材形成的时间。然而，解释这些差异的因素仍未确定，使得采样和估计生长动态成为一项复杂的任务，通常基于技术而非统计原因。本研究探索了加拿大魁北克省一个天然林分中的 159 株加拿大香脂冷杉（Abies balsamea（L.）Mill.）之间木质部物候的可变性。
2018 年 4 月至 10 月期间，每周从一株天然林中采集木质部微芯，以检测形成层活动和木材形成时间。我们测试了空间自相关、树木大小和细胞生产率作为木质部物候的解释变量。我们评估了在不同置信水平下评估木质部物候的样本量和误差幅度。
木质部形成持续时间为 40-110 天，产生 12-93 个细胞。个体的空间接近度或大小对木质部物候的时间没有影响。细胞生产率较高的树木具有较长的生长季节，较早开始木质部分化，较晚结束。样本量为 23 株树木可在 95%置信水平下，以 1 周的误差幅度估计木质部物候。
本研究突出了在 1 平方公里的区域内树木之间木质部形成时间的高度可变性。新木质部细胞数量与生长季节长度之间的相关性表明，木质部形成过程与碳封存之间存在密切联系。然而，木质部物候观察到的差异的原因仍部分未解决。我们指出，在评估木质部物候时需要仔细考虑样本量，以探索这种变异性的原因，并允许在森林中可靠地扩大碳分配。
