Service of Wood Biology, Royal Museum for Central Africa, Tervuren, Belgium.
UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Ghent, Belgium.
Nat Plants. 2019 Feb;5(2):133-140. doi: 10.1038/s41477-018-0316-5. Epub 2019 Jan 21.
Quantifying carbon dynamics in forests is critical for understanding their role in long-term climate regulation. Yet little is known about tree longevity in tropical forests, a factor that is vital for estimating carbon persistence. Here we calculate mean carbon age (the period that carbon is fixed in trees) in different strata of African tropical forests using (1) growth-ring records with a unique timestamp accurately demarcating 66 years of growth in one site and (2) measurements of diameter increments from the African Tropical Rainforest Observation Network (23 sites). We find that in spite of their much smaller size, in understory trees mean carbon age (74 years) is greater than in sub-canopy (54 years) and canopy (57 years) trees and similar to carbon age in emergent trees (66 years). The remarkable carbon longevity in the understory results from slow and aperiodic growth as an adaptation to limited resource availability. Our analysis also reveals that while the understory represents a small share (11%) of the carbon stock, it contributes disproportionally to the forest carbon sink (20%). We conclude that accounting for the diversity of carbon age and carbon sequestration among different forest strata is critical for effective conservation management and for accurate modelling of carbon cycling.
量化森林中的碳动态对于理解它们在长期气候调节中的作用至关重要。然而，人们对热带森林中的树木寿命知之甚少，而这是估计碳持久性的关键因素。在这里，我们使用（1）在一个地点具有独特时间戳的生长环记录，该记录准确地标定了 66 年的生长，以及（2）来自非洲热带雨林观测网络（23 个地点）的直径增量测量值，计算了非洲热带森林不同层次的平均碳龄（碳固定在树木中的时间段）。我们发现，尽管它们的体型小得多，但林下树木的平均碳龄（74 年）大于亚冠层（54 年）和冠层（57 年）树木，与突生树木的碳龄（66 年）相似。林下树木具有显著的碳长寿性，这是其对有限资源可用性的适应，表现为缓慢和非周期性的生长。我们的分析还表明，虽然林下植物仅占碳储量的一小部分（11%），但它对森林碳汇的贡献不成比例（20%）。我们的结论是，考虑到不同森林层次之间的碳龄和碳固存的多样性对于有效的保护管理和对碳循环的准确建模至关重要。
