The United Graduate School of Agricultural Science, Iwate University, Morioka, Iwate, 020-8550, Japan.
Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata, 997-8555, Japan.
J Plant Res. 2021 Sep;134(5):989-997. doi: 10.1007/s10265-021-01320-5. Epub 2021 Jun 11.
Both Moso bamboo (Phyllostachys pubescens) and tree forests have a large biomass; they are considered to play an important role in ecosystem carbon budgets. The scaling relationship between individual whole-shoot (i.e., aboveground parts) respiration and whole-shoot mass provides a clue for comparing the carbon budgets of Moso bamboo and tree forests. However, nobody has empirically demonstrated whether there is a difference between these forest types in the whole-shoot scaling relationship. We developed whole-shoot chambers and measured the shoot respiration of 58 individual mature bamboo shoots from the smallest to the largest in a Moso bamboo forest, and then compared them with that of 254 tree shoots previously measured. For 30 bamboo shoots, we measured the respiration rate of leaves, branches, and culms. We found that the scaling exponent of whole-shoot respiration of bamboo fitted by a simple power function on a log-log scale was 0.843 (95 % CI 0.797-0.885), which was consistent with that of trees, 0.826 (95 % CI 0.799-0.851), but higher than 3/4, the value typifying the Kleiber's rule. The respiration rates of leaves, branches, and culms at the whole-shoot level were proportional to their mass, revealing a constant mean mass-specific respiration of 1.19, 0.224, and 0.0978 µmol CO kg s, respectively. These constant values suggest common traits of organs among physiologically integrated ramets within a genet. Additionally, the larger the shoots, the smaller the allocation of organ mass to the metabolically active leaves, and the larger the allocation to the metabolically inactive culms. Therefore, these shifts in shoot-mass partitioning to leaves and culms caused a negative metabolic scaling of Moso bamboo shoots. The observed convergent metabolic scaling of Moso bamboo and trees may facilitate comparisons of the ecosystem carbon budgets of Moso bamboo and tree forests.
毛竹（Phyllostachys pubescens）和树木都具有较大的生物量；它们被认为在生态系统碳预算中起着重要作用。个体整株（即地上部分）呼吸与整株质量之间的比例关系为比较毛竹和森林的碳预算提供了线索。然而，没有人从实证上证明这两种森林类型在整株比例关系上是否存在差异。我们开发了整株室，并测量了毛竹林中 58 个从最小到最大的成熟竹芽的芽呼吸，然后将其与之前测量的 254 个树木芽的呼吸进行了比较。对于 30 个竹芽，我们测量了叶片、枝条和竹秆的呼吸速率。我们发现，简单幂函数拟合的毛竹整株呼吸比例指数为 0.843（95%置信区间 0.797-0.885），与树木的 0.826（95%置信区间 0.799-0.851）一致，但高于 3/4，这是克莱伯定律的典型值。叶片、枝条和竹秆在整株水平上的呼吸速率与其质量成正比，表明整株水平上的平均比呼吸速率分别为 1.19、0.224 和 0.0978 µmol CO kg s。这些常数表明，在生理整合的分株内，器官具有共同的特征。此外，芽越大，分配给代谢活跃叶片的器官质量越小，分配给代谢不活跃的竹秆的质量越大。因此，芽质量分配到叶片和竹秆的这些变化导致毛竹芽的负代谢比例。毛竹和树木的这种趋同代谢比例可能有助于比较毛竹和森林生态系统的碳预算。
