1. Bark contributes approximately 20% to the total above‐ground biomass of trees, yet bark is not properly accounted for when estimating carbon sequestered by trees. Current allometric functions estimate tree volume from diameter measured over the bark, and derive bark density and carbon content from estimates for wood. As the bark density of hardwood species is 40%–50% lower than the wood density, but nearly equivalent in conifers, bark carbon is overestimated for most species. The latter is further exacerbated by variation in bark volume with bark surface morphology.
2. Fissured bark volume is overestimated by diameter over bark measurements by up to 40%. The vacant space in fissures can be accounted for by a bark fissure index (BFI). We calculate bark carbon for Australian species from a non‐destructive and effective BFI using bark thickness measured in the field.
3. Bark volume, and in turn bark carbon, scaled inversely with tree size (diameter) so that bark volume comprised 42% of small trees (10 cm diameter at breast height, DBH) but 23% of large trees (50 cm DBH). Our BFI method using a bark thickness gauge (BGM) yielded similar results than using the less time‐efficient contour gauge method (CM) to estimate BFI (bias BGM‐CM −1.3%, non‐significant at p = 0.72). Both BGM and CM had an error of <4% compared to digitized BFI from destructive sampled stem disks. An average of 15 bark gauge measurements per tree estimated bark thickness (and inconsequence BFI) for both fissured and unfissured bark with <20% error relative to the exact value.
4. Using the bark gauge method, BFI can be rapidly measured from large numbers of trees needed for estimating bark carbon at the community level and modelling carbon uptake, storage and cycling in woody biomes.

中文翻译：

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量化树皮中的碳：树皮形态和树木大小的重要性

1. 
   树皮约占树木地上总生物量的 20%，但在估算树木固碳时并未正确考虑树皮。目前的异速生长功能根据树皮上测量的直径来估计树木体积，并根据木材的估计值得出树皮密度和碳含量。由于硬木树种的树皮密度比木材密度低 40%–50%，但针叶树的树皮密度几乎相同，因此大多数树种的树皮碳被高估了。后者因树皮体积随树皮表面形态的变化而进一步加剧。
2. 
   裂隙树皮体积的直径比树皮测量值高出 40%。裂缝中的空白空间可以通过树皮裂缝指数（BFI）来解释。我们使用现场测量的树皮厚度，通过非破坏性且有效的 BFI 计算澳大利亚物种的树皮碳。
3. 
   树皮体积以及树皮碳与树木大小（直径）成反比，因此树皮体积占小树（胸高直径 10 厘米，DBH）的 42%，但占大树（50 厘米 DBH）的 23%。我们使用树皮测厚仪 (BGM) 的 BFI 方法与使用时间效率较低的轮廓仪方法 (CM) 估算 BFI 产生的结果相似（BGM-CM 偏差为 -1.3%， p = 0.72 时不显着）。与破坏性采样茎盘的数字化 BFI 相比，BGM 和 CM 的误差均小于 4%。每棵树平均进行 15 次树皮厚度测量，估计有裂隙和无裂隙树皮的树皮厚度（和不相关的 BFI），相对于精确值的误差 <20%。
4. 
   使用树皮测量方法，可以快速测量大量树木所需的 BFI，以估算群落水平的树皮碳并模拟木本生物群落的碳吸收、储存和循环。