Data from: Carbon content of tree tissues: a synthesis

Assessing the potential for forest carbon (C) capture and storage requires accurate assessments of C in live tree tissues. In the vast majority of local, regional, and global assessments, C content has been assumed to be 50% of tree biomass; however, recent studies indicate that this assumption is not accurate, with substantial variation in C content among tree species as well as among tissue types. Here we conduct a comprehensive literature review to present a global synthesis of C content in tissues of live trees. We found a total of 253 species-specific stem wood C content records owing to 31 studies, and an additional 34 records of species with C content values of other tissues in addition to stem wood. Stem wood C content varied significantly as a function of biome (tropical, subtropical/ Mediterranean, temperate/ boreal) and species type (conifer, angiosperm). Conifer species exhibited greater wood C content than angiosperm species (50.8 ± 0.7% (95% C.I.) vs. 47.7 ± 0.3%, respectively), a trend that was consistent among all biomes. Although studies have documented differences in C content among plant tissues, interspecific differences in stem wood appear to be of greater importance overall: among species, stem wood C content explained 37, 76, 48, 81, and 63% respectively of the variation in bark, branch, twig, coarse root, and fine root C content values, respectively. In each case, these intraspecific patterns approximated 1:1 linear relationships. Most published stem wood C content values (and all values for other tree tissues) are based on dried wood samples, and so neglect volatile C constituents that constitute on average 1.3 – 2.5% of total C in live wood. Capturing this volatile C fraction is an important methodological consideration for future studies. Our review, and associated data compilation, provides empirically supported wood C fractions that can be easily incorporated into forest C accounting, and may correct systematic errors of ~1.6 – 5.8% in forest C assessments.

评估森林碳（C）捕获与封存潜力，需精准测定活树组织的碳含量。在绝大多数本地、区域乃至全球尺度的森林碳评估中，学界通常假定树木生物量的碳含量为50%；但近期研究表明这一假定并不严谨，不同树种及组织类型间的碳含量存在显著差异。本研究通过全面文献综述，构建了全球活树组织碳含量的综合数据集。基于31项已发表研究，我们共收集到253条针对特定树种的树干木材碳含量记录，另外还获取了34条包含除树干木材外其他组织碳含量的树种数据。树干木材碳含量随生物群区（biome：热带、亚热带/地中海型、温带/寒带）及树种类型（针叶树（conifer）、被子植物（angiosperm））的不同呈现显著差异。针叶树的木材碳含量高于被子植物（分别为50.8±0.7%（95% C.I.）与47.7±0.3%），该趋势在所有生物群区中均保持一致。尽管已有研究证实植物不同组织间碳含量存在差异，但总体而言，树干木材的种间差异更为关键：在树种水平上，树干木材碳含量分别可解释树皮、树枝、细枝、粗根及细根碳含量变异的37%、76%、48%、81%与63%。各类组织的种内相关模式均近似于1:1的线性关系。多数已发表的树干木材碳含量数据（以及所有其他树木组织的碳含量数据）均基于干燥木材样品，因此忽略了活体木材中平均占总碳含量1.3%~2.5%的挥发性碳组分。在未来研究中纳入该挥发性碳组分，是一项重要的方法学考量因素。本综述及配套的数据汇编提供了经实证支撑的木材碳组分参数，可直接应用于森林碳核算工作，同时能够修正森林碳评估中约1.6%~5.8%的系统误差。