Dissecting Variation in Biomass Conversion Factors across China’s Forests: Implications for Biomass and Carbon Accounting

Biomass conversion factors (BCFs, defined as the ratios of tree components (i.e. stem, branch, foliage and root), as well as aboveground and whole biomass of trees to growing stock volume, Mg m−3) are considered as important parameters in large-scale forest biomass carbon estimation. To date, knowledge of possible sources of the variation in BCFs is still limited at large scales. Using our compiled forest biomass dataset of China, we presented forest type-specific values of BCFs, and examined the variation in BCFs in relation to forest type, stand development and environmental factors (climate and soil fertility). BCFs exhibited remarkable variation across forest types, and also were significantly related to stand development (especially growing stock volume). BCFs (except Stem BCF) had significant relationships with mean annual temperature (MAT) and mean annual precipitation (MAP) (P生物量转换因子（Biomass conversion factors, BCFs，定义为树木各组分（即树干、树枝、树叶与根系）以及树木地上生物量、总生物量与林分蓄积量的比值，单位为Mg m⁻³）是大规模森林生物量碳估算中的重要参数。迄今为止，学界对大尺度下BCFs变异的潜在来源的认知仍较为有限。依托我们汇编的中国森林生物量数据集，本研究给出了分林分类型的BCFs数值，并分析了BCFs变异与林分类型、林分发育阶段以及环境因子（气候与土壤肥力）之间的关联。BCFs在不同林分类型间呈现出显著变异，且与林分发育阶段（尤其是林分蓄积量）显著相关。除树干BCFs外，其余BCFs均与年平均气温（MAT）和年平均降水量（MAP）存在显著关联（P