Although several studies have identified the effects of functional trait diversity (FTD) and/or identity, i.e. the community-weighted mean (CWM) of a trait, on aboveground biomass (AGB) along abiotic conditions, these effects on AGB in global forest metacommunities are still largely unexplored. Here, we modelled the effects of abiotic (i.e. climate, soil and plot physical conditions) and biotic [i.e. FTD, CWM of conservative traits (CWMCT), CWM of acquisitive traits (CWMAT) and functional dominance (FunDom; based on CWM of plant maximum height or diameter)] factors on AGB in 76 forest metacommunities (from 24 studies). Using multiple linear regression models and piecewise structural equation modeling (pSEM), we tested the hypothesis that both abiotic and biotic factors regulate AGB but that the mass ratio mechanism underpins AGB of metacommunities in global forests better than the niche complementarity mechanism. We found that abiotic and biotic factors contributed 45.39% and 54.07%, respectively, to the explained variance in AGB (R² = 0.59), and as such, abiotic factors shaped FTD (R² = 0.42–0.48), CWMCT (R² = 0.33–0.36), CWMAT (R² = 0.27–0.33) and FunDom (R² = 0.59–0.61) through divergent effect sizes and directions. The final best-fitted pSEM showed that FunDom increased (β = 0.49) but CWMCT (β = −0.35) and CWMAT (β = −0.11) decreased AGB (R² = 0.52) as compared to the negligible effect of FTD (β = 0.04). This study supports the mass ratio effect, specifically the overruling role of tall-stature or dominant trees on AGB, at a macroecological scale, and hence, suggests that a suitable species' functional strategy is important to promote carbon sequestration in forest metacommunities that underpins human well-being. We expect that our study will advance the field of biodiversity–ecosystem functioning at a macroecological scale by using the metacommunity concept and approach.

中文翻译：

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在全球森林元群落的非生物条件下，功能特性比性状多样性更好地调节地上生物量

尽管一些研究已经确定了功能性状多样性 (FTD) 和/或同一性，即一个性状的群落加权平均值 (CWM) 对沿非生物条件的地上生物量 (AGB) 的影响，但这些对全球森林元群落中 AGB 的影响仍然在很大程度上未开发。在这里，我们模拟了非生物（即气候、土壤和地块物理条件）和生物 [即 FTD、保守性状的 CWM (CWMCT)、获得性状的 CWM (CWMAT) 和功能优势 (FunDom；基于植物的 CWM) 的影响最大高度或直径）] 76 个森林元群落中 AGB 的因素（来自 24 项研究）。使用多元线性回归模型和分段结构方程建模（pSEM），我们检验了非生物和生物因素都调节 AGB 但质量比机制比生态位互补机制更好地支持全球森林中元群落 AGB 的假设。我们发现非生物和生物因素分别对 AGB (R²  = 0.59)，因此，非生物因素塑造了 FTD (R ²  = 0.42–0.48)、CWMCT (R ²  = 0.33–0.36)、CWMAT (R ²  = 0.27–0.33) 和 FunDom (R ²  = 0.59–0.61) ) 通过不同的效应大小和方向。最终的最佳拟合 pSEM 显示 FunDom 增加 (β = 0.49) 但 CWMCT (β = -0.35) 和 CWMAT (β = -0.11) 降低 AGB (R ² = 0.52) 与 FTD 的影响可以忽略不计 (β = 0.04)。这项研究在宏观生态尺度上支持质量比效应，特别是高大或优势树木对 AGB 的主导作用，因此，表明合适的物种功能策略对于促进支撑人类的森林元群落的碳固存很重要。福利。我们期望我们的研究将通过使用元社区概念和方法在宏观生态尺度上推进生物多样性 - 生态系统功能领域。