• Variations in crown forms promote canopy space‐use and productivity in mixed‐species forests. However, we have a limited understanding on how this response is mediated by changes in within‐tree biomass allocation. Here, we explored the role of changes in tree allometry, biomass allocation and architecture in shaping diversity–productivity relationships (DPRs) in the oldest tropical tree diversity experiment.
• We conducted whole‐tree destructive biomass measurements and terrestrial laser scanning. Spatially explicit models were built at the tree level to investigate the effects of tree size and local neighbourhood conditions. Results were then upscaled to the stand level, and mixture effects were explored using a bootstrapping procedure.
• Biomass allocation and architecture substantially changed in mixtures, which resulted from both tree‐size effects and neighbourhood‐mediated plasticity. Shifts in biomass allocation among branch orders explained substantial shares of the observed overyielding. By contrast, root‐to‐shoot ratios, as well as the allometric relationships between tree basal area and aboveground biomass, were little affected by the local neighbourhood.
• Our results suggest that generic allometric equations can be used to estimate forest aboveground biomass overyielding from diameter inventory data. Overall, we demonstrate that shifts in tree biomass allocation are mediated by the local neighbourhood and promote DPRs in tropical forests.

中文翻译：

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树木介导的树木生物量分配的邻里调节驱动热带物种混合物的过度增产。

• 冠状形态的变化促进了混合物种森林的冠层空间利用和生产力。但是，我们对树内生物量分配的变化如何介导此响应的了解有限。在这里，我们探索了树木的异度变化，生物量分配和结构变化在塑造最古老的热带树木多样性实验中的作用-形成多样性-生产力关系（DPR）。
• 我们进行了全树破坏性生物量测量和地面激光扫描。在树级别构建空间显式模型，以研究树大小和局部邻域条件的影响。然后将结果放大到标准水平，并使用自举程序探索混合效果。
• 生物量分配和结构在混合物中发生了显着变化，这是由于树木大小效应和邻里介导的可塑性引起的。分公司订单中生物量分配的变化解释了所观察到的过度生产的很大一部分。相比之下，根茎比以及树木基础面积与地上生物量之间的异速关系几乎不受当地社区的影响。
• 我们的结果表明，通用的等速方程可用于从直径清单数据中估算森林地上生物量过量。总体而言，我们证明了树木生物量分配的变化是由当地社区所介导的，并促进了热带森林中的DPR。