The relative importance of abiotic and biotic factors in shaping forest biomass stocks and fluxes remains a controversial issue. Here, using data gathered from 39 1 ha plots located in flooded and terra firme mature tropical lowland forests of the Amazon and Orinoquia regions of Colombia, we evaluated the importance of climate, soil fertility, and flooding, as well as tree taxonomic/phylogenetic diversity and forest structural properties, in determining the aboveground biomass stocks (AGB; Mg ha⁻¹) and aboveground woody productivity (AWP; Mg ha⁻¹ year⁻¹). Using information-theoretic multimodel inference and variance partitioning we found that forest structural features such as the number of trees with diameter at breast height ≥ 70 cm, and wood density, are the main drivers of variation in AGB. However, taxonomic diversity also contributes to AGB because it is associated with more large trees in these forests. In contrast, the key drivers of AWP in these forests were soil P and Mg concentrations, with no significant effects of diversity indices. These findings emphasize the need to include major soil cations other than N and P (e.g. Mg) in experimental studies to improve our understanding about the extent to which soil fertility can modulate increases in forest AWP due to climate change. Terra firme forests had higher AGB stocks than flooded forests, but both had similar AWP; and we found similar results for the drivers of AGB and AWP between flooded and terra firme forests. Our results provide limited evidence for strong effects of plant diversity on AGB or AWP. Therefore, we call for caution on generalizations of nature-based initiatives aiming to preserve diversity based on maximizing carbon stocks and productivity, due to the complex nature of the processes controlling carbon accumulation and carbon fluxes in tropical forests.

中文翻译：

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哥伦比亚低地森林地上木本生物量和地上木本生产力的对比驱动因素

非生物和生物因素在塑造森林生物量储量和通量方面的相对重要性仍然是一个有争议的问题。在这里，我们利用从位于哥伦比亚亚马逊和奥里诺基亚地区被淹没和陆地成熟热带低地森林的 39 1 公顷地块收集的数据，评估了气候、土壤肥力和洪水以及树木分类/系统发育多样性的重要性和森林结构特性，以确定地上生物量储量（AGB；Mg ha ^-1）和地上木本生产力（AWP；Mg ha ^-1年^-1）。利用信息论多模型推理和方差划分，我们发现森林结构特征（例如胸径≥70厘米的树木数量和木材密度）是AGB变化的主要驱动因素。然而，分类多样性也有助于 AGB，因为它与这些森林中更多的大树有关。相比之下，这些森林中 AWP 的主要驱动因素是土壤 P 和 Mg 浓度，多样性指数没有显着影响。这些发现强调需要在实验研究中纳入除氮和磷以外的主要土壤阳离子（例如镁），以提高我们对土壤肥力在多大程度上可以调节气候变化导致的森林 AWP 增加的理解。陆地森林的 AGB 储量高于被淹没的森林，但两者的 AWP 相似；我们发现水淹森林和陆地森林之间 AGB 和 AWP 的驱动因素有类似的结果。我们的结果为植物多样性对 AGB 或 AWP 的强烈影响提供了有限的证据。因此，由于热带森林碳积累和碳通量控制过程的复杂性，我们呼吁谨慎对待基于自然的举措，这些举措旨在最大限度地提高碳储量和生产力的基础上保护多样性。