The mass ratio (MRH) and niche complementarity (NCH) hypotheses can explain how leaf trait composition drives decomposition, an ecosystem process linked to nutrient cycling and carbon sequestration. However, few studies have used an experiment designed to disentangle the role of the mechanisms proposed by these hypotheses. This is especially true regarding the role of leaf functional traits for decomposition rates in tropical ecosystems. Here, we quantified the biomass loss of 120 leaf mixtures assembled according to four quasi-orthogonal combinations of different mean trait values (community-weighted mean; CWM) and trait variability (functional diversity; FD) of three leaf functional traits (leaf nitrogen and leaf magnesium concentrations and specific leaf area). We found that CWM values of leaf nutritional traits were positively related to greater biomass loss. This supports the hypothesis that the mean trait values of leaf mixtures can drive biomass loss (MRH). However, contrary to NCH expectations, in some circumstances, increasing trait variability of leaf nutritional traits decreased biomass loss. Our results reinforce some previous evidence that, together, CWM and FD can explain leaf decomposition and highlight that the mean resource quality of leaf mixtures is a driver of biomass loss. Also, as previously reported for temperate ecosystems, trait variability does not always increase leaf decomposition in tropical ecosystems. Therefore, there is a need to consider simultaneously both MRH and NCH in future studies, using an appropriate design, keeping in mind that both mechanisms will always be present in any species mixture or combination.

中文翻译：

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叶片分解取决于营养性状值，但增加性状变异并不总是提高分解效率

质量比 (MRH) 和生态位互补 (NCH) 假设可以解释叶片性状组成如何驱动分解，这是一个与养分循环和碳固存相关的生态系统过程。然而，很少有研究使用旨在解开这些假设提出的机制的作用的实验。对于热带生态系统中叶片功能性状对分解率的作用尤其如此。在这里，我们量化了根据不同平均性状值（社区加权平均值；CWM）和三个叶子功能性状（叶子氮和叶）的性状变异性（功能多样性；FD）的四种准正交组合组装的 120 种叶子混合物的生物量损失。叶镁浓度和比叶面积）。我们发现叶片营养性状的 CWM 值与更大的生物量损失呈正相关。这支持了叶子混合物的平均性状值可以驱动生物量损失 (MRH) 的假设。然而，与 NCH 的预期相反，在某些情况下，增加叶片营养性状的变异性会降低生物量损失。我们的结果加强了之前的一些证据，即 CWM 和 FD 可以一起解释叶片分解，并强调叶片混合物的平均资源质量是生物量损失的驱动因素。此外，正如之前针对温带生态系统所报道的那样，性状变异并不总是会增加热带生态系统中的叶子分解。因此，在未来的研究中需要同时考虑 MRH 和 NCH，使用适当的设计，