Barantal Sandra, Schimann Heidy, Fromin Nathalie, Hättenschwiler Stephan
Centre d'Ecologie Fonctionnelle et Evolutive (CEFE UMR 5175, CNRS-Université de Montpellier-Université Paul-Valéry Montpellier-EPHE), 1919 Route de MENDE, 34293 Montpellier Cedex 5, France Ecology of Guiana Forest ECOFOG UMR 745, INRA-CIRAD-CNRS-UAG-AgroParisTech, INRA Campus Agronomique, BP 16, Kourou Cedex 97310, France Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
Ecology of Guiana Forest ECOFOG UMR 745, INRA-CIRAD-CNRS-UAG-AgroParisTech, INRA Campus Agronomique, BP 16, Kourou Cedex 97310, France.
Proc Biol Sci. 2014 Dec 7;281(1796):20141682. doi: 10.1098/rspb.2014.1682.
Plant leaf litter generally decomposes faster as a group of different species than when individual species decompose alone, but underlying mechanisms of these diversity effects remain poorly understood. Because resource C : N : P stoichiometry (i.e. the ratios of these key elements) exhibits strong control on consumers, we supposed that stoichiometric dissimilarity of litter mixtures (i.e. the divergence in C : N : P ratios among species) improves resource complementarity to decomposers leading to faster mixture decomposition. We tested this hypothesis with: (i) a wide range of leaf litter mixtures of neotropical tree species varying in C : N : P dissimilarity, and (ii) a nutrient addition experiment (C, N and P) to create stoichiometric similarity. Litter mixtures decomposed in the field using two different types of litterbags allowing or preventing access to soil fauna. Litter mixture mass loss was higher than expected from species decomposing singly, especially in presence of soil fauna. With fauna, synergistic litter mixture effects increased with increasing stoichiometric dissimilarity of litter mixtures and this positive relationship disappeared with fertilizer addition. Our results indicate that litter stoichiometric dissimilarity drives mixture effects via the nutritional requirements of soil fauna. Incorporating ecological stoichiometry in biodiversity research allows refinement of the underlying mechanisms of how changing biodiversity affects ecosystem functioning.
一般来说，植物落叶作为一组不同物种一起分解时比单个物种单独分解时更快，但这些多样性效应的潜在机制仍知之甚少。由于资源的碳：氮：磷化学计量比（即这些关键元素的比率）对消费者有很强的控制作用，我们推测落叶混合物的化学计量差异（即物种间碳：氮：磷比率的差异）会提高对分解者的资源互补性，从而导致混合物分解更快。我们用以下方法验证了这一假设：（i）一系列新热带树种的落叶混合物，其碳：氮：磷差异各不相同；（ii）一项添加养分（碳、氮和磷）的实验，以创造化学计量相似性。落叶混合物在野外使用两种不同类型的垃圾袋进行分解，一种允许土壤动物进入，另一种则阻止。落叶混合物的质量损失高于单个物种分解时的预期，尤其是在有土壤动物的情况下。有了土壤动物，落叶混合物的协同效应随着落叶混合物化学计量差异的增加而增加，而这种正相关关系在添加肥料后消失。我们的结果表明，落叶的化学计量差异通过土壤动物的营养需求驱动混合物效应。将生态化学计量学纳入生物多样性研究，可以完善生物多样性变化如何影响生态系统功能的潜在机制。
