Université de Toulouse, UPS, INP, CNRS, EcoLab (Laboratoire d'Ecologie Fonctionnelle), 29 Rue Jeanne Marvig, F-31055 Toulouse, France.
Ecology. 2011 Jan;92(1):160-9. doi: 10.1890/10-0315.1.
Plant diversity influences many fundamental ecosystem functions, including carbon and nutrient dynamics, during litter breakdown. Mixing different litter species causes litter mixtures to lose mass at different rates than expected from component species incubated in isolation. Such nonadditive litter-mixing effects on breakdown processes often occur idiosyncratically because their direction and magnitude change with incubation time, litter species composition, and ecosystem characteristics. Taking advantage of results from 18 litter mixture experiments in streams, we examined whether the direction and magnitude of nonadditive mixing effects are randomly determined. Across 171 tested litter mixtures and 510 incubation time-by-mixture combinations, nonadditive effects on breakdown were common and on average resulted in slightly faster decomposition than expected. In addition, we found that the magnitude of nonadditive effects and the relative balance of positive and negative responses in mixtures change predictably over time, and both were related to an index of functional litter diversity and selected environmental characteristics. Based on these, it should be expected that nonadditive effects are stronger for litter mixtures made of functionally dissimilar species especially in smaller streams. Our findings demonstrate that effects of litter diversity on plant mixture breakdown are more predictable than generally thought. We further argue that the consequences of current worldwide homogenization in the composition of plant traits on carbon and nutrient dynamics could be better inferred from long-duration experiments that manipulate both functional litter diversity and ecosystem characteristics in "hotspots of biodiversity effects," such as small streams.
植物多样性会影响许多基本的生态系统功能，包括碳和养分动态，这些功能在凋落物分解过程中发挥作用。混合不同的凋落物物种会导致凋落物混合物的质量损失速度与单独培养的组成物种所预期的速度不同。这种非加性的凋落物混合对分解过程的影响通常是特殊的，因为它们的方向和幅度随培养时间、凋落物物种组成和生态系统特征而变化。利用溪流中 18 个凋落物混合物实验的结果，我们研究了非加性混合效应的方向和幅度是否是随机确定的。在 171 个测试的凋落物混合物和 510 个培养时间-混合物组合中，非加性对分解的影响很常见，平均而言，分解速度比预期的要快。此外，我们发现非加性效应的幅度以及混合物中正负反应的相对平衡随时间推移可预测地变化，并且两者都与功能多样性指数和选定的环境特征相关。基于这些，我们可以预计，由功能上不同的物种组成的凋落物混合物的非加性效应更强，特别是在较小的溪流中。我们的研究结果表明，凋落物多样性对植物混合物分解的影响比通常认为的更具有可预测性。我们进一步认为，目前全球范围内植物特征组成同质化对碳和养分动态的影响，可以从长期实验中更好地推断出来，这些实验可以同时操纵功能多样性和生态系统特征，例如在“生物多样性效应热点”，如小河流中。
