A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with detritivore diversity are key to advancing our understanding of litter mass loss in nature.

中文翻译：

---

植物凋落物功能多样性对凋落物质量损失的影响取决于大型碎屑动物群落

需要更好地了解垃圾多样性对分解的影响机制，以预测生物多样性丧失如何影响这一重要的生态系统过程。在一项微观研究中，我们研究了凋落物功能多样性和两大类土壤大型碎屑动物对树叶凋落物混合物质量损失的影响。此外，我们还测试了凋落物性状群落平均值和差异性对七个与分解相关的性状的凋落物质量损失的影响。我们预计，大型碎屑动物对凋落物质量损失的影响在高功能多样性的凋落物混合物中最为明显。我们使用了 24 种功能多样性不同的叶子混合物，它们由 16 种常见欧洲树种中的 4 个物种的枯枝落叶组成。将蚯蚓、等足类动物或两者的组合添加到每个窝组合中两个月。蚯蚓存在时的凋落物质量损失明显高于等足类动物，而大型碎屑动物混合物没有发现协同效应。在两个大型食腐动物群体存在的情况下，凋落物材料的功能多样性的影响最高，这支持了以下观点：在存在不同食腐动物物种的情况下，凋落物多样性的影响最为明显。物种特定的凋落物质量损失可以通过养分含量、次生化合物浓度和结构成分来解释。此外，氮浓度的差异增加了凋落物质量的损失，可能是因为碎屑动物可以获得营养多样化的食物来源。此外，两种大型食腐动物之间对土壤表面凋落物的强烈竞争导致两种大型食腐动物的存活率下降。这些结果表明，凋落物功能多样性对分解的影响取决于大型碎屑动物群落和组成。我们得出的结论是，凋落物性状多样性影响的时间动态及其与食腐动物多样性的相互作用是增进我们对自然界中凋落物质量损失的理解的关键。