Data from: Negative effects of litter richness on root decomposition in the presence of detritivores

1. Decomposition is a vital process underlying many ecosystem functions. Although a growing number of studies have tested how litter richness affects the decomposition of aboveground plant organs, knowledge remains limited about the decomposition of root mixtures. Here, we used a field experiment in a subtropical forest to investigate how species richness in root litter mixtures (air-dried fresh fine roots) affects the decomposition of root litter material.
2. Based on the concept of resource complementarity, we hypothesized that root litter would decompose faster as the richness of the root litter mixture increased. In addition, we expected the presence of detritivores to modify the effect of root richness on mass loss, because detritivores might experience bottom-up effects from specific plant species and might affect microbial decomposer communities.
3. We found that the richness level of root litter mixtures did not affect mass loss in the absence of detritivores. In the presence of detritivores, all root litter types decomposed faster. Notably, the positive effect of detritivores was stronger at low root litter richness than at high root litter richness, particularly during the early stages of decomposition (the first two sampling points) when litter mass loss was roughly double at low root litter richness compared to that at high root litter richness. The composition of the root fungal community measured at the last sampling point did not differ significantly across root richness levels, and was not affected by the presence of detritivores.
4. Synthesis. Our findings demonstrate that detritivores modify the relationship between root litter diversity and root litter decomposition in subtropical forest ecosystems. This highlights an importance of cascade effects between different trophic organisms on ecosystem functioning.

1. 分解（decomposition）是支撑诸多生态系统功能的核心过程。尽管已有越来越多的研究探讨了凋落物物种丰富度对地上植物器官分解的影响，但学界对根系混合物分解的认知仍较为匮乏。本研究依托亚热带森林野外原位实验，探究了根系凋落物混合物（风干新鲜细根，air-dried fresh fine roots）的物种丰富度对根系凋落物分解的调控效应。
2. 基于资源互补性（resource complementarity）理论，我们提出假说：根系凋落物混合物的物种丰富度越高，其分解速率越快。此外，我们预期食碎屑动物（detritivores）的存在会调控根系物种丰富度对凋落物质量丢失的影响——这是因为食碎屑动物可能会受到特定植物物种的上行效应（bottom-up effects）调控，同时也会作用于微生物分解者群落（microbial decomposer communities）。
3. 实验结果显示，在无食碎屑动物的情境下，根系凋落物混合物的物种丰富度并未对凋落物质量丢失产生显著影响。而当存在食碎屑动物时，所有类型的根系凋落物分解速率均显著提升。值得注意的是，食碎屑动物的促进效应在根系凋落物丰富度较低的组中更为显著，尤其在分解早期（前两个采样时段）——此时低丰富度组的凋落物质量丢失量约为高丰富度组的两倍。在最后一次采样时测得的根系真菌群落组成，并未随根系丰富度水平出现显著差异，同时也不受食碎屑动物存在与否的影响。
4. 综合分析：本研究结果表明，食碎屑动物会调控亚热带森林生态系统中根系凋落物多样性与根系凋落物分解之间的关系。这一发现凸显了不同营养级生物（trophic organisms）间的级联效应对生态系统功能（ecosystem functioning）的重要性。