Raw data of the copy numbers of the 16S rRNA gene and the ITS regions as a proxy for bacterial and fungal abundance and the mass loss of maize leaf litter in a 6-week incubation study using an agricultural soil from the LTFE Scheyern, and links to the 16S

Plant litter decomposition is an important process to restore carbon and other nutrients in soil. A large variety of bacterial species are involved in early phases of the litter decomposition. However, the impact of reduced soil and leaf bacterial diversity on the initial litter decomposition process is poorly understood. Thus, we performed a litter decomposition experiment under controlled conditions. We compared maize leaf litter decomposition rates in soils with different levels of bacterial diversity, prepared from one natural soil (NS) by manipulating its bacterial diversity. Autoclaving and reinoculation with an extract of microbes from NS eliminated parts of the “rare biosphere”. This approach substantially reduced bacterial diversity in autoclaved soil (AS) and inoculated soil (IS) compared to NS, while no significant differences in bacterial abundance were determined among the soil treatments after a preincubation period (Week −2 to 0). Natural and autoclaved maize leaves were applied to the soil treatments and incubated for 6 weeks. Bacterial diversity and community composition were assessed on Week −2, 0, and 6 using 16S rRNA gene metabarcoding. Bacterial and fungal abundance were assessed based on the copy number of the 16S rRNA gene and the ITS regions. Litter decomposition rates were assessed by calculating the quotient of remaining and initial litter amounts (dry weight basis). Due to the very small amount of litter materials left in litterbags on week 6, further molecular analysis was performed only on the maize samples collected on week 0. Our data suggested a positive correlation between litter decomposition rates and soil bacterial diversity. The soil with the highest bacterial diversity was dominated by oligotrophic bacteria including Acidobacteria, Nitrospiraceae, and Gaiellaceae, and its community composition did not change during the incubation. In the less diverse soils, oligotrophic bacteria were absent, but were replaced by copiotrophic bacteria such as Caulobacteraceae and Beijerinckiaceae, until the end of the incubation period. SourceTracker analysis revealed that litter-associated bacteria such as Beijerinckiaceae only became part of the bacterial communities in the less diverse soils. This suggests a pivotal role of oligotrophic bacteria during the early phases of litter decomposition and the predominance of copiotrophic bacteria at low diversity. The raw sequencing data are available at the sequencing read archive (SRA) under the BioProject PRJNA427490. Data are published in Chiba, A., Uchida, Y., Kublik, S., Vestergaard, G., Buegger, F., Schloter, M., and Schulz, S.: Soil bacterial diversity is positively correlated with decomposition rates during early phases of maize litter decomposition, Microorganisms 2021, 9(2), 357; https://doi.org/10.3390/microorganisms9020357

植物残体（plant litter）分解是恢复土壤碳及其他养分的关键过程。诸多细菌类群参与残体分解的早期阶段，但土壤与叶片细菌多样性降低对残体初始分解过程的影响仍有待阐明。为此，我们在可控条件下开展了残体分解实验。我们以1种天然土壤（NS）为起始材料，通过调控其细菌多样性构建不同细菌多样性水平的土壤，以此比较不同土壤中玉米叶残体的分解速率。对天然土壤进行高压灭菌后，再接种天然土壤的微生物提取物，可去除部分“稀有生物圈（rare biosphere）”。与天然土壤相比，该方法可显著降低高压灭菌土壤（AS）与接种土壤（IS）的细菌多样性；预培养阶段（第-2周至0周）后，各土壤处理组的细菌丰度无显著差异。将天然与高压灭菌处理的玉米叶残体施加至各土壤处理组，随后培养6周。分别于第-2周、0周及6周采用16S rRNA基因扩增子测序（16S rRNA gene metabarcoding）分析细菌多样性与群落组成，基于16S rRNA基因与内转录间隔区（ITS）的拷贝数评估细菌与真菌丰度。通过计算残体剩余量与初始量的比值（以干重计）评估残体分解速率。由于第6周分解袋内残体残留量极少，仅对第0周采集的玉米残体样本开展后续分子分析。研究数据表明，残体分解速率与土壤细菌多样性呈正相关。细菌多样性最高的土壤以贫营养细菌为主，包括酸杆菌门（Acidobacteria）、硝化螺旋菌科（Nitrospiraceae）与盖勒氏菌科（Gaiellaceae），且其群落组成在培养期间未发生显著变化。在多样性较低的土壤中，贫营养细菌未被检出，取而代之的是柄杆菌科（Caulobacteraceae）、拜叶林克氏菌科（Beijerinckiaceae）等富营养细菌，直至培养结束。SourceTracker分析显示，与残体相关的细菌（如拜叶林克氏菌科）仅在多样性较低的土壤群落中成为优势类群。这表明贫营养细菌在残体分解早期阶段发挥关键作用，而低多样性环境下富营养细菌占据主导地位。本研究的原始测序数据已提交至序列读取存档（SRA），对应的生物项目（BioProject）编号为PRJNA427490。本数据集已发表于：Chiba, A., Uchida, Y., Kublik, S., Vestergaard, G., Buegger, F., Schloter, M., and Schulz, S.: Soil bacterial diversity is positively correlated with decomposition rates during early phases of maize litter decomposition, Microorganisms 2021, 9(2), 357; https://doi.org/10.3390/microorganisms9020357