Despite the importance of soil microorganisms for ecosystem services, long-term surveys of their communities are largely missing. Using metabarcoding, we assessed temporal dynamics of soil bacterial and fungal communities in three land-use types, i.e., arable land, permanent grassland, and forest, over five years. Soil microbial communities remained relatively stable and differences over time were smaller than those among sites. Temporal variability was highest in arable soils. Indications for consistent shifts in community structure over five years were only detected at one site for bacteria and at two sites for fungi, which provided further support for long-term stability of soil microbial communities. A sliding window analysis was applied to assess the effect of OTU abundance on community structures. Partial communities with decreasing OTU abundances revealed a gradually decreasing structural similarity with entire communities. This contrasted with the steep decline of OTU abundances, as subsets of rare OTUs (<0.01%) revealed correlations of up to 0.97 and 0.81 with the entire bacterial and fungal communities. Finally, 23.4% of bacterial and 19.8% of fungal OTUs were identified as scarce, i.e., neither belonging to site-cores nor correlating to environmental factors, while 67.3% of bacterial and 64.9% of fungal OTUs were identified as rare but not scarce. Our results demonstrate high stability of soil microbial communities in their abundant and rare fractions over five years. This provides a step towards defining site-specific normal operating ranges of soil microbial communities, which is a prerequisite for detecting community shifts that may occur due to changing environmental conditions or anthropogenic activities.

中文翻译：

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土壤细菌和真菌群落结构的长期稳定性以其丰富和稀有的部分显示

尽管土壤微生物对生态系统服务很重要，但对其群落的长期调查却在很大程度上缺失。使用元条形码，我们评估了五年内三种土地利用类型（即耕地、永久草地和森林）的土壤细菌和真菌群落的时间动态。土壤微生物群落保持相对稳定，随时间的差异小于站点之间的差异。耕地土壤的时间变异性最高。仅在一个细菌位点和两个真菌位点检测到群落结构在五年内持续变化的迹象，这为土壤微生物群落的长期稳定性提供了进一步支持。应用滑动窗口分析来评估 OTU 丰度对群落结构的影响。OTU 丰度下降的部分群落与整个群落的结构相似性逐渐下降。这与 OTU 丰度的急剧下降形成鲜明对比，因为稀有 OTU 的子集 (<0.01%) 显示与整个细菌和真菌群落的相关性高达 0.97 和 0.81。最后，23.4% 的细菌 OTU 和 19.8% 的真菌 OTU 被确定为稀有，即既不属于位点核心也不与环境因素相关，而 67.3% 的细菌和 64.9% 的真菌 OTU 被确定为稀有但并不稀缺。我们的结果表明，土壤微生物群落的丰富和稀有部分在五年内具有高度稳定性。这为定义土壤微生物群落特定地点的正常运行范围提供了一个步骤，