Meisner Annelein, Jacquiod Samuel, Snoek Basten L, Ten Hooven Freddy C, van der Putten Wim H
Microbial Ecology, Department of Biology, Lund University, Lund, Sweden.
Sections of Microbiology and Terrestrial Ecology, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
Front Microbiol. 2018 Mar 7;9:294. doi: 10.3389/fmicb.2018.00294. eCollection 2018.
It is increasingly acknowledged that climate change is influencing terrestrial ecosystems by increased drought and rainfall intensities. Soil microbes are key drivers of many processes in terrestrial systems and rely on water in soil pores to fulfill their life cycles and functions. However, little is known on how drought and rainfall fluctuations, which affect the composition and structure of microbial communities, persist once original moisture conditions have been restored. Here, we study how simulated short-term drying and re-wetting events shape the community composition of soil fungi and prokaryotes. In a mesocosm experiment, soil was exposed to an extreme drought, then re-wetted to optimal moisture (50% WHC, water holding capacity) or to saturation level (100% WHC). Composition, community structure and diversity of microbes were measured by sequencing ITS and 16S rRNA gene amplicons 3 weeks after original moisture content had been restored. Drying and extreme re-wetting decreased richness of microbial communities, but not evenness. Abundance changes were observed in only 8% of prokaryote OTUs, and 25% of fungal OTUs, whereas all other OTUs did not differ between drying and re-wetting treatments. Two specific legacy response groups (LRGs) were observed for both prokaryotes and fungi. OTUs belonging to the first LRG decreased in relative abundance in soil with a history of drought, whereas OTUs that increased in soil with a history of drought formed a second LRG. These microbial responses were spread among different phyla. Drought appeared to be more important for the microbial community composition than the following extreme re-wetting. 16S profiles were correlated with both inorganic N concentration and basal respiration and ITS profiles correlated with fungal biomass. We conclude that a drying and/or an extreme re-wetting history can persist in soil microbial communities via specific response groups composed of members with broad phylogenetic origins, with possible functional consequences on soil processes and plant species. As a large fraction of OTUs responding to drying and re-wetting belonged to the rare biosphere, our results suggest that low abundant microbial species are potentially important for ecosystem responses to extreme weather events.
人们越来越认识到，气候变化正通过增加干旱和降雨强度来影响陆地生态系统。土壤微生物是陆地系统中许多过程的关键驱动因素，依赖土壤孔隙中的水分来完成其生命周期和功能。然而，对于影响微生物群落组成和结构的干旱和降雨波动在原始水分条件恢复后如何持续存在，人们知之甚少。在这里，我们研究模拟的短期干燥和再湿润事件如何塑造土壤真菌和原核生物的群落组成。在一个中型生态系统实验中，土壤经历了极端干旱，然后再湿润到最佳湿度（50% WHC，持水量）或饱和水平（100% WHC）。在恢复原始水分含量3周后，通过对ITS和16S rRNA基因扩增子进行测序来测量微生物的组成、群落结构和多样性。干燥和极端再湿润降低了微生物群落的丰富度，但没有降低均匀度。仅在8%的原核生物OTU和25%的真菌OTU中观察到丰度变化，而所有其他OTU在干燥和再湿润处理之间没有差异。对于原核生物和真菌都观察到了两个特定的遗留响应组（LRG）。属于第一个LRG的OTU在有干旱历史的土壤中相对丰度下降，而在有干旱历史的土壤中增加的OTU形成了第二个LRG。这些微生物反应分布在不同的门中。干旱似乎对微生物群落组成比随后的极端再湿润更重要。16S图谱与无机氮浓度和基础呼吸相关，ITS图谱与真菌生物量相关。我们得出结论，干燥和/或极端再湿润历史可以通过由具有广泛系统发育起源的成员组成的特定响应组在土壤微生物群落中持续存在，对土壤过程和植物物种可能产生功能影响。由于对干燥和再湿润作出反应的大部分OTU属于稀有生物圈，我们的结果表明，低丰度微生物物种可能对生态系统对极端天气事件的响应很重要。
