Climate change, snow cover and microbial diversity in mountain soils: critical processes during snowmelt

在高山地区，土壤微生物多样性和活性强烈依赖于积雪形成的年度模式。在冬季积雪中，微生物的生物量最高。在融雪时，微生物的数量急剧增加，但目前还没有得到很好的理解：冬季的细菌和真菌群落完全消失，取而代之的是春季的群落。全球变暖正在影响山脉，使年平均气温上升，冬季积雪减少，融雪时间提前，冻融循环频率增加。了解土壤微生物组如何受到变暖的影响，并反过来影响它，例如通过释放更多的温室气体，对于建立预测情景至关重要。我们计划调查土壤微生物的生物多样性（包括，第一次，原生生物）和它的功能之前，期间和之后的融雪，在融雪过程中的微生物周转的模式，以及它是如何受到变暖的影响。我们的研究将在阿尔卑斯山（瑞士达沃斯）的三座山上进行，在三个不同的海拔高度和三个季节进行，收集了200多个土壤样本。将记录植被、相关土壤和气候参数。此外，我们将通过实验性地修改积雪来模拟气候变暖的影响-压实和移除以模拟六个地点的早期融化。我们将使用RNA的高通量测序，同时获得有关土壤群落组成和功能的信息。因为我们正在寻找短期的时间变化，我们将提取RNA，只针对活细胞。简言之，核糖体RNA将用于鉴定细菌、真菌和原生生物群落及其相互作用;信使RNA将表征细菌和真菌的功能谱和解冻前、解冻期间和解冻后的代谢途径，以及实验处理如何影响这些动力学。我们的研究将有助于对春季土壤微生物动态的基本了解，这些土壤微生物动态负责解冻时的土壤有机质矿化和气候变暖导致的温室气体排放的地球化学循环。在我们的德国-瑞士合作项目（申请人：原生生物学，环境PCR，生物信息学; T。Urich：元转录组学，土壤中的细菌功能;积雪对土壤和植被的影响，取样地点的知识; Bonkowski：生态学，植物-微生物相互作用，土壤食物网）将确保项目的成功完成。因此，我们的项目将为了解高山和亚高山生态系统的功能做出重大贡献。

In alpine zones, soil microbial diversity and activity are strongly dependent on the annual patterns of snowpack formation. It is under the insulating winter snowpack where the highest microbial biomass is found. At snowmelt, there is a drastic and still not well understood rapid turnover: the winter bacterial and fungal communities entirely disappear and are replaced by spring communities. Global warming is affecting the mountain ranges by increasing the annual mean temperatures, reducing the winter snow cover, advancing the time of snowmelt and increasing the frequency of freeze-and-thaw cycles. Understanding how the soil microbiome is affected by warming and in turn affects it, e.g. by releasing more greenhouse gas, is essential for establishing predictive scenarios. We plan to investigate the soil microbial biodiversity (including, for the first time, protists) and its functions before, during and after snowmelt, the modalities of the microbial turnover during snowmelt and how it is affected by warming. Our study will be carried out on three mountains in the Alps (Davos, Switzerland), at three different altitudes and in three seasons, with a collection of more than 200 soil samples. Vegetation, relevant soil and climate parameters will be recorded. In addition, we will mimic the effects of climate warming by experimentally modifying the snow cover - compacting and removing to simulate earlier melt at six sites. We will use high-throughput sequencing of RNAs to simultaneously obtain information on both composition and function of the soil communities. Because we are looking for short-term temporal shifts, we will extract RNA to target only living cells. Briefly, the ribosomal RNAs will be used to identify the bacterial, fungal and protistan communities and their interactions; messenger RNAs will characterize bacterial and fungal functional profiles and metabolic pathways active before, during and after thaw and how the experimental treatments affect these dynamics. Our study will contribute to the fundamental understanding of spring soil microbial dynamics in the mountains responsible of soil organic matter mineralization at thaw and the biogeochemical cycles contributing to greenhouse gas emissions as a result of climate warming. The multiple qualifications assembled in our German-Swiss collaborative project (applicant: protistology, environmental PCR, bioinformatics; T. Urich: metatranscriptomics, bacterial functions in soils; C. Rixen: effects of snow cover on soil and vegetation, knowledge of the sampling sites; M. Bonkowski: ecology, plant-microbe interactions, soil food webs) will ensure a successful completion of the project. Our project will thus make a significant contribution to understanding the functioning of alpine and subalpine ecosystems.