Mayerhofer Johanna, Wächter Daniel, Calanca Pierluigi, Kohli Lukas, Roth Tobias, Meuli Reto Giulio, Widmer Franco
Molecular Ecology, Agroscope, Zurich, Switzerland.
Swiss Soil Monitoring Network, Agroscope, Zurich, Switzerland.
Front Microbiol. 2021 Mar 11;12:581430. doi: 10.3389/fmicb.2021.581430. eCollection 2021.
Mountain areas harbor large climatic and geographic gradients and form numerous habitats that promote high overall biodiversity. Compared to macroorganisms, knowledge about drivers of biodiversity and distribution of soil bacteria in mountain regions is still scarce but a prerequisite for conservation of bacterial functions in soils. An important question is, whether soil bacterial communities with similar structures share environmental preferences. Using metabarcoding of the 16S rRNA gene marker, we assessed soil bacterial communities at 255 sites of a regular grid covering the mountainous landscape of Switzerland, which is characterized by close location of biogeographic regions that harbor different land-use types. Distribution of bacterial communities was mainly shaped by environmental selection, as revealed by 47.9% variance explained by environmental factors, with pH (29%) being most important. Little additional variance was explained by biogeographic regions (2.8%) and land-use types (3.3%). Cluster analysis of bacterial community structures revealed six bacterial community types (BCTs), which were associated to several biogeographic regions and land-use types but overall differed mainly in their preference for soil pH. BCT I and II occurred at neutral pH, showed distinct preferences for biogeographic regions mainly differing in elevation and nutrient availability. BCT III and IV differed only in their preferred soil pH. BCT VI occurred in most acidic soils (pH 3.6) and almost exclusively at forest sites. BCT V occurred in soils with a mean pH of 4 and differed from BCT VI in preference for lower values of organic C, total nitrogen and their ratio. Indicator species and bipartite network analyses revealed 3,998 OTUs associating to different levels of environmental factors and BCTs. Taxonomic classification revealed opposing associations of taxa deriving from the same phyla. The results revealed that pH, land-use type, biogeographic region, and nutrient availability were the main factors shaping bacterial communities across Switzerland. Indicator species and bipartite network analyses revealed environmental preferences of bacterial taxa. Combining information of environmental factors and BCTs yielded increased resolution of the factors shaping soil bacterial communities and provided an improved biodiversity framework. OTUs exclusively associated to BCTs provide a novel resource to identify unassessed environmental drivers.
山区具有巨大的气候和地理梯度，形成了众多栖息地，促进了整体生物多样性的提高。与大型生物相比，关于山区土壤细菌生物多样性驱动因素和分布的知识仍然匮乏，但这是保护土壤细菌功能的前提条件。一个重要的问题是，结构相似的土壤细菌群落是否具有相同的环境偏好。我们利用16S rRNA基因标记的宏条形码技术，对覆盖瑞士山区景观的规则网格中的255个位点的土壤细菌群落进行了评估，该地区的特点是生物地理区域相邻，且拥有不同的土地利用类型。细菌群落的分布主要受环境选择的影响，环境因素解释了47.9%的变异，其中pH值（29%）最为重要。生物地理区域（2.8%）和土地利用类型（3.3%）解释的变异较少。细菌群落结构的聚类分析揭示了六种细菌群落类型（BCT），它们与几个生物地理区域和土地利用类型相关，但总体上主要在对土壤pH值的偏好上有所不同。BCT I和II出现在中性pH值环境中，对主要在海拔和养分可用性方面存在差异的生物地理区域表现出明显的偏好。BCT III和IV仅在其偏好的土壤pH值上有所不同。BCT VI出现在大多数酸性土壤（pH 3.6）中，几乎只出现在森林位点。BCT V出现在平均pH值为4的土壤中，在对较低有机碳、总氮及其比值的偏好上与BCT VI不同。指示物种和二分网络分析揭示了3998个操作分类单元（OTU）与不同水平的环境因素和BCT相关。分类学分类揭示了来自同一门的分类单元的相反关联。结果表明，pH值、土地利用类型、生物地理区域和养分可用性是塑造瑞士各地细菌群落的主要因素。指示物种和二分网络分析揭示了细菌分类单元的环境偏好。结合环境因素和BCT的信息，提高了对塑造土壤细菌群落的因素的分辨率，并提供了一个改进的生物多样性框架。仅与BCT相关的OTU提供了一种新资源，用于识别未评估的环境驱动因素。
