Patterns of bacterial composition in global peatlands and their controlling variables

Peatlands are a globally important carbon sink, storing up to 455 Pg C as soil organic carbon. One of the drivers of this immense storage relates to the extremely low rate of peat decomposition, which is ultimately regulated by the bacterial community of these peat soils. Previous studies note that vegetation type (e.g., bog vs. fen), depth of peat, water level and pH may determine bacterial composition in peatlands. However, in terms of global patterns, the key controlling variables remain elusive due to a lack of data synthesis and direct experimental evidence. To identify bacterial community composition in global peatlands and key controlling variables, we conducted a field survey of 7 peatland sites in Korea, a meta-analysis of published data from over 95 peatland sites, and pH-manipulation experiments in the UK, by employing NGS analysis targeting 16sRNA.

Although immense variabilities in bacterial composition among sites were observed, pH appears to be a dominant controlling variable shaping bacterial community structure. For example, high pH is associated with higher relative abundance of Proteobacteria, while low pH appears to be related to the abundance of Acidobacteria. Variations of bacterial composition at different depths or vegetation types in a single site are smaller than those among different locations, suggesting that environmental changes in local conditions such as water level fluctuation and carbon availability may be less critical than the mean temperature or overall pH of a given site. Our study further suggests that the long-term changes in pH may have much greater implications than previously assumed, with peat decomposition likely to accelerate during the current recovery from acidification being experienced by peatlands across the world.