Summary
Drained peatlands are significant sources of the greenhouse gas (GHG) carbon dioxide. Rewetting is a proven strategy to protect the large carbon stocks; however, it can also lead to increased emissions of the potent GHG methane. The response to rewetting of soil microbiomes as drivers of these processes is poorly understood, as are the biotic and abiotic factors that control community composition.
We analyzed the soil microbiomes of three contrasting pairs of minerotrophic fens subject to decade-long drainage and subsequent rewetting. Analyses comprised qPCR of methanogens, amplicon sequencing of prokaryotic and eukaryotic rRNA genes, and abiotic soil properties including moisture and dissolved organic matter.
The composition of pro- and eukaryotic communities was fen-type-specific, but all rewetted site showed higher abundance of anaerobic taxa. Based on multi-variate statistics and network analyses we identified soil moisture as major driver of community composition. Furthermore, salinity drove the separation between coastal and freshwater fen communities. Methanogens were more than tenfold more abundant in rewetted than in drained sites while their abundance was lowest in the coastal fen, likely due to competition with sulfate reducers. These results shed light on the factors that structure fen microbiomes via environmental filtering.
Footnotes
Figure 4 revised