Legacy of peatland erosion continues to shape microbial communities during recovery.

Peatland de-vegetation and surface erosion are common facets of peatland degradation in the uplands. These processes impact peatland function by limiting plant-derived carbon input, exposing previously deep peat to near-surface conditions, and disrupting peatland hydrology. Restoration of eroded peatlands typically aims both to re-establish vegetation cover and raise water tables. Here we present the impacts of physico-chemical alterations resulting from severe erosion and subsequent peatland recovery on microbial communities in a temperate upland bog.  Due to the central role of microbes in peatland organic matter decomposition, understanding their response to restoration measures is key to determining the success of these interventions. 

We determine key physico-chemical variables which control the composition of microbial communities and shape their function. By coupling detailed characterisation of geochemistry and the microbiome, the consequences of microbial community shifts for the peatland carbon store are considered. In upland ombrotrophic peat, where recovery has proceeded on formerly eroded surfaces, organic matter quality as investigated by pyrolysis-GCMS is presented and is determined to be a stronger predictor of community composition than water table position. Using amplicon sequencing we identify distinct microbial communities under degraded and re-vegetated surfaces, with significant depth relationships only present in peat which was actively accumulating. Re-vegetated areas support higher microbial biomass, with elevated dissolved organic carbon and CO2 concentrations evidencing altered carbon cycling following recovery. Functional profiling with shotgun metagenomics further reveals contrasting life-strategies which reflect the availability of organic substrates. Whilst water table position is often the primary control on peatland microbial function, we found this relationship to be obscured by the stronger role of organic substrate limitation in this eroded context. We discuss the consequences for restoration of eroded temperate peatlands where deep peat has been exposed.