Aspects of microbial communities in peatland carbon cycling under changing climate and land use pressures.

This is a perspective review authored by peatland scientists, microbial ecologists, land managers and non-governmental organisations who were attendees at a series of three workshops held at The University of Manchester in 2019-2020. Here we review the impacts of climate change (search criteria for references are given in the introduction to the section “Effects of climate change on peatland microbial communities”) and ecosystem restoration on peatland microbial communities and the implications for C sequestration and climate regulation.
Anthropogenic climate change puts continuous pressure on peatland ecosystems and modifies the geography of the environmental envelope that underpins peatland functioning. A probable impact of climate change is reduction in the water-logged conditions that are key to peatland formation and continued accumulation. Carbon (C) sequestration in peatlands arises from a delicate imbalance between primary production and decomposition, and microbial processes are potentially pivotal in regulating feedbacks between environmental change and the peatland C cycle. Globally, major efforts are being made to restore peatlands to maximise their resilience to changing climate. Here we review the impacts of climate change and ecosystem restoration on peatland microbial communities and the implications for C sequestration and climate regulation. Increased soil temperature, because of climate warming or disturbance of the natural vegetation cover and drainage, may result in reductions of long-term C storage via changes in microbial community composition and metabolic rates. Moreover, changes in water table alter the redox state and hence have broad consequences for microbial functions, including effects on fungal and bacterial communities, especially methanogens and methanotrophs. Our review suggests that the increase in methane flux sometimes observed when water tables are restored is predicated on the availability of labile carbon from vegetation and the absence of alternative terminal electron acceptors. Peatland microbial communities respond relatively rapidly to climate change-induced shifts in vegetation and subsequent changes in the quantity and quality of C substrate inputs belowground. Other effects of climate change on peatlands include alterations in snow cover and permafrost thaw that affect microbial communities and C cycling. In the face of rapid climate change, restoration of a resilient microbiome is essential to sustaining the climate regulation functions of peatland systems. Technological developments allowing quicker characterisation of microbial communities and function support progress towards this goal. Further progress will require a strong interdisciplinary approach.