A meta-analysis of peatland microbial diversity and function responses to climate change

Climate change threatens the capacity of peatlands to continue storing carbon (C) belowground. Microorganisms are crucial in regulating the peatland C sink function, but how climate change affects the richness, biomass and functions of peatland microbiomes still remains uncertain. Here, we conducted a global meta-analysis of the response of peatland bacterial, fungal and micro-eukaryote communities to climate change by synthesizing data from 120 climate change experiments. We show that climate drivers such as warming, drought and warminginduced vegetation shift strongly affect microbial diversity, community composition, trophic structure and functions. Using meta-analytic structural equation modelling, we developed a causal understanding among the different strands of microbial properties. We found that climate drivers influenced microbial metabolic rates, such as CO2 fixation and respiration, methane production and oxidation, directly through physiological effects, and indirectly, through microbial species turnover and shifts in the trophic structure of microbial communities. In particular, we found that the response of microbial CO2 fixation increased for each degree in air temperature gained, while the response of microbial CO2 respiration tended to decline. When extrapolated at the global peatland scale using the CMIP6 model under the SSP5-8.5 scenario, our findings suggest that the increasingly positive response of microbial CO2 fixation to temperature anomalies in northern latitudes might compensate to some extent for the possible loss of C from microbial CO2 respiration, possibly allowing peatlands to remain C sinks on long-term. Our findings have crucial implications for advancing our understanding of carbon-climate feedback from peatlands in a warming world.