Decade-Long Warming and Vegetation Change Drive Shifts in Peatland CH4 and CO2 Fluxes via Plant-Soil Feedbacks.

Plant functional types (PFTs) play a critical role in regulating greenhouse gas (GHG) fluxes in peatlands. Climate warming and vegetation loss can affect GHG fluxes directly and indirectly by affecting belowground biogeochemical cycling and altering ecosystem-scale carbon dynamics. To assess the long-term impacts of warming and PFT removal on GHG emissions, we conducted a decade-long field experiment in an ombrotrophic peatland. Treatments included passive warming and selective removal of graminoids, ericaceous shrubs, or both, under ambient and warmed conditions. During the growing season, we measured soil moisture, soil temperature, and dissolved organic matter (DOM) optical indices, alongside seasonal methane (CH4) and ecosystem respiration (ER) fluxes. Graminoid removal initially suppressed CH4 emissions, but under long-term warming, it led to a substantial increase. This shift likely resulted from warming-induced changes in microclimate and microbial access to carbon substrates. Structural equation modeling revealed that surface soil moisture, shaped by plant-soil interactions, was a central mediator linking vegetation change to GHG fluxes and DOM quality, influencing belowground biogeochemical processes. Our findings demonstrate that climate-driven shifts in vegetation composition can substantially reshape peatland GHG dynamics via plant-soil feedback.