Ground warming leads to changes in carbon cycling in northern fen peatlands: implications for carbon storage
Abstract
Northern peatlands store one third of the world’s soil carbon (C), as they remove more C from the atmosphere via photosynthesis than they release to the atmosphere through ecosystem respiration and methane (CH4) production. Climate change threatens this function by stimulating C release from peatland stores as peat temperatures warm and soil moisture is reduced. Ground heating of +4 °C above ambient peat temperatures was initiated in a Sphagnum moss-dominated, nutrient poor fen and a Carex sedge-dominated, intermediate nutrient fen. Over one growing season, Carex fen heated plots had increases in photosynthesis (+23%), ecosystem respiration (+22%), and CH4 production (+57%). While gas fluxes did not change at the Sphagnum fen, belowground organochemical properties revealed heated plots contained more phenolics, which are associated with belowground sedge root growth. Although Sphagnum fens may take longer to respond to climate change, both fen types are at risk for becoming weaker C sinks in the future.