Researchers are experimentally warming northern peatlands to understand carbon cycling in the climate of the future. 

Northern peatlands hold large stocks of organic carbon in their soils that are vulnerable to release into the atmosphere as the greenhouse gases carbon dioxide and methane as the climate warms. Emissions of methane, which has about 28 times the warming power of carbon dioxide over a 100-year period, are of particular concern. Prior studies have been limited to the effects of surface-level warming on carbon cycling, and the response of deeper layers of peat to warming—which could contribute significantly to future climate change—is not well understood. To address this gap, a multidisciplinary group of researchers from three DOE Laboratories, the USDA Forest Service, and a number of universities are using a ten-year warming study of a Minnesota black spruce peatland ecosystem, the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment, to investigate the stability of the ancient carbon stocks that lie beneath it.

In 2014, researchers initiated warming of deep peat by as much as 9°C above surrounding temperatures over 13 months—an upper limit on projected temperature increase by 2100 under the most extreme greenhouse gas emissions scenarios. Researchers found that while the deeper, 3,000–12,000-year-old carbon stocks under oxygen free, water-saturated conditions did not decompose under higher temperatures, more modern surface carbon associated with living vegetation cycled at a faster rate and resulted in increased methane and carbon dioxide emissions as warming increased (see figure). ^[1] This surface response associated with more recent carbon stores may have significant consequences for future climate warming.

Operation of the SPRUCE experiment continues under whole-ecosystem warming conditions for several years to measure peatland carbon, water, and biogeochemical cycles and the growth and survival of vegetation and microbial communities, all of which influence carbon storage in peatland soils. These data will inform efforts to model vegetation response under projected levels of climate change.