Models Must Be Informed About Peatland Carbon Sink Sensitivities to Warming

The Science

This research quantifies current inter-annual and seasonal variation in peatland carbon (C) emissions as a function of warming. It is imperative that we understand peatland because they cover only 3% of Earth’s land surface but contain about 20% of the global soil carbon pool. Under current ambient conditions, peatland net C sink capacity changes in sign and magnitude across seasons. Direct comparison of multiyear eddy covariance data sets with DOE’s Spruce and Peatland Responses Under Changing Environments (SPRUCE) experimental results shows that ambient variation in net C exchange is small in the context of warming responses under in situ experimental conditions.

The Impact

To best capture peatland C cycle warming responses, models will need to be reconciled with both observable variations under current climate and experimental warming responses that extend the response surface. This study will help improve understanding of peatland carbon cycle and potential impacts of a warming environment on the storage and release of carbon to the atmosphere.

Summary

Peatlands have acted as net carbon dioxide (CO₂) sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes where peatlands are abundant can disturb their CO₂ sink function. This study shows that sensitivity of peatland net CO₂ exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO₂ sink responses. Multiannual net CO₂ exchange observations from 20 northern peatlands showed that warmer early summers are linked to increased net CO₂ uptake, while warmer late summers lead to decreased net CO₂ uptake. Thus, net CO₂ sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. These results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO₂ uptake over the coming few decades.

Principal Investigator

Paul J. Hanson
Oak Ridge National Laboratory
hansonpj@ornl.gov

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
brian.benscoter@science.doe.gov

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

This research was supported by the Biological and Environmental Research (BER) Program within the US Department of Energy’s (DOE) Office of Science at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, for DOE under contract DE-AC05-00OR22725.

References