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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Local Heterogeneity of Carbon Accumulation Throughout the Peat Profile of an Ombrotrophic Northern Minnesota Bog

Karis McFarlane

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31 May 2018

Past carbon accumulation in peat of the SPRUCE bog helps understand response to experimental treatments

The Science  
Scientists from Oak Ridge National Laboratory (ORNL) and Lawrence Livermore National Laboratory (LLNL) measured carbon storage and age of 18 peat depth profiles at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experimental site, constructed peat age-depth models, and quantified rates of carbon accumulation over the history of the bog to assess potential sources for variation in accumulation of carbon over time and space. Calibrated peat ages and age-depth profiles are available for use by SPRUCE collaborators and the broader community.

The Impact
This study found that the bog has been accumulating carbon in peat for over 11,000 years. Carbon accumulation rates changed over time, with a period of low net carbon accumulation likely a result of warmer and drier environmental conditions between 100 and 3300 years before present. These results suggest that experimental warming treatments, as well as a future warmer climate, may reduce net carbon accumulation in peat in this and other southern boreal peatlands.

Summary
ORNL and LLNL scientists evaluated the spatial heterogeneity of historical carbon accumulation rates in a forested, ombrotrophic bog in Minnesota to aid understanding of responses to an ongoing decade-long warming manipulation (SPRUCE). Eighteen peat cores indicated that the bog has been accumulating carbon for over 11,000 years, to yield an average of 176 kg C per m2 to 225 cm of peat depth. The long-term apparent rate of carbon accumulation over the entire peat profile averaged 22 kg C m2 yr–1. Net carbon accumulation rates averaged 30 ± 2 g C m2 yr–1 prior to 3300 cal BP, when net carbon accumulation rates dropped to 15 ± 8 g C m2 yr–1. Net carbon accumulation rates increased again during the last century to 74 ± 57 g C m2 yr–1. During the period of low accumulation, regional droughts may have lowered the water table, allowing for enhanced aerobic decomposition and making the bog more susceptible to fire. These results suggest that experimental warming treatments, as well as a future warmer climate, may reduce net carbon accumulation in peat in this and other southern boreal peatlands.

Contacts
BER Program Manager
Daniel Stover
Terrestrial Ecosystem Science, SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

Principal Investigators
Karis McFarlane
Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory
Livermore, CA 94550
kjmcfarlane@llnl.gov (925-423-6285)

Paul Hanson
Oak Ridge National Laboratory
Oak Ridge, TN 37381
hansonpj@ornl.gov (865-574-5361)

Funding
This work was supported by the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, under project ERKP788 and SWC1447; and Lawrence Livermore National Laboratory, Laboratory Research and Development project 14-ERD-038.

Publications
McFarlane KJ, Hanson PJ, Iversen CM, Phillips JR, Brice DJ. “Local spatial heterogeneity of Holocene carbon accumulation throughout the peat profile of an ombrotrophic Northern Minnesota bog.” Radiocarbon 60(3), 941–962 (2018). [DOI:10.1017/RDC.2018.37].

Oak Ridge National Laboratory under BER project ERKP788, Lawrence Livermore National Laboratory under BER project SCW1447, and Lawrence Livermore National Laboratory under Laboratory Directed Research and Development

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