PDF Version of this ArticleFollowing Carbon’s Trail
by Sarah Farmer
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| SRS researchers excavate whole root systems to measure carbon and validate findings from the ground penetrating radar (GPR) methods they’ve developed. (photo by USDA Forest Service) |
Carbon, the chemical foundation of life, cycles through forests, seas and skies, and at some stages is stored or sequestered, from the atmosphere. Trees are one such storage vault.
The U.S. Department of Defense (DOD) hopes to use the longleaf pine forests on their lands to sequester carbon while protecting biodiversity and restoring ecosystems. Funded by DOD, SRS plant physiologist Kurt Johnsen and his Forest Genetics and Ecosystems and Biology team are working with university researchers to measure the carbon stored in longleaf pine ecosystems and construct a model that shows how carbon moves through young stands (0 to 50 years old) and older stands (40 to over 200 years old). DOD will use the model to evaluate different forest management strategies on three military bases in the South where they manage and restore longleaf pine forests.
Lisa Samuelson, director of the Center for Longleaf Pine Ecosystems at Auburn University, will direct the overall project and lead efforts to measure carbon in aboveground and taproot biomass. Tim Martin, director of the Carbon Resources Science Center at the University of Florida, and his team will combine data from the research project and other literature to develop the carbon model and management tools. Johnsen and his team will study belowground carbon to understand how it moves from living roots to soils, and measure coarse root biomass and the decomposition rates of taproots.
To examine belowground carbon, Johnsen’s team will use the ground-penetrating radar (GPR) techniques they’ve developed for measuring tree root biomass. GPR is a nondestructive tool that lets researchers peer belowground at roots, which can account for 15 to 45 percent of pine stand biomass. Along with using GPR, Johnsen and his crew will excavate whole root systems that have been dead for known periods of time to measure the remaining carbon. “By comparing these quantities to carbon present in living root systems, we can determine decomposition rates for the roots,” says Johnsen. “Longleaf pines have large taproots and are long lived, so they might store lots of carbon underground.”
Johnsen’s team will look closely at belowground black carbon, the sooty charcoal residue from incomplete burning of biomass deposited by wildfires and by prescribed fires used to manage fire-adapted species like longleaf pine. SRS scientists will use lab techniques to separate the black carbon in soil from other forms of carbon, providing data for the model of carbon’s belowground cycle while quantifying the role of black carbon in removing carbon from the atmosphere.
The project team will collect their data from three military bases in the Southeast where longleaf pine forests flourished in the past: Fort Polk, LA; Fort Benning, GA; and Camp Lejeune, NC. Once covering some 90 million acres in the South, longleaf pine forests were the largest temperate forest type in the United States, but have been in decline for decades because of land clearing for crops and pastures, logging, and other forest products. Longleaf pine ecosystems are some of the most diverse in the nation; nearly two-thirds of all declining, threatened, or endangered species in the Southeast call them home.
The carbon cycle model developed by project collaborators will support DOD’s continuing transition towards an ecological forestry model that protects habitat and offsets carbon emissions while sustaining military operations. Funded by DOD through the Strategic Environmental Research and Development Program, the research project is the most expansive and thorough carbon assessment ever conducted on southern military bases.
Recommended reading:
Butnor, J.; Johnsen, K.; Samuelson, L.; Pruyn, M. 2009. Current applications of GPR in forest research. In: Symposium on the application of geophysics to engineering and environmental problems (SAGEEP) Proceedings. March 29 - April 2, Fort Worth, TX. 885–894.
Sarah Farmer is studying biology, chemistry, and writing at Asheville-Buncombe Technical Community College.
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| With funding from the U.S. Department of Defense, SRS researchers and university collaborators are developing a model to show how carbon moves through longleaf pine stands of different ages. (photo by USDA Forest Service) |
For more information:
Kurt Johnsen at 919–549–4012 or kjohnsen@fs.fed.us
