Fate of Carbon in Soil Systems
Mark Waldrop, Dave McGuire, Miriam Jones, Kristen Manies, Jack McFarland, Jennifer Harden
USGS Climate, Research and Development Program for Climate and Land use Change
This project will quantitatively define the controls and vulnerabilities of terrestrial carbon using studies of soil incorporating both long term and recent perspectives. Over half of the flux and stock of actively cycling terrestrial organic carbon is derived from soil. Therefore, the fate of terrestrial carbon (and the potential to sequester or emit CO2
) is determined largely by the soil processes through hydrologic, sedimentation, and biological interactions. This project establishes the carbon mass balance for selected landscapes including a variety of landscapes such as permafrost, peatland, alluvial fan, and river terrace landscapes and disturbance regimes such as fire, erosion, and permafrost thaw. Using a combination of landscape, experiment, and modeling approaches, our goal is to establish both conceptual and quantitative constructs that specifically address how terrestrial carbon is stabilized and destabilized over a variety of timescales and spatial scales.
Results to date
Water table manipulations in a boreal rich fen found that mean anaerobic CO2 production potential was as high as aerobic CO2 production, suggesting that with continued drying or with a more variable water table, anaerobic CO2 production may be favored over CH4 production (Kane et al., 2013).
Although there is high carbon accumulation at the surface of newly formed boreal peatlands, carbon losses from rapid decomposition of thawed forest peat is even greater, suggesting that thawing peat will likely reduce the strength of northern permafrost-affected peatlands as a CO2 sink (O’Donnell et al, 2012).
Only about 20% of NPP of North American Boreal Forests enters soil, which sequester ~20 to 40gC/m2/yr across all successional stand ages (read more here: Harden et al., Biogeosciences 2012)
Thawing of permafrost results in rapid shifts of microbial, phyogenetic, and functional gene abundances and pathways, indicating that permafrost thaw will result in the rapid cycling of methane and nitrogen (read more here: Mackelprang et al., Nature 2012).
Modeling results of the Arctic Basin between 1997 and 2006 suggests that this area is a substantial net source of greenhouse gas (read more here: McGuire et al, Tellus 2010).