USGS Contributions to the Climate Change Science ProgramCARBON CYCLE
From studies of the geologic record, it is known that the distribution of carbon among major carbon sinks and reservoirs has changed with past changes in climate. Links between the global carbon cycle and the global climate system are complicated, involving atmospheric carbon dioxide (CO2) and the "greenhouse effect". Atmospheric CO2 concentrations are presently increasing as a result of human activities. This increase may affect the global climate. Therefore, it is important to understand the global budget of atmospheric CO2. USGS research is conducted in cooperation and partnership with other agencies and academic collaborators in direct support of the Carbon Cycle Science Program. USGS carbon cycle research includes the following activities:
USGS carbon cycle researchers are working with USDA scientists to measure carbon exported from eroding agricultural fields in Mississippi (National Sedimentation Laboratory), Iowa (National Soil Tilth Laboratory), and Ohio (North Appalachian Experimental Watersheds). These measurements are part of a larger study evaluating the redistribution of soil organic carbon from eroding uplands to alluvial and reservoir sediments. The deposition and burial of organic-rich sediments constitutes one important mechanism for carbon sequestration.
Spatial distribution for soil organic carbon (SOC) using site-specific soil-pedon data linked to (A) STATSGO map units (1:250,000 scale) for the Mississippi Basin, USA; and (B) SSURGO map units (1:12,000 to 1:24,000 scale) for Mitchell and Yancey Counties, in the Southern Appalachians of North Carolina.
Cold region (boreal) forests contain large carbon reserves that are today highly susceptible to changes in climate. Soils and wetlands comprise over 2/3 of the boreal carbon reserves and have sequestered large amounts of carbon since retreat of large glacial ice masses. Changes in fire and seasonal temperatures have been shown to cause changes in shallow permafrost, nutrient cycling, ecosystem structure, and ultimately carbon exchange. Large fires in the boreal forest are a basic element to forest regrowth, species diversity, carbon storage, and carbon exchange. Although fire is a primary mechanism for direct carbon loss from the ecosystem, forest regrowth and peat accumulation are mechanisms for carbon uptake. Fire disturbance drastically changes the active layer and its biogeochemistry for several decades, and this change in turn impacts the water table and bordering wetlands. In some areas, perhaps where fires are most severe or perhaps where fires recur more quickly, permafrost degrades irreversibly.
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