Simulation modelling of soil inorganic carbon in arid environments

Title	Simulation modelling of soil inorganic carbon in arid environments
Publication Type	Conference Paper
Year of Publication	2003
Authors	Mitchell K.A, Monger CH, Herrick JE, Peters DC
Conference Name	88th Annual Meeting, Ecological Society of America
Date Published	August 3-8, 2003
Conference Location	Savannah, GA
ARIS Log Number	153551
Abstract	Pedogenic carbonate, or soil inorganic carbon, is an important constituent of subhumid-to-arid soils throughout the world. Although terrestrial carbon cycling science has placed more emphasis on organic carbon, arid and semiarid soils store approximately ten times more inorganic carbon than organic. It has been estimated that more than 8 x 1014 kg of C are sequestered globally in calcic and petrocalcic horizons of Aridisols and Mollisols. Our goal was to examine and test hypotheses regarding the relationship of calcium carbonate (CaCO3) in arid lands to atmospheric CO2 sequestration. The magnitude of soil inorganic carbon flux with the atmosphere is difficult to estimate at local, regional or global scales. We developed a conceptual model and an associated process-based model to simulate the rate of formation and vertical distribution of CaCO3 in soil horizons in the arid southwestern U.S. The model depicts short term processes of CaCO3 precipitation and dissolution that occur in periods of days to centuries to millennia. We use the model to illustrate the environmental and biotic conditions that control the CaCO3 source-to-sink relation. Initial findings show that pedogenic carbonate can serve not only as a sink, but also as a source for CO2. Our simulation modelling framework helps illustrate the historic and future conditions under which soil carbonates alternate between storing and releasing CO2 to the atmosphere.