HR: 1340h
AN: H13F-1654 INVITED    [Abstracts]
TI: Using a Process-Based Numerical Model and Simple Empirical Relationships to Evaluate CO2 Fluxes from Agricultural Soils.
AU: Buchner, J
EM: jbuchner@web.de
AF: University of Heidelberg, Im Neuenheimer Feld 229, Heidelberg, D-69120, Germany
AU: * Simunek, J
EM: Jiri.Simunek@ucr.edu
AF: University of California Riverside, Department of Environmental Sciences, Riverside, CA 92521, United States
AU: Dane, J H
EM: danejac@auburn.edu
AF: Auburn University, Department of Agronomy and Soils, Auburn, AL 36849-5412, United States
AU: King, A P
EM: Apking@ucdavis.edu
AF: University of California Davis, Department Land, Air and Water Resources 123 Veihmeyer Hall, Davis, CA 95616, United States
AU: Lee, J
EM: ecolee@ucdavis.edu
AF: University of California Davis, Department Land, Air and Water Resources 123 Veihmeyer Hall, Davis, CA 95616, United States
AU: Rolston, D E
EM: derolston@gmail.com
AF: University of California Davis, Department Land, Air and Water Resources 123 Veihmeyer Hall, Davis, CA 95616, United States
AU: Hopmans, J W
EM: jwhopmans@ucdavis.edu
AF: University of California Davis, Department Land, Air and Water Resources 123 Veihmeyer Hall, Davis, CA 95616, United States
AB: Carbon dioxide emissions from an agricultural field in the Sacramento Valley, California, were evaluated using the process-based SOILCO2 module of the HYDRUS-1D software package and a simple empirical model. CO2 fluxes, meteorological variables, soil temperatures, and water contents were measured during years 2004-2006 at multiple locations in an agricultural field, half of which had been subjected to standard tillage and the other half to minimum tillage. Furrow irrigation was applied on a regular basis. While HYDRUS-1D simulates dynamic interactions between soil water contents, temperatures, soil CO2 concentrations, and soil respiration by numerically solving partially-differential water flow (Richards), and heat and CO2 transport (convection- dispersion) equations, an empirical model is based on simple reduction functions, closely resembling the CO2 production function of SOILCO2. It is assumed in this function that overall CO2 production in the soil profile is the sum of the soil and plant respiration, optimal values of which are affected by time, depth, water contents, temperatures, soil salinity, and CO2 concentrations in the soil profile. The effect of these environmental factors is introduced using various reduction functions that multiply the optimal soil CO2 production. While in the SOILCO2 module it is assumed that CO2 is produced in the soil profile and then transported, depending mainly on water contents, toward the soil surface, an empirical model relates CO2 emissions directly to various environmental factors. It was shown that both the numerical model and the simple reduction functions could reasonably well predict the CO2 fluxes across the soil surface. Regression coefficients between measured CO2 emissions and those predicted by the numerical and simple empirical models are compared.
DE: 1818 Evapotranspiration
DE: 1847 Modeling
DE: 1865 Soils (0486)
DE: 1866 Soil moisture
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting