1. DayCent-Chem Overview Melannie Hartman NREL CANS Project Meeting Feb. 15-17, 2006 Sylvan Dale Ranch Loveland, CO John Fielder SO 2 NO x

2. Why was DayCent-Chem developed? Biological cycling of nutrients is important to predicting deposition effects on stream/soil chemistry. Management of forests, croplands, and grasslands built into Century. Daily time step. Model of intermediate complexity. John Fielder

3. History of DayCent, cont’d 2001 CENTURY version 5 monthly, C++ DayCent version 5 daily, C++ DayCent version 4 daily FORTRAN/C DayCent version 4.5 daily FORTRAN/C DayCent- Chem daily, C++ PHREEQC version 2.7, C Keough Del Grosso Parton 2001-present Hillinski 1998 CENTURY version 4 monthly FORTRAN http://www.nrel.colostate.edu/projects/century5/ Parton, Ojima, Hartman 1994 Hartman, Baron, 2003-present Parton, Ojima, Schimel 1980s

4. PHREEQC soil reactions Cation Exchange Aqueous reactions Mineral denudation CO 2 dissolution DayCent-Chem Model Processes Stream Flow PHREEQC stream reactions Aqueous reactions Mineral denudation CO 2 degassing LEACHING Atmospheric Deposition Cations and Anions UPTAKE SOM DECOMP. MINERALIZATION NITRIF./DENITRIF. LITTERFALL TRANSLOCATION Snowpack CO 2 N 2 O NO x CO 2 Atmospheric CO 2 Soil Organic C,N,P,S INFILTRATION DOC, Cations, Anions, CEC Aquifer BASEFLOW RUNOFF SUBLIMATION ET ANC, pH, BC, Cl, Al, SO 4 2- NO 3 - NH 4 +

5. streamflow DayCent-Chem Data Flow KEY H2O + species H2O only aquifer solution 1 solution 2 solution n solution n+1 solution n+2 soln.pqi soln.sel PHREEQC phreeqc.dat soil layer 0 soil layer 1 soil layer n-1 snowpack yes melt sublimation ET water vapor loss no rain? atmospheric deposition aqueous species + exchanger aqueous species only runoff solution 1 solution 2 solution n solution n+1 solution n+2 dry

6. Labile C in surface litter Labile C in Organic Soil Layer Mineral Soil Stream DOC DayCent-Chem organic C leaching Soil DOC l = leaching intensity: f(soil water flow) * f(soil texture) r = release intensity: DOCReleaseFraction * total Q / baseflow r l

7. PHREEQC (pH/Redox/Equilibrium/Carbon) Speciation program to calculate saturation indices and distribution of aqueous species Multi-phase system equilibrium with gas phases (i.e. CO 2, O 2 ), minerals, aqueous species, exchange sites. Ion exchange (Gaines-Thomas convention) Surface complexation (generalized two-layer, explicit diffuse layer, or non-electrostatic model) Distributed with several data bases of reactions and equilibrium coefficients, enthalpy of reaction (∆H)*. * “careful selection of aqueous species and thermodynamic data is left to the user”

8. Century C-cycle

9. Century N-cycle

10. DayCent-Chem Inputs/Outputs Inputs: daily precipitation & min./max. air temperatures precipitation concentrations (NADP) dry:wet ratio or dry dep amounts soil properties: texture, Ksat, CEC Outputs: daily stream outflow and chemistry daily soil chemistry by soil layer SOM composition NPP/Biomass ET/Sublimation NO x, N 2 O emissions

11. DayCent-Chem Processes Does: speciation mineral weathering CO 2, O 2 dissolution cation exchange (permanent charge) plant/microbial uptake of NH 4 +, NO 3 -, P, S pH computed as charge balance elution Model development: sulfate adsorption / pH dependent charge plant/microbial uptake of base cations organic acids O 3 effects on production (?) John Fielder

12. DayCent Publications Del Grosso, S.J., W.J. Parton, A.R. Mosier, D.S. Ojima, and M.D. Hartman. 2000. Interaction of Soil Carbon Sequestration and N2O Flux with Different Land Use Practices. Pp. 303-311 in: J.van Ham et al. eds. Non-CO2 Greenhouse Gasses: Scientific Understanding, Control, and Implementation. Kluwer Academic Publishers. Netherlands. Del Grosso, S.J., W.J. Parton, A.R. Mosier, M.D. Hartman, J. Brenner, D.S. Ojima, and D.S. Schimel. 2001. Simulated interaction of carbon dynamics and nitrogen trace gas fluxes using the DAYCENT model. Pages 303-332 In: M.J. Shaffer, L. Ma and S. Hansen (eds.) Modeling Carbon and Nitrogen Dynamics for Soil Management. Lewis Publishers. Boca Raton, Florida. Del Grosso, S.J., W.J. Parton, A.R. Mosier, M.D. Hartman, C.A. Keough, G.A. Peterson, D.S. Ojima, D.S. Schimel. 2001. Simulated effects of land use, soil texture, and precipitation on N gas emissions using DAYCENT. Pages 413-431 In: Follett, R.F., Hatfield, J.L. (eds.), Nitrogen in the Environment: Sources, Problems, and Management, Elsevier Science Publishers, The Netherlands. Eitzinger, J., W.J. Parton, and M. Hartman. 2000. Improvement and validation of a daily soil temperature submodel for freezing/thawing periods. Soil Science 165:525-534. Kelly, R.H., W.J. Parton, M.D. Hartman, L.K. Stretch, D.S. Ojima, and D.S. Schimel. 2000. Intra-annual and interannual variability of ecosystem processes in shortgrass steppe. Journal of Geophysical Research. 105:D15:20093-20100. Parton, W.J., A. Haxeltine, P. Thornton, R. Anne, and M. Hartman. 1996. Ecosystem sensitivity to land-surface models and leaf area index. Global and Planetary Change. 13:89- 98. Parton, W.J., Hartman, M., Ojima, D., and David Schimel. 1998. DAYCENT and its land surface submodel: description and testing. Global and Planetary Change. 19:35-48. Parton, W.J., E.A. Holland, S.J. Del Grosso, M.D. Hartman, R.E. Martin, A.R. Mosier, D.S. Ojima and D.S. Schimel. 2001. Generalized model for NOx and N2O emissions from soils. Journal of Geophysical Research 106:17403-17419.

18. snowmelt winter Snowmelt: ANC modelled too high Winter: ANC modeled too low