Miguel Arango, Kansas State University, Manhattan, KS, Charles W. Rice, 2701 Throckmorton Hall, Kansas State University, Manhattan, KS, Jean L. Steiner, USDA-ARS Grazinglands Research Laboratory, El Reno, OK and Ali Saleh, Texas Institute for Applied Environmental Research, Stephenville, TX
Agricultural sector is a significant source of greenhouse gas emissions (GHG). In the U.S. the agricultural sector accounts for about 7.4% of the total emissions. The Central Great Plains region provides a source of CH4 and N2O associated with the beef-grazing systems. A number of process-based models have been used to estimate terrestrial C fluxes storage and greenhouse gas emissions. Among those models the Denitrification Decomposition model (DNDC) has shown success simulating C fluxes and GHG emission from cropping systems. The objective of this work is to evaluate the potential of DNDC model to simulate gross primary production (GPP), net ecosystems exchange (NEE), ecosystem respiration (ER) and soil greenhouse gases (N2O, CH4 and CO2). Carbon and N fluxes, and soils datasets from Konza Prairie experimental station (KZ), KS (2007-2012,2014) and from the Grasslands Research Laboratory (ARS-ER),OK (2005-2006,2014) were used to validated DNDC model. The DNDC was run for several years prior the validation years in order to achieve steady-state SOC pools. DNDC was not able to simulate properly C and N fluxes at the KZ site. However, the model was able to capture fluctuation in the end-of-season plant biomass due to changes in climate. DNDC was successful simulating C fluxes at the ARS-ER site. Plant biomass (monthly measurements) as well as N2O and CH4 emissions were not captured appropriately by the model. DNDC showed promising results simulating C and N fluxes from grassland ecosystems, even thought additional work is required to implement burning as well as better animal deposition events in grazing system.