Evaluating a Dissolved Organic Carbon Model For Daycent Within a Bayesian Framework.

The water-driven movement of dissolved organic carbon (DOC) through soils is an important component of vertical carbon (C) dynamics, acting as a C transport mechanism down the soil profile. DAYCENT- a widely used process-based plant/soil ecosystem model- is typically used to simulate plant/soil C and nitrogen dynamics as well as trace gas fluxes and other ecosystem variables in surface soil layers, generally from 0 – 20 or 30cm. Currently DAYCENT does not explicitly model DOC movement with water flow, which limits its ability to simulate vertical soil C dynamics and deep soil C storage. This affects the use of DAYCENT to evaluate bioenergy feedstock production systems, where deep-rooted and perennial species are considered in part for their potential contributions to soil C storage in deeper soil layers. We propose adding a DOC pool to the conceptual 3-pool DAYCENT soil C submodel, allowing us to use DAYCENT to simulate vertical C and deep soil C dynamics. We evaluated a proposed DOC model for the surface litter layer, testing model performance against experimental data for several types of litter using a Bayesian approach. We propose incorporating this soil DOC model into DAYCENT’s soil C submodel, to allow for the simulation of vertical soil C transfer by DOC. Combined with other vertical C movement mechanisms in soils, such as root inputs and animal mixing, this will allow us to develop the simulation of deep soil C dynamics in DAYCENT and improve the comparative evaluation of bioenergy feedstock production systems.