Modeling the Production, Decomposition, and Transport of Dissolved Organic Carbon in Boreal Soils

Abstract

Abstract: The movement of dissolved organic carbon (DOC) throughboreal ecosystems has drawn increased attention because of its poten-tial impact on the feedback of OC stocks to global environmentalchange in this region. Few models of boreal DOC exist. Herewe presenta one-dimensional modelwith simultaneous production, decomposition,sorption/desorption, and transport of DOC to describe the behavior ofDOC in the OC layers above the mineral soils. The field-observed con-centration profiles of DOC in two moderately well-drained black spruceforest sites (one with permafrost and one without permafrost), coupledwith hourly measured soil temperature and moisture, were used to in-versely estimate the unknown parameters associated with the sorption/desorption kinetics using a global optimization strategy. The model,along with the estimated parameters, reasonably reproduces the con-centration profiles of DOC and highlights some important potentialcontrols over DOC production and cycling in boreal settings. Thevaluesof estimated parameters suggest that humic OC has a larger potentialproduction capacity for DOC than fine OC, and most of the DOCproduced from fine OC was associated with instantaneous sorption/desorption whereas most of the DOC produced from humic OC wasassociated with time-dependent sorption/desorption. The simulatedDOC efflux at the bottom of soil OC layers was highly dependent onthe component and structure of the OC layers. The DOC efflux wascontrolled by advection at the site with no humic OC and moist con-ditions and controlled by diffusion at the sitewith the presence of humicOC and dry conditions.Key words: Black spruce, boreal, carbon, advection, diffusion,inversion.(Soil Science 2010;175: 223Y232)