Simulating the effect of surface residue on the energy, water and carbon budgets within and above a temperate deciduous forest

About 550 g m-2 of dry weight of leaf litter accumulates annually during the fall season on the floor below the deciduous oak forest of the Oak Ridge, TN research reservation. This large quantity of leaf litter takes nearly few years to decompose completely into humus soil surface material and the slow decomposition allows for a thick litter layer of about 0.05 m to persist on the forest floor. The presence of the litter layer over the soil surface influences the soil evaporation, heat conduction, and carbon flux, but routine field measurements of the conditions within the litter layer are tedious, time consuming, and expensive. To get a handle on some of the measurement issues, an Atmosphere-Vegetation-Land Exchange surface energy balance model called ALEX was successfully modified with a robust routine to account for the impact of the surface leaf litter on the forest floor exchange processes. The model successfully simulated the water content, evaporation, and heat conduction within the litter layer, as well as the water, energy, and carbon budgets at the soil surface and in the immediate atmosphere above the vegetation canopy; however, the modified model improved the simulation of the soil surface temperature and soil heat conduction. Results of this study demonstrate that correct representation of the land surface variability underneath the vegetation canopy is required in order to successfully simulate land-vegetation-atmosphere interactions