Modeling Carbon and Nitrogen Dynamics in the Soil-Plant-Atmosphere System

It is generally agreed that soils play an important role in gaseous exchange and water and matter dynamics in terrestrial ecosystems. Much experimental work has been undertaken in the last few years in attempts to quantify the emission of greenhouse gases in terrestrial ecosystems and to identify the key factors that govern them. However, fluxes vary greatly between ecosystems, and are often subject to great spatial and temporal variations, within ecosystems. Consequently, there is an essential role for modeling, to scale up observations made on relatively small areas to larger regions and ultimately to global level, and also to be able to predict the effects of environmental changes and changes in land management on future emissions. This chapter examines current knowledge regarding modeling approaches employed to describe soil-atmosphere gaseous exchange and carbon and nitrogen dynamics in soils. The extent to which the models have been used for predictive purposes for different natural and managed systems and at different levels of spatial aggregation is discussed. Since the number of models available is far too great to cover comprehensively, only examples are given to illustrate different types of model, and the modeling approaches applicable to different scales.