THE INFLUENCE OF THE TERRESTRIAL BIOSPHERE ON SEASONAL ATMOSPHERIC CARBON DIOXIDE: AN EMPIRICAL MODEL (CLIMATE, VEGETATION, SOIL RESPIRATION)

A simple global model of the seasonal exchange of CO(,2) between the biosphere and the atmosphere has been developed. The model is climate-driven allowing vegetation types as well as carbon fluxes to adjust to perturbed climates. Output from the model consists of two fluxes--one directed toward the biosphere the other directed toward the atmosphere. The prescription for change in vegetation type in response to climate change is based on annual temperature and precipitation. The carbon fluxes are based on published field and laboratory measurements of photosynthesis and soil respiration, which have been empirically related to climate variables. The biosphere-atmosphere exchanges are tested by comparing predicted atmospheric CO(,2) concentrations with observations at a number of monitoring stations.; Because the model incorporates spatial and temporal variability of vegetation at climate modeling resolution, the carbon fluxes are biologically more realistic than those of earlier global biospheric carbon models. This research is a first step toward relating climatic variables to seasonal properties of vegetation which influence atmospherically-important biospheric exchanges.