MODELING PRIMARY PRODUCTIVITY OF THE TERRESTRIAL BIOSPHERE IN CHANGING ENVIRONMENTS - TOWARD A DYNAMIC BIOSPHERE MODEL

There is a widespread perception that the atmosphere and the climate a re beginning to change, and that these changes could have profound imp acts on the primary productivity of the terrestrial biosphere. The ter restrial biosphere is a dynamic system that interacts with the atmosph ere and climate principally through the exchanges of energy, water, an d elements. Due to the limitations of equilibrium terrestrial biospher e models, new generation models - dynamic biosphere models, are critic ally needed for assessing and predicting the primary production and bi ogeochemical cycles of the terrestrial biosphere in changing global en vironment. The goal of dynamic biosphere modeling is to model terrestr ial ecosystem dynamics induced by natural and anthropogenic disturbanc es, as well as the interactions of energy, water, and carbon cycles wi thin the terrestrial biosphere and between the terrestrial biosphere a nd the atmosphere. The critical gaps in developing such a terrestrial biosphere model are not our inability to construct model code but inst ead the poorly developed links between empiricism and the concepts we used to construct our models, especially a lack of data that would hel p to make our models mechanistic, an incomplete fundamental knowledge about how complex terrestrial ecosystems work, a poor understanding of how to scale up what we do know and of how to validate such a model. The interaction among data, model structure, parameter sets, and predi ctive uncertainty will Bead to important progress in the development o f dynamic biosphere models.