Terrestrial Ecosystem Model Group Figure: An overview of our model studies of CO2 exchange between the atmosphere and terrestrial ecosystems This group is working on modeling of carbon dioxide (CO2) exchange between terrestrial ecosystems (e.g., forest and grassland) and the atmosphere, to simulate the responses to global environmental change. This issue is important, because terrestrial CO2 exchange should affect the global warming in the future, as the Kyoto Protocol takes net CO2 uptake by forests into account. The carbon cycle model we are developing is a simple box-flow model, in which photosynthetic CO2 uptake and respiratory CO2 release are simulated in a mechanistic manner. The model estimation of CO2 exchange has been validated by comparing with observational data at several sites, which were obtained by micrometeorological methods. To apply the model to various sites, we are actively participating in several projects and collaborating with external research groups. On the other hand, the model is used to estimate vegetation productivity and ecosystem. Figure: A virtual forest model, which explicitly represent three-dimensional forest architecture. This model will clarify relationships between physiological processes and vegetation dynamics at forest stand level. The purpose of this subgroup (Ecosystem Architecture Model) is to forecast long-term changes in forest ecosystems, which form the largest terrestrial organic carbon pool, in response to climate and environment change, through modeling ecological processes at various scales paying attention to three-dimensional ecosystem architecture. To predict long-term dynamics of forest systems, this subgroup intends to fill the gap between physiological processes and tree population processes applying individual-tree-based model, and extending stand-based simulators to geographic scale to predict forest-zone response to climatic change.