Development of advanced evaluation method for terrestrial CO2 budget by improving nitrogen-cycle processes

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Temperature and nitrogen manipulation experiments were conducted in a forest ecosystem in Japan to understand the responses of ecosystem function and structure to the changes in temperature and nitrogen deposition. Environmental control on the CO2 exchange between ecosystems and the atmosphere was also investigated using long-term CO2 flux data over various ecosystems in Japan and in Asia. In addition, a terrestrial biosphere model was upgraded to consider nitrogen cycling processes based on the observed data from various ecosystems. The model successfully simulated the seasonal patterns of C/N ratio in the canopy leaves as well as the ecosystem carbon budget. The carbon and nitrogen budgets in terrestrial ecosystems around Japan were estimated by the model with a spatial resolution of 1km, and the temporal and spatial variations were analyzed in the viewpoint of responses of ecosystems to the changes in the atmospheric nitrogen deposition.