Development of a model for evaluation of biogeochemical interactions between the atmosphere and terrestrial ecosystems

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This study constructed a model for simulating biogeochemical interactions between the atmosphere and biosphere, particularly concerning greenhouse gas exchange. We put focus of the exchange of carbon dioxide (CO_2), methane (CH_4), and nitrous oxide (N_2O), because terrestrial ecosystems exchange these important greenhouse gases. Based on a process-based terrestrial ecosystem model (Sim-CYCLE), several schemed of CH_4 oxidation and N_2O emission were introduced. Two schemed of CH_4 oxidation, by Ridgewell et al. (1999) and Potter et al. (1996a), were considered, and also two schemes of N2O emission, by Parton et al. (1996) and Potter et al. (1996b), were tried. The model was applied to a cool-temperate deciduous broad-leaved forest and an evergreen needle-leaved forest in central Japan. Also, we examined the estimated ecosystem and soil respiration rates by comparing with flux measurement data, implying model validity and some problems in retrieving short-term variability in nighttime ecosystem respiration. These results were presented at the IGBP-iLEAPS Conference at Boulder, and partly published as a scientific paper. To examine the range of uncertainty in model estimation, we compared simulation results using different climate datasets, including the new Japanese dataset (JRA25), and using different ecosystem models. This intercomparison study suggested that simulation results would be strongly dependent on input data and ecosystem model used. The results were published from a coupled of scientific papers.