Long-Term Carbon Dioxide Exchange Measurements above Japanese Forests by FFPRI FluxNet

AsiaFlux has started in September 2000. In the East Asia, the development of flux observation of heat, water vapor and carbon dioxide is expected for the various types of the terrestrial ecosystems especially characterized by the monsoon climate, complex terrain and human impacts. In relation to global change, the forest function of carbon dioxide uptake has attracted considerable attention, though the data insufficiency still stands in the way of positive discussion in the East Asia. Then we have to clarify the exchanging processes of energy and carbon dioxide between the forest and the atmosphere by intensive observations, and accumulate data for the establishment and the testing of biome models. In Forestry and Forest Products Research Institute (FFPRI), the flux observation of heat, water vapor and carbon dioxide was initiated at Kawagoe forest site in 1995. After the establishment of the fundamental instrumentation, the flux observation was extended to six forest sites, named FFPRI FluxNet, since 1999. Those are different in latitude and forest type, and widely distributed in Japan. In the presentation, approaches to determine the annual carbon dioxide uptake are introduced for individual sites; cool-temperate deciduous broadleaf forest (Sapporo), temperate beech forest (Appi), warm-temperate deciduous broadleaf forest (Kawagoe), temperate pine forest (Fujiyoshida), warm-temperate mixed forest on complex terrain (Yamashiro), and warm-temperate needle-leaf forest on complex terrain (Kahoku). We can report at present, the annual observed NEE in 2000 ranged from 286 to 566 gCm^-2yr^-1, which basically increases with the decrease of the latitude. This tendency may not be changed but the values will be modified, because the procedure for the data quality control is also now in progress.