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www.biogeosciences-discuss.net/6/8311/2009/
doi:10.5194/bgd-6-8311-2009
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Simulating carbon and water cycles of larch forests in East Asia by the BIOME-BGC model with AsiaFlux data
1Osaka Prefecture Univ., Graduate School of Life and Environmental Sciences, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka, Japan
2Fukushima Univ., Faculty of Symbiotic Systems Science, 1 Kanayagawa, Fukushima, Japan
3National Institute for Agro-Environmental Sciences, 3-1-1 Kannondai, Tsukuba, Ibaraki, Japan
4Hokkaido University, Field Science Center for Northern Biosphere, North 3-jo West 8-chome, Sapporo, Hokkadio, Japan
5University of Tsukuba, Graduate School of Life and Environmental Sciences, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan
6Osaka University, Graduate School of Engineering, 2-1 Yamadaoka, Suita, Osaka, Japan
7Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Japan
8Nagoya University, Graduate School of Bioagricultural Sciences, Furo-cho, Chikusa Ward, Nagoya, Aichi, Japan
9National Institute for Environmental Studies, Center for Global Change Environmental Research, 16-2 Onogawa, Tsukuba, Ibaraki, Japan
10Hokkaido University, Research Faculty of Agriculture, Kita 9, Nishi 9, Kita-ku, Sapporo, Hokkadio, Japan
Abstract. Larch forests are widely distributed across many cool-temperate and boreal regions, and they are expected to play an important role in global carbon and water cycles. Model parameterizations for larch forests still contain large uncertainties owing to a lack of validation. In this study, a process-based terrestrial biosphere model, BIOME-BGC, was tested for larch forests at six AsiaFlux sites and used to identify important environmental factors that affect the carbon and water cycles at both temporal and spatial scales.
The model simulation performed with the default deciduous conifer parameters produced results that had large differences from the observed net ecosystem exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), and evapotranspiration (ET). Therefore, we adjusted several model parameters in order to reproduce the observed rates of carbon and water cycle processes. This model calibration, performed using the AsiaFlux data, significantly improved the model performance. The simulated annual GPP, RE, NEE, and ET from the calibrated model were highly consistent with observed values.
The observed and simulated GPP and RE across the six sites are positively correlated with the annual mean air temperature and annual total precipitation. On the other hand, the simulated carbon budget is partly explained by the stand disturbance history in addition to the climate. The sensitivity study indicates that spring warming enhances the carbon sink, whereas summer warming decreases it across the larch forests. The summer radiation is the most important factor that controls the carbon fluxes in the temperate site, but the VPD and water conditions are the limiting factors in the boreal sites. One model parameter, the allocation ratio of carbon between aboveground and belowground, is site-specific, and it is negatively correlated with the annual climate of annual mean air temperature and total precipitation. Although this study significantly improves the model performance, the uncertainties that remain in terms of the sensitivity to water conditions should be examined in ongoing and long-term observations.
Discussion Paper (PDF, 1844 KB) Interactive Discussion (Closed, 4 Comments) Final Revised Paper (BG)
Citation: Ueyama, M., Ichii, K., Hirata, R., Takagi, K., Asanuma, J., Machimura, T., Nakai, Y., Ohta, T., Saigusa, N., Takahashi, Y., and Hirano, T.: Simulating carbon and water cycles of larch forests in East Asia by the BIOME-BGC model with AsiaFlux data, Biogeosciences Discuss., 6, 8311-8357, doi:10.5194/bgd-6-8311-2009, 2009. Bibtex EndNote Reference Manager XML
