Evapotranspiration Patterns for Tropical Rainforests in Southeast Asia: A Model Performance Examination of the Biome-BGC Model.

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Ecosystem simulations of tropical rainforest biomes can significantly lead to a better understanding of global primary productivity. Our study site was located at Lambir Hills National Park (4°12’N, 114°02’E) Sarawak, Malaysia. Our main objective was to examine the application of Biome-BGC in estimating evapotranspiration and carbon dynamics. Meteorological data collected in an undisturbed lowland evergreen tropical forest were used asthe main inputs for a Biome-BGC model. Meteorological data, such as temperature, precipitation, shortwave radiation and vapor pressure deficit were used in the model. They were collected for the period from July 2001 to June 2002. Several modifications of individual ecophysiological parameters were necessary to obtain a reasonable modeled estimation and to corroborate the observational data. Our final modified parameter result showed that the leaf area index, LAI was simulated at an estimated value of 5.29 m2m-2, which was within the observational range of 4.8 – 6.8 m2m-2. The simulated annual interception value was 197.57mm with CWI=0.01. With the boundary layer conductance ratio, gb and the maximum stomatal conductance ratio, gs values 0.02 and 0.005, the simulated total transpiration and soil evaporation was estimated at 947.88, which was 20% lower than the observational result. However, our annual modeled evapotranspiration, ET, computed using the Biome-BGC model showed a slightly lower amount, 1145.47mm, compared to the observed annual ET which totaled 1401.1mm. A consistent pattern of seasonality was discovered in the modeled and observational results. This was clearly shown in the months of October 2001 and November 2001 with large values of monthly ET, and low values of monthly ET in the months of December 2001 and January 2002. In our simulation for the net carbon balance, the net ecosystem productivity (NEP) value was estimated to be positive and have a value of 0.68 tC ha-1 year-1. The NEP is usually positive and indicates that, according to the model, the Lambir Hills National Park has reached a certain maturity point. The net primary production, NPP, of the undisturbed tropical rainforest was estimated at 4.19 tC ha-1 year-1. Observational gross primary productivity, GPP, in Lambir Hills National Park, was slightly higher compare with annual simulated GPP estimated at 24.5 tC ha-1year-1 In conclusion, the proposed parameters in this paper shows a good correspondence with evapotranspiration and LAI, while GPP was slightly underestimated.生態系の水・炭素循環を再現するBiome －BGCモデルの東南アジア熱帯雨林への適用性をマレーシア，サラワク州ランビル国立公園（4º12’N, 114º02’E）の熱帯雨林で観測された各種の観測記録を用いて検討した。ランビル国立公園は，低地フタバガキ林で，蒸発散量，樹冠遮断量，NPP，地上部現存量などの観測値が蓄積されている。2001 年７月から2002 年６月のランビルの気象記録を用いて，温帯の常緑広葉樹林で得られたBiome －BGCモデルのパラメータセットによって求めた推定は，葉面積指数が小さく，蒸発散量が著しく小さい結果となった。光合成産物の地上部への分配割合，空気力学的コンダクタンス，気孔コンダクタンスのパラメータを変更すると，葉面積指数が観測結果に一致し，年間の蒸発散量とその季節変化をかなり再現する結果を得た。しかし，GPPと炭素蓄積量については水収支特性の再現性に比べて低い段階に留まった。
東京大学大学院農学生命科学研究科附属演習林,The Tokyo University Forests,Department of Forest Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo,kasuya Research Forest, Kyushu University,School of Forestry and Resourse Conservation, National Taの論文

Evapotranspiration Patterns for Tropical Rainforests in Southeast Asia: A Model Performance Examination of the Biome-BGC Model.

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