标题: A modified two-leaf light use efficiency model for improving the simulation of GPP using a radiation scalar
作者: Guan, XB (Guan, Xiaobin); Chen, JM (Chen, Jing M.); Shen, HF (Shen, Huanfeng); Xie, XY (Xie, Xinyao)
来源出版物: AGRICULTURAL AND FOREST METEOROLOGY 卷: 307 文献号: 108546 DOI: 10.1016/j.agrformet.2021.108546 出版年: SEP 15 2021
摘要: Two-leaf light use efficiency (TL-LUE) models are efficient methods to simulate regional and global gross primary productivity (GPP). A TL-LUE model has previously been shown to outperform the big-leaf MOD17 model through separate consideration of the contributions of sunlit and shaded leaves. However, the impacts of radiation intensity on LUE are inadequately considered in the TL-LUE model, and the maximum LUEs of sunlit and shaded leaves are assigned as different constants, which often induce large uncertainties. Therefore, a TL-LUE model modified with a radiation scalar (RTL-LUE) is developed in this paper. The same maximum LUE is used for both sunlit and shaded leaves, and the difference in LUE between sunlit and shaded leaf groups is determined by the same radiation scalar. The RTL-LUE model was calibrated and validated at global 169 FLUXNET eddy covariance (EC) sites. Results indicate that although GPP simulations from the TL-LUE model match well with the EC GPP, the RTL-LUE model can further improve the simulation, for half-hour, 8-day, and yearly time scales. The TL-LUE model tends to overestimate GPP under conditions of high incoming photosynthetically active radiation (PAR), because the radiation-independent LUE values for both sunlit and shaded leaves are only suitable for low-medium (e.g., average) incoming PAR conditions. The errors in the RTL-LUE model show lower sensitivity to PAR, and its GPP simulations can better track the diurnal and seasonal variations of EC GPP by alleviating the overestimation at noon and growing seasons associated with the TL-LUE model. This study demonstrates the necessity of considering a radiation scalar in GPP simulation in LUE models even if the first-order effect of radiation is already considered through differentiating sunlit and shaded leaves. The simple RTL-LUE developed in this study would be a useful alternative to complex process-based models for global carbon cycle research.
作者关键词: Gross Primary Productivity; Light Use Efficiency Models; Two-Leaf Models; Radiation Scalar; Eddy Covariance Flux Measurements
地址: [Guan, Xiaobin; Shen, Huanfeng] Wuhan Univ, Sch Resource & Environm Sci, Wuhan 430079, Peoples R China.
[Guan, Xiaobin; Chen, Jing M.] Univ Toronto, Dept Geog & Planning, Toronto, ON M5S 3G3, Canada.
[Chen, Jing M.] Fujian Normal Univ, Sch Geog Sci, Fuzhou 350117, Peoples R China.
[Shen, Huanfeng] Collaborat Innovat Ctr Geospatial Technol, Wuhan 430079, Peoples R China.
[Xie, Xinyao] Chinese Acad Sci, Inst Mt Hazards & Environm, Chengdu 610041, Peoples R China.
通讯作者地址: Chen, JM (通讯作者)，Univ Toronto, Dept Geog & Planning, Toronto, ON M5S 3G3, Canada.
Chen, JM (通讯作者)，Fujian Normal Univ, Sch Geog Sci, Fuzhou 350117, Peoples R China.
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