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Chinese Journal of Applied Ecology ›› 2017, Vol. 28 ›› Issue (8): 2461-2469.doi: 10.13287/j.1001-9332.201708.024

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Simulating canopy reflectance time series for typical subtropical forest by coupling PROSPECT5 and 4SAIL models

ZHANG Lu-ying1,2,3, LI Xue-jian1,2,3, DU Hua-qiang1,2,3*, CUI Lu1,2,3, MAO Fang-jie1,2,3, LIU Yu-li1,2,3, LI Yang-guang1,2,3, ZHU Di-en1,2,3   

  1. 1State Key Laboratory of Subtropical Silviculture, Lin’an 311300, Zhejiang, China
    2Zhejiang Province Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration, Lin’an 311300, Zhejiang, China
    3School of Environmental and Resources Science, Zhejiang A&F University, Lin’an 311300, Zhejiang, China
  • Received:2017-01-22 Published:2017-08-18
  • Contact: * E-mail: dhqrs@126.com
  • Supported by:
    This work was supported by the National Natural Science Foundation (31670644, 31370637), the Joint Research fund of Department of Forestry of Zhejiang Province and Chinese Academy of Forestry (2017SY04) and the Natural Science Foundation of Zhejiang Province (LR14C160001, LQ15C160003)

Abstract: Canopy reflectance has important meanings in the aspects of accurate interpretation of forest vegetation type and key parameter (leaf area index, chlorophyll content, etc.) retrieval of forest carbon assimilation. In this study, the canopy reflectance time series of three typical subtropical forests (moso bamboo forest, MBF; lei bamboo forest, LBF; evergreen and deciduous broadleaf forest, EDBF) was simulated by coupling PROSPECT5 and 4SAIL models. First, the sensitivity of parameters in PROSPECT5 and 4SAIL model was analyzed to discuss the effects of parameters on the canopy reflectance simulation. Second, unsensitive parameters were optimized using the observed reflectance. Finally, the canopy reflectances of three typical subtropical forests were simulated using PROSPECT5 and 4SAIL models, and compared with MODIS reflectance dataset. The results showed that leaf area index was most sensitive to bands 1, 2, 3, 5 and 7, with the total-order sensitivity indexes of 0.80, 0.83, 0.49, 0.66 and 0.47, respectively. Chlorophyll content was most sensitive to band 4, with the total-order sensitivity index of 0.59. Leaf water content was most sensitive to band 6, with the total-order sensitivity index of 0.54. Leaf structure, carotenoids content, dry matter content, hot parameter and soil factors were not/low sensitive to these bands. Canopy reflectance simulated using the optimized PROSPECT5 and 4SAIL models had the capability in reflecting the real seasonal changes of three typical subtropical forests. The simulated canopy reflectance significantly correlated with MODIS reflectance, with high R2 of 0.86, 0.90, 0.93, and low root mean square of 0.09, 0.07, 0.05 for MBF, LBF, and EDBF, respectively. The simulated canopy reflectance solved to some extent the problems of influence on MODIS reflectance products by precipitation and snow in winter, and mixed pixels.