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Estimation of light-use efficiency of China’s midsubtropical planted coniferous forest based on flux measurements and spectral observations.

CHEN Die-cong1,2, WANG Shao-qiang1, HUANG Kun1,2, ZHOU Lei1, YU Quan-zhou1,2, WANG Hui-min1,3, SUN Lei-gang4   

  1. (1Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; 2University of Chinese Academy of Sciences, Beijing 100049, China; 3Qianyanzhou Integrated Ecological Station of Red Soil Hilly Land, Chinese Academy of Sciences, Taihe 343700, Jiangxi, China; 4Institute of Geographical Sciences, Hebei Academy of Sciences, Shijiazhuang 050000, China)
  • Online:2015-11-18 Published:2015-11-18

Abstract: The photochemical reflectance index (PRI) calculated from spectral reflectance has universally become a proxy for the lightuse efficiency (LUE), which significantly improves the LUEbased estimation of ecosystem gross primary productivity on a large scale through upscaling. In this study, we observed the vegetation spectral reflectance of a planted subtropical coniferous forest from the top of a flux tower at Qianyanzhou Station, one of the ChinaFLUX sites, in September and December 2013, and simultaneously measured CO2 flux and meteorological variables for correlation and regression analysis. Results showed that PRI had a better correlation with LUE (R2=0.20, P<0.001) than that of normalized difference vegetation index (NDVI), i.e., PRI was preferred in LUE retrieval. During the whole observation period, PRI and soil water content (SWC)based bivariate regression model correlated well with LUE (R2=0.29, P<0.001 and R2=0.30, P<0.01 for daytime and midday observation, respectively), but in autumn the bivariate regression model of PRI and vapor pressure deficit (VPD) had a higher correlation with LUE (R2=0.448, P<0.001) for midday observation, which showed that environmental factors, i.e., SWC and VPD, had a potential in improving the LUE retrieval from PRI, but the choice of appropriate environmental factors depended on season.