Remote sensing of variation of light use efficiency in two age classes of Douglas-fir

Relationship between Light Use Efficiency and Photochemical Reflectance Index Corrected Using a BRDF Model at a Subtropical Mixed Forest

“…Light use efficiency (LUE) is determined by environmental factors such as nutrients, moisture, and atmospheric temperature, resulting in differences in time and space in the photochemical reaction process. The photochemical reflectance index (PRI), based on remote sensing technology, provides the possibility to establish a link between changes in LUE and changes in the spectral characteristics of vegetation [9][10][11]. Some previous studies have shown that LUE is not a constant value in different ecosystems [12].…”

“…On a long-term seasonal scale, the change of PRI is driven by the ratio of carotenoid to chlorophyll pigment pools [9,[23][24][25]. Third, some studies have found that there is a good correlation between LUE and PRI in evergreen forests [11].PRI reflects the optical information of vegetation based on spectrometer observation. It is worth noting that the forest canopy, like most ground features, belongs to the non-Lambertian body, and it will show different degrees of anisotropy.…”

“…In general, multi-angle remote sensing observations are used to obtain multi-angle information of the vegetation canopy to improve the monitoring and inversion accuracy of crop biochemical parameters [26,27]. Recent studies provided that the eddy covariance (EC) based LUE and PRI, normalized by the bidirectional reflectance distribution function (BRDF) model, can be explored to validate the relationship [11].However, it is unclear whether PRI can capture LUE changes in subtropical forests, which are also among the most powerful types of carbon sequestration on earth. The lack of data contributes to the uncertainty in the relationship between PRI and LUE in subtropical evergreen coniferous mixed forests [28].…”

“…The lack of data contributes to the uncertainty in the relationship between PRI and LUE in subtropical evergreen coniferous mixed forests [28]. The results of two Northern forest studies in Canada show that the correlations between PRI and LUE are 0.74 and 0.79, respectively [11]. A study on evergreen broad-leaved forests in Malaysia showed that the correlation between PRI and LUE reached R 2 = 0.12.…”

“…The LAI e is an important parameter for quantitatively characterizing the vegetation canopy structure [32][33][34][35][36].Remote Sens. 2020, 12, 550 3 of 17 Therefore, investigating patterns of LUE changes across different canopy structures can provide insights into how differences in forest structure affect LUE [11,37].In this study, we investigated the relationship between PRI and LUE, obtained from measurements of an AMSPEC spectrometer and eddy covariance (EC) system in a subtropical mixed forest in China. The objectives of this study are: (1) to use the BRDF model to correct the PRI observed by a multi-angle spectrometer;(2) to study the effects of environmental and climatic factors on the relationship between PRI and LUE, and analyze the changes in the relationship between the PRI and LUE; (3) to use the TLS data to extract the vegetation canopy structure parameters, and to determine the influence of the vegetation canopy structure on LUE.…”