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Mechanisms Underlying Diurnal Variations in the Canopy Spectral Reflectance of Winter Wheat in the Jointing Stage


Affiliations
1 International Institute for Earth System Science, School of Geographic and Oceanographic Sciences, Nanjing University, No.163, Xianlin Avenue, Qixia District, Nanjing, China
2 School of Urban and Rural Planning and Landscape Architecture, Xuchang University, No. 88, Bayi Road, Weidu District, Xuchang, China
3 Aerospace Information Research Institute, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, No. 20, Datun Road, Chaoyang District, Beijing, China
4 Henan Key Laboratory of Big Data Analysis and Processing, School of Computer and Information Engineering, Henan University, Jinming Avenue, Longting District, Kaifeng, China
 

Information regarding diurnal variations in vegetation canopy spectra and vegetation indices (VIs) is necessary for plant growth modelling. We analysed the diurnal change characteristics of canopy spectral reflectance and VIs of winter wheat in the jointing stage based on field-measured and simulated spectral data. The visible–near infrared reflectance showed a double peak followed by a deep trough. The double-peak period occurred from 11:00 to 13:00 h (UTC + 8), and reflectance fluctuated greatly during this period. This change was attributed to midday depression of photosynthesis caused by stomatal closure induced by strong solar radiation. We found that the vegetation canopy reflectance was mainly affected by photosynthesis rate, solar irradiation intensity and surplus leaf water content. All selected VIs (normalized difference vegetationindex (NDVI), photochemical reflectance index (PRI), water band index (WBI) and mSR705) exhibited distinct intraday variations, and VIs during the double-peak period tended to fluctuate strongly or decrease (NDVI, WBI and mSR705). Thus, field measurements during the double-peak period are not recommended for winter wheat in the jointing stage, with the exception of carotenoid content monitoring. A comparison of VIs showed that SVNIR, NDVI and mSR705 were more sensitive to canopy structure in comparison with PRI and WBI.

Keywords

Canopy Reflectance, Diurnal Variation, Jointing Stage, Photosynthesis Rate, Winter Wheat.
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  • Mechanisms Underlying Diurnal Variations in the Canopy Spectral Reflectance of Winter Wheat in the Jointing Stage

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Authors

Yinghao Lin
International Institute for Earth System Science, School of Geographic and Oceanographic Sciences, Nanjing University, No.163, Xianlin Avenue, Qixia District, Nanjing, China
Huaifei Shen
School of Urban and Rural Planning and Landscape Architecture, Xuchang University, No. 88, Bayi Road, Weidu District, Xuchang, China
Qingjiu Tian
International Institute for Earth System Science, School of Geographic and Oceanographic Sciences, Nanjing University, No.163, Xianlin Avenue, Qixia District, Nanjing, China
Xingfa Gu
Aerospace Information Research Institute, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, No. 20, Datun Road, Chaoyang District, Beijing, China
Ranran Yang
International Institute for Earth System Science, School of Geographic and Oceanographic Sciences, Nanjing University, No.163, Xianlin Avenue, Qixia District, Nanjing, China
Baojun Qiao
Henan Key Laboratory of Big Data Analysis and Processing, School of Computer and Information Engineering, Henan University, Jinming Avenue, Longting District, Kaifeng, China

Abstract


Information regarding diurnal variations in vegetation canopy spectra and vegetation indices (VIs) is necessary for plant growth modelling. We analysed the diurnal change characteristics of canopy spectral reflectance and VIs of winter wheat in the jointing stage based on field-measured and simulated spectral data. The visible–near infrared reflectance showed a double peak followed by a deep trough. The double-peak period occurred from 11:00 to 13:00 h (UTC + 8), and reflectance fluctuated greatly during this period. This change was attributed to midday depression of photosynthesis caused by stomatal closure induced by strong solar radiation. We found that the vegetation canopy reflectance was mainly affected by photosynthesis rate, solar irradiation intensity and surplus leaf water content. All selected VIs (normalized difference vegetationindex (NDVI), photochemical reflectance index (PRI), water band index (WBI) and mSR705) exhibited distinct intraday variations, and VIs during the double-peak period tended to fluctuate strongly or decrease (NDVI, WBI and mSR705). Thus, field measurements during the double-peak period are not recommended for winter wheat in the jointing stage, with the exception of carotenoid content monitoring. A comparison of VIs showed that SVNIR, NDVI and mSR705 were more sensitive to canopy structure in comparison with PRI and WBI.

Keywords


Canopy Reflectance, Diurnal Variation, Jointing Stage, Photosynthesis Rate, Winter Wheat.

References





DOI: https://doi.org/10.18520/cs%2Fv118%2Fi9%2F1401-1406