1. Hangzhou Dianzi Univ, Coll Life Informat Sci & Instrument Engn, Hangzhou 310018, Peoples R China
2. Chinese Acad Sci, Acad Optoelect, Key Lab Quantitat Remote Sensing Informat Technol, Beijing 100094, Peoples R China
3. Univ Tuscia, Dept Agr & Forestry Sci DAFNE, Via San Camillo de Lellis, I-01100 Viterbo, Italy
4. ARS, USDA, Crop Prod Syst Res Unit, Stoneville, MS 38776 USA
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Abstract
Accurate estimation of the ratio of carotenoid (Car) to chlorophyll (Chl) content is crucial to provide valuable insight into diagnoses of plant physiological and phenological status in crop fields. Studies for assessing the ratio of Car to Chl content have been extensively conducted with semi-empirical approaches using spectral indices. However, spectral indices established in previous studies generally relied on site- or species-specific measured data and these indices typically lacked sufficient estimation accuracy for the ratio of Car to Chl content to be used across various species and under different physiological conditions. In this study, we propose a novel combined carotenoid/chlorophyll ratio index (CCRI) in the form of the carotenoid index (CART) divided by the red-edge chlorophyll index (CIred-edge): The value of the index is illustrated using synthetic data simulated from the leaf radiative transfer model PROSPECT-5 and with extensive measured datasets at both the leaf and canopy level from the ANGERS dataset and winter wheat and maize field experiments. Results show that CCRI was the index with the highest correlation with the ratio of Car to Chl content in PROSPECT-5 simulations (R-2 = 0.99, RRMSE = 8.65%) compared to other spectral indices. Calibration and validation results using the ANGERS and winter wheat leaf level data showed that CCRI achieved accurate estimation of the ratio of Car to Chl content (R-2 = 0.52, RRMSE = 14.10%). CCRI also showed a good performance (R-2 = 0.54, RRMSE = 17.08%) for estimation of the ratio of Car to Chl content in both calibration and validation with the winter wheat and maize canopy spectra measured in field experiments. Further investigation of the effect of the correlation between leaf Chl and Car content on the performance of CCRI indicated that variation of the correlation affected the retrieval accuracy of CCRI, and CCRI might not be very sensitive to changes of the ratio of Car to Chl content with low values (< 0.10).
Key words
Ratio of Car to Chl content/Hyperspectral/Spectral index/Leaf optical modeling/Crop monitoring
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出版年
2019
International journal of applied earth observation and geoinformation
NSTL
Elsevier