Abstract
The PROSPECT leaf optical model has, to date, well-separated the effects of total chlorophyll and carotenoids on leaf reflectance and transmittance in the 400–800 nm. Considering variations in chlorophyll a:b ratio with leaf age and physiological stress, a further separation of total plant-based chlorophylls into chlorophyll a and chlorophyll b is necessary for advanced monitoring of plant growth. In this study, we present an extended version of PROSPECT model (hereafter referred to as PROSPECT-MP) that can combine the effects of chlorophyll a, chlorophyll b and carotenoids on leaf directional hemispherical reflectance and transmittance (DHR and DHT) in the 400–800 nm. The LOPEX93 dataset was used to evaluate the capabilities of PROSPECT-MP for spectra modelling and pigment retrieval. The results show that PROSPECT-MP can both simultaneously retrieve leaf chlorophyll a and b, and also performs better than PROSPECT-5 in retrieving carotenoids concentrations. As for the simulation of DHR and DHT, the performances of PROSPECT-MP are similar to that of PROSPECT-5. This study demonstrates the potential of PROSPECT-MP for improving capabilities of remote sensing of leaf photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids) and for providing a framework for future refinements in the modelling of leaf optical properties.
Highlights
Monitoring the biochemical constituents of plant leaves using remote sensing techniques can improve our understanding of the dynamics of vegetation physiological and ecological functions
In view of the above the present study develops an algorithm for the separation of multiple photosynthetic pigment absorption coefficients (Chla, chlorophyll b (Chlb) and Cars) by using a modified G-L function, and proposes an extended version of the PROSPECT model in the 400–800 nm range, referred to as PROSPECT-Multiple Pigment (PROSPECT-MP)
This paper demonstrates that the extended version of PROSPECT (PROSPECT-MP) proposed in this study can reliably simulate leaf hemispherical reflectance and transmittance in the 400–800 nm region, and it can retrieve accurately, multiple photosynthetic pigment concentrations comparing to PROSPECT-5 from spectra of fresh leaves by model inversion
Summary
PROSPECT models are a type of leaf radiative transfer (RT) models, which have been widely used in the remote sensing community[4, 12]. Until PROSPECT-5 version, this model separated photosynthetic pigments into total chlorophylls and carotenoids Within this version (PROSPECT-5), the separation of Chls and Cars absorption coefficients was band-by-band derived based on a minimum distance fitting method using modeled and measured in vivo spectra[13]. With this method, the specific absorption coefficients of Chla and Chlb could not be separated in PROSPECT-511. G-L function fitting can be applied in the spectral absorption peak separation of mixed constituents by fitting the parameters (absorption peak height, full width at half maximum (FWHM) and Gauss ratio), given the absorption peak number and position[14] These parameters holds explicit physical significance of material absorption spectra. PROSPECT-MP is capable of incorporating the in vivo absorption coefficients of Chla, Chla and Cars pigments and describes leaf optical properties from 400 to 800 nm in order to facilitate the simultaneous retrieval of these multiple individual photosynthetic pigment concentrations by model inversion
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