An advanced leaf optical properties model including photosynthetic pigments

PROSPECT, a widely-used leaf directional-hemispherical reflectance and transmittance model, currently treats the behaviour of chlorophylls a, b, carotenoids, and anthocyanins uniformly, leading to errors. A finer discrimination among these pigments in light-absorbing plant tissues should improve the model. In this paper, a new calibration and validation phase of PROSPECT is performed using two comprehensive databases containing hundreds of leaves collected in temperate latitudes in Angers, France, and in a tropical environment in Hawaii, USA. Leaf biochemical (chlorophylls a, b, carotenoids, water, and dry matter) and optical properties (directional-hemispherical reflectance and transmittance measured from 400 nm to 2500 nm) were measured and used in the model development steps. The first step consists in providing distinct in vivo specific absorption coefficients for the leaf pigments using the Angers database. The model is then inverted to predict the biochemical content of intact leaves from both data sets. The main result of this preliminary study is that the new chlorophyll and carotenoid specific absorption coefficients are in good agreement with available in vitro absorption spectra, that the chlorophyll predictions are improved, and that the carotenoids are reasonably retrieved.