Simulating fluorescence light-canopy interaction in support of laser-induced fluorescence measurements

Abstract

In the Netherlands an operational field instrument for the measurement of laser induced fluorescence of vegetation (LEAF) is developed. In addition, plant physiological and remote sensing research is done to support this new remote sensing instrument. This paper presents a general introduction on the subject of laser-induced fluorescence, including the relation between chlorophyll fluorescence and photosynthesis, spectral characteristics, and previous research. Also the LEAF .system is briefly described. Subsequently, the development of a leaf fluorescence model (KMF) and a canopy fluorescence model (FLSAIL) are reported. With these simulation models a sensitivity study is carried out. Fluorescence of 685 nm appears to be most suitable to obtain information on photosynthesis and stress, but is also influenced by canopy structure. Separation of these two effects is studied.

FluorMODleaf: A new leaf fluorescence emission model based on the PROSPECT model

“…In this approach, radiation inside a homogeneous medium is modeled by two fluxes traveling in opposite directions and the leaf is characterized by an absorption coefficient k and a scattering coefficient s. At any wavelength λ, the reflectance R(λ) and transmittance T(λ) can be derived analytically as a function of these two coefficients. An adaptation of the KM theory to fluorescing media has been introduced by Allen (1964), whereas Fukshansky and Kazarinova (1980) and Rosema et al (1991) extended it to the case of a leaf. Here we use an analytical expression of the first order fluorescence emission, called KMF, derived by integration of the KM propagation equation with Mathematica (Wolfram Research, Inc., Champaign, USA) (see Appendix A).…”

“…The simplest ones assume an exponential light decay within the blade, which follows Beer's law (Agati et al, 1993;Ounis et al, 2001). The Kubelka-Munk differential equations are preferred by Rosema et al (1991), Zarco-Tejada et al (2000), and Ramos and Lagorio (2004) who solve the system analytically by successive approximations or numerically using the adding-doubling technique. Other approaches like Markov chains (Maier, 2000) or Monte Carlo photon transport (Sušila & Nauš, 2007) have also been developed.…”

FLEX: an imaging spectrometer for measurement of vegetation fluorescence

“…For example about 10 years ago in the Netherlands a sensor called LEAF (= Laser Environmental Active Fluorosensor) was developed both for field measurements (distance < 100 m) and conditioned laboratory investigations 3,4 . Herewith the first steps for remote sensing application have been made, albeit for application at a moderate distance.…”

Progress on the development of an integrated canopy fluorescence model

“…The literature on canopy level fluorescence models presents only the model of Olioso et al [9] and the FLSAIL model [10].…”

“…Recent modeling of chlorophyll fluorescence at the leaf level for broad band illumination has been carried out with the FRT (Fluorescence-Reflectance-Transmittance) model [7] which used an adaptation of a doubling method solution of the Kubelka-Munk equations [10] and a two Gaussian representation of the fluorescence emission peaks near 690 nm and 740 nm. In another approach, the SLOP (Stochastic model for Leaf Optical Properties) model [8] has been used to investigate the chlorophyll fluorescence contribution to the observed reflectance signature.…”