Vegetation Stress Detection through Chlorophyll a + b Estimation and Fluorescence Effects on Hyperspectral Imagery

Abstract

Physical principles applied to remote sensing data are key to successfully quantifying vegetation physiological condition from the study of the light interaction with the canopy under observation. We used the fluorescence-reflectance-transmittance (FRT) and PROSPECT leaf models to simulate reflectance as a function of leaf biochemical and fluorescence variables. A series of laboratory measurements of spectral reflectance at leaf and canopy levels and a modeling study were conducted, demonstrating that effects of chlorophyll fluorescence (CF) can be detected by remote sensing. The coupled FRT and PROSPECT model enabled CF and chlorophyll a + b (Ca + b) content to be estimated by inversion. Laboratory measurements of leaf reflectance (r) and transmittance (t) from leaves with constant Ca + b allowed the study of CF effects on specific fluorescence-sensitive indices calculated in the Photosystem I (PS-I) and Photosystem II (PS-II) optical region, such as the curvature index [CUR; (R675.R690)/R2(683)]. Dark-adapted and steady-state fluorescence measurements, such as the ratio of variable to maximal fluorescence (Fv/Fm), steady state maximal fluorescence (F'm), steady state fluorescence (Ft), and the effective quantum yield (delta F/F'm) are accurately estimated by inverting the FRT-PROSPECT model. A double peak in the derivative reflectance (DR) was related to increased CF and Ca + b concentration. These results were consistent with imagery collected with a compact airborne spectrographic imager (CASI) sensor from sites of sugar maple (Acer saccharum Marshall) of high and low stress conditions, showing a double peak on canopy derivative reflectance in the red-edge spectral region. We developed a derivative chlorophyll index (DCI; calculated as D705/D722), a function of the combined effects of CF and Ca + b content, and used it to detect vegetation stress.

Impact of scale insect infestation on the content of photosynthetic pigments and chlorophyll fluorescence in two host plant species

“…The impact of insect feeding often varies by plant species. According to the available information, leaf chlorophyll content is one of the most important factors in determining the rate of photosynthesis and a useful indicator of both potential photosynthetic productivity and general plant vigor (Zarco-Tejada et al 2002;Mao et al 2007). C. hesperidum infestation was shown to reduce the value of some of the analysed photosynthesis indicators in the leaves of their host plants: maximum quantum efficiency of photosystem PSII (F v /F m ), effective quantum gain of PSII [DF=F 0…”

A Novel Principal Component Analysis Method for the Reconstruction of Leaf Reflectance Spectra and Retrieval of Leaf Biochemical Contents

“…The statistical-empirical method is typically based on a regression function that links measured biochemical or biophysical parameters to spectral measurements [7,8], such as spectral reflectance [9,10], spectral indices [11][12][13][14], red-edge features [15][16][17][18], absorption features [19][20][21][22], and band combinations made using the wavelet transformation or principal transformation [23][24][25][26]. However, the leaf spectrum depends on a complex interaction between internal and external factors that may vary significantly from one species to another, and it is hard to build a universal relationship between a single vegetation variable and a spectral signature [27].…”

Estimating Canopy Nitrogen Concentration in Sugarcane Using Field Imaging Spectroscopy

“…To solve this problem, field spectroscopy or hyperspectral remote sensing with narrow spectral bands (<10 nm) over a contiguous range should be considered [22]. In fact, previous studies using a predictive approach based on hyperspectral remote sensing mainly focused on a single crop species [10,23,24] or one age group [25]. Few studies have attempted to apply hyperspectral data to determine the status of sugarcane nutrients at the foliar or canopy level [26][27][28][29].…”