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All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Media Effects on Lettuce Growth in "Pillows" Designed for the VEGGIE Spaceflight Growth Chamber

VEGGIE is a prototype vegetable production unit for space designed by Orbital Technologies Corporation that is being developed to fly on the International Space Station. A modular plant rooting system "pillow" is being designed to support plant growth in VEGGIE under microgravity conditions. VEGGIE pillows are small self-contained packets of media with time-release fertilizer that can wick water passively from a root mat reservoir. Seeds are planted in pillows and the entire root system of a plant is contained as the crop develops, preventing loss into the spacecraft cabin. This study compared five media types and three lettuce cultivars in pillows growing in a VEGGIE analog environment.. Media consisted of a peat-based potting mix (Fafard #2,Conrad Fafard Inc., Agawam, MA), and a calcined clay, (arcillite, 1-2 mm sifted, Turface Proleague, Profile LLC, Buffalo Grove IL) as well as three different blends of the two, 70:30, 50:50, and 30:70. Lettuce cultivars tested were 'Sierra', a bi-colored French crisp Batavia lettuce, 'Outredgeous', a red romaine lettuce and 'Flandria', a green butter head variety. Plants were grown for 28 days, harvested, biometric data was obtained, and tissue mineral analysis was performed. For all cultivars, lettuce plants grown in the media blends were more productive than those in the individual media types. All cultivars showed bell-shaped curves in response to increases in arcillite / decreases in Fafard #2 for leaf area, fresh, and dry mass. Plants in 100% Fafard #2 and in 100% arcillite were stunted, but only those in higher levels of Fafard #2 (70% and 100%) had reduced shoot percent moisture, possibly indicating that mechanisms causing stunting differed. Variation in tissue nutrient content are consistent with this, with Mg and Mn highest in plants grown in 100% Fafard and decreasing as the concentration of arcillite increased. Color also varied with media, especially in the 'Sierra' lettuce, with plants grown in increasing levels of Fafard #2 being much more red and those in 100% arcillite almost completely green. The red-leaf cultivar 'Outredgeous' showed increasing chlorophyll (SPAD values) with increasing percentage of arcillite. In all cultivars tested it appears that a mixture of media types, usually 50:50 or 30:70 Fafard #2: arcillite, sustained healthier, more productive plants. Smaller, less productive plants in either of the individual media may indicate stress issues, however more work is needed to understand the reasons for this sub-optimal growth. This work was supported by NASA

Massa, Gioia↗
NASA NTRS1981

Spectral-agronomic relationships of corn, soybean and wheat canopies

During the past six years several thousand reflectance spectra of corn, soybean, and wheat canopies were acquired and analyzed. The relationships of biophysical variables, including leaf area index, percent soil cover, chlorophyll and water content, to the visible and infrared reflectance of canopies are described. The effects on reflectance of cultural, environmental, and stress factors such as planting data, seeding rate, row spacing, cultivar, soil type and nitrogen fertilization are also examined. The conclusions are that several key agronomic variables including leaf area index, development stage and degree of stress are strongly related to spectral reflectance and that it should be possible to estimate these descriptions of crop condition from satellite acquired multispectral data.

Bauer, M. E.↗
NASA NTRS1992

Inherent limitations of nondestructive chlorophyll meters: a comparison of two types of meters

Two types of nondestructive chlorophyll meters were compared with a standard, destructive chlorophyll measurement technique. The nondestructive chlorophyll meters were 1) a custom built, single-wavelength meter, and 2) the recently introduced, dual-wavelengh, chlorophyll meter from Minolta (model SPAD-502). Data from both meters were closely correlated with destructive measurements of chlorophyll (r2 = 0.90 and 0.93; respectively) for leaves with chlorophyll concentrations ranging from 100 to 600 mg m-2, but both meters consistently overestimated chlorophyll outside this range. Although the dual-wavelength meter was slightly more accurate than the single-wavelength meter (higher r2), the light-scattering properties of leaf cells and the nonhomogeneous distribution of chlorophyll in leaves appear to limit the ability of all meters to estimate in vivo chlorophyll concentration.

NASA Program CELSS↗
NASA NTRS1989

Ecological applications of high resolution spectrometry

Future directions of NASA's space program plans include a significant effort at studying the Earth as a system of interrelated ecosystems. As part of NASA's Earth Observing System (Eos) Program a series of space platforms will be launched and operated to study the Earth with a variety of active and passive instruments. Several of the Eos instruments will be capable of imaging the planet's surface reflectance on a large number of very narrow portions of the solar spectrum. After the development of appropriate algorithms, this reflectance information will be used to determine key parameters about the structure and function of terrestrial and aquatic ecosystems and the pattern and processes of those systems across large areas of the globe. Algorithm development applicable to terrestrial systems will permit the inference of ecological processes from high resolution spectrometry data, similar to that to be forthcoming from the Eos mission. The first summer was spent working with tropical soils and relating their reflectance characteristics to particle size, iron content, and color. This summer the emphasis is on vegetation and work was begun with the Forest Ecosystems Dynamics Project in the Earth Resources Branch where both optical and radar characteristics of a mixed conifer/hardwood forest in Maine are being studied for use in a ecological modeling effort. A major series of aircraft overflights will take place throughout the summer. Laboratory and field spectrometers are used to measure the spectral reflectance of a hierarchy of vegetation from individual leaves to whole canopies for eventual modeling of their nutrient content using reflectance data. Key leaf/canopy parameters are being approximated including chlorophyll, nitrogen, phosphorus, water content, and leaf specific weight using high resolution spectrometry alone. Measurements are made of carbon exchange across the landscape for input to a spatial modeling effort to gauge production within the forest. A Geographic Information System approach is used to associate these data, images, and other collateral information for the forest into a database with a common projection suitable for spatial modeling.

Lawrence, William T.↗
NASA NTRS1969

Plant tissue and the color infrared record

Green plant tissue should not be considered as having a uniguely high near-infrared reflectance but rather a low visual reflectance. Leaf tissue without chloroplasts appears to reflect well both visual and near infrared wavelengths. The sensitometry of color infrared film is such that a spectral imbalance strongly favoring infrared reflection is necessary to yield a red record. It is the absorption of visual light by chlorophyll that creates the imbalance that makes the typical red record for plants possible. Reflectance measurements of leaves that have been chemically blanched or which have gone into natural chloride decline strongly suggests that it is the rise in the visual reflectance that is most important in removing the imbalance and degrading the red CIR record. The role of water in leaves appears to be that of rendering epidermal membranes translucent so that the underlying chlorophyll controls the reflection rather than the leaf surface.

Pease, R. W.↗
NASA NTRS2001

Airborne Hyperspectral Imagery for the Detection of Agricultural Crop Stress

Multispectral digital imagery from aircraft or satellite is presently being used to derive basic assessments of crop health for growers and others involved in the agricultural industry. Research indicates that narrow band stress indices derived from hyperspectral imagery should have improved sensitivity to provide more specific information on the type and cause of crop stress, Under funding from the NASA Earth Observation Commercial Applications Program (EOCAP) we are identifying and evaluating scientific and commercial applications of hyperspectral imagery for the remote characterization of agricultural crop stress. During the summer of 1999 a field experiment was conducted with varying nitrogen treatments on a production corn-field in eastern Nebraska. The AVIRIS (Airborne Visible-Infrared Imaging Spectrometer) hyperspectral imager was flown at two critical dates during crop development, at two different altitudes, providing images with approximately 18m pixels and 3m pixels. Simultaneous supporting soil and crop characterization included spectral reflectance measurements above the canopy, biomass characterization, soil sampling, and aerial photography. In this paper we describe the experiment and results, and examine the following three issues relative to the utility of hyperspectral imagery for scientific study and commercial crop stress products: (1) Accuracy of reflectance derived stress indices relative to conventional measures of stress. We compare reflectance-derived indices (both field radiometer and AVIRIS) with applied nitrogen and with leaf level measurement of nitrogen availability and chlorophyll concentrations over the experimental plots (4 replications of 5 different nitrogen levels); (2) Ability of the hyperspectral sensors to detect sub-pixel areas under crop stress. We applied the stress indices to both the 3m and 18m AVIRIS imagery for the entire production corn field using several sub-pixel areas within the field to compare the relative sensitivity of each stress index; and (3) Comparative sensitivity of stress indices to realistic measurement uncertainties. We compare the stress indices calculated with several levels of spectral uncertainty (by shifting the wavelengths) and reflectance uncertainty (by systematically varying the reflectance retrieval code initialization).

Cassady, Philip E.↗
NASA NTRS1990

Light-stimulated cell expansion in bean (Phaseolus vulgaris L.) leaves. I. Growth can occur without photosynthesis

Cell expansion in dicotyledonous leaves is strongly stimulated by bright white light (WL), at least in part as a result of light-induced acidification of the cell walls. It has been proposed that photosynthetic reactions are required for light-stimulated transport processes across plasma membranes of leaf cells, including proton excretion. The involvement of photosynthesis in growth and wall acidification of primary leaves of bean has been tested by inhibiting photosynthesis in two ways: by reducing chlorophyll content of intact plants with tentoxin (TX) and by treating leaf discs with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Exposure to bright WL stimulated growth of intact leaves of TX-treated plants. Discs excised from green as well as from TX-or DCMU-treated leaves also responded by growing faster in WL, as long as exogenous sucrose was supplied to the photosynthetically inhibited tissues. The WL caused acidification of the epidermal surface of intact TX-leaves, but acidification of the incubation medium by mesophyll cells only occurred when photosynthesis was not inhibited. It is concluded that light-stimulated cell enlargement of bean leaves, and the necessary acidification of epidermal cell walls, are mediated by a pigment other than chlorophyll. Light-induced proton excretion by mesophyll cells, on the other hand, may require both a photosynthetic product (or exogenous sugars) and a non-photosynthetic light effect.

NASA Discipline Number 29-20↗
NASA NTRS2021

Scaling photosynthetic function and CO2 dynamics from leaf to canopy level for maize – dataset combining diurnal and seasonal measurements of vegetation fluorescence, reflectance and vegetation indices with canopy gross ecosystem productivity

Recent advances in leaf fluorescence measurements and canopy proximal remote sensing currently enable the non-destructive collection of rich diurnal and seasonal time series, which are required for monitoring vegetation function at the temporal and spatial scales relevant to the natural dynamics of photosynthesis. Remote sensing assessments of vegetation function have traditionally used actively excited foliar chlorophyll fluorescence measurements, canopy optical reflectance data and vegetation indices (VIs), and only recently passive solar induced chlorophyll fluorescence (SIF) measurements. In general, reflectance data are more sensitive to the seasonal variations in canopy chlorophyll content and foliar biomass, while fluorescence observations more closely relate to the dynamic changes in plant photosynthetic function. With this dataset we link leaf level actively excited chlorophyll fluorescence, canopy proximal reflectance and SIF, with eddy covariance measurements of gross ecosystem productivity (GEP). The dataset was collected during the 2017 growing season on maize, using three automated systems (i.e., Monitoring Pulse-Amplitude-Modulation fluorimeter, Moni-PAM; Fluorescence Box, FloX; and from eddy covariance tower). The data were quality checked, filtered and collated to a common 30 minutes timestep. We derived vegetation indices related to canopy functioning (e.g., Photochemical Reflectance Index, PRI; Normalized Difference Vegetation Index, NDVI; Chlorophyll Red-edge, Clre) to investigate how SIF and VIs can be coupled for monitoring vegetation photosynthesis. The raw datasets and the filtered and collated data are provided to enable new processing and analyses.

Petya Campbell↗
NASA NTRS1990

Exploring the Relationship Between Reflectance Red Edge and Chlorophyll Content in Slash Pine

Chlorophyll is a key indicator of the physiological status of a forest canopy. However, its distribution may vary greatly in time and space, so that the estimation of chlorophyll content of canopies or branches by extrapolation from leaf values obtained by destructive sampling is labor intensive and potentially inaccurate. Chlorophy11 content is related positively to the point of maximum slope in vegetation reflectance spectra which occurs at wavelengths between 690-740 nm and is known as the "red edge." The red edge of needles on individual slash pine (Piniis elliottii Engelm.) branches and in whole forest canopies was measured with a spectroradiometer. Branches were measured on the ground against a spectrally flat reflectance target and canopies were measured from observation towers against a spectrally variable understory and forest floor. There was a linear relationship between red edge and chlorophyll content of branches (R(exp 2) = 0.91). Measurements of the red edge and this relationship were used to estimate the chlorophyll content of other branches with an error that was lower than that associated with the colorimetric (laboratory) method. There was no relationship between the red edge and the chlorophyll content of whole canopies. This can be explained by the overriding influence of the understory and forest floor, an influence that was illustrated by spectral mixture modeling. The results suggest that the red edge could be used to estimate the chlorophyll content in branches but it is unlikely to be of value for the estimation of chlorophyll content in canopies unless the canopy cover is high.

Curran, Paul J.↗
NASA NTRS2023

Leaf Functional Traits in Relation to Species Composition in an Arctic–Alpine Tundra Grassland

The relict arctic–alpine tundra provides a natural laboratory to study the potential impacts of climate change and anthropogenic disturbance on tundra vegetation. The Nardus stricta-dominated relict tundra grasslands in the Krkonoše Mountains have experienced shifting species dynamics over the past few decades. Changes in species cover of the four competing grasses—Nardus stricta, Calamagrostis villosa, Molinia caerulea, and Deschampsia cespitosa—were successfully detected using orthophotos. Leaf functional traits (anatomy/morphology, element accumulation, leaf pigments, and phenolic compound profiles), were examined in combination with in situ chlorophyll fluorescence in order to shed light on their respective spatial expansions and retreats. Our results suggest a diverse phenolic profile in combination with early leaf expansion and pigment accumulation has aided the expansion of C. villosa, while microhabitats may drive the expansion and decline of D. cespitosa in different areas of the grassland. N. stricta—the dominant species—is retreating, while M. caerulea did not demonstrate significant changes in territory between 2012 and 2018. We propose that the seasonal dynamics of pigment accumulation and canopy formation are important factors when assessing potential “spreader” species and recommend that phenology be taken into account when monitoring grass species using remote sensing.

Lena Hunt↗
NASA NTRS1995

Balancing photosynthetic light-harvesting and light-utilization capacities in potato leaf tissue during acclimation to different growth temperatures

We investigated the effect of temperature during growth and development on the relationship between light-harvesting capacity, indicated by chlorophyll concentration, and light-utilization potential, indicated by light- and bicarbonate-saturated photosynthetic oxygen evolution, in Solanum tuberosum L. cv. Norland. Clonal plantlets were transplanted and grown at 20 degrees C for 2 weeks before transfer to 12, 16, 20, 24 and 28 degrees C for 6 weeks. After 4 weeks of the temperature treatments, leaf tissue fresh weights per area were one-third higher in plants grown at 12 degrees C vs those grown at 28 degrees C. Conversely, chlorophyll content per area in tissue grown at 12 degrees C was less than one-half of that of tissue grown at 28 degrees C at 4 weeks. Photosynthetic capacity measured at a common temperature of 20 degrees C and expressed on a chlorophyll basis was inversely proportional to growth temperature. Leaf tissue from plants grown at 12 degrees C for 4 weeks had photosynthetic rates that were 3-fold higher on a chlorophyll basis than comparable tissue from plants grown at 28 degrees C. These results suggest that the relationship between light-harvesting capacity and light-utilization potential varies 3-fold in response to the growth temperatures examined. The role of this response in avoidance of photoinhibition is discussed.

NASA Center KSC↗
NASA NTRS1973

Spectra of normal and nutrient-deficient maize leaves

Reflectance, transmittance and absorptance spectra of normal and six types of nutrient-deficient (N, P, K, S, Mg, and Ca) maize (Zea mays L.) leaves were analyzed at 30 selected wavelengths from 500 to 2600 nm. The analysis of variance showed significant differences in reflectance, transmittance and absorptance in the visible wavelengths among leaf numbers 3, 4, and 5, among the seven treatments, and among the interactions of leaf number and treatments. In the infrared wavelengths only treatments produced significant differences. The chlorophyll content of leaves was reduced in all nutrient-deficient treatments. Percent moisture was increased in S-, Mg-, and N-deficiencies. Polynomial regression analysis of leaf thickness and leaf moisture content showed that these two variables were significantly and directly related. Leaves from the P- and Ca-deficient plants absorbed less energy in the near infrared than the normal plants; S-, Mg-, K-, and N-deficient leaves absorbed more than the normal. Both S- and N-deficient leaves had higher temperatues than normal maize leaves.

Al-Abbas, A. H.↗
NASA NTRS2007

Canopy Level Solar Induced Fluorescence for Vegetation in Controlled Experiments

Solar induced chlorophyll fluorescence (SIF) was retrieved from high resolution reflectance spectra acquired one meter above saplings of three deciduous tree species during springtime (three weeks after leaf flush) and in late summer when foliage was mature. SIF was determined by application of the Fraunhofer Line Depth (FLD) Principal to above-canopy spectra acquired with an Analytical Spectral Devices (ASD) Fieldspec spectroradiometer (3.2 nm resolution with 1.2 nm sampling interval). SIF retrievals were made at the two atmospheric oxygen (O2) absorption features that occur in the chlorophyll fluorescence (ChlF) region (660 -780 nm). These telluric features are 02V, the broader and deeper feature centered at 760 nm, but located on the shoulder of the far-red ChlF peak at 740 nm; and 023, a narrow feature centered at 688 nm that is positioned near the red ChlF peak at 685 nm. Supporting, coincident leaf level fluorescence, reflectance, photochemical and other measurements were also made. At the leaf level, these measurements included in situ photosynthetic capacity (Pmax) and light adapted total chlorophyll fluorescence (Fs') collected at steady state under high light and controlled chamber conditions (e.g., temperature, PAR, humidity, and COz); optical properties (reflectance, transmittance, absorptance); chlorophyll and carotenoid content; specific leaf mass; carbon (C) and nitrogen (N) content; fluorescence emission spectra at multiple excitation wavelengths; the ChlF contribution to red (R) and far-red (FR) reflectance; fluorescence imagery; and fluorescence excitation-emission matrices (EEMs). The tree species examined were tulip poplar (Liriodendron tulipifera L.), red maple (Acer rubrum L.), and sweetgum (Liquidambar styraczflua L.), and each had been provided four levels of N augmentation (0, 19, 37, and 75 kg Nhectare seasonally) to simulate atmospheric deposition from air pollution. Whole-plant SIF measurements of these species were compared with SIF estimates derived using FluorMOD, a radiative transfer model that includes fluorescence properties of foliage, when provided with our supporting measurements. Simulated values for SIF were also compared with similar estimates made over three years for corn (Zea mays L) crops under N treatments (20, 50,70, and 140 kg Nhectare) and with corn and pepper (Capsicum annuum L.) plants provided dimethyl urea (DCMU, 0 and 5 x 10" M) which were grown in pots and grouped in artificial canopies for spectral measurements. For near-surface measurements of healthy and stressed vegetation, red SIF retrieved at 688 nm (023) varied between 2-7 mW/m(exp 2)/nm/sr while far-red SIF retrieved at 760 nm (O2A) varied between 0.5 and 4.0 mW/m(exp 2)/nm/sr. Typical values for the SIF red/far-red ratio ranged between 1.75 and 4.0. Relationships of SIF to spectral reflectance indices and foliar photochemical indices were examined, such as photosynthetic light use efficiency. Initial investigations of the variability in these measurements at the same leaf temperature for sunlit and shaded foliage showed us that shaded foliage produced higher ChlF and light use efficiency. Other factors that affect SIF determinations are discussed. These results will assist in determine the expected intensity of the SIF signal from vegetation near the surface, as well as to identify enhancements needed for FluorMOD (or other such models), and will assist in determining relationships of SIF to reflectance indices and carbon dynamics.

Middleton, E. M.↗
NASA NTRS1987

Reflectance characteristics of dry plant materials

Chlorophyll and water obscure the absorption features of all other leaf constituents in the spectra of green leaves. The predominant near-IR and thermal IR spectral features of dry plant materials originate from lignin, cellulose, and hemicellulose. These compounds account for 80 to 98 percent of the dry weight in most plant materials.

Elvidge, Christopher D.↗
NASA NTRS1994

Leaf absorbance and photosynthesis

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Schurer, Kees↗
NASA NTRS1977

Use of near infrared/red radiance ratios for estimating vegetation biomass and physiological status

The application of photographic infrared/red (ir/red) reflectance or radiance ratios for the estimation of vegetation biomass and physiological status were investigated by analyzing in situ spectral reflectance data from experimental grass plots. Canopy biological samples were taken for total wet biomass, total dry biomass, leaf water content, dry green biomass, dry brown biomass, and total chlorophyll content at each sampling date. Integrated red and photographic infrared radiances were regressed against the various canopy or plot variables to determine the relative significance between the red, photographic infrared, and the ir/red ratio and the canopy variables. The ir/red ratio is sensitive to the photosynthetically active or green biomass, the rate of primary production, and actually measures the interaction between the green biomass and the rate of primary production within a given species type. The ir/red ratio resulted in improved regression significance over the red or the ir/radiances taken separately. Only slight differences were found between ir/red ratio, the ir-red difference, the vegetation index, and the transformed vegetation index. The asymptotic spectral radiance properties of the ir, red, ir/red ratio, and the various transformations were evaluated.

Tucker, C. J.↗
NASA NTRS1995

Prospect redux

The remote estimation of leaf biochemical content from spaceborne platforms has been the subject of many studies aimed at better understanding of terrestrial ecosystem functioning. The major ecological processes involved in exchange of matter and energy, like photosynthesis, primary production, evaportranspiration, respiration, and decomposition can be related to plant properties e.g., chlorophyll, water, protein, cellulose and lignin contents. As leaves represent the most important plant surfaces interacting with solar energy, a top priority has been to relate optical properties to biochemical constituents. Two different approaches have been considered: first, statistical correlations between the leaf reflectance (or transmittance) and biochemical content, and second, physically based models of leaf scattering and absorption developed using the laws of optics. Recently reviewed by Verdebout et al., the development of models of leaf optical properties has resulted in better understanding of the interaction of light with plant leaves. Present radiative transfer models mainly use chlorophyll and/or water contents as input parameters to calculate leaf reflectance. Inversion of these models allows to retrieve these constituents from spectrophotometric measurements. Conel et al. recently proposed a two-stream Kubelka-Munk model to analyze the influence of protein, cellulose, lignin, and starch on leaf reflectance, but in fact, the estimation of leaf biochemistry from remote sensing is still an open question. In order to clarify it, a laboratory experiment associating visible/infrared spectra of plan leaves both with physical measurements and biochemical analyses was conducted at the Joint Research Center during the summer of 1993. This unique data set has been used to upgrade the PROSPECT model, by including leaf biochemistry.

Jacquemoud, S.↗
NASA NTRS1994

The Use of High Spectral Resolution Bands for Estimating Absorbed Photosynthetically Active Radiation (A Par)

Most remote sensing estimations of vegetation variables such as Leaf Area Index (LAI), Absorbed Photosynthetically Active Radiation (APAR), and phytomass are made using broad band sensors with a bandwidth of approximately 100 nm. However, high resolution spectrometers are available and have not been fully exploited for the purpose of improving estimates of vegetation variables. A study directed to investigate the use of high spectral resolution spectroscopy for remote sensing estimates of APAR in vegetation canopies in the presence of nonphotosynthetic background materials such as soil and leaf litter is presented. A high spectral resolution method defined as the Chlorophyll Absorption Ratio Index (CARI) was developed for minimizing the effects of nonphotosynthetic materials in the remote estimates of APAR. CARI utilizes three bands at 550, 670, and 700 nm with bandwidth of 10 nm. Simulated canopy reflectance of a range of LAI were generated with the SAIL model using measurements of 42 different soil types as canopy background. CARI obtained from the simulated canopy reflectance was compared with the broad band vegetation indices (Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI), and Simple Ratio (SR)). CARI reduced the effect of nonphotosynthetic background materials in the assessment of vegetation canopy APAR more effectively than broad band vegetation indices.

Kim, Moon S.↗