scholarly journals Floral Radiometry: A Biophysical Basis to Characterize Landscapes

2016 ◽  
Author(s):  
R. Jaishanker ◽  
N.P. Sooraj ◽  
M. Somasekheran Pillai ◽  
K. Athira ◽  
Ammini Joseph ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Flower Color ◽  
Electromagnetic Spectrum ◽  
Ecological Research ◽  
Near Infrared Reflectance ◽  
Early Results ◽  
Representative Species ◽  
Spectrum Characteristic ◽  
Angiosperm Species

AbstractThis paper presents early results on studies of floral spectral reflectance of angiosperms and introduces floral radiometry as an emergent dimension of ecological research in India. Floral spectral reflectance of 121 angiosperm species was measured using hand-held spectroradiometer. The authors describe spectral reflectance of seven representative species within 350-800 nanometer region of the electromagnetic spectrum. Characteristic absorption and reflection of flowers, in ultraviolet and visible regions of the spectrum is reported. Near infrared reflectance was consistently high for all species studied. Flower color is unique to a species and importance of understanding flower color from pollinator’s perspective is highlighted.

Spectral reflectance characteristics of eucalypt foliage damaged by insects

2001 ◽  
Vol 49 (6) ◽  
pp. 687 ◽  
Author(s):  
C. Stone ◽  
L. Chisholm ◽  
N. Coops
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Leaf Age ◽  
Electromagnetic Spectrum ◽  
Similar Response ◽  
Leaf Ontogeny ◽  
Maximum Slope ◽  
Mature Leaves ◽  
Eucalypt Species ◽  
Red Coloration

Variables related to foliar damage, leaf morphology, spectral reflectance, chlorophyll fluorescence and chlorophyll content were measured from leaves sampled from mature eucalypts exhibiting symptoms of crown dieback associated with bell miner colonisation located in Olney State Forest, near Wyong, New South Wales. Insect-damaged mature leaves and healthy young expanding leaves of some species exhibited a conspicuous red coloration caused by the presence of anthocyanin pigmentation. For the mature leaves, the level of red coloration was significantly correlated with insect herbivory and leaf necrosis. Significant correlations were also found between the level of red pigmentation and the following four spectral features: maximum reflectance at the green peak (550 nm); the wavelength position and maximum slope of the red edge (690–740 nm) and the maximum reflectance at 750 nm in the near-infrared portion of the electromagnetic spectrum. While it has been shown that anthocyanin pigments are synthesised in some eucalypt species in response to certain abiotic stresses causing photoinhibition and activation of photoprotective mechanisms, this work proposes that biotic agents such as leaf damaging insects and fungal pathogens may induce a similar response in eucalypt foliage resulting in increased levels of anthocyanins. The potential of anthocyanin levels to be related to leaf ontogeny for some eucalypt species was also illustrated in the reflectance spectra. Thus, it is essential that leaf age be considered. This work demonstrates that the identification of a number of key features of leaf spectra can provide a basis for the development of a robust forest health indicator that may be obtained from airborne or spaceborne hyperspectral sensors.

scholarly journals Wavelength-Dependent Seeing Systematically Changes the Normalized Slope of Telescopic Reflectance Spectra of Mercury

2022 ◽  
Vol 14 (2) ◽  
pp. 405
Author(s):  
Kay Wohlfarth ◽  
Christian Wöhler
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Emission Angle ◽  
Reflectance Spectra ◽  
Infrared Reflectance ◽  
Spectral Slope ◽  
Near Infrared Reflectance ◽  
Photometric Property ◽  
Simulation Results ◽  
Measurement Campaigns

Telescopic observations of Mercury consistently report systematic variations of the normalized spectral slope of visible-to-near-infrared reflectance spectra. This effect was previously assumed to be a photometric property of the regolith, but it is not yet fully understood. After the MESSENGER mission, detailed global spectral maps of Mercury are available that better constrain Mercury’s photometry. So far, wavelength-dependent seeing has not been considered in the context of telescopic observations of Mercury. This study investigates the effect of wavelength-dependent seeing on systematic variations of Mercury’s normalized spectral reflectance slope. Therefore, we simulate the disk of Mercury for an idealized scenario, as seen by four different telescopic campaigns using the Hapke and the Kaasalainen–Shkuratov photometric model, the MDIS global mosaic, and a simple wavelength-dependent seeing model. The simulation results are compared with the observations of previous telescopic studies. We find that wavelength-dependent seeing affects the normalized spectral slope in several ways. The normalized slopes are enhanced near the limb, decrease toward the rim of the seeing disk, and even become negative. The decrease of the normalized spectral slope is consistent with previous observations. However, previous studies have associated the spectral slope variations with photometric effects that correlate with the emission angle. Our study suggests that wavelength-dependent seeing may cause these systematic variations. The combined reflectance and seeing model can also account for slope variations between different measurement campaigns. We report no qualitative differences between results based on the Hapke model or the Kaasalainen–Shkuratov model.

scholarly journals Flower Color Preferences of Western Flower Thrips

2005 ◽  
Vol 15 (4) ◽  
pp. 846-853 ◽  
Author(s):  
Meredith R. Blumthal ◽  
L. Art Spomer ◽  
Daniel F. Warnock ◽  
Raymond A. Cloyd
Keyword(s):  
Frankliniella Occidentalis ◽  
Near Infrared ◽  
Western Flower Thrips ◽  
Flower Color ◽  
Color Preference ◽  
Reflectance Spectra ◽  
Spectral Features ◽  
Trap Crop ◽  
Near Infrared Reflectance ◽  
Flower Thrips

Flower color preference of western flower thrips [WFT (Frankliniella occidentalis) (Thysanoptera: Thripidae)] was assessed by observing insect location after introduction into chambers containing four different colored flowers of each of three plant species: transvaal daisy (Gerbera jamesonii), matsumoto aster (Callistephus chinensis), and chrysanthemum (Dendranthema ×grandiflorum). Preference was based on the number of WFT adults found on each flower 72 hours after infestation. Significantly higher numbers of WFT were found on yellow transvaal daisy and yellow chrysanthemum. When these accessions were compared in a subsequent experiment, WFT displayed a significant greater preference for the yellow transvaal daisy. Visible and near infrared reflectance spectra of the flowers used in the study were measured to determine the presence of distinct spectral features that would account for the relative attractiveness of the flowers. Likewise, the reflectance spectra of three commercially available sticky cards (blue, yellow, and yellow with a grid pattern) that are used to trap or sample for WFT were compared to those of the flowers to determine any shared spectral features that would support observed WFT flower color preference. The observed similarity between the yellow transvaal daisy and yellow sticky card reflectance spectra supports the hypothesis that flower color contributes to attractiveness of WFT. In particular, the wavelengths corresponding to green-yellow (500 to 600 nm) seem to be responsible for attracting WFT. These findings also indicate that yellow sticky cards may be more appropriate in sampling for WFT than blue sticky cards. Although further research is needed, under the conditions of this study, yellow transvaal daisy appears to be a potentially useful trap crop for WFT.

scholarly journals Comparable Discrimination of Soil Constituents Using Spectral Reflectance Data (400–1000 nm) Acquired with Hyperspectral Radiometry

Soil Systems ◽  
2021 ◽  
Vol 5 (3) ◽  
pp. 45
Author(s):  
Patrick J. Starks ◽  
Ann-Marie Fortuna
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Technical Assistance ◽  
Wavelength Region ◽  
High Signal ◽  
Electromagnetic Spectrum ◽  
Proximal Sensing ◽  
The Impact ◽  
Soil Constituents ◽  
Reflectance Data

Currently, a gap exists in inventorying and monitoring the impact of land use and management on soil resources. Reducing the number of samples required to determine the impact of land management on soil carbon (C) and mineral constituents via proximal sensing techniques such as hyper-spectral radiometry can reduce the cost and personnel required to monitor changes in our natural resource base. Previously, we used an expensive, high signal-to-noise ratio (SNR) field spectrometer to correlate soil constituents to hyperspectral diffuse reflectance (HDR), over the 350–2500 nm (VIS-SWIR) wavelength range. This research is an extension of preceding research but focuses solely on the 400–1000 nm (VIS-NIR) region of the electromagnetic spectrum. This region can be measured using less expensive (albeit with lower SNR), miniaturized, field spectrometers that allow minimal sample preparation. Our objectives are to: (1) further evaluate the use of soil HDR in the visible and near-infrared (VIS-NIR) region acquired using an expensive field hyperspectral spectroradiometer for prediction of soil C and selected fractions and nitrogen (N) constituents, (2) repeat the above measurements using HDR data from samples examined in objective (1) using lower SNR hyperspectral radiometers, and (3) add to the limited literature that addresses determinations of selected soil properties using proximal sensing in the VIS-NIR region. Data analyzed in this study confirms that good to satisfactory prediction equations for soil constituents can be developed from spectral reflectance data within the 400–1000 nm wavelength region obtained using relatively inexpensive field radiometers. This application could reduce the time and resources required to monitor gains or losses in carbon constituents, information that can be used in programing such as Conservation Technical Assistance (CTA), the Conservation Reserve Program (CRP) and Climate-smart agriculture (CSA).

scholarly journals On the reflectance spectroscopy of snow

2018 ◽  
Author(s):  
Alexander Kokhanovsky ◽  
Maxim Lamare ◽  
Biagio Di Mauro ◽  
Ghislain Picard ◽  
Laurent Arnaud ◽  
...  
Keyword(s):  
Spectral Reflectance ◽  
Near Infrared ◽  
Reflectance Spectroscopy ◽  
System Of Nonlinear Equations ◽  
Electromagnetic Spectrum ◽  
European Alps ◽  
Snow Surface ◽  
Snow Albedo ◽  
Observation Geometry ◽  
Reflectance Measurements

Abstract. We propose a system of analytical equations to retrieve snow grain size and absorption coefficient of pollutants from snow reflectance or snow albedo measurements in the visible and near-infrared regions of the electromagnetic spectrum. It is assumed that ice grains and impurities (e.g., dust, black and brown carbon) are externally mixed. The system of nonlinear equations is solved analytically in the assumption that impurities influence registered spectra in the visible and not at near-infrared (and vice versa for ice grains). The theory is validated using spectral reflectance measurements and albedo of clean and polluted snow at various locations (Antarctica Dome C, European Alps). The technique to derive the snow albedo (plane and spherical) from reflectance measurements at a fixed observation geometry is proposed. The technique also enables the simulation of hyperspectral snow reflectance measurements in the broad spectral range from ultraviolet to the near-infrared for a given snow surface in the case, if the actual measurements are performed at restricted number of wavelengths (2–4, depending on the type of snow and the measurements system).

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