Canopy vertical heterogeneity plays a critical role in reflectance simulation

Wang, Quan; Li, Pingheng

doi:10.1016/j.agrformet.2012.10.004

Cited by 60 publications

(47 citation statements)

References 45 publications

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“…As expected, reducing the number of observations by averaging brought a higher similarity between all three types of measurements and it caused smaller differences between observations (Table 2B). The Tukey's HSD test performed on the BioC/P and ASD CP data revealed that there were stands significantly different from others and it also confirmed results published earlier about differences of the pigment and water contents in the tree vertical profile [26] and between younger and older tree shoots (e.g. [19]).…”

Section: Resultssupporting

confidence: 73%

“…A low significance is obtained as soon as the measurements are averaged on the position and stand levels in the cases of relative water content and WI. The results of the Tukey's HSD test are in correspondence with results found in literature-the content of photosynthetic pigments (expressed on needle dry mass) increases from the upper to lower parts of the tree crown and with the age of the shoots, while the water content shows an opposite trend [7], [26]. Averaging the BioC/P and ASD CP observations per tree brought better agreement with the optical hyperspectral data.…”

Section: Discussionsupporting

confidence: 77%

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Statistical comparison of spectral and biochemical measurements on an example of Norway spruce stands in the Ore Mountains, Czech Republic

Potůčková

Červená

Kupková

et al. 2016

Geoinformatics FCE CTU

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Section: Resultssupporting

confidence: 73%

Section: Discussionsupporting

confidence: 77%

Statistical comparison of spectral and biochemical measurements on an example of Norway spruce stands in the Ore Mountains, Czech Republic

Potůčková

Červená

Kupková

et al. 2016

Geoinformatics FCE CTU

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show abstract

“…In addition, the accuracy of the EWT estimation is heavily affected by the canopy structure, understorey vegetation and soil moisture content [15,18]. The vertical heterogeneity of the biophysical and biochemical properties of the canopy is often ignored, despite affecting the light penetration and scattering within the canopy [19,20]. There is a unique opportunity to overcome such issues using terrestrial laser scanning (TLS).…”

Section: Introductionmentioning

confidence: 99%

Estimation of vegetation water content at leaf and canopy level using dual-wavelength commercial terrestrial laser scanners

2018

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Vegetation water content, quantified as the leaf equivalent water thickness (EWT), can serve as an indicator of vegetation stress. The intensity data recorded by terrestrial laser scanning (TLS) instruments, operating at shortwave infrared wavelengths, can be used to estimate the three-dimensional distribution of EWT, after a full and rigorous calibration for the range and incidence angle effects. However, TLS instruments do not record the incidence angles automatically, making calibration challenging. In this study, intensity data from two commercially available TLS instruments (Leica P40, 1550 nm shortwave infrared wavelength, and Leica P20, 808 nm near-infrared wavelength) were combined in a normalized difference index (NDI). The NDI was found to minimize the incidence angle effects with no need for further calibration. A dry-down experiment was conducted using deciduous and conifer canopies. The NDI was found to be highly correlated to EWT at leaf level ( of 0.91 and 0.74) and at canopy level ( of 0.89 and 0.74) for the deciduous and conifer canopies, respectively. Three-dimensional distributions of EWT at canopy level were generated, which revealed some vertical heterogeneity.

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“…Our results show that the vertical distribution of reflectance is significantly changed in relation to agronomic measures. The understanding of the vertical heterogeneity sources is necessary to ensure generally valid interpretation of reflectance data and also to create a multiple-layer canopy radiative transfer model, the development of which in recent years is gaining increased attention (Wang & Li 2013).…”

Section: Discussionmentioning

confidence: 99%

Changes in Vertical Distribution of Spectral Reflectance within Spring Barley Canopy as an Indicator of Nitrogen Nutrition, Canopy Structure and Yield Parameters

Klem¹,

Rajsnerová²,

Novotná³

et al. 2014

Agriculture (Pol'nohospodárstvo)

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The main objective of this study was to evaluate the spectral reflectance in the vertical profile of spring barley canopy at the booting growth stage and to determine how the reflectance gradient changes in relation to crop density and nitrogen (N) nutrition. Vertical gradients of spectral reflectance were studied in field trials with three sowing densities (2, 4 and 6 million of germinating seeds/ha) and two levels of N nutrition (0 and 90 kg/ha). It was found that differences in vegetation indices caused by N nutrition are most pronounced in the second and third leaf from the top, and these increase with increasing sowing density. The vertical gradient of reflectance, specifically the ratio between the leaves F-3/F-1 for vegetation indices based on red-edge reflectance, represents a reliable indicator of number of ears per area unit (R = –0.87 for Normalised Red Edge-Red Index (NRERI) and –0.93 for Zarco-Teja-da and Miller Simple Ratio Index (ZM)). A close relationship to ear productivity was found almost for all observed vegetation indices and any leaf in vertical profile (R = 0.79–0.97). In contrast, the prediction of protein content in barley grain was the most reliable when the red-edge reflectance indices (ZM and NRERI) particularly from upper three leaves were used (R = 0.81–0.88). The results show that the knowledge of reflectance heterogeneity in the vertical profile of canopy can significantly contribute to the interpretation of the measured data, to the differentiation of the N nutrition effect from the response to canopy density, and finally to a more accurate estimation of yield parameters and protein content in grain.

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Canopy vertical heterogeneity plays a critical role in reflectance simulation

Cited by 60 publications

References 45 publications

Statistical comparison of spectral and biochemical measurements on an example of Norway spruce stands in the Ore Mountains, Czech Republic

Statistical comparison of spectral and biochemical measurements on an example of Norway spruce stands in the Ore Mountains, Czech Republic

Estimation of vegetation water content at leaf and canopy level using dual-wavelength commercial terrestrial laser scanners

Changes in Vertical Distribution of Spectral Reflectance within Spring Barley Canopy as an Indicator of Nitrogen Nutrition, Canopy Structure and Yield Parameters

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