Seasonal Course of the Spectral Properties of Alder and Birch Leaves

Mõttus, Matti; Sulev, Madis; Hallik, Lea

doi:10.1109/jstars.2013.2294242

Cited by 51 publications

(15 citation statements)

References 42 publications

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“…UAVSpec3 has 3.3 nm sampling interval, thus there are two spectral measurements/bands between 717 nm and 727 nm and the two-modal result cannot be explained only by the low spectral sampling interval of the spectrometer. A somewhat similar effect of peak jump has also been demonstrated at leaf level [18]. At canopy level, the number of distinct peaks locations appeared to depend on growth form as the third location of first derivatives maximum occurred at 700 nm and disappeared after the removal of clearcut plots.…”

Section: Comparison Of Different Methods To Calculate Red-edge Inflecsupporting

confidence: 66%

“…Pigment absorption declines sharply after 700 nm where the absorption maximum of the reaction center of photosystem I (P700) is located and this spectral region of fast change is called "red-edge". This sharp increase in reflectance (decline in absorption) is the most characteristic feature of vegetation spectra and special methods including different spectral fitting [18] and linear extrapolation techniques for hyperspectral [19] and multispectral [20,21] data have been developed to track and determine the precise location of the fastest change. The signal in Sentinel-2 MSI bands 5 and 6 of 15 nm spectral resolution compared to each other and to the neighbor bands allows estimating the position and steepness of the red edge.…”

Section: Introductionmentioning

confidence: 99%

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Reflectance Properties of Hemiboreal Mixed Forest Canopies with Focus on Red Edge and Near Infrared Spectral Regions

et al. 2019

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This study present the results of airborne top-of-canopy measurements of reflectance spectra in the spectral domain of 350-1050 nm over the hemiboreal mixed forest. We investigated spectral transformations that were originally designed for utilization at very different spectral resolutions. We found that the estimates of red edge inflection point by two methods-the linear four-point interpolation approach (S2REP) and searching the maximum of the first derivative spectrum (D max ) according to the mathematical definition of red edge inflection point-were well related to each other but S2REP produced a continuously shifting location of red edge inflection point while D max resulted in a discrete variable with peak jumps between fixed locations around 717 nm and 727 nm for forest canopy (the third maximum at 700 nm appeared only in clearcut areas). We found that, with medium high spectral resolution (bandwidth 10 nm, spectral step 3.3 nm), the in-filling of the O 2 -A Fraunhofer line (F area ) was very strongly related to single band reflectance factor in NIR spectral region (ρ = 0.91, p < 0.001) and not related to Photochemical Reflectance Index (PRI). Stemwood volume, basal area and tree height of dominant layer were negatively correlated with reflectance factors at both visible and NIR spectral region due to the increase in roughness of canopy surface and the amount of shade. Forest age was best related to single band reflectance at NIR region (ρ = −0.48, p < 0.001) and the best predictor for allometric LAI was the single band reflectance at red spectral region (ρ = −0.52, p < 0.001) outperforming all studied vegetation indices. It suggests that Sentinel-2 MSI bands with higher spatial resolution (10 m pixel size) could be more beneficial than increased spectral resolution for monitoring forest LAI and age. The new index R 751 /R 736 originally developed for leaf chlorophyll content estimation, also performed well at the canopy level and was mainly influenced by the location of red edge inflection point (ρ = 0.99, p < 0.001) providing similar info in a simpler mathematical form and using a narrow spectral region very close to the O 2 -A Fraunhofer line.

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Section: Comparison Of Different Methods To Calculate Red-edge Inflecsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Reflectance Properties of Hemiboreal Mixed Forest Canopies with Focus on Red Edge and Near Infrared Spectral Regions

et al. 2019

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“…NIR reflectance slightly increases [11,43] and transmittance slightly decreases [11] from summer to autumn. The seasonal courses of NIR spectra in current-year needles, therefore, resemble those of deciduous broadleaved species [11,54], and are probably related to changes in structure (thickness) and water content [43]. Seasonal variations observed for current-year needles in SWIR are similar to those in NIR region [11,43].…”

Section: Seasonal Variation In Needle Spectramentioning

confidence: 66%

Spectral Properties of Coniferous Forests: A Review of In Situ and Laboratory Measurements

Rautiainen

Lukeš²,

Homolová³

et al. 2018

Remote Sensing

107

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Abstract:Coniferous species are present in almost all major vegetation biomes on Earth, though they are the most abundant in the northern hemisphere, where they form the northern tree and forest lines close to the Arctic Circle. Monitoring coniferous forests with satellite and airborne remote sensing is active, due to the forests' great ecological and economic importance. We review the current understanding of spectral behavior of different components forming coniferous forests. We look at the spatial, directional, and seasonal variations in needle, shoot, woody element, and understory spectra in coniferous forests, based on measurements. Through selected case studies, we also demonstrate how coniferous canopy spectra vary at different spatial scales, and in different viewing angles and seasons. Finally, we provide a synthesis of gaps in the current knowledge on spectra of elements forming coniferous forests that could also serve as a recommendation for planning scientific efforts in the future.

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“…Also Mõttus et al (2014) observed differences between leaf sides in visible reflectance of birch and alder. However, based on our data we can conclude that the effect of needle side in conifers is highly dependent on species, which has not previously been possible to report due to a limited number of sampled species.…”

Section: Discussionmentioning

confidence: 84%

“…Later, peak season spectra for three Finnish species have been reported by Lukeš et al (2013) and 12 tree species (some of them boreal) in Japan by Noda et al (2014). Seasonal time series of spectra for two Estonian broadleaved species was reported by Mõttus et al (2014). However, a larger comparative analysis of both Eurasian and North American species in the boreal region has not been reported.…”

Section: Introductionmentioning

confidence: 99%

A spectral analysis of 25 boreal tree species

Hovi¹,

Raitio²,

Rautiainen³

2017

Silva Fenn.

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A spectral analysis of 25 boreal tree speciesHovi A., Raitio P., Rautiainen M. (2017). A spectral analysis of 25 boreal tree species. Silva Fennica vol. 51 no. 4 article id 7753. 16 p. https://doi.org/10.14214/sf.7753 Highlights• An extensive spectral library containing leaf and needle reflectance and transmittance spectra was collected.• The spectra openly available in SPECCHIO Spectral Information System.• Effects of tree species, leaf/needle side, canopy position, and needle age on spectra were quantified.• Seasonal variations were measured for four species.• Spectra analysis highlights the importance of shortwave-infrared region in separating tree species. AbstractSpectral libraries have a fundamental role in the development of interpretation methods for airborne and satellite-borne remote sensing data. This paper presents to-date the largest spectral measurement campaign of boreal tree species. Reflectance and transmittance spectra of over 600 leaf and needle samples from 25 species were measured in the Helsinki area (Finland) using integrating sphere systems attached to an ASD FieldSpec 4 spectroradiometer. Factors influencing the spectra and red edge inflection point (REIP) were quantified using one-way analysis of variance. Tree species differed most in the shortwave-infrared (1500-2500 nm) and least in the visible (400-700 nm) wavelength region. Species belonging to same genera showed similar spectral characteristics. Upper (adaxial) and lower (abaxial) leaf sides differed most in the visible region. Canopy position (sunlit/shaded) had a minor role in explaining spectral variation.For evergreen conifers, current and previous year needles differed in their spectra, current-year needles resembling those of broadleaved and deciduous conifers. Two broadleaved species were monitored throughout the growing season (May-October), and two conifers were measured twice during summer (June, September). Rapid changes were observed in the spectra in early spring and late autumn, whereas seasonal variations during summer months were relatively small for both broadleaved and coniferous species. Based on our results, shortwave-infrared seems promising in separating tree species, although it is to-date least studied. The spectral library reported here (Version 1.0) is publicly available through the SPECCHIO Spectral Information System.

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Seasonal Course of the Spectral Properties of Alder and Birch Leaves

Cited by 51 publications

References 42 publications

Reflectance Properties of Hemiboreal Mixed Forest Canopies with Focus on Red Edge and Near Infrared Spectral Regions

Reflectance Properties of Hemiboreal Mixed Forest Canopies with Focus on Red Edge and Near Infrared Spectral Regions

Spectral Properties of Coniferous Forests: A Review of In Situ and Laboratory Measurements

A spectral analysis of 25 boreal tree species

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