Seasonal reflectance dynamics of common understory types in a northern European boreal forest

Rautiainen, Miina; Mõttus, Matti; Heiskanen, Janne; Akujärvi, Anu; Majasalmi, Titta; Stenberg, Pauline

doi:10.1016/j.rse.2011.06.005

Cited by 95 publications

(54 citation statements)

References 19 publications

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“…Forty measurement points were made for each understory type at intervals of 0.7 m on a 28 m long permanent transect. The ground area sampled at each point was approximately a circle with radius of 25 cm (Rautiainen et al, 2011). Spectra of understory HCRFs are shown in Fig.…”

Section: Field Datamentioning

confidence: 99%

Estimation of leaf area index and its sunlit portion from DSCOVR EPIC data: Theoretical basis

Yang

Knyazikhin

Mõttus

et al. 2017

Remote Sensing of Environment

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This paper presents the theoretical basis of the algorithm designed for the generation of leaf area index and diurnal course of its sunlit portion from NASA's Earth Polychromatic Imaging Camera (EPIC) onboard NOAA's Deep Space Climate Observatory (DSCOVR). The Look-up- Table (LUT) approach implemented in the MODIS operational LAI/FPAR algorithm is adopted. The LUT, which is the heart of the approach, has been significantly modified. First, its parameterization incorporates the canopy hot spot phenomenon and recent advances in the theory of canopy spectral invariants. This allows more accurate decoupling of the structural and radiometric components of the measured Bidirectional Reflectance Factor (BRF), improves scaling properties of the LUT and consequently simplifies adjustments of the algorithm for data spatial resolution and spectral band compositions. Second, the stochastic radiative transfer equations are used to generate the LUT for all biome types. The equations naturally account for radiative effects of the three-dimensional canopy structure on the BRF and allow for an accurate discrimination between sunlit and shaded leaf areas. Third, the LUT entries are measurable, i.e., they can be independently derived from both below canopy measurements of the transmitted and above canopy measurements of reflected radiation fields. This feature makes possible direct validation of the LUT, facilitates identification of its deficiencies and development of refinements. Analyses of field data on canopy structure and leaf optics collected at 18 sites in the Hyytiälä forest in southern boreal zone in Finland and hyperspectral images acquired by the EO-1 Hyperion sensor support the theoretical basis.

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Section: Field Datamentioning

confidence: 99%

Estimation of leaf area index and its sunlit portion from DSCOVR EPIC data: Theoretical basis

Yang

Knyazikhin

Mõttus

et al. 2017

Remote Sensing of Environment

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“…Their seasonal course of understory reflectance is very characteristic of stand type, and the reflectance differences between stands tend to become more pronounced as the growing period progresses (Miller et al, 1997). Furthermore, Rautiainen et al (2011b) reported that the spectral differences between and within boreal understory types are the largest at the peak of the growing season whereas in the beginning www.intechopen.com and end of the growing season the differences between the understory types are marginal. They also noted that understory vegetation growing on fertile sites had the brightest near infrared (NIR) spectra throughout the growing season whereas infertile sites appeared darker in NIR.…”

Section: Wwwintechopencommentioning

confidence: 99%

“…The stands range from herb-rich Silver birch forests to xeric Scots pine forests with understory dominated by lichens and heather. A more detailed description of the Hyytiälä forest is available in Rautiainen et al (2011b). The Hyytiälä area is used only in the landscape-level analysis of MODIS data (Section 3.5).…”

Section: Wwwintechopencommentioning

confidence: 99%

“…Due to extremely high variability of irradiance at the ground level it is difficult to obtain reliable measured reflectance spectra and their seasonal trends for understory vegetation. Typically, pure patches of understory vegetation have been measured (Miller et al, 1997;Peltoniemi et al, 2005;Rautiainen et al, 2011b). As a first approximation, the linear mixture approach can be used with cover fractions of community components serving as weights of the components.…”

Section: Seasonal Reflectance Changes In Understory Vegetationmentioning

confidence: 99%

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Seasonal Reflectance Courses of Forests

Nilson¹,

Rautiainen²,

Písek³

et al. 2012

New Advances and Contributions to Forestry Research

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“…measured spectral libraries of common background components such as shrub, grass, lichen, and moss [e.g., Lang et al, 2002;Miller et al, 1997;Peltoniemi et al, 2005;Rautiainen et al, 2007;Rees et al, 2004] as input in forest canopy models. However, the limited spectral libraries would not represent well the optical properties of real forest background which often has highly spatial and temporal variations [Peltoniemi et al, 2005;Rautiainen et al, 2011]. The misrepresentation of forest background would finally result in great uncertainty in the retrieved canopy LAI.…”

Section: Introductionmentioning

confidence: 99%

Mapping global seasonal forest background reflectivity with Multi‐angle Imaging Spectroradiometer data

Jiao

Liu

et al. 2014

JGR Biogeosciences

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Forest background reflectivities with seasonal and spatial variations are critically important in the estimation of canopy biophysical parameters of the forest canopy. In this paper, seasonal background reflectivity for global forested areas was mapped at 1.1 km resolution using four-scale model and Multi-angle Imaging Spectroradiometer data of the nadir and 45°forward directions. The largest seasonal variation of forest background reflectivities was observed in middle and high latitudes of Northern Hemisphere. The background reflectivity differs between deciduous broadleaf forest and coniferous forest in the near-infrared band and varies with increasing canopy leaf area index. The partial validation of forest background reflectivity with adjacent grassland in the Northern Hemisphere and the comparison of understory leaf area index on leaf appearance day for larch forest in North Asia both indicate the relative reliability of results. The nearly 70% spatial coverage of retrieval with high-quality flags makes it eligible for applications over global coniferous and deciduous broadleaf forest areas.

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Seasonal reflectance dynamics of common understory types in a northern European boreal forest

Cited by 95 publications

References 19 publications

Estimation of leaf area index and its sunlit portion from DSCOVR EPIC data: Theoretical basis

Estimation of leaf area index and its sunlit portion from DSCOVR EPIC data: Theoretical basis

Seasonal Reflectance Courses of Forests

Mapping global seasonal forest background reflectivity with Multi‐angle Imaging Spectroradiometer data

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