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Modern satellite and airborne optical images have increasingly higher resolutions and enable the study of all layers of forests, not just the forest canopy. To understand the contribution of different types of understory on the overall spectral reflectance signal, ground reference data are needed from different types of forests. In this paper, we present the analysis of spectral reflectance factors (350-2300 nm) and fractional covers of understory from 36 boreal forest stands. The data were collected during peak growing season in a southern boreal forest area in Finland. The study stands represent four different forest site fertility types. We used a spectrometer to measure understory spectra in nadir and vegetation quadrats to estimate fractional cover. We showed that the understory has specific spectral features related to the site fertility type and fractional cover. Our results suggest that remote sensing can be used to differentiate forest site fertility types and estimate understory green fractional cover in northern European boreal forests. The collected data are openly available in an open data repository.
Petri R. Forsström; Jussi Juola; Miina Rautiainen. Relationships between understory spectra and fractional cover in northern European boreal forests. Agricultural and Forest Meteorology 2021, 308-309, 108604 .
AMA StylePetri R. Forsström, Jussi Juola, Miina Rautiainen. Relationships between understory spectra and fractional cover in northern European boreal forests. Agricultural and Forest Meteorology. 2021; 308-309 ():108604.
Chicago/Turabian StylePetri R. Forsström; Jussi Juola; Miina Rautiainen. 2021. "Relationships between understory spectra and fractional cover in northern European boreal forests." Agricultural and Forest Meteorology 308-309, no. : 108604.
Aarne Hovi; Petri Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. Corrigendum to “Empirical validation of photon recollision probability in single crowns of tree seedlings” [ISPRS J. Photogramm. Remote Sens. 169 (2020) 57–72]. ISPRS Journal of Photogrammetry and Remote Sensing 2021, 178, 135 .
AMA StyleAarne Hovi, Petri Forsström, Giulia Ghielmetti, Michael E. Schaepman, Miina Rautiainen. Corrigendum to “Empirical validation of photon recollision probability in single crowns of tree seedlings” [ISPRS J. Photogramm. Remote Sens. 169 (2020) 57–72]. ISPRS Journal of Photogrammetry and Remote Sensing. 2021; 178 ():135.
Chicago/Turabian StyleAarne Hovi; Petri Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. 2021. "Corrigendum to “Empirical validation of photon recollision probability in single crowns of tree seedlings” [ISPRS J. Photogramm. Remote Sens. 169 (2020) 57–72]." ISPRS Journal of Photogrammetry and Remote Sensing 178, no. : 135.
Aarne Hovi; Petri R. Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. Corrigendum to ‘A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species’ [Data in Brief 35 (2021) 106820]. Data in Brief 2021, 37, 107236 .
AMA StyleAarne Hovi, Petri R. Forsström, Giulia Ghielmetti, Michael E. Schaepman, Miina Rautiainen. Corrigendum to ‘A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species’ [Data in Brief 35 (2021) 106820]. Data in Brief. 2021; 37 ():107236.
Chicago/Turabian StyleAarne Hovi; Petri R. Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. 2021. "Corrigendum to ‘A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species’ [Data in Brief 35 (2021) 106820]." Data in Brief 37, no. : 107236.
Forest extent mapping is required for climate modeling and monitoring changes in ecosystem state. Different global land cover (LC) products employ simple tree cover (referred also as “forest cover” or even “vegetation cover”) definitions to differentiate forests from non-forests. Since 1990, a large number of forest extent maps have become available. Although many studies have compared forest extent data, they often use old data (i.e., around the year 2000). In this study, we assessed tree cover representations of three different annual, global LC products (MODIS VCF (MOD44B, Collection 6 (C6)), MCD12Q1 (C6), and CCI LC (v.2.1.1)) using the Finnish Multi-Source National Forest Inventory (MS-NFI) data for the year 2017. In addition, we present an intercomparison approach for analyzing spatial representations of coniferous and deciduous species. Intercomparison of different LC products is often overlooked due to challenges involved in non-standard and overlapping LC class definitions. Global LC products are used for monitoring changes in land use and land cover and modeling of surface fluxes. Given that LC is a major driver of global change through modifiers such as land surface albedo, more attention should be paid to spatial mapping of coniferous and deciduous species. Our results show that tree cover was either overestimated or underestimated depending on the LC product, and classification accuracy varied between 42 and 75%. Intercomparison of the LC products showed large differences in conifer and deciduous species spatial distributions. Spatial mapping of coniferous and deciduous tree covers was the best represented by the CCI LC product as compared with the reference MS-NFI data.
Titta Majasalmi; Miina Rautiainen. Representation of tree cover in global land cover products: Finland as a case study area. Environmental Monitoring and Assessment 2021, 193, 1 -19.
AMA StyleTitta Majasalmi, Miina Rautiainen. Representation of tree cover in global land cover products: Finland as a case study area. Environmental Monitoring and Assessment. 2021; 193 (3):1-19.
Chicago/Turabian StyleTitta Majasalmi; Miina Rautiainen. 2021. "Representation of tree cover in global land cover products: Finland as a case study area." Environmental Monitoring and Assessment 193, no. 3: 1-19.
This article describes a dataset of multiangular scattering properties of small trees (height = 0.38–0.7 m) at visible, near-infrared, and shortwave-infrared wavelengths (350–2500 nm), and provides supporting auxiliary data that comprise leaf, needle, and bark spectra, and structural characteristics of the trees. Multiangular spectra were measured for 18 trees belonging to three common European tree species: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst), and sessile oak (Quercus petraea (Matt.) Liebl.). The measurements were performed in 47 different view angles across a hemisphere, using a laboratory goniometer and a non-imaging spectrometer. Leaf and needle spectra were measured for each tree, using a non-imaging spectrometer coupled to an integrating sphere. Bark spectra were measured for one sample tree per species. In addition, leaf and needle fresh mass, surface area of leaves, needles, and woody parts, silhouette area, and spherically averaged silhouette to total area ratio (STAR) for each tree were measured or derived from the measurements. The data are useful for modeling the shortwave reflectance characteristics of small trees and potentially forests, and thus benefit climate modeling or interpretation of remote sensing data.
Aarne Hovi; Petri R. Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species. Data in Brief 2021, 35, 106820 .
AMA StyleAarne Hovi, Petri R. Forsström, Giulia Ghielmetti, Michael E. Schaepman, Miina Rautiainen. A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species. Data in Brief. 2021; 35 ():106820.
Chicago/Turabian StyleAarne Hovi; Petri R. Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. 2021. "A dataset composed of multiangular spectral libraries and auxiliary data at tree, leaf, needle, and bark level for three common European tree species." Data in Brief 35, no. : 106820.
Understanding the reflectance anisotropy of forests and the underlying scattering mechanisms is needed to improve the accuracy of retrievals of fundamental forest characteristics from optical remote sensing data. In this paper, we developed a laboratory measurement set-up for a large goniometer (LAGOS) and measured multi-angular spectra (350–2500 nm) of 18 small trees, composed of three common European tree species: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst), sessile oak (Quercus petraea (Matt.) Liebl.). For all trees, we measured tree spectra in 47 view angles in the upper hemisphere. To our knowledge, this is the first study reporting multi-angular reflectance spectra of single trees. We also measured the reflectance and transmittance spectra of needles and leaves, as well as reflectance spectra of bark of the sample trees. We analyzed the spectro-directional characteristics of the trees, and the inter- and intraspecific variations of these characteristics. The anisotropy of trees was shown to be strongly asymmetrical and characteristic to species: while pine and spruce exhibited strong hotspot effects, oak showed a strong specular component. Our results indicate that simultaneous measurements of both spectral and directional characteristics of trees may enhance the discrimination of species and thus, support the retrieval of information of their biophysical properties.
Petri R. Forsström; Aarne Hovi; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. Multi-angular reflectance spectra of small single trees. Remote Sensing of Environment 2021, 255, 112302 .
AMA StylePetri R. Forsström, Aarne Hovi, Giulia Ghielmetti, Michael E. Schaepman, Miina Rautiainen. Multi-angular reflectance spectra of small single trees. Remote Sensing of Environment. 2021; 255 ():112302.
Chicago/Turabian StylePetri R. Forsström; Aarne Hovi; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. 2021. "Multi-angular reflectance spectra of small single trees." Remote Sensing of Environment 255, no. : 112302.
Miina Rautiainen. Euroopan tutkimusneuvoston (ERC) niukka rahoitus metsäntutkimukselle. Metsätieteen aikakauskirja 2021, 2021, 1 .
AMA StyleMiina Rautiainen. Euroopan tutkimusneuvoston (ERC) niukka rahoitus metsäntutkimukselle. Metsätieteen aikakauskirja. 2021; 2021 ():1.
Chicago/Turabian StyleMiina Rautiainen. 2021. "Euroopan tutkimusneuvoston (ERC) niukka rahoitus metsäntutkimukselle." Metsätieteen aikakauskirja 2021, no. : 1.
The clumping of coniferous needles into shoots is widely acknowledged as a structural feature that cannot be ignored in radiation regime models of coniferous forests. However, higher level clumping, i.e. the aggregation of leaves and shoots in tree crowns and forest stands, is still rarely accounted for in the models. Clumping reduces the light interception of and increases the light penetration depth in a plant stand. To improve forest radiation regime models with respect to this forest structural parameter, we propose a method that can quantify clumping at different hierarchical levels by estimating the silhouette to total area ratio from point clouds acquired by laser scanners. Our method is based on estimating attenuation coefficients in a voxel grid, and subsequently computing the total leaf area and spherically averaged silhouette area of a tree crown or forest stand. We tested our method with empirical data in young Norway spruce trees, where we compared leaf area and silhouette area to destructive and photogrammetric reference measurements. The accuracy of leaf area estimates depended strongly on the voxel size, with voxel sizes below 10 cm side length exhibiting up to 100% higher estimates than the reference leaf area, and large voxels with 90 cm side length being closest to the reference measurements due to crown clumping. The silhouette area estimates varied less with voxel size and were slightly higher than the reference estimates. We analyzed possible error sources and point out ways to improve the measurements of leaf and silhouette area for conifer trees using laser scanning data.
Daniel Schraik; Aarne Hovi; Miina Rautiainen. Crown level clumping in Norway spruce from terrestrial laser scanning measurements. Agricultural and Forest Meteorology 2020, 296, 108238 .
AMA StyleDaniel Schraik, Aarne Hovi, Miina Rautiainen. Crown level clumping in Norway spruce from terrestrial laser scanning measurements. Agricultural and Forest Meteorology. 2020; 296 ():108238.
Chicago/Turabian StyleDaniel Schraik; Aarne Hovi; Miina Rautiainen. 2020. "Crown level clumping in Norway spruce from terrestrial laser scanning measurements." Agricultural and Forest Meteorology 296, no. : 108238.
Physically-based methods in remote sensing provide benefits over statistical approaches in monitoring biophysical characteristics of vegetation. However, physically-based models still demand large computational resources and often require rather detailed informative priors on various aspects of vegetation and atmospheric status. Spectral invariants and photon recollision probability theories provide a solid theoretical framework for developing relatively simple models of forest canopy reflectance. Empirical validation of these theories is, however, scarce. Here we present results of a first empirical validation of a model based on photon recollision probability at the level of individual trees. Multiangular spectra of pine, spruce, and oak tree seedlings (height = 0.38–0.7 m) were measured using a goniometer, and tree hemispherical reflectance was derived from those measurements. We evaluated the agreement between modeled and measured tree reflectance. The model predicted the spectral signatures of the tree seedlings in the wavelength range between 400 and 2300 nm well, with wavelength-specific bias between −0.048 and 0.034 in reflectance units. In relative terms, the model errors were the smallest in the near-infrared (relative RMSE up to 4%, 7%, and 4% for pine, spruce, and oak seedlings, respectively) and the largest in the visible wavelength region (relative RMSE up to 34%, 20%, and 60%). The errors in the visible region could be partly attributed to wavelength-dependent directional scattering properties of the leaves. Including woody parts of tree seedlings in the model improved the results by reducing the relative RMSE by up to 10% depending on species and wavelength. Spectrally invariant model parameters, i.e. total and directional escape probabilities, depended on spherically averaged silhouette to total area ratio (STAR) of the tree seedlings. Overall, the modeled and measured tree reflectance mainly agreed within measurement uncertainties, but the results indicate that the assumption of isotropic scattering by the leaves can result in large errors in the visible wavelength region for some tree species. Our results help increasing the confidence when using photon recollision probability and spectral invariants -based models to interpret satellite images, but they also lead to an improved understanding of the assumptions and limitations of these theories.
Aarne Hovi; Petri Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. Empirical validation of photon recollision probability in single crowns of tree seedlings. ISPRS Journal of Photogrammetry and Remote Sensing 2020, 169, 57 -72.
AMA StyleAarne Hovi, Petri Forsström, Giulia Ghielmetti, Michael E. Schaepman, Miina Rautiainen. Empirical validation of photon recollision probability in single crowns of tree seedlings. ISPRS Journal of Photogrammetry and Remote Sensing. 2020; 169 ():57-72.
Chicago/Turabian StyleAarne Hovi; Petri Forsström; Giulia Ghielmetti; Michael E. Schaepman; Miina Rautiainen. 2020. "Empirical validation of photon recollision probability in single crowns of tree seedlings." ISPRS Journal of Photogrammetry and Remote Sensing 169, no. : 57-72.
The aim of this paper is to share our experiences and thoughts about a project course in geoinformatics. The course has been organised annually since 2017. We hope that this article provides ideas about when new project-based courses are designed or existing ones are renewed. We wanted to increase students’ motivation by providing assignments from companies or other organisations as well as cooperation with them. Working with real clients makes the project work much more interesting than projects without a real-life connection. We provide topics from various fields of geoinformatics, such as geoinformation technology, geodesy, photogrammetry, laser scanning and remote sensing. The students worked in small groups that were supported by an advisor and a facilitator. The advisor helps with substance and the facilitator assists with reflection and improving working process, i.e. not only to complete the task but also to learn about capabilities for project work, self-directive teamwork and learning to learn (meta learning). To sum up, during the course students increase their knowledge and expertise on geoinformatics, learn skills for client-centered project work and learn how to support their learning through self- and peer-reflection. In other words, the course aims to develop skills that are useful throughout the students’ forthcoming careers.
H. Haggrén; P. Ståhle; M. Vaaja; P. Rönnholm; P. Sarkola; M. Rautiainen; M. Nordman; J. Nikander. EXPERIENCES FROM THE PROJECT COURSE IN GEOINFORMATICS. ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences 2020, V-5-2020, 17 -22.
AMA StyleH. Haggrén, P. Ståhle, M. Vaaja, P. Rönnholm, P. Sarkola, M. Rautiainen, M. Nordman, J. Nikander. EXPERIENCES FROM THE PROJECT COURSE IN GEOINFORMATICS. ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2020; V-5-2020 ():17-22.
Chicago/Turabian StyleH. Haggrén; P. Ståhle; M. Vaaja; P. Rönnholm; P. Sarkola; M. Rautiainen; M. Nordman; J. Nikander. 2020. "EXPERIENCES FROM THE PROJECT COURSE IN GEOINFORMATICS." ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences V-5-2020, no. : 17-22.
Key message Leaf area index and species composition influence red-to-near-infrared and red-to-shortwave-infrared transmittance ratios of boreal and temperate forest canopies. In this short communication paper, we present how the spectral composition of transmitted shortwave radiation (350–2200 nm) varies in boreal and temperate forests based on a detailed set of measurements conducted in Finland and Czechia. Our results show that within-stand variation in canopy transmittance is wavelength dependent, and is the largest for sparse forest stands. Increasing leaf area index (LAI) reduces the overall level of transmittance as well as red-to-near-infrared and red-to-shortwave-infrared transmittance ratios. Given the same LAI, these ratios are lower for broadleaved than for coniferous forests. These results demonstrate the importance of both LAI and forest type (broadleaved vs. coniferous) in determining light quality under forest canopies.
Aarne Hovi; Miina Rautiainen. Spectral composition of shortwave radiation transmitted by forest canopies. Trees 2020, 34, 1499 -1506.
AMA StyleAarne Hovi, Miina Rautiainen. Spectral composition of shortwave radiation transmitted by forest canopies. Trees. 2020; 34 (6):1499-1506.
Chicago/Turabian StyleAarne Hovi; Miina Rautiainen. 2020. "Spectral composition of shortwave radiation transmitted by forest canopies." Trees 34, no. 6: 1499-1506.
Lichens dominate a significant part of the Earth's land surface, and are valuable bioindicators of various environmental changes. In the northern hemisphere, the largest lichen biomass is in the woodlands and heathlands of the boreal zone and in tundra. Despite the global coverage of lichens, there has been only limited research on their spectral properties in the context of remote sensing of the environment. In this paper, we report spectral properties of 12 common boreal lichen species. Measurements of reflectance spectra were made in laboratory conditions with a standard spectrometer (350–2500 nm) and a novel mobile hyperspectral camera (400–1000 nm) which was used in a multiangular setting. Our results show that interspecific differences in reflectance spectra were the most pronounced in the ultraviolet and visible spectral range, and that dry samples always had higher reflectance than fresh (moist) samples in the shortwave infrared region. All study species had higher reflectance in the backward scattering direction compared to nadir or forward scattering directions. Our results also reveal, for the first time, that there is large intraspecific variation in reflectance of lichen species. This emphasizes the importance of measuring several replicates of each species when analyzing lichen spectra. In addition, we used the data in a spectral clustering analysis to study the spectral similarity between samples and species, and how these similarities could be linked to different physical traits or phylogenetic closeness of the species. Overall, our results suggest that spectra of some lichen species with large ground coverage can be used for species identification from high spatial resolution remote sensing imagery. On the other hand, for lichen species growing as small assemblages, mobile hyperspectral cameras may offer a solution for in-situ species identification. The spectral library collected in this study is available in the SPECCHIO Spectral Information System.
Nea Kuusinen; Jussi Juola; Bijay Karki; Soili Stenroos; Miina Rautiainen. A spectral analysis of common boreal ground lichen species. Remote Sensing of Environment 2020, 247, 111955 .
AMA StyleNea Kuusinen, Jussi Juola, Bijay Karki, Soili Stenroos, Miina Rautiainen. A spectral analysis of common boreal ground lichen species. Remote Sensing of Environment. 2020; 247 ():111955.
Chicago/Turabian StyleNea Kuusinen; Jussi Juola; Bijay Karki; Soili Stenroos; Miina Rautiainen. 2020. "A spectral analysis of common boreal ground lichen species." Remote Sensing of Environment 247, no. : 111955.
Photon recollision probability p is a spectrally invariant structural parameter and a powerful tool to link canopy optical properties at any wavelengths to model reflectance, transmittance, or absorption of vegetation canopies. The concepts of the p-theory have been reported and examined at the shoot and canopy scales, but not yet for the crown level. Currently, the p-value is estimated indirectly, such as converted from the spherically averaged silhouette to total area ratio (STAR¯) or canopy transmittance measurements. In this work, we first validate the theoretical considerations of the p concept at the crown level (e.g., its relationship with STAR¯), and then provide the first method to directly estimate photon recollision probability using Terrestrial Laser Scanning (TLS) data. The proposed geometric method is data-driven and avoids explicit reconstructions of tree structures. The p-value estimated here is the average recollision probability over spatial locations. We showed that the average recollision probability can be interpreted as the local spherical openness on phytoelement (leaf or needle) surfaces, which enabled a simple visibility calculation by avoiding explicit ray tracing. The developed method was tested on synthetic crowns of needle-leaved tree species, for which the reference p-values were known. Results confirmed the validity of the p-STAR¯ relationship at the crown level, and showed that p-values can be accurately estimated from TLS point clouds with a relative root measure square error of less than 10%. This study displays the distinct advantage of TLS in delineating detailed tree crown structures and highlights its potential in studies of forest reflectance modeling.
Di Wang; Daniel Schraik; Aarne Hovi; Miina Rautiainen. Direct estimation of photon recollision probability using terrestrial laser scanning. Remote Sensing of Environment 2020, 247, 111932 .
AMA StyleDi Wang, Daniel Schraik, Aarne Hovi, Miina Rautiainen. Direct estimation of photon recollision probability using terrestrial laser scanning. Remote Sensing of Environment. 2020; 247 ():111932.
Chicago/Turabian StyleDi Wang; Daniel Schraik; Aarne Hovi; Miina Rautiainen. 2020. "Direct estimation of photon recollision probability using terrestrial laser scanning." Remote Sensing of Environment 247, no. : 111932.
Forests are critical in regulating climate by altering the Earth's surface albedo. Therefore, there is an urgent need to enhance our knowledge about the effects of forest structure on albedo. Here, we present a global assessment of the links between forest structure and albedo at a 1-km spatial resolution using generalized additive models (GAMs). We used remotely sensed data to obtain variables representing forest structure, including forest density, leaf area index, and tree cover, during the peak growing season in 2005 with pure forest pixels that cover ~7% of the Earth's surface. Furthermore, we estimated black-sky albedo at a solar zenith angle of 38° using the most recent collection of the moderate resolution imaging spectroradiometer (MODIS; version 6) at shortwave, near-infrared, and visible spectral regions. In addition, for the first time, we mapped the magnitude of the relationship between forest structure and albedo at each pixel with a 0.5-degree spatial resolution. Our results suggested that forest structure may modulate albedo in most of the sub-biomes. The response of shortwave albedo was always positive to the leaf area index and negative to the tree cover (except for deciduous broadleaf forests in mediterranean and temperate regions), while the response to forest density varied across space in 2005. The spatial map affirmed that the links between forest structure and albedo vary over geographical locations. In sum, our study emphasized the importance of forest structure in the surface albedo regulation. This paper provides the first spatially explicit evidence of the magnitude of relationships between forest structure and albedo on a global scale.
Sara Alibakhshi; Babak Naimi; Aarne Hovi; Thomas W. Crowther; Miina Rautiainen. Quantitative analysis of the links between forest structure and land surface albedo on a global scale. Remote Sensing of Environment 2020, 246, 111854 .
AMA StyleSara Alibakhshi, Babak Naimi, Aarne Hovi, Thomas W. Crowther, Miina Rautiainen. Quantitative analysis of the links between forest structure and land surface albedo on a global scale. Remote Sensing of Environment. 2020; 246 ():111854.
Chicago/Turabian StyleSara Alibakhshi; Babak Naimi; Aarne Hovi; Thomas W. Crowther; Miina Rautiainen. 2020. "Quantitative analysis of the links between forest structure and land surface albedo on a global scale." Remote Sensing of Environment 246, no. : 111854.
A field data set from 301 forest plots was collected during peak-growing season (June 24 - July 17, 2013) around Hyytiälä forestry field station in Southern Finland (61° 50′ N, 24° 17′ E). For all plots, forest variables were collected following local forest inventory practice, and understory cover fractions were estimated using a traditional sampling quadrat. The understory layer in each plot was classified into four site fertility types: herb-rich, mesic, sub-xeric, and xeric. The upper understory layer fractional covers were estimated for: (1) dwarf shrubs, (2) pteridophytes and herbaceous species, and (3) graminoids, and the lower ground layer fractional covers for: (1) mosses, (2) lichens, and (3) litter (including all non-photosynthetic material). Canopy transmittance data were collected using two LAI-2000 device. The transmittance data were used to calculate effective leaf area index, true leaf area index, canopy openness and canopy cover for all plots. The data can be used to parameterize tree canopy and understory compositions in e.g., physically-based reflectance models, land surface models, and regional carbon cycle models. Interpretations of the results are provided in the related article [1].
Titta Majasalmi; Miina Rautiainen. Dataset of tree canopy structure and variation in understory composition in a boreal forest site. Data in Brief 2020, 30, 105573 .
AMA StyleTitta Majasalmi, Miina Rautiainen. Dataset of tree canopy structure and variation in understory composition in a boreal forest site. Data in Brief. 2020; 30 ():105573.
Chicago/Turabian StyleTitta Majasalmi; Miina Rautiainen. 2020. "Dataset of tree canopy structure and variation in understory composition in a boreal forest site." Data in Brief 30, no. : 105573.
Information on understory composition and its relationships with the overstory tree canopy, especially leaf area index (LAI), is crucially needed in, e.g., modeling land-atmosphere interactions and productivity of forests. There are also several global LAI products produced from satellite data which need to be validated with ground reference data. However, to date, only scarce field data on simultaneous structural properties of under- and overstory vegetation, and tree canopy LAI, have been available in boreal forests. This paper shows how understory composition and fractional cover of different species types varies in a boreal forest site, and how it is linked to structural properties of the tree layer. The study is based on 301 understory plots collected in an area of ∼16 km2 around Hyytiälä forestry field station, Finland (61°50′N, 24°17′E) in a southern boreal forest site. Forest understory plot data was accompanied with measurements of both standard forest inventory variables and optically-based canopy light transmittance data. Clear differences in average species composition between different site fertility types were observed, but also large variation within each site fertility type was noted. Forest understory composition was better correlated with structural forest canopy measures (e.g., tree canopy LAI, canopy cover, canopy openness) than with traditional forest inventory variables such as tree height or diameter. Forest canopy LAI and the fractional cover of understory were strongly related, especially in more fertile sites. Our results highlight the role of tree canopy structural metrics as modifiers of the understory light climate and growing conditions, also, in boreal forests.
Titta Majasalmi; Miina Rautiainen. The impact of tree canopy structure on understory variation in a boreal forest. Forest Ecology and Management 2020, 466, 118100 .
AMA StyleTitta Majasalmi, Miina Rautiainen. The impact of tree canopy structure on understory variation in a boreal forest. Forest Ecology and Management. 2020; 466 ():118100.
Chicago/Turabian StyleTitta Majasalmi; Miina Rautiainen. 2020. "The impact of tree canopy structure on understory variation in a boreal forest." Forest Ecology and Management 466, no. : 118100.
Environmental camera networks are growing in usage in different parts of the globe. Time series of webcam imagery from the camera networks are used in estimating snow cover properties. Fractional snow cover (FSC) and snow depth (SD) are two important parameters which can be estimated from the webcam imagery using image processing algorithms. Monitoring of snow cover from webcam imagery has the potential to be used in gap filling and validation of satellite derived products. It can also be used as a data source for snow monitoring in remote areas where manual measurements and in-situ sensor installation and maintenance are costly, especially under forest canopy which retrieval of signal from ground by satellites is a challenge. In this paper, we have used multiple webcams from MONIMET Camera Network in Finland and Finnish Meteorological Institute Image Processing Toolbox (FMIPROT) on the cloud to establish an automated processing chain which reports FSC and SD estimations in near real time, available in FMIPROT website. Image processing algorithms are implemented in the toolbox, the images from last year are also processed and the results are compared with ultrasonic in-situ measurements and values generated by visual inspections on images. In the website, estimations from the day-time images of the latest one month are visualized on interactive plots, along with time-lapse animations of images, with a latency of 3 hours.
Cemal Melih Tanis; Ali Nadir Arslan; Miina Rautiainen. Near real time monitoring of snow cover using webcam imagery. 2020, 1 .
AMA StyleCemal Melih Tanis, Ali Nadir Arslan, Miina Rautiainen. Near real time monitoring of snow cover using webcam imagery. . 2020; ():1.
Chicago/Turabian StyleCemal Melih Tanis; Ali Nadir Arslan; Miina Rautiainen. 2020. "Near real time monitoring of snow cover using webcam imagery." , no. : 1.
Despite the importance of spectral properties of woody tree structures, they are seldom represented in research related to forests, remote sensing, and reflectance modeling. This study presents a novel imaging multiangular measurement set-up that utilizes a mobile handheld hyperspectral camera (Specim IQ, 400â1000 nm), and can measure stem bark spectra in a controlled laboratory setting. We measured multiangular reflectance spectra of silver birch ( Roth), Scots pine ( L.) and Norway spruce ( (L.) Karst.) stem bark, and demonstrated the potential of using bark spectra in identifying tree species using a Support Vector Machine (SVM) based approach. Intraspecific reflectance variability was the lowest in visible (400â700 nm), and the highest in near-infrared (700â1000 nm) wavelength regions. Interspecific variation was the largest in the red, red-edge and near-infrared spectral bands. Spatial variation of reflectance along the tree height and different sides of the stem (north and south) were found. Both birch and pine had increased reflectance in the forward-scattering directions for visible to near-infrared wavelength regions, whilst spruce displayed the same only for the visible wavelength region. In addition, spruce had increased reflectance in the backward-scattering directions. In spite of the intraspecific variations, SVM could identify tree species with 88.8% overall accuracy when using pixel-specific spectra, and with 97.2% overall accuracy when using mean spectra per image. Based on our results it is possible to identify common boreal tree species based on their stem bark spectra using images from mobile hyperspectral cameras.Betula pendulaPinus sylvestrisPicea abies
Jussi Juola; Aarne Hovi; Miina Rautiainen. Multiangular spectra of tree bark for common boreal tree species in Europe. Silva Fennica 2020, 54, 1 .
AMA StyleJussi Juola, Aarne Hovi, Miina Rautiainen. Multiangular spectra of tree bark for common boreal tree species in Europe. Silva Fennica. 2020; 54 (4):1.
Chicago/Turabian StyleJussi Juola; Aarne Hovi; Miina Rautiainen. 2020. "Multiangular spectra of tree bark for common boreal tree species in Europe." Silva Fennica 54, no. 4: 1.
Leaf reflectance and transmittance spectra are essential information in many applications such as developing remote sensing methods, computing shortwave energy balance (albedo) of forest canopies, and monitoring health or stress of trees. Measurement of coniferous needle spectra has usually been carried out with single integrating spheres, which has involved a lot of tedious manual work. A small double integrating sphere would make the measurements considerably faster, because of its ease of operation and small sample sizes required. Here we applied a compact double integrating sphere setup, used previously for measurement of broad leaves, for measurement of coniferous needles. Test measurements with the double integrating sphere showed relative underestimation of needle albedo by 5â39% compared to a well-established single integrating sphere setup. A small part of the bias can be explained by the bias of the single sphere. Yet the observed bias is quite significant if absolute accuracy of measurements is required. For relative measurements, e.g. for monitoring development of needle spectra over time, the double sphere system provides notable improvement. Furthermore, it might be possible to reduce the bias by building an optimized measurement setup that minimizes absorption losses in the sample port. Our study indicates that double spheres, after some technical improvement, may provide a new and fast way to collect extensive spectral libraries of tree species.
Aarne Hovi; Matti Mõttus; Jussi Juola; Farshid Manoocheri; Erkki Ikonen; Miina Rautiainen. Evaluating the performance of a double integrating sphere in measurement of reflectance, transmittance, and albedo of coniferous needles. Silva Fennica 2020, 54, 1 .
AMA StyleAarne Hovi, Matti Mõttus, Jussi Juola, Farshid Manoocheri, Erkki Ikonen, Miina Rautiainen. Evaluating the performance of a double integrating sphere in measurement of reflectance, transmittance, and albedo of coniferous needles. Silva Fennica. 2020; 54 (2):1.
Chicago/Turabian StyleAarne Hovi; Matti Mõttus; Jussi Juola; Farshid Manoocheri; Erkki Ikonen; Miina Rautiainen. 2020. "Evaluating the performance of a double integrating sphere in measurement of reflectance, transmittance, and albedo of coniferous needles." Silva Fennica 54, no. 2: 1.
Miina Rautiainen; Nea Kuusinen; Aarne Hovi; Titta Majasalmi. Boreaalisten metsien albedosta. Metsätieteen aikakauskirja 2020, 2020, 1 .
AMA StyleMiina Rautiainen, Nea Kuusinen, Aarne Hovi, Titta Majasalmi. Boreaalisten metsien albedosta. Metsätieteen aikakauskirja. 2020; 2020 ():1.
Chicago/Turabian StyleMiina Rautiainen; Nea Kuusinen; Aarne Hovi; Titta Majasalmi. 2020. "Boreaalisten metsien albedosta." Metsätieteen aikakauskirja 2020, no. : 1.