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  • 1.
    Fjeld, Dag
    et al.
    Swedish University of Agricultural Sciences, Sweden;Norwegian Inst Bioecon Res, Norway.
    Persson, Magnus
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Skogforsk, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Bjerketvedt, Jan
    Norwegian Inst Bioecon Res, Norway.
    Brathen, Martin
    Skogkurs, Norway.
    Modelling forest road trafficability with satellite-based soil moisture variables2024Ingår i: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 35, nr 1, s. 93-104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent decades have seen increased temperatures and precipitation in the Nordic countries with long-term projections for reduced frost duration and depth. The consequence of these trends has been a gradual shift of delivery volumes to the frost-free season, requiring more agile management to exploit suitable weather conditions. Bearing capacity and trafficability are dependent on soil moisture state and in this context two satellite missions offer potenially useful information on soil moisture levels; NASA's SMAP (Soil Moisture Active Passive) and ESA's Sentinel-1. The goal of this pilot study was to quantify the performance of such satellite-based soil moisture variables for modeling forest road bearing capacity (e-module) during the frost-free season. The study was based on post-transport registrations of 103 forest road segments on the coastal and interior side of the Scandinavian mountain range. The analysis focused on roads of three types of surface deposits. Weekly SMAP soil moisture values better explained the variation in road e-module than soil water index (SWI) derived from Sentinel-1. Soil Water Index (SWI), however, reflected the weather conditions typical for operations on the respective surface deposit types. Regression analysis using (i) SMAP-based soil dryness index and (ii) its interaction with surface deposit types, together with (iii) the ratio between a combined SMAP_SWI dryness index and segment-specific depth to water (DTW) explained over 70% of the variation in road e-module. The results indicate a future potential to monitor road trafficability over large supply areas on a weekly level, given further refinement of study methods and variables for improved prediction.

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  • 2.
    Ulander, Lars M.H.
    et al.
    Chalmers University of Technology, Sweden.
    Monteith, Albert R.
    Chalmers University of Technology, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Development and Initial Evaluation of the Tower-based Borealscat-2 P- and L-Band Tomographic SAR2023Ingår i: IGARSS 2023 - 2023 IEEE International Geoscience and Remote Sensing Symposium: Pasadena, CA, USA, 2023, IEEE, 2023, s. 2192-2194Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes the development and initial evaluation of the BorealScat-2 radar. It is installed on a 50 m tall tower at a boreal forest site in northern Sweden and acquires tomographic and multi-polarization measurements at P- and L-band every 5 min. It is of the same design as its predecessor BorealScat except that the antenna frame can be moved along a 4 m horizontal track. A moveable antenna position is motivated by the need to acquire independent samples to reduce backscatter fluctuations. It also enables focused 3D imaging by combing tomographic and SAR processing when the backscatter fluctuations are temporally stable. We show results from data acquired in 2022, which demonstrates 3D imaging of a forest as well as the response from a trihedral.

  • 3.
    Aksoy, Samet
    et al.
    Istanbul Technical University, Türkiye.
    Hasan Al Shwayyat, Shouq Zuhter
    Marmara University, Türkiye.
    Nur Topgül, Şule
    Istanbul Technical University, Türkiye.
    Sertel, Elif
    Istanbul Technical University, Türkiye.
    Ünsalan, Cem
    Marmara University, Türkiye.
    Salo, Jari
    University of Helsinki, Finland.
    Holmström, Anton
    Katam Technologies, Sweden.
    Wallerman, Jörgen
    Swedish University of Agricultural Sciences, Sweden.
    Nilsson, Mats
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Forest Biophysical Parameter Estimation via Machine Learning and Neural Network Approaches2023Ingår i: IGARSS 2023 - 2023 IEEE International Geoscience and Remote Sensing Symposium: Pasadena, CA, USA, 2023, IEEE, 2023, s. 2661-2664Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the first results of the ongoing development of new forest mapping methods for the Swedish national forest mapping case using Airborne Laser Scanning (ALS) data, utilizing the recent findings in machine learning (ML) and Artificial Intelligence (AI) techniques. We used Random Forest (RF) and eXtreme Gradient Boosting (XGBoost) as ML models. In addition, Neural networks (NN) based approaches were utilized in this study. ALS derived features were used to estimate the stem volume (V), above-ground biomass (AGB), basal area (B), tree height (H), stem diameter (D), and forest stand age (A). XGBoost ML algorithm outperformed RF 1 % to 3 % in the R² metric. NN model performed similar to ML model, however it is superior in the estimation of V, AGB, and B parameters.

  • 4.
    Fransson, Johan
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Sertel, Elif
    Istanbul Technical University, Türkiye.
    Ünsalan, Cem
    Marmara University, Türkiye.
    Salo, Jari
    University of Helsinki, Finland.
    Holmström, Anton
    Katam Technologies, Sweden.
    Wallerman, Jörgen
    Swedish University of Agricultural Sciences, Sweden.
    Nilsson, Mats
    Swedish University of Agricultural Sciences, Sweden.
    ForestMap: Mapping Forest Attributes Across the Globe - First Case Study2023Ingår i: IGARSS 2023 - 2023 IEEE International Geoscience and Remote Sensing Symposium, IEEE, 2023, s. 3395-3397Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the project ForestMap – a project aiming to develop and distribute new methods, which provide the benefits of accurate forest maps to a global audience. Using the recent developments in remote sensing, machine learning, and Artificial Intelligence (AI) the goal is to export the Scandinavian success stories to a wide range of stakeholders in the world.

  • 5.
    Peichl, Matthias
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Martinez-Garcia, Eduardo
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Swedish University of Agricultural Sciences, Sweden.
    Wallerman, Jörgen
    Swedish University of Agricultural Sciences, Sweden.
    Laudon, Hjalmar
    Swedish University of Agricultural Sciences, Sweden.
    Lundmark, Tomas
    Swedish University of Agricultural Sciences, Sweden.
    Nilsson, Mats B.
    Swedish University of Agricultural Sciences, Sweden.
    Landscape-variability of the carbon balance across managed boreal forests2023Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 29, nr 4, s. 1119-1132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Boreal forests are important global carbon (C) sinks and, therefore, considered as a key element in climate change mitigation policies. However, their actual C sink strength is uncertain and under debate, particularly for the actively managed forests in the boreal regions of Fennoscandia. In this study, we use an extensive set of biometric- and chamber-based C flux data collected in 50 forest stands (ranging from 5 to 211 years) over 3 years (2016-2018) with the aim to explore the variations of the annual net ecosystem production (NEP; i.e., the ecosystem C balance) across a 68 km(2) managed boreal forest landscape in northern Sweden. Our results demonstrate that net primary production rather than heterotrophic respiration regulated the spatio-temporal variations of NEP across the heterogeneous mosaic of the managed boreal forest landscape. We further find divergent successional patterns of NEP in our managed forests relative to naturally regenerating boreal forests, including (i) a fast recovery of the C sink function within the first decade after harvest due to the rapid establishment of a productive understory layer and (ii) a sustained C sink in old stands (131-211 years). We estimate that the rotation period for optimum C sequestration extends to 138 years, which over multiple rotations results in a long-term C sequestration rate of 86.5 t C ha(-1) per rotation. Our study highlights the potential of forest management to maximize C sequestration of boreal forest landscapes and associate climate change mitigation effects by developing strategies that optimize tree biomass production rather than heterotrophic soil C emissions.

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  • 6.
    Peichl, Matthias
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Martinez-Garcia, Eduardo
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Wallerman, Jörgen
    Swedish University of Agricultural Sciences, Sweden.
    Laudon, Hjalmar
    Swedish University of Agricultural Sciences, Sweden.
    Lundmark, Tomas
    Swedish University of Agricultural Sciences, Sweden.
    Nilsson, Mats B.
    Swedish University of Agricultural Sciences, Sweden.
    On the uncertainty in estimates of the carbon balance recovery time after forest clear-cutting2023Ingår i: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 29, nr 15, s. e1-e3Artikel i tidskrift (Refereegranskat)
  • 7.
    Huuva, Ivan
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Persson, Henrik J.
    Swedish University of Agricultural Sciences, Sweden.
    Wallerman, Jörgen
    Swedish University of Agricultural Sciences, Sweden.
    Ulander, Lars M.H.
    Chalmers University of Technology, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Prediction of Hemi-Boreal Forest Biomass Change Using Alos-2 Palsar-2 L-Band SAR Backscatter2023Ingår i: IGARSS 2023 - 2023 IEEE International Geoscience and Remote Sensing Symposium, IEEE, 2023, s. 3326-3329Konferensbidrag (Refereegranskat)
    Abstract [en]

    Pairs of fully polarimetric ALOS-2 PALSAR-2 L-band SAR images were used to model biomass on backscatter change over seven growth seasons in a hemi-boreal forest. The biomass change was related to backscatter change via consecutive field surveys of 263 field plots with a 10 m radius. To correct for differences in backscatter not related to biomass abundance, a HV-VV polarization ratio based correction, previously used on airborne L-band data, was applied to the data. The uncertainty of obtained predictions (lowest model mean RMSE 65.1 t/ha, lowest model mean bias 7.1 t/ha) was almost identical whether model fitting and prediction used data from the same scene pair, or different scene pairs. This could possibly attest to the feasibility of the backscatter correction for PALSAR-2 data, but no large backscatter offsets were observed for uncorrected data, and significant variance in predictions, due to the inherent noise in the data and the comparatively small area of evaluation plots, inhibit the analysis.

  • 8.
    Huuva, Ivan
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Wallerman, Jörgen
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Persson, Henrik J.
    Swedish University of Agricultural Sciences, Sweden.
    Prediction of Site Index and Age Using Time Series of TanDEM-X Phase Heights2023Ingår i: Remote Sensing, E-ISSN 2072-4292, Vol. 15, nr 17, artikel-id 4195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Site index and stand age are important variables in forestry. Site index describes the growing potential at a given location, expressed as the height that trees can attain at a given age under favorable growing conditions. It is traditionally used to classify forests in terms of future timber yield potential. Stand age is used for the planning of management activities such as thinning and harvest. SI has previously been predicted using remote sensing, but usually relying on either very short time series or repeated ALS acquisitions. In this study, site index and forest stand age were predicted from time series of interferometric TanDEM-X data spanning seven growth seasons in a hemi-boreal forest in Remningstorp, a test site located in southern Sweden. The goal of the study was to see how satellite-based radar time series could be used to estimate site index and stand age. Compared to previous studies, we used a longer time series and applied a penetration depth correction to the phase heights, thereby avoiding the need for calibration using ancillary field or ALS data. The time series consisted of 30 TanDEM-X strip map scenes acquired between 2011 and 2018. Established height development curves were fitted to the time series of TanDEM-X-based top heights. This enabled simultaneous estimation of both age and site index on 91 field plots with a 10 m radius. The RMSE of predicted SI and age were 6.9 m and 38 years for untreated plots when both SI and age were predicted. When predicting SI and the age was known, the RMSE of the predicted SI was 4.0 m. No significant prediction bias was observed for untreated plots, while underestimation of SI and overestimation of age increased with the intensity of treatment.

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  • 9.
    Jiang, Wen
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Acid-catalyzed Liquefaction of Industrial Side-streams for Producing Wood Adhesives and Particleboard2022Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Big quantities of residues and side-streams are generated annually from forest-based and agricultural industries all around the world and present a relatively unexplored renewable resource. Due to the absence of a regularly updated and systematic database of supply, industrial residues and side-streams usually end up in landfill disposal, are used for energy generation, or remain at the production sites. These renewable side-streams are mainly lignocellulosic materials that can be used for fuels, chemicals, and other value-added materials. However, the difficulty in recovering useful components from industrial wastes from a techno-economic point of view is hindering the use of these materials. There are different methods for converting biomass into fuels, chemicals, and materials, including thermochemical, biochemical, and physical conversion. Negative environmental impacts from direct incineration of waste materials and increasing interest in reducing the dependency on fossil-based sources have increased the need for the valorization of the industrial side-streams for material and chemical applications. 

    Among the different thermochemical conversion methods, liquefaction of lignocellulosic materials is an efficient way to convert solid biomass into liquids. Liquefaction including hydrothermal liquefaction (HTL) and moderate acid-catalyzed liquefaction (MACL), is often carried out in an aqueous environment by employing organic solvents with or without catalyst under pressure or ambient conditions. A liquefaction process is influenced by many factors such as material type, solvent, catalyst, time, and temperature. All the parameters of the liquefaction are related to each other, and they affect the yields and the properties of the final products. Studies on the utilization of industrial waste and side-streams as feedstock for liquefaction have increased in recent years, generating significant interest from both academia and industry.  

    This PhD study included a literature review on liquefaction technologies that provide liquefied products for wood adhesives, followed by experimental work on MACL and its optimization for different industrial side-streams, such as wood sawdust, bark, and oat husks. Liquefaction of those materials led to different liquefaction yields (LY) due to their different chemical compositions. When the same liquefaction conditions were applied, liquefied wood sawdust had the highest LY while liquefied bark had the lowest. This was mainly attributed to wood sawdust having a higher cellulose and lower lignin content, when compared to bark and oat husks. After optimizing the liquefaction of wood sawdust, obtained products were applied in wood adhesive formulations successfully. Crude liquefied wood (CLW) and purified liquefied wood (PLW) polyols were obtained from the liquefaction of wood sawdust with the highest LY of 99.7% and used for the synthesis of polyurethane (PU) adhesives by reacting them with polymeric diphenylmethane diisocyanate (pMDI). The bonding strength and penetration to wood adherends of the PU adhesives were affected by the molar ratios between the isocyanate groups (NCO) in pMDI and the hydroxyl groups (OH) in the CLW and PLW. The highest bonding strength of PU adhesives was achieved at an NCO:OH molar ratio of 1.5:1. The thermal stability of the PU adhesives was improved by increasing the NCO:OH molar ratio. PU adhesives based on CLW and PLW with the same adhesive formulation did not show significant differences in their properties while CLW polyol contained more water and alcohols than PLW.  

    A novel method called partial liquefaction of lignocellulosic biomass was also proposed. Partially liquefied bark (PLB) was prepared and used to replace wood particles for producing particleboards (PB) with or without the presence of a commercial synthetic adhesive, i.e. melamine-urea-formaldehyde (MUF). PLB was shown to provide single-layer PBs with good adhesion, mechanical strength, and water repellency. The overall mechanical properties of non-MUF single-layer PBs were inferior to those of MUF-bonded PBs. Increasing the PLB content up to 9.5% led to enhanced mechanical properties for MUF-bonded PBs. PLB prepared from bark with a particle size less than 2 mm ensured good mechanical behavior of single-layer PBs. Moreover, three-layer particleboards prepared from PLB and wood particles had comparable mechanical properties to the reference PBs made solely from wood particles, and PLB had less influence on the mechanical properties of the PBs when used in the surface layer than in the core layer. Formaldehyde emissions from the three-layer PBs were below the limits required by European Standard EN 13986:2004 and major volatile organic compounds (VOCs) were carboxylic acids. 

    This research provided a comprehensive understanding of converting different lignocellulosic materials by a MACL process into valuable polymers and raw materials, which are suitable for the synthesis of wood adhesives and for the manufacturing of particleboards. Due to time constraints related to conducting the PhD, it was not possible to conduct a full characterization of the liquefied products from the selected materials. Such studies should be part of future research in order to supplement our knowledge of MACL mechanisms. 

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  • 10.
    Jones, Grace
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Birch Stem and Wood Traits in Genetic and Silviculture Trials in Southern Sweden2022Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Swedish tree species of birch (silver: Betula pendula and downy: B. pubescens) are often neglected during forest management activities, resulting in low value logs. This thesis investigated birch stem characteristics and wood properties important for solid wood products, in genetics and management trials in southern Sweden. As well as visual stem size and form measurements, non-destructive testing and evaluation (NDT) tools were used to indirectly estimate wood density (hardness), wood stiffness, and grain angle.

    The results of this work suggest that for the 19-year-old silver birch and 15-year-old downy birch sites, important solid wood traits were under a reasonable degree of genetic control. It seems possible to breed birch to improve grain angle since heritability and genetic variation was high for this trait. Silver birch genotypes are expected to perform similarly across sites. At a site with both birch species, silver birch was larger with denser wood than downy birch. Few genetic correlations between measurements means selection for one trait will not inadvertently affect another trait. The radial density profiles showed density was continuing to increase. Acoustic velocity (AV) and fibre length were highly correlated, hardness and density were related, and ring width was related to ring density. 

    In a 35-year-old planted Norway spruce stand, naturally regenerated birch AV was not different between treatments (20% or 50% of plot trees were birch by number). However, a correlation was observed between DBH and AV. This older site may reflect common Swedish conditions since planting birch is rare, and likely had more mature birch wood than the genetics trials. 

    Although meeting an immediate need for studies of birch wood properties from managed stands, this work covered few sites. To meet this limitation the tools and techniques applied in this thesis could be used in further studies. The results of this thesis work will be of interest to forest managers who want to breed birch, or select birch stands, for solid wood products.

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  • 11.
    Huo, Langning
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Lindberg, Eva
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Swedish University of Agricultural Sciences, Sweden.
    Persson, Henrik J.
    Swedish University of Agricultural Sciences, Sweden.
    Comparing spectral differences between healthy and early infested spruce forests caused by bark beetle attacks using satellite images2022Ingår i: IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium, Hybrid Symposium, Kuala Lumpur, Malaysia, 17-21 July, 2022, IEEE, 2022, s. 7709-7712Konferensbidrag (Refereegranskat)
    Abstract [en]

    Detecting forest insect damage before the visible discoloration (green attacks) using remote sensing data is challenging, but important for damage control. In recent years, the European spruce bark beetle (Ips typographus, L.) has damaged large amounts of forest in Europe. However, it is still debatable how early the infestations can be detected with remote sensing data. Some studies showed a spectral difference between healthy and green-attacked spruce trees at the plot level, while others showed that spectral  differences existed before attacks. Therefore, a hypothesis is proposed that no spectral difference can be identified between green-attacked forests compared to healthy forests if the differences do not exist before the attacks. In this study, we tested this hypothesis using Sentinel-2 and WorldView-3 SWIR images on 24 healthy plots and 24 plots with mild, moderate, and severe attacks. In the results, the severely attacked plots did not show significant spectral differences in the Sentinel-2 images until August, and the sensitivity was found in the blue, red, red-edge, and SWIR band. Only the red band showed a significant difference between the healthy and moderately attacked plots in August, and only the blue, red, and SWIR band showed significant differences in September, October, and November. No significant differences were observed in the WorldView-3 images at the plot or individual tree level. We accepted the hypothesis that green attacks do not show spectral differences with the healthy forests when the differences do not exist before the attacks. We concluded that the SWIR bands were sensitive to attacks in the Sentinel-2 images with 10 m resolution, but not in the WorldView-3 images with 3.7 m resolution. Further studies are needed to explore the methodology of using WorldView-3 SWIR images for the early detection of forest infestation.

  • 12.
    Persson, Henrik J.
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Mukhopadhyay, Ritwika
    Swedish University of Agricultural Sciences, Sweden.
    Huuva, Ivan
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Swedish University of Agricultural Sciences, Sweden.
    Comparison of Boreal Biomass Estimations Using C-and X-Band Polsar2022Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS), Volume 2022-July, IEEE, 2022, Vol. 2022-July, s. 5555-5558Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study investigated the potential of using polarimetric synthetic aperture radar (PolSAR) data acquired at C-and X-band to estimate forest aboveground biomass (biomass) at a test site in southern Sweden. The SAR data were acquired with RADARSAT-2 and TerraSAR-X in September 2015, and the biomass estimations were cross-validated with 48 field inventoried plots of 40 m radius (0.5 ha), covering dominantly coniferous hemi-boreal forest. The quad-pol SAR data (HH, HV, VH, VV) were decomposed using the Yamaguchi model and the mean modelled scatter components for the plots were extracted and used as predictors in linear regression models to estimate the biomass. The model performances were quantified using the root mean square error (RMSE) and adjusted coefficient of determination, R2adj. The leave-one-out cross-validated RMSEs were 58.1 (37.1%) and 60.6 (38.6%) tons/ha for C-and X-band, respectively, and the R2adj were 0.52 and 0.47, respectively. The regression model for C-band data used the volume and helix scattering components in the Yamaguchi decomposition as predictors, while the corresponding X-band model used the double bounce and surface components. The differences were likely due to the different penetrations at C-and X-band. We noticed a tendency to saturation at about 300 tons/ha in the X-band predictions, while no such tendency was noticed for the C-band model. We conclude that the Yamaguchi polarimetric decomposition technique is a useful approach when estimating biomass in a hemi-boreal forest. The strengths are not comparable to approaches where height information are available (e.g., single-pass interferometry from TanDEM-X), but this polarimetric approach based on single satellite images showed sensitivity to the entire biomass range (0-400 tons/ha) in our dataset. The potential of using quad-pol SAR data is, therefore, important to investigate further.

  • 13.
    Huuva, Ivan
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Persson, Henrik J.
    Swedish University of Agricultural Sciences, Sweden.
    Wallerman, Jorgen
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Swedish University of Agricultural Sciences, Sweden.
    Detectability of Silvicultural Treatments in Time Series of Penetration Depth Corrected Tandem-X Phase Heights2022Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS), Volume 2022-July, IEEE (Institute of Electrical and Electronics Engineers) , 2022, Vol. 2022-July, s. 5909-5912Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study investigated the potential of utilizing time series of TanDEM-X phase heights, corrected for penetration depth, to detect silvicultural treatments in hemi-boreal forest. In total, 34 field plots with 40 m radius were used in conjunction with detailed forest management records to construct a reliable data set of treatments. The study area is situated in Remningstorp, a forest test site in southern Sweden. In the analysis, the temporal mean corrected phase heights were compared before and after a silvicultural treatment in order to quantify the effects of thinnings and clear-cuts on the phase height. As expected clear-cuts were highly distinguishable, but thinnings, while exhibiting a negative change in phase height on average, were not individually distinct from all untreated plots. Moreover, the results regarding the utility of applying penetration depth correction for the task were inconclusive. Overall, the results look very promising for using time series of phase height from TanDEM-X to map thinnings and clear-cuts, especially when several observations are available before and after the silvicultural treatment.

  • 14.
    Habite, Tadios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Abdeljaber, Osama
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Determination of pith location along Norway spruce timber boards using one dimensional convolutional neural networks trained on virtual timber boards2022Ingår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 329, artikel-id 127129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge of pith location is needed for modelling of sawn timber and for real time assessment of wood material in the wood working industry. However, the methods that are available and implemented in optical scanner today seldom meet customer requirements on accuracy and/or speed. In the present research data of greyscale images of the four longitudinal sides of board and a one-dimensional convolutional neural network were used to determine pith location along Norway spruce timber boards. A novel stochastic model was developed to generate thousands of virtual timber boards, with photo-realistic surfaces and known pith location, by which the network was trained before it was successfully applied to determine pith location along real boards.

  • 15.
    Persson, Magnus
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Evaluating thinning practices and assessment methods for improved management in coniferous production forests in southern Sweden2022Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Most of our knowledge about wood production of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) and associated silvicultural guidelines are based on field experiments. These have been established in rather small, homogenous stands. In practical forestry there is probably a comparatively larger gradient in within-stand variation due to varying site conditions and less controlled silviculture than in experiments. The extent of the within-stand variation in coniferous production stands and how thinning guides are used in relation to the within-stand variation, is not well understood. Also, the freely available Forest resource maps (sv. Skogliga grunddata) and satellite data offer the possibility to accounts for the within-stand variation in forest management, but this is also poorly researched.

    This thesis evaluates within-stand variation at first thinning: its extent, its effect on silviculture and its importance for future stand development. Additionally, optical satellite data from Sentinel-2 is used to detect thinning operations, estimate growth after thinning and classify tree species. The thesis is mainly based on a survey carried out in the fall of 2018 in planted conifer-dominated production stands planned for first commercial thinning in which the thinning method of the forest workers was observed. The survey was inventoried directly after thinning and three growing seasons later.

    The survey showed an unprecedented within-stand variation before thinning in stem volume, stem density, dominant height, mean height quadratic mean diameter and basal area. The thinning operations did not reduce the within-stand variation in any of the attributes measured with the relative standard deviation. The stands were thinned heavily, and the harvested basal area increased with basal area before thinning at sample plot level, which suggest an ambition to reduce the variation. 

    The stands were also monitored using Sentinel-2 satellite data. The thinning detection model separated unthinned, lightly thinned and heavily thinned sample plots with a moderate overall accuracy of 62% (Kappa of 0.34). A set of satellite images over the whole observation period was used estimate the periodical annual volume increment after thinning and did so with a root mean squared error (RMSE) of 1.8 m3 ha-1 y-1 (relative RMSE: 24%).

    The long-term effects of optimizing the thinning regime on pixel level versus conventional stand-level thinning was evaluated using the Heureka system. No benefits in terms of stand economy or production was found, but the within-stand variation in basal area decreased over the rotation.

    Tree-species classification, rendering maps with the dominant tree species at pixel level over a forest holding, were made using multi-temporal Sentinel-2 satellite data and the Random Forest classifier. The major tree species in the forest holding were Scots pine, Norway spruce, Pedunculate oak (Quercus robur), Birch (Betula spp.) and Hybrid larch (Larix × marschlinsii). These species were classified with a high overall accuracy of 88.2% (Kappa of 0.82). 

    This thesis illustrates that considerable within-stand variation could be expected before and after first thinning for coniferous dominated stands in southern Sweden. The average stand basal area after thinning was consistently lower than the required basal area in the thinning guides from the Swedish Forest Agency, which means that reduced total production over the rotation may be a result. The increasing harvested basal area with basal area before thinning, suggests an ambition to reduce the within-stand variation in basal area. Thinning at the pixel level by adapting the thinning regime to the within-stand variation did not have any long-term effects on stand economy or volume production compared to conventional stand-level thinning. Despite the non-significant results, high-resolution maps are probably needed anyway to support forest workers in thinning operations to avoid heavy thinning. The Sentinel-2 satellite data proved its relevance for practical forestry for thinning detection, assessing growth after thinning, and classifying tree species. These methods can be used in combination the already existing Forest resource maps to reduce uncertainties for the management of planted forest. 

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  • 16.
    Fagerberg, Nils
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Individual-tree-selection in uneven-sized Norway spruce stands in southern Sweden: Developments of tools for simulation and optimization2022Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Kontinuitetsskogsbruk, eller som det ofta benämns hyggesfritt skogsbruk, kännetecknas av brukningsmetoder som undviker kalhyggesfasen. Kontinuitetsskogsbruk kan i sin tur delas upp i två huvudkategorier, enskiktad respektive skiktad skogsskötsel, beroende på vilken beståndsstruktur som skötseln eftersträvar. I skiktad skogsskötsel fattas avverkningsbesluten antingen per trädgrupp (luckhuggning) eller per enskilt träd (individuella trädval). Denna avhandling fördjupar sig i metoden skiktad skogsskötsel med individuella trädval. Det svenska begreppet plockhuggning kan anses vara synonymt till individuella trädval under förutsättning att träden ”plockas” och ”huggs” efter medvetna överväganden om skogens långsiktiga avkastning.

    Nyligen redovisad forskning i Norden visar att skiktad barrskogsskötsel med individuella trädval har möjlighet att skapa en högre andel total nytta från skogsmarken samt ofta även en bättre lönsamhet för skogsägaren jämfört med traditionellt kalhyggesbruk. Idag tillämpas dock plockhuggning i olika former endast på mindre än 1 % av skogsarealen i de nordiska länderna. En huvudorsak till detta är att det finns bristande kunskaper och färdigheter hos alla intressenter (skogsägare, entreprenörer och rådgivare). Den uppkomna situationen beror sannolikt även på att forskningen endast i begränsad utsträckning har presenterat fältanpassade vägledningar för hur de individuella trädvalen bör utföras för att optimera den långsiktiga avkastningen.

    I en beslutssituation där ett specifikt träd utvärderas ifall det ska avverkas eller inte, kommer beslutet att påverka alla omgivande träd som delar tillväxtresurser med det aktuella trädet (trädets trädgrupp). Av de två tillgängliga beslutsalternativen, är det optimalt att välja det alternativ som ger högst värdeavkastning för hela trädgruppen. Det är ett komplext beslut med många dimensioner. Förutsättningarna är dessutom unika för varje träd och påverkas av dynamiska processer som förändras över tid. En optimering av generella besluts kriterier blir endast möjligt om problemställningen avgränsas och delas upp i hanterbara delproblem, där de mest inflytelserika variablerna inkluderas i analysen. Kompletterande analyser som hanterar olika delproblem kan sedan slås ihop till heltäckande beslutsvägledningar. Oavsett val av optimeringsmetod är grunden för sådana analyser att det finns tillgång till tillförlitliga och representativa simuleringsmodeller.

    Avhandlingens övergripande syfte är att undersöka sambanden mellan ekonomisk avkastning, skötsel och rundvirkeskvalitet för grandominerad skiktad skogsskötsel i södra Sverige. Under arbetets gång har detta, inom ovangivna ramar, specificerats till:

    1. att undersöka hur årsringsbredden beror på trädstorlek och gallringsuttag (artikel I).
    2. att utvärdera tillförlitligheten för befintliga tillväxtmodeller för enskilda träd (artikel I).
    3. att utveckla tillväxtmodeller för enskilda träd som är avståndsberoende (artikel II).
    4. att optimera beslutskriterier för individuella trädval i fält (artikel III).
    5. att utveckla en modell för största kviststorlek beroende av lokal konkurrens och position på stammen (artikel IV).

    Underlaget för analyserna har i huvudsak hämtats från fem olika provytor i Götaland bestående av grandominerad skiktad granskog med lång kontinuitet och mer eller mindre aktiv skötsel.

    Resultaten indikerar att i skiktade bestånd kan storleken på gallringsuttaget användas för att aktivt påverka den brösthöjdsdiameter där mindre diameterklasser får en hämmad tillväxt. Detta innebär att årsringsutvecklingen hos de mindre träden, vilket är en viktig kvalitetsregel, skulle kunna kontrolleras genom anpassning av gallringsuttaget. När de befintliga tillväxtmodellerna (för enskilda träd) testades på skiktad granskog, visade resultaten att tillväxten överskattades för små träd och underskattades för stora träd. När grundytan är hög försvinner underskattningen för stora träd med en brösthöjdsdiameter över 40 cm. Som ett alternativ till HEUREKA-modellerna presenteras nya avståndsberoende tillväxtmodeller för enskilda träd, som är anpassade för skiktad granskog. Med dessa tillväxtmodeller är det möjligt att studera betydelsen av avstånden mellan konkurrerande träd för det individuella trädvalet.

    Vidare presenteras en modellstruktur för att beräkna storleken på den största kvisten på en given höjd på stammen. Modellen tar även hänsyn till graden av lokal konkurrens runt det enskilda trädet. Modellstrukuren består av en uppsättning delmodeller som beskriver allometriska statistiska samband mellan några centrala fysiska proportioner hos granar i skiktade bestånd. Den modulära konstruktionen gör modellen anpassningsbar och den kan användas för att uppskatta förväntad rundvirkeskvalitet, avseende på tillåten kviststorlek.

    En metod som optimerar måldiametern hos det enskilda trädet beroende på vald diskonteringsränta samt graden av konkurrens runt trädet redovisas. Det optimerade resultatet presenteras i diagramform som kan användas som beslutsstöd direkt i fält. Beslutsstödet är anpassat för medelgoda till bördiga grandominerade ståndorter i södra Sverige. Optimal måldiameter, när ingen hänsyn tas till den lokala konkurrensen, var mellan 33 cm och 23 cm beroende på räntenivå (1–3 %). Slutligen presenteras ett förslag till beslutsstruktur för optimerade individuella trädval i fält, beskrivet med ett konkret exempel.

    Avhandlingen presenterar exempel på metodik och resultat som kan användas för att ta fram rekommendationer som optimerar trädvalen, men resultaten täcker endast en begränsad del av möjliga förutsättningar. Den mesta forskningen återstår således att göra för att täcka in fler geografiska områden, ståndorter, trädslag och beslutskriterier.

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  • 17.
    Martinez-Garcia, Eduardo
    et al.
    Swedish University of Agricultural Sciences, Sweden.
    Nilsson, Mats B.
    Swedish University of Agricultural Sciences, Sweden.
    Laudon, Hjalmar
    Swedish University of Agricultural Sciences, Sweden.
    Lundmark, Tomas
    Swedish University of Agricultural Sciences, Sweden.
    Fransson, Johan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Swedish University of Agricultural Sciences, Sweden.
    Wallerman, Jorgen
    Swedish University of Agricultural Sciences, Sweden.
    Peichl, Matthias
    Swedish University of Agricultural Sciences, Sweden.
    Overstory dynamics regulate the spatial variability in forest-floor CO2 fluxes across a managed boreal forest landscape2022Ingår i: Agricultural and Forest Meteorology, ISSN 0168-1923, E-ISSN 1873-2240, Vol. 318, artikel-id 108916Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The forest-floor represents an important interface for various carbon dioxide (CO2) fluxes, however, our knowledge of their variability and drivers across a managed boreal forest landscape is limited. Here, we used a three-year (2016-2018) data set of biometric- and chamber-based flux measurements to investigate the net forest-floor CO2 exchange (NEff) and its component fluxes across 50 forest stands spanning different soil types, tree species, and age classes within a 68 km2 boreal catchment in Sweden. We found that the forest-floor acted as a net CO2 source with the 10th-90th percentile (used hereafter for describing reported variations) ranging from 149 to 399 g C m- 2 yr-1. Among the key landscape attributes, stand age strongly affected most NEff component fluxes, whereas tree species and soil type effects were weak and absent, respectively. Specifically, forest-floor net CO2 emissions increased with stand age due to declining understory gross and net primary production, ranging between 77-275 and 49-163 g C m- 2 yr- 1, respectively. Furthermore, we observed higher understory production rates in pine than in spruce stands. Across the 50 stands, the total forest-floor respiration ranged between 340 and 549 g C m- 2 yr-1 and its spatial variation was primarily regulated by its autotrophic components, i.e., understory and tree root respiration, which displayed divergent increasing and decreasing age-related trends, respectively. Furthermore, heterotrophic soil respiration remained within a relatively narrow range (154-290 g C m- 2 yr- 1), possibly owing to compensating gradients in forest-floor properties. We further identified tree biomass as the major driver of the landscape-scale variations of CO2 fluxes, likely attributable to modulating effects on forest-floor resource availability and growing conditions. This implies that tree growth responses to forest management and global change will be particularly important for regulating magnitudes and spatial variations of forest-floor CO2 fluxes in boreal forests.

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  • 18.
    Habite, Tadios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Pith location and annual ring detection for modelling of knots and fibre orientation in structural timber: A Deep-Learning-Based Approach2022Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Detection of pith, annual rings and knots in relation to timber board cross-sections is relevant for many purposes, such as for modelling of sawn timber and for real-time assessment of strength, stiffness and shape stability of wood materials. However, the methods that are available and implemented in optical scanners today do not always meet customer accuracy and/or speed requirements. The primary purpose of this doctoral dissertation was to gain an increased knowledge and a better understanding of how different characteristics and surface defects of timber boards can be identified automatically and robustly. The secondary purpose was to explore the possibilities of how such identified features/defects can be used to add value to the wood manufacturing industry. 

    In the present study, three different methods were developed to non-destructively and automatically detect annual rings and pith location based on images obtained by optical scanning of the four longitudinal surfaces of the timber board. In the first method, a signal-processing-based approach and an optimisation algorithm were applied. In the second method, a deep-learning-based conditional generative adversarial network (cGAN) and a shallow artificial neural network (ANN) were used. In the third method, a single step deep-learning approach with a one-dimensional convolutional neural network (1D CNN) was applied. A novel stochastic model was also proposed to generate an unlimited number of virtual timber boards, with photo-realistic surfaces and known pith location, by which the proposed 1D CNN was trained before it was successfully applied to real timber boards. Concerning accuracy, all the three methods gave prediction errors of the same magnitude, between 4 mm and 6 mm. The 1D CNN method needed only 1.1 ms to locate the pith at a single section, which was 165 and 127 times faster than the signal-processing based and the cGAN based methods, respectively. Hence, the 1D CNN method proved to be the fastest, most operationally simple and robust method.

    In sawn timber, the presence of knots causes the fibres to deviate from the longitudinal direction of the board, leading to a significant reduction of strength and stiffness. In the current study, a computer algorithm was proposed to detect knots on board surfaces and to reconstruct the knots in three dimensions (3D) by using the detected pith location. Moreover, a fibre modelling method was also proposed and used to produce the 3D fibre orientation within the volume of timber boards. Furthermore, the detected pith location and annual rings visible on the board surfaces were also utilised to estimate the radial annual ring profiles along the longitudinal direction of timber boards.

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  • 19.
    Jalilzadehazhari, Elaheh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Vadiee, Amir
    Mälardalen University, Sweden.
    Johansson, Peter
    Jönköping University, Sweden.
    Achieving a trade‐off construction solution using BIM, an optimization algorithm, and a multi‐criteria decision‐making method2019Ingår i: Buildings, E-ISSN 2075-5309, Vol. 9, nr 4, s. 1-14, artikel-id 81Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Energy Performance of Building Directive obligated all European countries to reduce the energy requirements of buildings while simultaneously improving indoor environment quality. Any such improvements not only enhance the health of the occupants and their productivity, but also provide further economic benefits at the national level. Accomplishing this task requires a method that allows building professionals to resolve conflicts between visual and thermal comfort, energy demands, and life‐cycle costs. To overcome these conflicts, this study exploits the incorporation of building information modelling (BIM), the design of experiments as an optimization algorithm, and the analytical hierarchy process (AHP) into a multi‐criteria decision‐ making method. Any such incorporation can (i) create constructive communication between building professionals, such as architects, engineers, and energy experts; (ii) allow the analysis of the performance of multiple construction solutions with respect to visual and thermal comfort, energy demand, and life‐cycle costs; and (iii) help to select a trade‐off solution, thereby making a suitable decision. Three types of energy‐efficient windows, and five types of ground floors, roofs, and external wall constructions were considered as optimization variables. The incorporation of several methods allowed the analysis of the performance of 375 construction solutions based on a combination of optimization variables, and helped to select a trade‐off solution. The results showed the strength of incorporation for analyzing big‐data through the intelligent use of BIM and a simulation in the field of the built environment, energy, and costs. However, when applying AHP, the results are strongly contingent on pairwise comparisons

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  • 20.
    Habite, Tadios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Automatic detection of pith location along boards of Norway spruce on the basis of data from optical scanning of longitudinal surfaces2019Ingår i: CompWood 2019 - International Conference on Computational Methods in Wood Mechanics - from material properties to Timber Structures, Växjö, Sweden, June 17-19, 2019, Växjö: Lnu Press , 2019, s. 64-64Konferensbidrag (Refereegranskat)
    Abstract [en]

    Different mechanical and physical properties of wood are related to the location of pith. Norway spruce wood from the centre of logs, close to the pith, is characterized by lower longitudinal MOE, larger spiral grain angle, and larger longitudinal shrinkage coefficient than what wood farther away from the pith is [1]. Thus, knowledge of pith location along timber boards may play an important role in both appearance grading and in assessment of mechanical properties such as strength [2]. The current work aims to develop an algorithm which is capable of automatically estimating the pith location of Norway spruce boards, along the boards’ length direction, by utilizing optical scanning of longitudinal surfaces. The initial step of the algorithm is to identify defect free sections along the timber board. This is done by utilizing data from tracheid effect scanning of the four sides of the timber board. Thereafter, a continuous wavelet transform (CWT), similar to fast Fourier transform, is applied on grey scale images from scanning, to analyse the variation of light intensity across the four surfaces at selected positions along the board. Obtained local frequencies correspond to the local annular ring pattern on surfaces. Then, assuming that annular growth rings are concentric circles with the pith in the centre, detected local annular ring wavelengths (using CWT) and artificial annual ring wavelengths corresponding to different hypothetical locations of pith are compared, and an optimization procedure is used to identify the location of pith that minimizes the discrepancy between the detected and artificial sets of annular ring wavelengths. Figure 1 shows grey scale images of short segments of longitudinal surfaces, graphs of the detected local annual ring widths, and a photograph of the board cross section where the determined location of pith is marked out. Preliminary results reveal that data from optical scanners and the suggested method allow for accurate detection of annular ring width and location of pith along boards.

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  • 21.
    Habite, Tadios
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Detection of Pith Location of Norway Spruce Timber Boards on the Basis of Optical Scanning2019Ingår i: Proceedings, 21st international nondestructive testing and evaluation of wood symposium: Freiburg, Germany / [ed] Xiping Wang; Udo H. Sauter; Robert J. Ross, Madison, U.S.A: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory , 2019, s. 268-275Konferensbidrag (Refereegranskat)
    Abstract [en]

    Optical scanners are used in the woodworking industry to detect various defects, such as dead and live knots, cracks, and fibre distortions, which are important for the visual appearance grading of wood. Data from scanning is also used to assess mechanical properties such as bending and tensile strength, for the purpose of machine strength grading of sawn timbers. Knowledge of annular ring width and location of pith in relation to board cross-sections, and how these properties vary in the longitudinal direction of boards, is relevant for many purposes, such as assessment of shape stability and mechanical properties of timber. Therefore, the purpose of the present research is to evaluate possibilities to determine annular ring width and location of pith on the basis of scanning of surfaces parallel to the longitudinal board direction. The first step of this novel method is to identify clear wood sections, free of defects along boards. Then time-frequency analysis is applied to assess the variation of light intensity over surfaces of these sections, such that local wavelengths, related to the annular ring width patterns are detected on all four surfaces around the board. Finally, the location of pith is calculated by comparing annular ring width distributions on the different surfaces, and assuming that annular rings are concentric circles with the pith in the centre. Results indicate that optical scanners and the suggested method allow for accurate detection of annular ring width and location of pith along boards.

  • 22.
    Jalilzadehazhari, Elaheh
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Johansson, Jimmy
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Material properties of wooden surfaces used in interiors and sensory stimulation2019Ingår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, nr 4, s. 192-200Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By covering interiors, such as walls, ceilings and floors, with wooden surfaces, one can change the quality of indoor environments and thereby affect both psychological and physiological responses. Psychological responses refer to individuals’ emotional reactions toward interiors, while physiological responses include changes in the activity of the brain, the autonomic nervous system, the endocrine system, and the immune system. The above-mentioned responses considered in this study are those caused by visual, auditory, olfactory and tactile stimulation from interior wooden surfaces. Although earlier studies have presented valuable information on this subject, questions remain about the material properties of wood which are associated with the stimulation. Specifying the material properties can support architects, designers and engineers who intend to use wood in interiors for improving psychological and physiological responses. A literature study therefore has been conducted to determine (i) the material properties of wood which are associated with sensory stimulation, and (ii) to specify relevant recommendations or requirements which should be fulfilled when covering interiors with wooden surfaces. The results show a lack of knowledge regarding the material properties of wood and the degree in which it affects sensory stimulation.

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  • 23.
    Persson, Magnus
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Lindberg, Eva
    Swedish University of Agricultural Sciences, Sweden.
    Reese, Heather
    University of Gothenburg, Sweden.
    Tree Species Classification with Multi-Temporal Sentinel-2 Data2018Ingår i: Remote Sensing, E-ISSN 2072-4292, Vol. 10, nr 11, artikel-id 1794Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Sentinel-2 program provides the opportunity to monitor terrestrial ecosystems with a high temporal and spectral resolution. In this study, a multi-temporal Sentinel-2 data set was used to classify common tree species over a mature forest in central Sweden. The tree species to be classified were Norway spruce (Picea abies), Scots pine (Pinus silvestris), Hybrid larch (Larix x marschlinsii), Birch (Betula sp.) and Pedunculate oak (Quercus robur). Four Sentinel-2 images from spring (7 April and 27 May), summer (9 July) and fall (19 October) of 2017 were used along with the Random Forest (RF) classifier. A variable selection approach was implemented to find fewer and uncorrelated bands resulting in the best model for tree species identification. The final model resulting in the highest overall accuracy (88.2%) came from using all bands from the four image dates. The single image that gave the most accurate classification result (80.5%) was the late spring image (27 May); the 27 May image was always included in subsequent image combinations that gave the highest overall accuracy. The five tree species were classified with a user's accuracy ranging from 70.9% to 95.6%. Thirteen of the 40 bands were selected in a variable selection procedure and resulted in a model with only slightly lower accuracy (86.3%) than that using all bands. Among the highest ranked bands were the red edge bands 2 and 3 as well as the narrow NIR (near-infrared) band 8a, all from the 27 May image, and SWIR (short-wave infrared) bands from all four image dates. This study shows that the red-edge bands and SWIR bands from Sentinel-2 are of importance, and confirms that spring and/or fall images capturing phenological differences between the species are most useful to tree species classification.

  • 24.
    van Blokland, Joran
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Nasir, Vahid
    University of Britisch Columbia, Canada.
    Cool, Julie
    University of Britisch Columbia, Canada.
    Avramidis, Stavros
    University of Britisch Columbia, Canada.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Assessment of weathered thermally modified timber using board initial properties: Machine learling-based prediction of internal checksManuskript (preprint) (Övrigt vetenskapligt)
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