Browsing by Subject "Forestry"

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  • Sirkiä, Saija; Lindén, Andreas; Helle, Pekka; Nikula, Ari; Knape, Jonas; Lindén, Harto (2010)
  • Pyorala, Jiri; Liang, Xinlian; Saarinen, Ninni; Kankare, Ville; Wang, Yunsheng; Holopainen, Markus; Hyyppa, Juha; Vastaranta, Mikko (2018)
    Terrestrial laser scanning (TLS) accompanied by quantitative tree-modeling algorithms can potentially acquire branching data non-destructively from a forest environment and aid the development and calibration of allometric crown biomass and wood quality equations for species and geographical regions with inadequate models. However, TLS's coverage in capturing individual branches still lacks evaluation. We acquired TLS data from 158 Scots pine (Pinus sylvestris L.) trees and investigated the performance of a quantitative branch detection and modeling approach for extracting key branching parameters, namely the number of branches, branch diameter (b(d)) and branch insertion angle (b) in various crown sections. We used manual point cloud measurements as references. The accuracy of quantitative branch detections decreased significantly above the live crown base height, principally due to the increasing scanner distance as opposed to occlusion effects caused by the foliage. b(d) was generally underestimated, when comparing to the manual reference, while b was estimated accurately: tree-specific biases were 0.89cm and 1.98 degrees, respectively. Our results indicate that full branching structure remains challenging to capture by TLS alone. Nevertheless, the retrievable branching parameters are potential inputs into allometric biomass and wood quality equations.
  • Kansanen, Kasper; Vauhkonen, Jari; Lahivaara, Timo; Seppanen, Aku; Maltamo, Matti; Mehtatalo, Lauri (2019)
    Errors in individual tree detection and delineation affect diameter distribution predictions based on crown attributes extracted from the detected trees. We develop a methodology for circumventing these problems. The method is based on matching cumulative distribution functions of field measured tree diameter distributions and crown radii distributions extracted from airborne laser scanning data through individual tree detection presented by Vauhkonen and Mehtatalo (2015). In this study, empirical distribution functions and a monotonic, nonlinear model curve are introduced. Tree crown radius distribution produced by individual tree detection is corrected by a method taking into account that all trees cannot be detected. The evaluation is based on the ability of the developed model sequence to predict quadratic mean diameter and total basal area. The studied data consists of 36 field plots in a typical boreal managed forest area in eastern Finland. The suggested enhancements to the model sequence produce improved results in most of the test cases. Most notably, in leaveone-out cross-validation experiments the modified models improve RMSE of basal area 13% in the full data and RMSE of quadratic mean diameter and basal area 69% and 11%, respectively, in pure pine plots. Better modeling of the crown radius distribution and improved matching between crown radii and stem diameters add the operational premises of the full distribution matching.
  • Weiss, Gerhard; Hansen, Eric; Ludvig, Alice; Nybakk, Erlend; Toppinen, Anne (2021)
    Innovation in the forest sector is a growing research interest and within this field, there is a growing attention for institutional, policy and societal dimensions and particular when it comes to the question of how to support innovativeness in the sector. This Special Issue therefore focuses on governance aspects, relating to and bridging business and political-institutional-societal levels. This includes social/societal factors, goals and implications that have recently been studied under the label of social innovation. Furthermore, the emergence of bioeconomy as a paradigm and policy goal has become a driver for a variety of innovation processes on company and institutional levels. Our article provides a tentative definition of & ldquo;innovation governance & rdquo; and attempts a stateof-art review of innovation governance research in the forest sector. For structuring the research field, we propose to distinguish between organizational/managerial, policy or innovation studies. For the forestry sector, specifically, we suggest to distinguish between studies focusing on (i) innovative governance of forest management and forest goods and services; on (ii) the governance of innovation processes as such, or (iii) on specific (transformational) approaches that may be derived from combined goals such as innovation governance for sustainability, regional development, or a bioeconomy. Studies in the forest sector are picking up new trends from innovation research that increasingly include the role of societal changes and various stakeholders such as civil society organizations and users. They also include public-private partnership models or participatory governance. We finally should not only look in how far research approaches from outside are applied in the sector but we believe that the sector could contribute much more to our general scientific knowledge on ways for a societal transformation to sustainability.
  • Korhonen, Arto (Helsingin yliopisto, 2020)
    This study is aimed at discovering if Virtual reality (VR) has restorative effects on people and how it compares to real environment as a restorative environment. Theory frame used in this research is Attention restoration theory which is widely used in previous restorativeness studies. As the world is urbanizing rapidly, people spend less time in the nature than ever before. Previous researches have shown that nature has a restorative effect on people and it recovers aimed attention. This research tries to find a solution by using the VR environment as a substitute for real environments as a restorative place. Our hypothesis was; VR does have restorative effect and VR forest is perceived as restorative as physical forest. This VR experience study was executed as a quantitative study that was executed randomly picking students and staff of nearby corporations of university campus. Test subjects were exposed to the VR environment for a five-minute period. Information was gathered via questionnaires that were answered both before and after the VR experience. Both questionnaires measured the mood, vitality and restoration at the moment when answered. The data consisted of N=100. Addition to our own data, we had the data from similar research by Hauru et al (2012). With that it was possible to compare the VR environment to real environments. The results showed that the perceived restorativeness of VR was similar as the real forest environment, but the restorativeness was felt even stronger in the VR environment. People felt significantly better after the experience. From the research point-of-view VR could be used as a restoration in urban areas and for example during workdays/school days. It clearly showed its potential for future use. There is still a little concern about the results, as the participants visited the VR environment only once, the long-term effects are yet unknown. Due to that there is still need for future research regarding the long-term use of VR as a restorative environment.
  • Markelin, L.; Honkavaara, E.; Näsi, R.; Viljanen, N.; Rosnell, T.; Hakala, T.; Vastaranta, M.; Koivisto, T.; Holopainen, M. (2017)
    Novel miniaturized multi- and hyperspectral imaging sensors on board of unmanned aerial vehicles have recently shown great potential in various environmental monitoring and measuring tasks such as precision agriculture and forest management. These systems can be used to collect dense 3D point clouds and spectral information over small areas such as single forest stands or sample plots. Accurate radiometric processing and atmospheric correction is required when data sets from different dates and sensors, collected in varying illumination conditions, are combined. Performance of novel radiometric block adjustment method, developed at Finnish Geospatial Research Institute, is evaluated with multitemporal hyperspectral data set of seedling stands collected during spring and summer 2016. Illumination conditions during campaigns varied from bright to overcast. We use two different methods to produce homogenous image mosaics and hyperspectral point clouds: image-wise relative correction and image-wise relative correction with BRDF. Radiometric datasets are converted to reflectance using reference panels and changes in reflectance spectra is analysed. Tested methods improved image mosaic homogeneity by 5% to 25%. Results show that the evaluated method can produce consistent reflectance mosaics and reflectance spectra shape between different areas and dates. © Authors 2017.
  • Oliveira, R.A.; Khoramshahi, E.; Suomalainen, J.; Hakala, T.; Viljanen, N.; Honkavaara, E. (2018)
    The use of drones and photogrammetric technologies are increasing rapidly in different applications. Currently, drone processing workflow is in most cases based on sequential image acquisition and post-processing, but there are great interests towards real-time solutions. Fast and reliable real-time drone data processing can benefit, for instance, environmental monitoring tasks in precision agriculture and in forest. Recent developments in miniaturized and low-cost inertial measurement systems and GNSS sensors, and Real-time kinematic (RTK) position data are offering new perspectives for the comprehensive remote sensing applications. The combination of these sensors and light-weight and low-cost multi- or hyperspectral frame sensors in drones provides the opportunity of creating near real-time or real-time remote sensing data of target object. We have developed a system with direct georeferencing onboard drone to be used combined with hyperspectral frame cameras in real-time remote sensing applications. The objective of this study is to evaluate the real-time georeferencing comparing with post-processing solutions. Experimental data sets were captured in agricultural and forested test sites using the system. The accuracy of onboard georeferencing data were better than 0.5 m. The results showed that the real-time remote sensing is promising and feasible in both test sites. © Authors 2018. CC BY 4.0 License.
  • Arts, Bas; Ingram, Verina; Brockhaus, Maria (2019)
  • Karttunen, K.; Karhunen, A.; Laihanen, M.; Ranta, T.; Ahtikoski, A.; Kojola, S.; Salminen, H.; Hynynen, J.; Kujala, S.; Hakala, O.; Törmä, H.; Kinnunen, J. (ETA-Florence Renewable Energies, 2019)
    European Biomass Conference and Exhibition Proceedings
    The aim of the study is to promote ways to reach the goals of the carbon neutrality at the South Savo region in eastern Finland by examining the solutions for emission reductions and forest use. The study has taken the first step for reaching the cost-effective carbon neutrality at the regional level in Finland. The carbon dioxide neutral region means that the region's internal activity does not change the carbon content of the atmosphere. The carbon neutral society produces just as much carbon emissions as it can bind from the atmosphere. The study started by updating the regional energy balance and its carbon influence. Second, the carbon impact on forest use was measured. Finally, the cost-efficiency of alternative carbon neutrality solutions will be estimated. The study will be carried out by combining alternative emission reduction solutions and forest management simulations with computable general equilibrium (CGE) modelling. Permanent National Forest Inventory plots were used as an input of forest management simulations. Then, applying a modified CGE model (RegFinDyn), the economic and emission impacts of alternative carbon balance solutions will be assessed at the regional level. Earlier results have shown that a more intensive use of forests decreases the carbon sequestration potential but increases the regional socio-economic benefits. The carbon balance should be compensated either for emission reduction solutions or by controlling the use of forests. It is important to choose the solutions which are not only the emission efficient but also cost-efficient at the regional level. © 2019 ETA-Florence Renewable Energies.
  • Njoghomi, Elifuraha Elisha (Helsingin yliopisto, 2021)
    This research focuses on stand dynamics and ecological recovery in miombo woodlands, Morogoro, Tanzania. The study uses the Kitulangalo Permanent Sample Plots (PSPs) to analyse tree species’ site-specific growth, regeneration dynamics, and stand development using empirical and modeling approaches. The high number of tree species in miombo necessitated the formulation of three species groups involving 1) trees that grow relatively rapidly to be dominants in top canopy layers 2) trees that stay mainly in the lower and middle canopy levels and 3) trees that grow slowly but persistently and may eventually rise to dominant and codominant canopy positions applied in studies I and III. Study III also applies three harvesting alternatives, which align with the recommended harvesting practices for these woodlands. Diameter increment varied with the change in basal area growth across species groups, reaching a maximum of 3.2 cm (group 1) during 2008-2016. Density-dependent mortality and ingrowth also varied with species group as higher mortality rates dominated the lower and middle canopy layers due to asymmetrical competitions. Fencing the plots prompted thick grass cover. The drop in the total number of regeneration stems and the simultaneous increase in the number of main stems in fenced areas and dense plots indicated a self-thinning process induced by competition. This is linked to multi-stem regeneration undergoing a morphological transformation into single-stem saplings (main stems) and eventually becoming small trees. Harvesting intensity, density-dependent mortality, and ingrowth regulated stand basal area and therefore stand growth and development during the simulation. Stand structural development was dominated by species groups 1 and 2, indicating sustainability in species composition and structures. Stand development was affected by the addition of new stems of each species in each simulation year. Miombo stands have demonstrated the potential to attain a steady-state condition over the medium-term under-regulated stand conditions and silvicultural treatments. The developed models, treatments, and harvesting alternatives may be limited in application to Kitulangalo and similar lowland miombo woodlands in Tanzania. Future studies concerning stand conditions, silvicultural treatments, and harvesting alternatives are vital for a better understanding of stand dynamics in miombo woodlands in Tanzania. Keywords: Forest disturbance, tree growth and stand dynamics, regeneration dynamics, silvicultural treatment, harvesting alternative, miombo woodlands
  • Simula, Juhana (Helsingin yliopisto, 2020)
    Single Photon LiDAR (Light Detection and Ranging) is a novel and promising technology that can make laser scanning faster and cheaper. Compared to typical linear mode LiDARs (LML), SPL (Single Photon LiDAR) can be operated from higher altitude which means wider bandwidth on ground and a larger scanning area at once. Due to capability of SPL systems to create denser point clouds than current typical LML systems, the flight altitude can be higher in SPL which means quick remote sensing data collations abilities over large areas. Additionally, SPL can penetrate thin clouds and fog which gives airborne ALS better time frame as flight can be operated earlier in the morning than with LML. To the best of authors knowledge, this is pioneering research in Finland to analyse the applicability of SPL in Finnish forests and compare it with LML dataset. This thesis focuses on applying and comparing two LiDAR systems (SPL and LML) for extracting individual tree level (ITD) forest inventorying attributes and generating canopy height models in mature forests. Results were validated over 49 field measured plots, located in southern boreal forest. Additionally, the suitability of two crown segmentation methods (local maxima and watershed) were tested in both datasets. Watershed segmentation method yielded more accurate results for tree density and height estimation in both LML and SPL datasets. Tree density was underestimated by 4.7% (rRMSE: 32.3%) for all species. Comparing tree density estimation in different species, it was most accurate in deciduous plots (rRMSE: 17.0%, rBias: -9.5). Tree height estimation with SPL was highly correlated (R 2=0.93) with field-measured height and reliability accurate with underestimation of 3.4% (rRMSE of 7.0%). Comparing the tree height estimation in different species, it was most accurate between pine plots (rRMSE: 1.1%, rBias: 4.9%). In this research, SPL represented reliable and usable point cloud data for forest remote sensing and quality similar to LML. As expected, SPL had more deviation and higher bias compared to LML in tree density but yielded more accurate results for height estimations. Further studies with more accurate geolocated plots and individual tree maps are required. The hypothesis, the applicability of SPL data for forest inventorying and extracting tree density and tree height in mature forests, is valid.
  • Manninen, Terhikki; Jääskeläinen, Emmihenna; Lohila, Annalea; Korkiakoski, Mika; Räsänen, Aleksi; Virtanen, Tarmo; Muhić, Filip; Marttila, Hannu; Ala-Aho, Pertti; Markovaara-Koivisto, Mira; Liwata-Kenttälä, Pauliina; Sutinen, Raimo; Hänninen, Pekka (2022)
    A soil moisture estimation method was developed for Sentinel-1 synthetic aperture radar (SAR) ground range detected high resolution (GRDH) data to analyze moisture conditions in a gently undulating and heterogeneous subarctic area containing forests, wetlands, and open orographic tundra. In order to preserve the original 10-m pixel spacing, PIMSAR (pixel-based multitemporal nonlocal averaging) nonlocal mean filtering was applied. It was guided by multitemporal statistics of SAR images in the area. The gradient boosted trees (GBT) machine learning method was used for the soil moisture algorithm development. Discrete and continuous in situ soil moisture values were used for training and validation of the algorithm. For surface soil moisture, the root mean square error (RMSE) of the method was 6.5% and 8.8% for morning and evening images, respectively. The corresponding maximum errors were 34.1% and 33.8%. The pixelwise sensitivity to the training set and method choice was estimated as the variance of the soil moisture values derived using the algorithms for the three best methods with respect to the criteria: the smallest maximum error, the smallest RMSE value, and the highest coefficient of determination (R-2) value. It was, on average, 6.3% with a standard deviation of 5.7%. Our approach successfully produced instantaneous high-resolution soil moisture estimates on daily basis for the subarctic landscape and can further be applied to various hydrological, biogeochemical, and management purposes.
  • Kuuluvainen, Timo; Gauthier, Sylvie (2018)
    The circumboreal forest encompasses diverse landscape structures, dynamics and forest age distributions determined by their physical setting, and historical and current disturbance regimes. However, due to intensifying forest utilisation, and in certain areas due to increasing natural disturbances, boreal forest age-class structures have changed rapidly, so that the proportion of old forest has substantially declined, while that of young post-harvest and post-natural-disturbance forest proportions have increased. In the future, with a warming climate in certain boreal regions, this trend may further be enhanced due to an increase in natural disturbances and large-scale use of forest biomass to replace fossil-based fuels and products. The major drivers of change of forest age class distributions and structures include the use of clearcut short-rotation harvesting, more frequent and severe natural disturbances due to climate warming in certain regions. The decline in old forest area, and increase in managed young forest lacking natural post-disturbance structural legacies, represent a major transformation in the ecological conditions of the boreal forest beyond historical limits of variability. This may introduce a threat to biodiversity, ecosystem resilience and long-term adaptive capacity of the forest ecosystem. To safeguard boreal forest biodiversity and ecosystem functioning, and to maintain the multiple services provided to societies by this forest biome, it is pivotal to maintain an adequate share and the ecological qualities of young post-disturbance stages, along with mature forest stages with old-growth characteristics. This requires management for natural post-disturbance legacy structures, and innovative use of diverse uneven-aged and continuous cover management approaches to maintain critical late-successional forest structures in landscapes.
  • Kuuluvainen, Timo; Gauthier, Sylvie (Springer Singapore, 2018)
    Abstract The circumboreal forest encompasses diverse landscape structures, dynamics and forest age distributions determined by their physical setting, and historical and current disturbance regimes. However, due to intensifying forest utilisation, and in certain areas due to increasing natural disturbances, boreal forest age-class structures have changed rapidly, so that the proportion of old forest has substantially declined, while that of young post-harvest and post-natural-disturbance forest proportions have increased. In the future, with a warming climate in certain boreal regions, this trend may further be enhanced due to an increase in natural disturbances and large-scale use of forest biomass to replace fossil-based fuels and products. The major drivers of change of forest age class distributions and structures include the use of clearcut short-rotation harvesting, more frequent and severe natural disturbances due to climate warming in certain regions. The decline in old forest area, and increase in managed young forest lacking natural post-disturbance structural legacies, represent a major transformation in the ecological conditions of the boreal forest beyond historical limits of variability. This may introduce a threat to biodiversity, ecosystem resilience and long-term adaptive capacity of the forest ecosystem. To safeguard boreal forest biodiversity and ecosystem functioning, and to maintain the multiple services provided to societies by this forest biome, it is pivotal to maintain an adequate share and the ecological qualities of young post-disturbance stages, along with mature forest stages with old-growth characteristics. This requires management for natural post-disturbance legacy structures, and innovative use of diverse uneven-aged and continuous cover management approaches to maintain critical late-successional forest structures in landscapes.