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Silva Fennica vol. 58 no. 3 | 2024

Category : Climate resilient and sustainable forest management – Research article

article id 23075, category Climate resilient and sustainable forest management – Research article
Lauri Männistö, Jari Miina, Saija Huuskonen. (2024). How to utilize natural regeneration of birch to establish mixed spruce-birch forests in Finland? Silva Fennica vol. 58 no. 3 article id 23075. https://doi.org/10.14214/sf.23075
Keywords: Betula pendula; Picea abies; Betula pubescens; mixed model; Chapman-Richards; mixed stands
Highlights: Naturally emerging birch admixture provides a sufficient starting point for mixed forest in young, planted spruce stands; Creating mixed forest is a time sensitive process, as different growth patterns among tree species might cause a situation where one tree species suppresses the other, leading to monoculture or two-storied mixed forest; Birch admixture should be retained during early cleaning.
Abstract | Full text in HTML | Full text in PDF | Author Info

Mixed forests are known for their ability to provide a wide range of ecosystem services. Such forests have higher biodiversity compared to monocultures, are resilient against disturbances and may mitigate the effects of climate change. Despite well-known benefits, there is still little information on how these forests should be established and managed. The aim of this study was to describe the early growth dynamics of current boreal young mixed stands of planted Norway spruces (Picea abies (L.) Karst.) and naturally regenerated birches (Betula spp.). We collected data from 9  stands planted for spruce 8–14 years ago in Southern and Central Finland. Stem analysis was conducted to 144 spruces and to 144 birches to determine previous growth. We modelled the height and diameter development of individual trees in relation to tree age at stump height using non-linear mixed Chapman-Richards model. There were no significant differences between spruce and seed-origin birch in diameter growth at stump height, but the initial height increments of natural birches were larger than those of planted spruces. However, planted spruces were able to keep up with the height development of birches, if spruces received a head start over naturally regenerated seed-origin birch for two growing seasons. Thus, naturally regenerated birch admixture can be utilized to establish single-storied spruce-birch mixtures, and the admixture should be retained during the early cleaning of planted spruce stands.

  • Männistö, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID https://orcid.org/0009-0009-0213-1972 E-mail: lauri.mannisto@luke.fi (email)
  • Miina, Natural Resources Institute Finland (Luke), Natural resources, Yliopistokatu 6 B, FI-80100 Joensuu, Finland ORCID https://orcid.org/0000-0002-8639-4383 E-mail: jari.miina@luke.fi
  • Huuskonen, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID https://orcid.org/0000-0001-8630-3982 E-mail: saija.huuskonen@luke.fi
article id 23069, category Climate resilient and sustainable forest management – Research article
John Alexander Pulgarin Diaz, Markus Melin, Tiina Ylioja, Päivi Lyytikäinen-Saarenmaa, Heli Peltola, Olli-Pekka Tikkanen. (2024). Relationship between stand and landscape attributes and Ips typographus salvage loggings in Finland. Silva Fennica vol. 58 no. 3 article id 23069. https://doi.org/10.14214/sf.23069
Keywords: Picea abies; wind damage; clear-cuts; European spruce bark beetle; stand attributes
Highlights: In Finland, the European spruce bark beetle (SBB) prefers mature stands (high age and mean diameter at breast hight), herb-rich heath forest sites and semi-coarse or coarse heath forest soil type, as well as a short distance to the closest wind damage from the previous-year, SBB damage from previous-year and particularly to clear-cuts; These stand types should be prioritised for monitoring SBB damage.
Abstract | Full text in HTML | Full text in PDF | Author Info

Disturbances caused by the European spruce bark beetle (SBB; Ips typographus L.) on Norway spruce (Picea abies (L.) H. Karst.), have increased immensely across Central and Northern Europe, and are expected to increase further as a result of climate change. While this trend has been noted in Finland, so far limited research has been published. To support proper SBB risk management in Finland, we compared stand properties between salvage loggings due to SBB damage during 2012–2020 (4691 cases) and spruce stands free of SBB damage. Also, we explored the role of landscape attributes as drivers of SBB damage. We considered the forest stand attributes of site fertility class, stand development class, soil type, stand mean diameter at breast height and mean stand age. Considered forest landscape attributes were the distance from SBB-damaged stands to the closest clear-cut, to previous-year SBB-damaged stands and to the previous-year wind-damaged stand. We used nationwide forest logging and forest stock data, and analysed forest stand attributes using chi-squared and Mann-Whitney U tests and landscape attributes using generalised linear mixed models. Based on our findings, the SBB didn’t damage stands randomly, but prevailed in mature stands (high age and high mean diameter at breast height), in herb-rich heath forest site types and in semi-coarse or coarse heath forest soil soils. We found correlation between the landscape variables and the number of salvage loggings, with a higher number of loggings due to SBB damage close to clear-cuts. Our results help to find risk areas of SBB damage.

  • Pulgarin Diaz, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0003-0554-8254 E-mail: alexander.pulgarin.diaz@uef.fi (email)
  • Melin, Natural Resources Institute Finland (Luke), P.O. Box 68, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0001-7290-9203 E-mail: markus.melin@luke.fi
  • Ylioja, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-0079 Helsinki, Finland ORCID https://orcid.org/0000-0002-8840-7504 E-mail: tiina.ylioja@luke.fi
  • Lyytikäinen-Saarenmaa, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0003-1884-3084 E-mail: paivi.lyytikainen-saarenmaa@ef.fi
  • Peltola, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@uef.fi
  • Tikkanen, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0002-3875-2772 E-mail: olli-pekka.tikkanen@uef.fi
article id 23061, category Climate resilient and sustainable forest management – Research article
Noora Tienaho, Ninni Saarinen, Tuomas Yrttimaa, Ville Kankare, Mikko Vastaranta. (2024). Quantifying fire-induced changes in ground vegetation using bitemporal terrestrial laser scanning. Silva Fennica vol. 58 no. 3 article id 23061. https://doi.org/10.14214/sf.23061
Keywords: forest fires; biomass; boreal forest; LIDAR; controlled burning; surface differencing; surface fires
Highlights: Bitemporal terrestrial laser scanning provided a means for identifying surface areas exposed to fire by utilizing a surface differencing method developed in this study; The developed method allowed for the quantification of fire-induced volumetric changes in ground vegetation at high resolution, facilitating the assessment of the impact of surface fires on forest ecosystems.
Abstract | Full text in HTML | Full text in PDF | Author Info

Forest fires pose a significant threat to forest carbon storage and sinks, yet they also play a crucial role in the natural dynamics of boreal forests. Accurate quantification of biomass changes resulting from forest fires is essential for damage assessment and controlled burning evaluation. This study utilized terrestrial laser scanning (TLS) to quantify changes in ground vegetation resulting from low-intensity surface fires. TLS data were collected before and after controlled burnings at eight one-hectare test sites in Scots pine (Pinus sylvestris L.) dominated boreal forests in Finland. A surface differencing-based method was developed to identify areas exposed to fire. Validation, based on visual interpretation of 1 × 1 m surface patches (n = 320), showed a recall, precision, and F1-score of 0.9 for the accuracy of identifying burned surfaces. The developed method allowed the assessment of the magnitude of fire-induced vegetation changes within the test sites. The proportions of burned 1 × 1 m areas within the test sites varied between 51–96%. Total volumetric change in ground vegetation was on average –1200 m³ ha-1, with burning reducing the vegetation volume by 1700 m³ ha-1 and vegetation growth increasing it by 500 m³ ha-1. Substantial variations in the volumetric changes within and between the test sites were detected, highlighting the complex dynamics of surface fires, and emphasizing the importance of having observations from multiple sites. This study demonstrates that bitemporal TLS measurements provide a robust means for characterizing fire-induced changes, facilitating the assessment of the impact of surface fires on forest ecosystems.

article id 23042, category Climate resilient and sustainable forest management – Research article
Johanna Jääskeläinen, Lauri Korhonen, Mikko Kukkonen, Petteri Packalen, Matti Maltamo. (2024). Individual tree inventory based on uncrewed aerial vehicle data: how to utilise stand-wise field measurements of diameter for calibration? Silva Fennica vol. 58 no. 3 article id 23042. https://doi.org/10.14214/sf.23042
Keywords: laser scanning; calibration; mixed-effects model; single-tree detection
Highlights: A practical scheme to improve the accuracy of predicted tree and stand attributes in an uncrewed aerial vehicle based individual tree inventory; Accuracy was considerably improved with data from 2–4 sample trees from the target stand; Calibrated existing models and the construction of local models performed equally well; The laborious task of constructing a local model can be avoided by using a calibrated transferred model.
Abstract | Full text in HTML | Full text in PDF | Author Info
Uncrewed aerial vehicles (UAV) have great potential for use in forest inventories, but in practice they can be expensive for relatively small inventory areas as a large number of field measurements are needed for model construction. One proposed solution is to transfer previously constructed models to a new inventory area and to calibrate these with a small number of local field measurements. Our objective was to compare calibration of general models and the construction of new models to determine the best approach for UAV-based forest inventories. Our material included field measurements and UAV-based laser scanning data, from which individual trees were automatically identified. A general mixed-effects model for diameter at breast height (DBH) had been formulated earlier based on data from a geographically wider area. It was calibrated to the study area with field measurements from 2–10 randomly selected calibration trees. The calibrated diameters were used to calculate the diameter of a basal area median tree (DGM), tree volumes, and the volume of all trees at plot-level. Next, new DBH-models were formulated based on the 2–10 randomly selected trees and calibrated with plot-level random effects estimated during model construction. Finally, plot-specific height-diameter regression models were formulated by randomly selecting 10 trees from each plot. Calibration reduced the prediction errors of all variables. An increase in the number of calibration trees decreased error rates by 1–6% depending on the variable. Calibrated predictions from the general mixed-effects model were similar to the separately formulated mixed-effects models and plot-specific regression models.

Category : Research article

article id 23073, category Research article
Curt Almqvist. (2024). High stand density improves seed production in seed orchards of the masting species Picea abies. Silva Fennica vol. 58 no. 3 article id 23073. https://doi.org/10.14214/sf.23073
Keywords: Norway spruce; thinning; cone production
Highlights: Cone production per tree in a Picea abies seed orchard is independent of stand density up to at least 800 stems ha–1; The higher the stand density, the higher per hectare cone production will be in the seed orchard.
Abstract | Full text in HTML | Full text in PDF | Author Info

Reproduction in masting species is characterised by long intervals between good cone and seed production years, and only sparse reproduction between mast years. The physiological mechanisms behind masting, and how these are linked to internal resource status and external weather factors, is still a subject of scientific exploration and debate, as is the effect of climate change on masting. This study investigates cone production in one operational seed orchard in Sweden which was established with two different spacings and has since been subject to three tree thinning experiments. The spacings before thinning varied between 800 and 400 stems ha–1, and then thinning reduced the stand density in all trials to half, i.e. between 400 and 200 stems ha–1. In all three experiments cone production per tree was equal in un-thinned and thinned treatments, both in mast years and in non-mast years. Thus, the cone production per unit area was twice as high in the un-thinned areas. The conclusion from these experiments is that the establishment of Picea abies (L.) H. Karst. seed orchards with wide tree spacing is both a misuse of good orchard locations and bad economics.

article id 23030, category Research article
Harri Silvennoinen, Laura Pikkarainen, Heini Nakola, Matti Koivula, Liisa Tyrväinen, Jukka Tikkanen, Philip Chambers, Heli Peltola. (2024). Consistency of video and photo surveys in measuring attractiveness of forest stands managed with varying intensities. Silva Fennica vol. 58 no. 3 article id 23030. https://doi.org/10.14214/sf.23030
Keywords: environment; assessment; forest treatment; preference; visualization
Highlights: The more intensely a forest is treated silviculturally, the less it corresponds to people’s wishes and expectations for nature; It is possible to assess the attractiveness of nature from both photographs and videos; Evaluations from videos and images differed slightly, but these differences do not affect how treatments are ranked; Photo and video assessments are not easy for everyone.
Abstract | Full text in HTML | Full text in PDF | Author Info

We evaluated the consistency of video, ordinary photo, and panoramic photo surveys in measuring the attractiveness (recreational use, scenic values etc.) of forest stands managed with varying intensities. We also evaluated possible effects on the results caused by the personal background of citizen respondents and how the respondents experienced the evaluation events. Our experimental sites were in mature Scots pine (Pinus sylvestris L.) forests in eastern Finland and included two replicate sites which were unharvested (control, basal area 26 m2 ha–1), a selective cutting site (basal area 18 m2 ha–1), small openings sites (gap cut) with 5 and 20% retained trees, respectively, and one site which was clear cut with 3% retained trees. In our study, 71 volunteer forestry students evaluated the attractiveness of these sites from an ordinary photo, a panoramic photo, and a video, with a 0–10 scale. Based on this study, the unharvested forest was the most attractive and clear cutting was the least attractive, regardless of the evaluation method. This result was in line with a previous study using on-site evaluations of the same sites. The differences of respondents considering in how easy they felt to assess the attractiveness of the environment as a whole and in using different visualisation methods affected the result, unlike background variables of the respondents. The results of forest attractiveness were consistent between panoramic and ordinary photos, and the attractiveness scoring was slightly higher for them than for the video. We conclude that all the compared visualisation methods seem to be suitable for assessment of the attractiveness of forest views.

  • Silvennoinen, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0002-9095-7986 E-mail: harri.silvennoinen@uef.fi (email)
  • Pikkarainen, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0001-5301-3639 E-mail: laura.pikkarainen@uef.fi
  • Nakola, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heini.nakola@gmail.com
  • Koivula, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID https://orcid.org/0000-0001-6415-4904 E-mail: matti.koivula@luke.fi
  • Tyrväinen, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID https://orcid.org/0000-0001-5144-7150 E-mail: liisa.tyrvainen@luke.fi
  • Tikkanen, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0002-9693-8209 E-mail: jukka.tikkanen@uef.fi
  • Chambers, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0002-0586-3142 E-mail: philip.chambers@uef.fi
  • Peltola, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi
article id 23018, category Research article
Anssi Ahtikoski, Kari Väätäinen, Perttu Anttila, Juha Laitila, Antti Mutanen, Jari Lindblad, Lauri Sikanen, Johanna Routa. (2024). The effects of the EU’s forest-related policies on harvesting costs in Finland. Silva Fennica vol. 58 no. 3 article id 23018. https://doi.org/10.14214/sf.23018
Keywords: forests; scenario approach; harvesting costs; directives and regulations; EU legislation; structural systems analysis
Highlights: The EU’s forest-related policies set direct and indirect limitations on the harvesting operations and operating environment; The effect on harvesting costs of Directives and Regulations depends on the magnitude of policy implementation; In a high-impact scenario, harvesting costs could increase by as much as 18% from the current level of costs.
Abstract | Full text in HTML | Full text in PDF | Author Info

The EU’s influence on national forest policies is growing, and the implementation of forest-related policies proposed by the Commission will affect the practice of forestry in Europe. For instance, the Nature Restoration Law sets concrete areal goals for restoring forest ecosystems and for conservation, the Deforestation Regulation requires meticulous tracking of wood’s origin, and the renewed Renewable Energy Directive (RED III) sets new criteria to sustainable forest biomass procurement. So far there have been no studies that have looked into the impacts from the economic and operational point of view. In this study, structural systems analysis was first performed to discover the relevant variables (and their functioning) associated with the roundwood harvesting operations and the operating environment. A scenario approach was then applied to capture the potential levels of implementation of the EU’s forest-related policies. Finally, using different scenarios (low-, moderate- and high-impact) and a systems analysis framework, the impact of alternative levels of implementation was quantified in terms of harvesting costs, measured in € m–3. The results indicate that with the low- and moderate-impact scenarios the harvesting costs would increase by less than 10% from the current levels in three different regions in Finland. Such an increase (less than 10%) could be tolerated over a period of a few years, but a sudden increase is likely to lead to challenges to the running of businesses. With the high-impact scenario the harvesting costs would increase by between 15% and 18%, depending on the region. This magnitude of increase (of approximately a sixth) corresponds to a severe change in the roundwood harvesting operations and operating environment.

  • Ahtikoski, Natural Resources Institute Finland (Luke), Tekniikankatu 1, FI-33720 Tampere, Finland ORCID https://orcid.org/0000-0003-1658-3813 E-mail: anssi.ahtikoski@luke.fi (email)
  • Väätäinen, Natural Resources Institute Finland (Luke), Yliopistonkatu 6, FI-80100 Joensuu, Finland ORCID https://orcid.org/0000-0002-6886-0432 E-mail: kari.vaatainen@luke.fi
  • Anttila, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID https://orcid.org/0000-0002-6131-392X E-mail: perttu.anttila@luke.fi
  • Laitila, Natural Resources Institute Finland (Luke), Yliopistonkatu 6, FI-80100 Joensuu, Finland E-mail: juha.laitila@luke.fi
  • Mutanen, Natural Resources Institute Finland (Luke), Yliopistonkatu 6, FI-80100 Joensuu, Finland ORCID https://orcid.org/0000-0003-0533-9356 E-mail: antti.mutanen@luke.fi
  • Lindblad, Natural Resources Institute Finland (Luke), Yliopistonkatu 6, FI-80100 Joensuu, Finland ORCID https://orcid.org/0009-0003-6766-6587 E-mail: jari.lindblad@luke.fi
  • Sikanen, Natural Resources Institute Finland (Luke), Yliopistonkatu 6, FI-80100 Joensuu, Finland E-mail: lauri.sikanen@luke.fi
  • Routa, Natural Resources Institute Finland (Luke), Yliopistonkatu 6, FI-80100 Joensuu, Finland ORCID https://orcid.org/0000-0001-7225-1798 E-mail: johanna.routa@luke.fi

Category : Research note

article id 23064, category Research note
Henrik Lindberg, Tuomas Aakala, Ilkka Vanha-Majamaa. (2024). Ignition probability and fuel consumption of boreal ground vegetation fuels – an experimental study in Finland. Silva Fennica vol. 58 no. 3 article id 23064. https://doi.org/10.14214/sf.23064
Keywords: forest fires; ground vegetation; prescribed burning; flammability; fuel moisture content; mass loss rate
Highlights: Ignition probability and mass loss rates clearly differed in experimental burnings among four common circumboreal moss and lichen species; Cladonia rangiferina was the most flammable, Dicranum spp. the least flammable and Pleurozium schreberi and Hylocomium splendens intermediate.
Abstract | Full text in HTML | Full text in PDF | Author Info

In boreal forests fires often ignite and spread within the dominant moss and lichen cover of the ground layer vegetation, which thus greatly influences fire hazard. We used an experimental set-up in greenhouse conditions to study the differences in how (1) fuel moisture and (2) wind velocity influence the ignition probability and fuel consumption among four common circumboreal ground vegetation fuels, Pleurozium schreberi (Willd. ex Brid.) Mitt., Hylocomium splendens Schimp., Dicranum spp. and Cladonia rangiferina (L.) F. H. Wigg. Our results show that the reindeer lichen C. rangiferina was clearly the most flammable species, with high ignition probability even at high moisture contents and low wind velocities. Of the mosses, Dicranum was the least flammable, with low ignition probability and mass loss at low wind velocities regardless of moisture content. P. schreberi and H. splendens behaved somewhat similarly with wind velocities quickly increasing the initially low ignition probability and mass loss observed in the absence of wind. However, especially for mass loss, among-species differences tended to disappear with stronger winds. The observed differences can be explained by the different structures and growth forms of the studied species and open a potential avenue for improving forest fire risk predictions.

  • Lindberg, Häme University of Applied Sciences, School of Bioeconomy, Visamäentie 35 A, P.O. Box 230, FI-13100 Hämeenlinna, Finland ORCID https://orcid.org/0000-0001-9045-2673 E-mail: henrik.lindberg@hamk.fi (email)
  • Aakala, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID https://orcid.org/0000-0003-0160-6410 E-mail: tuomas.aakala@uef.fi
  • Vanha-Majamaa, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland E-mail: ilkka.vanha-majamaa@luke.fi

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