Current issue: 60(2)

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Scopus CiteScore 2023: 3.5
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Silva Fennica vol. 60 no. 3 | 2026

Category : Research article

article id 26021, category Research article

Riku Tarvainen, Kirsi Riekki, Heikki Ovaskainen, Kalle Kärhä, Jukka Malinen. (2026). Strip-road tree identification and stand structure estimation using harvester data. Silva Fennica vol. 60 no. 3 article id 26021. https://doi.org/10.14214/sf.26021

Keywords: simulation; sampling; harvester data; accurate positioning

Highlights: Three methods for identifying strip-road trees from hpr data with accurate positioning were compared; Inner-stand spatial arrangement of trees and strip-road sampling sensitivity were quantified using theoretical strip-road layouts; Harvester-based strip-road sampling offers a practical and cost-efficient alternative for forest inventory, but estimates based solely on realised strip-road locations may be biased in certain stand conditions.

Abstract | Full text in HTML | Full text in PDF | Author Info

Harvester data are a potentially valuable source of detailed information on forest inventory in first-thinning stands. In first-thinning operations performed using modern cut-to-length harvesters, all the trees within the strip roads are removed. The resulting systematic strip road network covers approximately 15–20% of the stand area. We investigated how strip-road trees can be identified from harvested production data to quantify within-stand variation and evaluate how strip-road sample placement affects the representativeness of the sample. Three different strip-road tree identification methods were evaluated: (1) a boom-angle and -length method; (2) a buffer method using reconstructed strip-road centrelines in a global coordinate system; and (3) a boom-angle method. The accuracy of the resulting diameter distributions, stem counts and basal-area estimates was assessed using Reynold’s error index and root mean square error metrics against detailed field reference data. In addition, theoretical offset strip roads were established and systematically shifted across each measurement area to quantify within-stand variation and sampling sensitivity. The most accurate stem count estimates were obtained using the boom-angle and -length method and the buffer method, whereas the boom-angle sector method performed poorly. Offset strip-road tree samples revealed substantial variation in stem count and basal area in some stands, indicating that strip-road alignment and spatial heterogeneity can significantly influence the representativeness of the sample. Our findings show that, in general, harvester-based strip-road sampling is a feasible and cost-efficient approach for estimating stand-level forest variables in first thinnings if tree identification methods and spatial biases are carefully considered.

Tarvainen, Metsäteho Oy, Vernissakatu 1, FI-01300 Vantaa, Finland https://orcid.org/0009-0001-2336-3125 E-mail: riku.tarvainen@metsateho.fi
Riekki, Metsäteho Oy, Vernissakatu 1, FI-01300 Vantaa, Finland https://orcid.org/0009-0007-8366-3297 E-mail: kirsi.riekki@metsateho.fi
Ovaskainen, Metsäteho Oy, Vernissakatu 1, FI-01300 Vantaa, Finland https://orcid.org/0000-0001-5063-6662 E-mail: heikki.ovaskainen1@gmail.com
Kärhä, University of Eastern Finland, School of Forest Sciences, Faculty of Science, Forestry and Technology, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: kalle.karha@uef.fi
Malinen, Metsäteho Oy, Vernissakatu 1, FI-01300 Vantaa, Finland https://orcid.org/0000-0002-5023-1056 E-mail: jukka.malinen@metsateho.fi

article id 26018, category Research article

Jori Uusitalo, Zhu Mao, Son Cao, Omid Abdi. (2026). Assessing logging trail network performance using spatial configuration metrics. Silva Fennica vol. 60 no. 3 article id 26018. https://doi.org/10.14214/sf.26018

Keywords: silviculture; sustainable forest management; forest operations; timber harvesting; forest machines; GNSS positioning

Highlights: Proposes two complementary metrics – Coverage Coefficient and Structural Efficiency – to assess spatial arrangement performance of logging trail networks beyond traditional density measures; A new method is also introduced that computes geometrically meaningful mean spacing between adjacent trails, overcoming limitations of density-based approaches that may produce geometrically uneven trail distributions; Demonstrates how new metrics can be applied to data gathered from thinning operations in Central Finland; The new metrics support improved harvesting efficiency, automated trail planning, and sustainable forest management.

Abstract | Full text in HTML | Full text in PDF | Author Info

Logging trails are a critical component of modern forest harvesting operations, particularly in thinning and partial cutting, where trail layout strongly influences harvesting efficiency, soil disturbance, future stand growth, and carbon balance. Despite their importance, existing regulations and commonly used metrics – such as mean trail spacing and trail density – primarily address quantitative properties of logging trail networks and do not capture the qualitative aspects of network design. In this study, we introduce a novel concept for assessing the spatial arrangement performance of logging trail networks based on two complementary spatial configuration metrics: a Coverage Coefficient, describing the proportion of forest area reachable by harvesting machinery, and a Structural Efficiency Coefficient, comparing the actual trail length to an idealized network layout. Together, these metrics provide a geometrically meaningful and operationally relevant evaluation of trail network spatial arrangement beyond conventional density-based measures. We also introduce a method for computing a geometrically meaningful mean spacing between adjacent trails. The methodology is demonstrated using ten thinning sites from Central Finland. The results reveal clear differences in the spatial pattern of trail layouts among sites that are not detectable using traditional metrics alone. The proposed approach offers a practical tool for evaluating spatial arrangement performance of logging trail networks after harvesting, supporting operator feedback, regulatory assessment, and the development of automated trail network design and planning procedures. More broadly, the metrics provide a foundation for improving harvesting efficiency, reducing unnecessary trail density, and supporting environmentally sustainable forest management.

Uusitalo, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0000-0003-3793-1215 E-mail: jori.uusitalo@helsinki.fi
Mao, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0000-0002-8464-2558 E-mail: zhu.mao@helsinki.fi
Cao, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0009-0007-5285-7312 E-mail: caothaison@outlook.com.vn
Abdi, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0000-0002-8048-8792 E-mail: omid.abdi@helsinki.fi

article id 26012, category Research article

Alwin A. Hardenbol, Hans Ole Ørka, Terje Gobakken, Joel Kostensalo. (2026). Optimising rare tree species detection for large-area mapping: a case study on European aspen (Populus tremula). Silva Fennica vol. 60 no. 3 article id 26012. https://doi.org/10.14214/sf.26012

Keywords: Bayesian statistics; biodiversity conservation; base rate problem; broadleaves; individual tree map; model transferability

Highlights: Balancing false discovery and false negative rates improves rare tree species detection; Preferring volume- over count-based approaches makes ecological sense for rare tree species; We detected 70% of aspen volume and classified this volume with 31% false discovery rate and 54% false negative rate; Base rates of rare tree species have been overlooked in remote sensing literature.

Abstract | Full text in HTML | Full text in PDF | Author Info

Some locally rare tree species – like European aspen (Populus tremula L.) – contribute disproportionately to forest biodiversity, making their accurate monitoring important for conservation. However, most remote sensing studies of rare tree species ignore their low prevalence/base rate, necessary for model transferability. We aimed to assess European aspen classification under realistic landscape prevalence and find methods to improve classification performance. Across 253 plots from field data in Våler, Norway we detected and segmented 5455 living trees, including 55 European aspens (ca. 1% prevalence), from high-density airborne laser scanning (ALS) data merged with multispectral aerial imagery. Individual segments were then classified as European aspen or non-aspen using random forest and synthetic minority oversampling (SMOTE). We evaluated classification based on tree counts and summed tree volumes. To underpin the importance of prevalence consideration and compare our results, we also re-analysed published Fennoscandian European aspen classification studies. Contrary to a perfect balance, we found an optimal SMOTE-ratio at ca. 0.07 (European aspen–non-aspen ratio). Our count-based classification achieved 32% (16–52) false discovery rate (FDR) and 73% (60–83) false negative rate (FNR), whereas volume-based classification achieved 31% (11–51) FDR and 54% (38–71) FNR. Re-analysed studies averaged 66% FDR and 33% FNR at a 1% prevalence. Our results demonstrate that rare tree species classification benefits from optimising majority–minority ratios and, given the ecological value of larger trees, volume-based approaches are warranted. Finally, we urge reporting landscape prevalence and adjust classification metrics to reflect these to enable transferability to real-world applications in rare tree species classification.

Hardenbol, Natural Resources Institute Finland (Luke), Natural Resources Unit, Yliopistokatu 6B, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-0615-505X E-mail: alwin.hardenbol@luke.fi
Ørka, Norwegian University of Life Sciences (NMBU), Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0000-0002-7492-8608 E-mail: hans-ole.orka@nmbu.no
Gobakken, Norwegian University of Life Sciences (NMBU), Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0000-0001-5534-049X E-mail: terje.gobakken@nmbu.no
Kostensalo, Natural Resources Institute Finland (Luke), Natural Resources Unit, Yliopistokatu 6B, FI-80100 Joensuu, Finland https://orcid.org/0000-0001-9883-1256 E-mail: joel.kostensalo@luke.fi

article id 26011, category Research article

Kalle Kemppainen, Jari Miina, Eetu Tarvainen, Ville Kankaanhuhta, Juha Laitila, Heli Peltola, Markus Strandström, Kalle Kärhä. (2026). Quality of drill-based site preparation and early performance of Norway spruce and Scots pine seedlings planted in different seasons. Silva Fennica vol. 60 no. 3 article id 26011. https://doi.org/10.14214/sf.26011

Keywords: forest regeneration; seedling survival; manual planting; mechanical soil preparation

Highlights: A drill-based device for mechanical site preparation significantly reduces soil exposure; The drill created mostly good (61%) or satisfactory (34%) planting spots for conifer seedlings; Two years after planting, Norway spruce seedlings performed better than Scots pine seedlings.

Abstract | Full text in HTML | Full text in PDF | Author Info

Mechanical site preparation (MSP) is essential for successful forest regeneration. However, excessively exposed soil may harm the environment and increase the total costs of seedling stand management. A drill-based MSP device (drill), designed to reduce soil exposure, was recently tested in Finland. This study investigated the quality of drill-based MSP and the early performance of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) seedlings planted in different seasons on five mineral soil stands. The findings showed that the mean area of the drilling spots (0.18 m²) was about 20% of that reported for mounding. The drill mostly resulted in good (61%) or satisfactory (34%) planting spot quality (e.g., good spots were covered with mineral soil). Ground and soil obstacles, such as roots, stones, stumps, and logging residues, negatively affected planting spot quality. About 13% of the planting spots did not have a pure mineral soil cover, which is required to mitigate pine weevil (Hylobius abietis L.) damage. Most seedlings were still alive one year after planting, but the proportion of healthy seedlings was 71% for Norway spruce and 48% for Scots pine two years after planting. Overall, drill-based MSP may be most feasible for drier sites with less competitive ground vegetation. However, the productivity and costs, the performance of the planted seedlings, and other potential benefits of drill-based MSP should be further tested under varying operating conditions and compared with those of conventional MSP methods.

Kemppainen, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland; Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0009-0000-6184-8812 E-mail: kalle.kemppainen@uef.fi
Miina, Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-8639-4383 E-mail: jari.miina@luke.fi
Tarvainen, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland E-mail: eetu.tarvainen@harvestia.fi
Kankaanhuhta, Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0001-5785-5972 E-mail: ville.kankaanhuhta@luke.fi
Laitila, Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0003-4431-3319 E-mail: juha.laitila@luke.fi
Peltola, Natural Resources Institute Finland, Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi
Strandström, Metsäteho Oy, Vernissakatu 1, FI-01300 Vantaa, Finland https://orcid.org/0009-0004-0868-3042 E-mail: markus.strandstrom@metsateho.fi
Kärhä, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-8455-2974 E-mail: kalle.karha@uef.fi

article id 26005, category Research article

Therese Strömvall Nyberg, Mikolaj Lula, Hammed Adekunle, Urban Nilsson, Göran Örlander, Emma Holmström. (2026). Forest development and financial outcomes under shelterwood and clearcut regimes in mixed stands. Silva Fennica vol. 60 no. 3 article id 26005. https://doi.org/10.14214/sf.26005

Keywords: Pinus sylvestris; Picea abies; land expectation value; combination method; Drettinge method

Highlights: Shelterwood and mixed species regeneration can be a viable strategy under suitable conditions; Active management and timely overstory removal in shelterwood systems are important for financial revenue and stand development; Clearcuts consistently yielded higher financial returns than shelterwood.

Abstract | Full text in HTML | Full text in PDF | Author Info

We assessed long-term outcomes of a regeneration experiment comparing clearcutting and shelterwood treatments, each with and without mechanical site preparation (MSP). The experiment was established in the early 1990s across Sweden and combined natural regeneration of Scots pine (Pinus sylvestris L.) with planting of Norway spruce (Picea abies (L.) H. Karst.; 2500 seedlings ha^–1). The first assessment showed Norway spruce dominance on southern sites and potential for mixed stands in central and northern regions. In 2022–2023, sites were re-measured to assess stand structure and productivity at mid-rotation, and the measured data were then used to parameterize Heureka decision support system (DSS) for simulations to final harvest. Southern sites developed into Norway spruce-dominated stands, with higher volume in clearcut than shelterwood treatments. Central and northern sites developed into mixed species stands, with higher volumes in shelterwood treatments in central Sweden. In northern Sweden, retained shelterwood negatively affected understory growth, highlighting the importance of active management while using shelterwood. Despite these regional differences, land expectation value (LEV) was consistently higher for clearcut treatments. Even in central Sweden, higher volumes in shelterwood treatments did not compensate for the additional costs associated with shelterwood cuttings. Our results show that establishing mixed species stands through shelterwood and planting can be viable depending on site conditions, but likely results in lower revenue than clearcutting.

Strömvall Nyberg, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, 234 56 Alnarp, Sweden https://orcid.org/0009-0007-0280-6023 E-mail: therese.stromvall@slu.se
Lula, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, 234 56 Alnarp, Sweden E-mail: mikolaj.lula@slu.se
Adekunle, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, 234 56 Alnarp, Sweden E-mail: hammedadekunle43@yahoo.com
Nilsson, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, 234 56 Alnarp, Sweden E-mail: urban.nilsson@slu.se
Örlander, Department of Forestry and Wood Technology, Linnaeus University, 351 95 Växjö, Sweden E-mail: goran.orlander@outlook.com
Holmström, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, 234 56 Alnarp, Sweden https://orcid.org/0000-0003-2025-1942 E-mail: emma.holmstrom@slu.se

article id 25005, category Research article

Tom Erik Thorkildsen, Eirik Ogner Jåstad, Per Kristian Rørstad, Erik Trømborg. (2026). Forest sector impacts from increased reutilization of post-consumer wood in the Nordic-Baltic region. Silva Fennica vol. 60 no. 3 article id 25005. https://doi.org/10.14214/sf.25005

Keywords: circular economy; forest sector modeling; harvest leakage; reclaimed wood; recycling targets; wood waste

Highlights: Wood reutilization strongly promotes particleboard production and harvest-residue use; Because of leakage effects, multilateral wood-reutilization policy is far more efficient than unilateral policy in reducing domestic roundwood harvesting; As wood reutilization increases, harvest-residue use rises by about twice the reduction in roundwood harvest, measured in solid cubic meters.

Abstract | Full text in HTML | Full text in PDF | Author Info

Global roundwood harvests are projected to increase by 49 percent by 2050, and can negatively affect carbon sequestration, biodiversity, and essential ecosystem services. Employing a circular cascading strategy for wood resources may increase the carbon stock accumulated in wood products and reduce harvest. This study investigates a) how reutilizing 30, 50, and 70 percent of generated post-consumer wood by weight will affect the Nordic-Baltic forest sector, and b) the difference between adopting unilateral Norwegian and multilateral Nordic-Baltic wood reutilization policies. We apply the Nordic Forest Sector Model, a spatial partial equilibrium model, which includes 37 assorted forest products, and make a novel extension by including reutilized wood products. The model calculates hypothetical harvest and production volumes as well as prices when each country is forced to meet the selected reutilization targets based on constrained welfare maximization. The results show that reutilization of wood promotes increased particleboard production, mainly in the Baltics, and increased utilization of harvest residues, foremost in Sweden and Finland, to maintain bioheat production. In the Nordic-Baltic area, between 0.42 and 0.73 cubic meters of roundwood would be saved for every cubic meter of wood reutilized, while the corresponding rates for Norway are 0.26 to 0.36. Due to leakage effects, unilateral Norwegian policies result in domestic roundwood reduction to reutilization rates as low as 0.03 to 0.05. This implies that it is vital to coordinate policies with adjacent countries to reduce leakage if the objective of wood reutilization is to reduce domestic extraction of roundwood.

Thorkildsen, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0009-0009-7221-698X E-mail: tom.erik.thorkildsen@nmbu.no
Jåstad, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway https://orcid.org/0000-0002-1089-0284 E-mail: eirik.jastad@nmbu.no
Rørstad, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway E-mail: per.kristian.rorstad@nmbu.no
Trømborg, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway E-mail: erik.tromborg@nmbu.no

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