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Articles by Erkki Verkasalo

Category: Commentary

article id 462, category Commentary
Jean-Michel Leban, Heli Peltola, Sanna Leinonen, Christine Todoroki, Sophie D'Amours, Barry Gardiner, Jim Goudie, Eini Lowell, Thomas Seifert, Erkki Verkasalo, Lars Wilhelmsson, Tuula Nuutinen. (2009). Preface. Silva Fennica vol. 43 no. 3 article id 462. https://doi.org/10.14214/sf.462
The 6th IUFRO Workshop on Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software.
  • Leban, ORCID ID:E-mail:
  • Peltola, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: heli.peltola@uef.fi
  • Leinonen, ORCID ID:E-mail:
  • Todoroki, ORCID ID:E-mail:
  • D'Amours, ORCID ID:E-mail:
  • Gardiner, ORCID ID:E-mail:
  • Goudie, ORCID ID:E-mail:
  • Lowell, ORCID ID:E-mail:
  • Seifert, ORCID ID:E-mail:
  • Verkasalo, Finnish Forest Research Institute, Joensuu Unit, P.O. Box 68, FI-80101, Joensuu, Finland ORCID ID:E-mail: erkki.verkasalo@metla.fi
  • Wilhelmsson, ORCID ID:E-mail:
  • Nuutinen, European Forest Institute, Torikatu 34, FI-80100 Joensuu, Finland ORCID ID:E-mail: tuula.nuutinen@efi.int

Category: Research article

article id 9972, category Research article
Jukka Malinen, Harri Kilpeläinen, Erkki Verkasalo. (2018). Validating the predicted saw log and pulpwood proportions and gross value of Scots pine and Norway spruce harvest at stand level by Most Similar Neighbour analyses and a stem quality database. Silva Fennica vol. 52 no. 4 article id 9972. https://doi.org/10.14214/sf.9972
Highlights: Non-parametric prediction together with external stem quality database provides predictions usable for pre-harvest assessment at a stand level; The prediction of Norway spruce assortment recovery and value proved to be more accurate than the predictions for Scots pine; RMSE and bias of unit prices were 3.50 € m–3 and 0.58 € m–3 for pine and 2.60 € m–3 and 0.35 € m–3 for spruce.

Detailed pre-harvest information about the volumes and properties of growing stocks is needed for increased precision in wood procurement planning for just-in-time wood deliveries by cut-to-length (CTL) harvesters. In the study, the non-parametric Most Similar Neighbour (MSN) methodology was evaluated for predicting external quality of Scots pine and Norway spruce, expressed as stem sections fulfilling the saw log dimension and quality requirements of Finnish forest industry, as they affect the recovery of timber assortments and the value of a pre-harvest stand. Effects of external tree quality were evaluated using saw log recovery and saw log reduction caused by stem defects, as well as total timber value (€) and average unit value (€ m–3) in a stand. Root mean square error (RMSE) of saw log recovery and reduction were 9.12 percentile points (pp) for Scots pine and 6.38 pp for Norway spruce stands. In the unit value considerations, the predictions compared with measurements resulted in the RMSE of 3.50 € m–3 and the bias of 0.58 € m–3 in Scots pine stands and 2.60 € m–3, and 0.35 € m–3 in Norway spruce stands, respectively. The presented MSN based approach together with the utilization of the external stem quality database included in the ARVO software could provide dimension and external quality predictions usable for pre-harvest assessment of timber stock at a stand level. This prediction methodology is usable especially in analyses where timber assortment recoveries, values and unit prices are compared when different bucking objectives are used.

  • Malinen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: jukka.malinen@uef.fi (email)
  • Kilpeläinen, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: harri.kilpelainen@luke.fi
  • Verkasalo, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: erkki.verkasalo@luke.fi
article id 1293, category Research article
Jukka Malinen, Mika Haring, Harri Kilpeläinen, Erkki Verkasalo. (2015). Comparison of alternative roundwood pricing systems – a simulation approach. Silva Fennica vol. 49 no. 3 article id 1293. https://doi.org/10.14214/sf.1293
Highlights: A discrete event simulation model was developed for studying roundwood pricing systems; For a single buyer, pricing based on residual value appraisal produced (RVA) 4.87 per cent higher wood paying capability and 3.70 per cent higher stumpage price than pricing based on average unit prices; As the number of buyers using RVA increases, the competition increased and the advantage decreased.

In a closed market, roundwood buyers pricing system affect the roundwood flow from the stands to different roundwood users. If a buyer is capable to discriminate higher value stands from low quality stands better than its competitors, the buyer should be able to buy better raw material. In the study, a discrete event simulation was used to examine the effect of residual value appraisal (RVA) -based pricing of roundwood by log dimensions and grades compared to the traditional pricing based on average unit prices (UP) of roundwood assortments on roundwood flow. The core of the simulation model was the data containing 51 pine dominated stands from southern Finland. Sample trees were theoretically bucked by the bucking simulator in order to estimate the volumes, dimensions and grades of the logs and roundwood assortments. The simulation model of roundwood markets included four roundwood buyers, two corporations and two saw milling enterprises. The main finding of the study was that the buyers who use RVA gains an advantage and receives better quality compared to buyers who use UP. As the number of buyers using RVA increases, the competition increased and the advantage decreased.

  • Malinen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: jukka.malinen@uef.fi (email)
  • Haring, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: mika.haring@gmail.com
  • Kilpeläinen, Natural Resources Institute Finland (Luke), Bio-based business and industry, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: harri.kilpelainen@luke.fi
  • Verkasalo, Natural Resources Institute Finland (Luke), Bio-based business and industry, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: erkki.verkasalo@luke.fi
article id 117, category Research article
Harri Kilpeläinen, Jari Lindblad, Henrik Heräjärvi, Erkki Verkasalo. (2011). Saw log recovery and stem quality of birch from thinnings in southern Finland. Silva Fennica vol. 45 no. 2 article id 117. https://doi.org/10.14214/sf.117
The objective of this study was to examine the timber quality of silver birch (Betula pendula Roth) and European white birch (Betula pubescens Ehrh.) trees in the first and second thinnings in southern parts of Finland, from the viewpoint of sawing of small-diameter, short logs, in particular. The average stem volume of birch was 0.140 m3 in the first thinning stands and 0.206 m3 in the second thinning stands. In planted stands, the trees were larger in the first thinnings but slightly smaller in the second thinnings, compared with naturally regenerated pure birch stands or mixed stands of Norway spruce and birch species. Almost 60% of the harvested and 35% of the remaining stems that could provide saw logs were graded as pulpwood for timber quality due to the occurrence of stem defects. The most common stem defects were multiple crooks and middle crooks. Only minor between-stratum differences were detected in the numbers of defects. Depending on the bucking option, the total percentage of saw and plywood logs from the total birch recovery in the thinning of the sample stands varied between 11.7 and 18.2. The recovery of saw logs was clearly higher in the second thinnings, 12–19%, than in the first thinnings, 8–14%. Of the stand types, saw log recovery was the highest in planted birch stands, 12–19%, but lower in naturally regenerated pure birch stands and mixed stands of Norway spruce and birch. The highest share of saw logs was in the second thinning of planted stands, 17–25%. This study shows that the harvesting recoveries of end-use based timber assortments can be estimated in different kinds of thinning birch stands. Based on tree and log dimensions and stem squality, silver birch firstly from plantations and secondly from mixed stands should be the most interesting source of raw material for the saw milling, furniture and interior product sectors.
  • Kilpeläinen, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail:
  • Lindblad, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail:
  • Heräjärvi, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: henrik.herajarvi@metla.fi (email)
  • Verkasalo, Finnish Forest Research Institute, Eastern Finland Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail:

Category: Article

article id 5483, category Article
Erkki Verkasalo. (1992). Relationships of the modulus of elasticity and the structure of Finnish Scots pine wood. Silva Fennica vol. 26 no. 3 article id 5483. https://doi.org/10.14214/sf.a15644

The paper presents preliminary results on the relationships of the longitudinal modulus of elasticity (E) in bending, based on ISO Standard 3349 tests on small, clear specimens, and some basic characteristics of Finnish Scots pine (Pinus sylvestris L.) wood. A manual image analysis method – quantitative stereological counting – was introduced and applied for the investigations of wood structure.

The main results were consistent with those from the prior research. The range of E was 9.7 to 19.1 GPa. Increase in especially fibre density index (R2 = 0.95), weight density and specific gravity (R2 = 0.90), Runkel’s ratio, coefficient of cell rigidity and number of growth rings per cross-sectional unit area, but also in latewood percentage (R2 = 0.58) resulted in an increase in E. Increase in growth ring width, particularly in the width of the late wood section within a ring (R2 = 0.63 to 0.90) had a reverse effect. Cell wall thickness did not show any clear effect. Except for tracheid diameter, the relationships were stronger for the variables determined in the tangential than in the radial wood direction.

Quantitative stereological counting has been used to some degree in the Finnish wood research. The procedure is technically feasible and easy to use. A large sample of counting areas is frequently needed to obtain accurate mean results for the size and distribution of the features. Because the actual analysis points are located at a fixed distance from each other, the method is not in principle well suited for wood with a regular and simple structure, as Scots pine. However, the good correlations between E and some characteristics obtained with stereological counting did not support this misgiving.

The PDF includes an abstract in Finnish.

  • Verkasalo, ORCID ID:E-mail:
article id 5480, category Article
Erkki Verkasalo. (1992). Forest industry as a producer and consumer of wood-based energy in Finland. Silva Fennica vol. 26 no. 2 article id 5480. https://doi.org/10.14214/sf.a15641

This article summarises the importance of forest industry in the acquisition and consumption of wood-based energy in Finland. Opportunities to increase the efficiency of energy utilization further are discussed, as well.

The forest industry uses 25% of the total energy and 40% of the total electricity. It also generates considerable amounts of heat and electric power as by-products of wood-processing. Wood in different forms accounts for 64% of the fuels of the forest industry. Consequently, the need for outside, imported energy is minute. Black liquor of pulping is dominant as a source of wood-based energy. In addition, plenty of wood residues (bark, saw dust, planer shavings, grinder dust, screening reject of chips) and minor amounts of for wood processing unsuitable fractions obtained in conjunction with harvesting small-sized whole-trees, tree selections and logging residues are used for energy production.

The PDF includes an abstract in Finnish.

  • Verkasalo, ORCID ID:E-mail:

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