Current issue: 58(5)

Under compilation: 59(1)

Scopus CiteScore 2023: 3.5
Scopus ranking of open access forestry journals: 17^th
PlanS compliant

Articles by Heli Peltola

Category : Article

article id 5618, category Article

Marja-Leena Nykänen, Marianne Broadgate, Seppo Kellomäki, Heli Peltola, Christopher Quine. (1997). Factors affecting snow damage of trees with particular reference to European conditions. Silva Fennica vol. 31 no. 2 article id 5618. https://doi.org/10.14214/sf.a8519

Keywords: stem breakage; stand management; snow accumulation; topography; risk assessment; snow damage; snowfall; risk model

Abstract | View details | Full text in PDF | Author Info

Within the European Community snow damage affects an estimated 4 million m³ of timber every year, causing significant economic losses to forest owners. In Northern Europe, for example, the occurrence of snow damage has increased over the last few decades mainly due to the increase in total growing stock. The most common form of damage is stem breakage, but trees can also be bent or uprooted. Trees suffering snow damage are also more prone to consequential damage through insect or fungal attacks.

Snow accumulation on trees is strongly dependent upon weather and climatological conditions. Temperature influences the moisture content of snow and therefore the degree to which it can accumulate on branches. Wind can cause snow to be shed, but can also lead to large accumulations of wet snow, rime or freezing rain. Wet snow is most likely in late autumn or early spring. Geographic location and topography influence the occurrence of damaging forms of snow, and coastal locations and moderate to high elevations experience large accumulations. Slope plays a less important role and the evidence on the role of aspect is contradictory. The occurrence of damaging events can vary from every winter to once every 10 years or so depending upon regional climatology. In the future, assuming global warming in northern latitudes, the risk of snow damage could increase, because the relative occurrence of snowfall near temperatures of zero could increase.

The severity of snow damage is related to tree characteristics. Stem taper and crown characteristics are the most important factors controlling the stability of trees. Slightly tapering stems, asymmetric crowns, and rigid horizontal branching are all associated with high risk. However, the evidence on species differences is less clear due to the interaction with location. Management of forests can alter risk through choice of regeneration, tending, thinning and rotation. However, quantification and comparison of the absolute effect of these measures is not yet possible. An integrated risk model is required to allow the various locational and silvicultural factors to be assessed. Plans are presented to construct such a model, and gaps in knowledge are highlighted.

Nykänen, E-mail: mn@mm.unknown
Broadgate, E-mail: mb@mm.unknown
Kellomäki, E-mail: sk@mm.unknown
Peltola, E-mail: hp@mm.unknown
Quine, E-mail: cq@mm.unknown

article id 5505, category Article

Heli Peltola, Jorma Aho, Alpo Hassinen, Seppo Kellomäki, Matti Lemettinen. (1993). Swaying of trees as caused by wind: analysis of field measurements. Silva Fennica vol. 27 no. 2 article id 5505. https://doi.org/10.14214/sf.a15666

Keywords: Pinus sylvestris; wind; windspeed; wind loads; dynamic load; bending

Abstract | View details | Full text in PDF | Author Info

Measurements of wind and subsequent swaying of two Scots pines (Pinus sylvestris L.) were made at stand edge conditions. The horizontal windspeed was measured ten meters outside of the stand edge for four heights using cup anemometers. The compass directions were determined using a directional vane placed above the canopy. Tree swaying was measured by accelerometers at xy-coordinates. The shape of the wind profile at the stand edge varied to some degree depending on windspeed, but the form was a logarithmic one. Swaying of trees increased along with increasing windspeed. Furthermore, swaying was more or less irregular in relation to xy-coordinates, but it occurred, however, mainly perpendicularly to the direction of mean windspeed. The maximum bending of trees to the direction of mean windspeed varied also only little for various gusting windspeeds (average windspeed of 20 seconds) and dynamic wind loads. The maximum bending of trees was also in most cases less or equal to those predicted on the basis of static wind loads, when the mean windspeed for static load is taken as equal to the gusting windspeed.

The PDF includes an abstract in Finnish.

Peltola, E-mail: hp@mm.unknown
Aho, E-mail: ja@mm.unknown
Hassinen, E-mail: ah@mm.unknown
Kellomäki, E-mail: sk@mm.unknown
Lemettinen, E-mail: ml@mm.unknown

article id 5504, category Article

Heli Peltola, Seppo Kellomäki. (1993). A mechanistic model for calculating windthrow and stem breakage of Scots pines at stand age. Silva Fennica vol. 27 no. 2 article id 5504. https://doi.org/10.14214/sf.a15665

Keywords: Pinus sylvestris; wind; stems; breakage; windspeed; breaking stress; bending models

Abstract | View details | Full text in PDF | Author Info

A model for the mechanism of windfall and stem breakage was constructed for single Scots pine (Pinus sylvestris L.) at the stand edge. The total turning moment arising from the wind drag and from the bending of stem and crown was calculated along with the breaking stress of the stem. Similarly, the support given by the root -soil plate anchorage was calculated. Windspeed variation within the crown and the vertical distribution of stem and crown weight were taken into account. Model computations showed that trees having a large height to diameter ratio were subjected to greater risk of falling down or breaking than trees with a small height to diameter ratio. The windspeed required to blow down a tree or break the stem of a tree decreased if the height to diameter ratio or the crown to stem ratio of trees increased.
The PDF includes an abstract in Finnish.

Peltola, E-mail: hp@mm.unknown
Kellomäki, E-mail: sk@mm.unknown

Category : Climate resilient and sustainable forest management – Research article

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 https://orcid.org/0000-0003-0554-8254 E-mail: alexander.pulgarin.diaz@uef.fi
Melin, Natural Resources Institute Finland (Luke), P.O. Box 68, FI-80101 Joensuu, Finland 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 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 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 https://orcid.org/0000-0002-3875-2772 E-mail: olli-pekka.tikkanen@uef.fi

Category : Research article

article id 25004, category Research article

Kalle Kemppainen, Kalle Kärhä, Juha Laitila, Antti Sairanen, Ville Kankaanhuhta, Heli Viiri, Heli Peltola. (2025). Evaluation of the productivity and costs of excavator-based mechanized tree planting in Finland based on automated data collection. Silva Fennica vol. 59 no. 1 article id 25004. https://doi.org/10.14214/sf.25004

Keywords: site preparation; cost-efficiency; mechanization; forest regeneration; planting machine; site selection

Highlights: With proper site selection and competent machine operators, it is possible to achieve a higher productivity than 200 seedlings per operating hour in excavator-based mechanized planting; The hectare-based regeneration costs from excavator-based mechanized planting can be 3% lower than those of conventional manual planting chains; The most cost-efficient planting chain was a continuously advancing mounder combined with manual planting.

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

The poor cost-effectiveness of mechanized planting (MECP) is the main reason for the low mechanization rate of planting. In this study, we investigated the productivity of the mechanized excavator-based planting of Norway spruce (Picea abies [L.] H. Karst.) seedlings based on data collected by the Risutec Asta documentation system. We also compared the costs of a MECP chain with two different manual planting (MAP) chains, where mounding was carried out by a crawler excavator (EXC) or a continuously advancing mounder (CONT). The MECP of seedlings was carried out using an EXC equipped with a Risutec PM-160 planting device. Generally, the nine study sites in western Finland contained few surface obstacles (e.g., the logging residues had mainly been harvested), which made the conditions very suitable for MECP. The average production time taken by the MECP was 9 h ha^–1. The operating hour (G₁₅-h) productivity averaged 215 seedlings G₁₅-h⁻¹, with the mean planting time being 13.8 s seedling⁻¹. Loading 160 seedlings into the seedling cassette took approximately 10 min (3.8 s seedling⁻¹). Overall, the cost of the MECP was about 3% lower than for the EXC + MAP. However, when productivity was set at <210 seedlings G₁₅-h⁻¹, the cost of the MECP was higher than that of the EXC + MAP. Based on our findings, the most cost-efficient planting chain was CONT + MAP. However, based on our results, the required level of productivity can be achieved if the sites are suitable for MECP and the machine operators are skilled.

Kemppainen, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland; Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0009-0000-6184-8812 E-mail: kalle.kemppainen@uef.fi
Kärhä, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland E-mail: kalle.karha@uef.fi
Laitila, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0003-4431-3319 E-mail: juha.laitila@luke.fi
Sairanen, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0009-0008-8632-3797 E-mail: anttsair@student.uef.fi
Kankaanhuhta, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0001-5785-5972 E-mail: ville.kankaanhuhta@luke.fi
Viiri, UPM-Kymmene Plc, UPM Forest, Peltokatu 26 C 4, FI-33100 Tampere, Finland https://orcid.org/0000-0003-3952-9481 E-mail: heli.viiri@upm.com
Peltola, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi

article id 24041, category Research article

Johanna Jetsonen, Annamari Laurén, Heli Peltola, Katariina Laurén, Samuli Launiainen, Marjo Palviainen. (2025). Volume growth responses of Scots pine and Norway spruce to nitrogen fertilization: quantitative synthesis of fertilization experiments in Finland. Silva Fennica vol. 59 no. 1 article id 24041. https://doi.org/10.14214/sf.24041

Keywords: precipitation; growth response; mineral soils; site fertility

Highlights: Volume growth responses increased linearly with the applied nitrogen (N) dose up to 200 kg N ha^–1; Precipitation, site fertility, and time since fertilization affected the growth responses; Volume growth response to nitrogen fertilization was larger for Scots pine than for Norway spruce; Results can support planning of environmentally responsible and economically viable precision fertilization.

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

The effects of nitrogen (N) fertilization on tree growth have been studied widely in boreal forests in Finland, but a quantitative synthesis is still lacking. We performed a quantitative synthesis on volume growth responses to N fertilization in Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands in experiments established on mineral soils across Finland. Our study employed findings of 9 published studies including 108 Scots pine and 57 Norway spruce observations covering a wide range of N fertilization treatments, as well as forest stand- and climatic conditions. Based on these observations, we built linear mixed models to describe the N fertilization-induced annual volume growth response of Scots pine and Norway spruce stands. Our models showed that the N dose was the best predictor for volume growth response, and the growth response increased linearly with increasing N dose for both tree species. The volume growth responses also increased along with an increase in mean annual precipitation. The annual volume growth response decreased with the time since fertilization. For Scots pine, the best model also contained site fertility; increase in site fertility increased the volume growth response. These findings emphasize the need for site-specific precision fertilization schemes to sustainably improve growth and carbon sequestration of boreal forests.

Jetsonen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0009-0006-4878-8951 E-mail: johanna.jetsonen@helsinki.fi
Laurén, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland; Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0002-6835-9568 E-mail: annamari.lauren@helsinki.fi
Peltola, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi
Laurén, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland; University of Helsinki, Faculty of Medicine, Haartmaninkatu 8, 00290 Helsinki, Finland https://orcid.org/0009-0009-4677-9826 E-mail: katariina.lauren@helsinki.fi
Launiainen, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, 00790 Helsinki, Finland https://orcid.org/0000-0001-6611-6573 E-mail: samuli.launiainen@luke.fi
Palviainen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland https://orcid.org/0000-0001-9963-4748 E-mail: marjo.palviainen@helsinki.fi

article id 24047, category Research article

Kalle Kemppainen, Kalle Kärhä, Juha Laitila, Antti Sairanen, Ville Kankaanhuhta, Heli Viiri, Heli Peltola. (2024). RETRACTED: Evaluation of the productivity and costs of excavator-based mechanized tree planting in Finland based on automated data collection. Silva Fennica vol. 58 no. 5 article id 24047. https://doi.org/10.14214/sf.24047

Keywords: site preparation; cost-efficiency; mechanization; forest regeneration; planting machine; site selection

Highlights: With proper site selection and competent machine operators, it is possible to achieve a higher productivity than 200 seedlings per operating hour in excavator-based mechanized planting; The hectare-based regeneration costs from excavator-based mechanized planting can be 5% lower than those of conventional manual planting chains; The most cost-efficient planting chain was a continuously advancing mounder combined with manual planting.

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

The poor cost-effectiveness of mechanized planting (MECP) is the main reason for the low mechanization rate of planting. In this study, we investigated the productivity of the mechanized excavator-based planting of Norway spruce (Picea abies [L.] H. Karst.) seedlings based on data collected by the Risutec Asta documentation system. We also compared the costs of a MECP chain with two different manual planting (MAP) chains, where mounding was carried out by a crawler excavator (EXC) or a continuously advancing mounder (CONT). The MECP of seedlings was carried out using an EXC equipped with a Risutec PM-160 planting device. Generally, the nine study sites in western Finland contained few surface obstacles (e.g., the logging residues had mainly been harvested), which made the conditions very suitable for MECP. The average production time taken by the MECP was 9 h ha^-1. The operating hour (G₁₅-h) productivity averaged 215 seedlings G₁₅-h^-1 , with the mean planting time being 13.8 s seedling^-1. Loading 160 seedlings into the seedling cassette took approximately 10 min (3.8 s seedling^-1). Overall, the cost of the MECP was about 5% lower than for the EXC + MAP. However, when productivity was set at <200 seedlings G₁₅-h^-1 , the cost of the MECP was higher than that of the EXC + MAP. Based on our findings, the most cost-efficient planting chain was CONT + MAP. However, based on our results, the required level of productivity can be achieved if the sites are suitable for MECP and the machine operators are skilled.

Kemppainen, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland; Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0009-0000-6184-8812 E-mail: kalle.kemppainen@uef.fi
Kärhä, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0000-0002-8455-2974 E-mail: kalle.karha@uef.fi
Laitila, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0003-4431-3319 E-mail: juha.laitila@luke.fi
Sairanen, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0009-0008-8632-3797 E-mail: anttsair@student.uef.fi
Kankaanhuhta, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland https://orcid.org/0000-0001-5785-5972 E-mail: ville.kankaanhuhta@luke.fi
Viiri, UPM-Kymmene Plc, UPM Forest, Peltokatu 26 C 4, FI-33100 Tampere, Finland https://orcid.org/0000-0003-3952-9481 E-mail: heli.viiri@upm.com
Peltola, School of Forest Sciences, University of Eastern Finland (UEF), P.O. Box 111, FI-80101 Joensuu, Finland https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi

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 https://orcid.org/0000-0002-9095-7986 E-mail: harri.silvennoinen@uef.fi
Pikkarainen, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland 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 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 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 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 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 https://orcid.org/0000-0003-1384-9153 E-mail: heli.peltola@uef.fi

article id 23045, category Research article

Laura Pikkarainen, Harri Strandman, Eerik Vento, Aaron Petty, Olli-Pekka Tikkanen, Antti Kilpeläinen, Heli Peltola. (2024). Effects of forest conservation and management on timber, ecosystem carbon, dead wood and habitat suitability area in a boreal forest under climate change. Silva Fennica vol. 58 no. 2 article id 23045. https://doi.org/10.14214/sf.23045

Keywords: saproxylic species; simulation; carbon storage; forest fertilization; Fennoscandia; forest ecosystems services; improved regeneration material

Highlights: Increasing forest conservation areas increased all other ecosystem services except timber yield. Intensive forest management enhanced this increase; Increased conservation area decreased timber yield, but intensive forest management reduced this effect and even overcompensated it at the end of simulation period in the 10% conservation scenario with intensified forest management; Climate change increased all other ecosystem services, except carbon stocks.

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

We used forest ecosystem model simulations to study how forest conservation and management intensity affected timber yield, ecosystem carbon stocks, amount of dead wood, and habitat suitability area in a middle boreal forest region of Finland under changing climate over a 90-year simulation period. We used the following forest conservation and management scenarios: baseline forest management (BM), BM with 10 or 20% increase of conservation area with or without intensified forest management (i.e. improved forest regeneration material and forest fertilization). The simulations were done under current climate (reference period of 1981–2010), and Representative Concentration Pathway (RCP) climate change projections under the RCP2.6 and RCP4.5 forcing scenarios. Overall, increasing the forest conservation area decreased timber yield and increased the ecosystem carbon stock, the amount of dead wood and consequently the area of suitable habitat for saproxylic species. The use of intensified forest management reduced the loss of timber yield, increased ecosystem carbon stock, the amount of dead wood and area of suitable habitat for saproxylic species. At the end of simulation period, the use of intensified forest management even overcompensated (4–6% higher) the timber loss from 10% increase of conservation area. Under changing climate, timber yield, the amount of dead wood and the area of suitable habitats for saproxylic species increased. To conclude, with intensified forest management it is possible, in the short term, to decrease the loss of timber yield through increased forest conservation area and in the long term maintain or even increase it compared to baseline forest management.

Pikkarainen, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland https://orcid.org/0000-0001-5301-3639 E-mail: laura.pikkarainen@uef.fi
Strandman, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-9400-6424 E-mail: harri.strandman@uef.fi
Vento, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland E-mail: eerik.vento@gmail.com
Petty, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland https://orcid.org/0009-0006-6595-1386 E-mail: aaron.petty@uef.fi
Tikkanen, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland https://orcid.org/0000-0002-3875-2772 E-mail: olli-pekka.tikkanen@uef.fi
Kilpeläinen, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland https://orcid.org/0000-0003-4299-0578 E-mail: antti.kilpelainen@uef.fi
Peltola, School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland E-mail: heli.peltola@uef.fi

article id 23058, category Research article

Johanna Jetsonen, Annamari Laurén, Heli Peltola, Olli Muhonen, Juha Nevalainen, Veli-Pekka Ikonen, Antti Kilpeläinen, Eeva-Stiina Tuittila, Elisa Männistö, Nicola Kokkonen, Marjo Palviainen. (2024). Effects of nitrogen fertilization on the ground vegetation cover and soil chemical properties in Scots pine and Norway spruce stands. Silva Fennica vol. 58 no. 1 article id 23058. https://doi.org/10.14214/sf.23058

Keywords: boreal forest; competition index; forest fertilization; upland forests; vegetation cover

Highlights: Nitrogen (N) fertilization decreased the total cover of ground vegetation; N fertilization decreased the cover of mosses and dwarf shrubs and increased the cover of herbaceous plants; N concentration of the mor humus layer increased with the N fertilization; The magnitude of these changes depended on the intensity of the N fertilization.

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

The aim of this study was to investigate the short-term effects of nitrogen (N) fertilization intensity on the ground vegetation cover and soil chemical properties in two Scots pine (Pinus sylvestris L.) and two Norway spruce (Picea abies (L.) Karst.) dominated stands on upland forest sites in Eastern Finland. The fertilizer was applied using a helicopter in the spruce stands and a forwarder in the pine stands. The distribution and the amount of fertilizer was measured with funnel traps. Cover of each species of ground vegetation was estimated before fertilization and 3–4 years after it in pine and 2–3 years after it in spruce stands. Further, the cover observations were aggregated by plant types. Based on measurements, we analyzed the effects of the funnel-trap-observed amount of N fertilizer on the cover and plant type composition of ground vegetation and soil N and C concentration. In addition, we analyzed the impacts of competition caused by trees on the ground vegetation cover based on competition indices. N fertilization increased the cover of herbaceous plants and decreased the cover of mosses and dwarf shrubs, and the total cover of ground vegetation. Further, it increased the N concentration of the mor humus layer. The magnitude of the changes increased with the intensity of the N fertilization. The competition caused by trees did not affect the cover of ground vegetation.

Jetsonen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland E-mail: johanna.jetsonen@helsinki.fi
Laurén, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland; Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0002-6835-9568 E-mail: annamari.lauren@helsinki.fi
Peltola, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland E-mail: heli.peltola@uef.fi
Muhonen, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0009-0007-4051-8567 E-mail: olli.muhonen@forestvital.com
Nevalainen, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0009-0000-2972-4385 E-mail: juha.hs.nevalainen@gmail.com
Ikonen, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0003-1732-2922 E-mail: veli-pekka.ikonen@uef.fi
Kilpeläinen, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0003-4299-0578 E-mail: antti.kilpelainen@uef.fi
Tuittila, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland E-mail: eeva-stiina.tuittila@uef.fi
Männistö, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0003-3869-6739 E-mail: elisa.mannisto@uef.fi
Kokkonen, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu, Finland https://orcid.org/0000-0003-0197-2672 E-mail: nicola.kokkonen@uef.fi
Palviainen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 University of Helsinki, Finland E-mail: marjo.palviainen@helsinki.fi

article id 10243, category Research article

Laura Pikkarainen, Jaana Luoranen, Antti Kilpeläinen, Teppo Oijala, Heli Peltola. (2020). Comparison of planting success in one-year-old spring, summer and autumn plantings of Norway spruce and Scots pine under boreal conditions. Silva Fennica vol. 54 no. 1 article id 10243. https://doi.org/10.14214/sf.10243

Keywords: Pinus sylvestris; Picea abies; seedling damage; forest regeneration; field performance; planting season

Highlights: In Norway spruce, 84% of all plantings were successful, whereas in Scots pine, the corresponding number was 52%; The major reason for poor planting results was poor work quality; An extended planting season is possible for Norway spruce in southern and central Finland; In Scots pine, there are still large uncertainties in the success of summer and autumn plantings.

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

In Nordic countries, tree planting of seedlings is mainly performed during spring and early summer. Interest has increased in extending the planting window throughout the unfrozen growing season. This study compared the success of one-year-old spring, summer and autumn plantings in practical forestry in Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in southern and central Finland. Planting success was based on the number of viable seedlings per hectare relative to a species-specific target density. The influence of different factors to poor planting results were determined, including quality of site preparation and planting, and sources of natural damage. Overall, in Norway spruce, 85, 69 and 84% and in Scots pine 53, 55 and 40% of spring, summer and autumn plantings succeeded. In Norway spruce, the planting results were consistent between the southern and central regions, whereas in Scots pine, the success was slightly lower in the south. The poor work quality and a low density of appropriate planting spots, contributed to poor planting results, regardless of planting season, region or tree species. Considering different damages, especially mammal damage contributed to the failure of Scots pine spring plantings, whereas in summer plantings, corresponding single failure reason could not be identified. Based on our findings, extending the planting season of Norway spruce could be recommended in both regions. For Scots pine, there is still significant uncertainty about the success of summer and autumn plantings, partially due to the limited number of plantings available for analyses.

Pikkarainen, School of Forest Sciences, University of Eastern Finland, Yliopistonkatu 7, FI-80100 Joensuu, Finland E-mail: laura.pikkarainen@uef.fi
Luoranen, Natural Resources Institute Finland (Luke), Production Systems, Neulaniementie 5, FI-70210 Kuopio, Finland E-mail: jaana.luoranen@luke.fi
Kilpeläinen, School of Forest Sciences, University of Eastern Finland, Yliopistonkatu 7, FI-80100 Joensuu, Finland E-mail: antti.kilpelainen@uef.fi
Oijala, Metsä Group, Metsä Forest, Kuormaajantie 7, FI-40320 Jyväskylä, Finland E-mail: teppo.oijala@metsagroup.com
Peltola, School of Forest Sciences, University of Eastern Finland, Yliopistonkatu 7, FI-80100 Joensuu, Finland E-mail: heli.peltola@uef.fi

article id 9980, category Research article

Eino Levkoev, Lauri Mehtätalo, Katri Luostarinen, Pertti Pulkkinen, Anatoly Zhigunov, Heli Peltola. (2018). Development of height growth and frost hardiness for one-year-old Norway spruce seedlings in greenhouse conditions in response to elevated temperature and atmospheric CO₂ concentration. Silva Fennica vol. 52 no. 3 article id 9980. https://doi.org/10.14214/sf.9980

Keywords: climate change; Picea abies; needles; tree growth; seedlings; cold acclimation

Highlights: Elevated temperature resulted in increased height growth, delayed onset and shortened duration of autumn frost hardiness development in Norway spruce seedlings; Elevated temperature increased variation between genotypes in height growth and frost hardiness development; Elevated atmospheric CO₂ concentration had no effect on the development of height or autumn frost hardiness in Norway spruce seedlings.

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The mean temperature during the potential growing season (April–September) may increase by 1 °C by 2030, and by 4 °C, or even more, by 2100, accompanied by an increase in atmospheric CO₂ concentrations of 536–807 ppm, compared to the current climate of 1981–2010, in which atmospheric CO₂ is at about 350 ppm. This may affect both the growth and frost hardiness of boreal trees. In this work, we studied the responses of height and autumn frost hardiness development in 22 half-sib genotypes of one-year-old Norway spruce (Picea abies (L.) Karst.) seedlings to elevated temperatures and atmospheric CO₂ concentration under greenhouse conditions. The three climate treatments used were: T+1 °C above ambient and ambient CO₂; T+4 °C above ambient and ambient CO₂; and T+4 °C above ambient and elevated CO₂ (700 ppm). The height growth rate and final height were both higher under T+4 °C compared to T+1 °C. Temperature increase also delayed the onset, and shortened the duration, of autumn frost hardiness development. Elevated CO₂ did not affect the development of height or frost hardiness, when compared to the results without CO₂ elevation under the same temperature treatment. Higher temperatures resulted in greater variation in height and frost hardiness development among genotypes. Three genotypes with different genetic backgrounds showed superior height growth, regardless of climate treatment; however, none showed a superior development of autumn frost hardiness. In future studies, clonal or full-sib genetic material should be used to study the details of autumn frost hardiness development among different genotypes.

Levkoev, University of Eastern Finland, Faculty of Science and Forestry, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: eino.levkoev@uef.fi
Mehtätalo, University of Eastern Finland, Faculty of Science and Forestry, School of Computing, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: lauri.mehtatalo@uef.fi
Luostarinen, University of Eastern Finland, Faculty of Science and Forestry, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: katri.luostarinen@uef.fi
Pulkkinen, Natural Resources Institute Finland (Luke), Production systems, Haapastensyrjä Breeding Station, FI-16200 Läyliäinen, Finland E-mail: pertti.pulkkinen@luke.fi
Zhigunov, Saint-Petersburg State Forest Technical University, Forestry Faculty, RU-194021, Institutskiy per. 5, Saint-Petersburg, Russia E-mail: a.zhigunov@bk.ru
Peltola, University of Eastern Finland, Faculty of Science and Forestry, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@uef.fi

article id 441, category Research article

Ane Zubizarreta-Gerendiain, Petri Pellikka, Jordi Garcia-Gonzalo, Veli-Pekka Ikonen, Heli Peltola. (2012). Factors affecting wind and snow damage of individual trees in a small management unit in Finland: assessment based on inventoried damage and mechanistic modelling. Silva Fennica vol. 46 no. 2 article id 441. https://doi.org/10.14214/sf.441

Keywords: Pinus sylvestris; Picea abies; Betula spp.; critical wind speed; snow loading; damage risk

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In this work, we assessed the factors affecting wind and snow damage of individual trees in a small management unit in western Finland. This was done based on inventoried damage and observed wind speeds and snow loading in storms Pyry and Janika in 2001 and Mielikki in 2002 together with mechanistic model. First, we studied which factors explain the observed damage in individual trees. Secondly, we studied how well the mechanistic model (HWIND) could predict the wind speed needed to uproot individual trees at the margins of permanent upwind edges. We found that Pyry storm caused 70% and Janika and Mielikki 18 and 12% of observed damage. In Janika storm, all trees uprooted. In other storms, both uprooting and stem breakage occurred. Scots pine suffered the most damage. Recently thinned stands on the upwind edges of open areas suffered the most damage. But, damage occurred also on soils with relatively shallow anchorage. HWIND predicted correctly damage for 69% of all uprooted trees. No-uprooting was correctly predicted for 45 and 19% of standing trees (all Scots pines), which were measured within and at the immediate upwind edge of same stands. HWIND model needs further validation at the permanent edges and/or on soils with shallow rooting to improve its prediction accuracy in such conditions.

Zubizarreta-Gerendiain, Technical University of Lisbon, School of Agriculture, Forest Research Centre, Lisbon, Portugal E-mail: azg@nn.po
Pellikka, University of Helsinki, Dept. of Geosciences and Geography, Helsinki, Finland E-mail: pp@nn.fi
Garcia-Gonzalo, Technical University of Lisbon, School of Agriculture, Forest Research Centre, Lisbon, Portugal E-mail: jgg@nn.po
Ikonen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: vpi@nn.fi
Peltola, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: heli.peltola@uef.fi

article id 30, category Research article

Hilppa Gregow, Heli Peltola, Mikko Laapas, Seppo Saku, Ari Venäläinen. (2011). Combined occurrence of wind, snow loading and soil frost with implications for risks to forestry in Finland under the current and changing climatic conditions. Silva Fennica vol. 45 no. 1 article id 30. https://doi.org/10.14214/sf.30

Keywords: A1B-scenario; climate change; snow loads; soil frost; stem breakage; uprooting; wind

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This work focuses on the combined occurrence of wind, snow loading and soil frost with implications for risks to forestry in Finland under the current and changing climatic conditions. For this purpose, we employ meteorological datasets, available for the period of 1971–2009 and global climate model (GCM) simulations for the current climate 1971–2000, and periods 2046–65 and 2081–2100 applying the A1B-climate change scenario. Based on our results, the wind and snow induced risks to Finnish forests are projected to increase in the future although the change in the occurrence of strong winds is small. This is because soil frost depths that support tree anchorage from late autumn to early spring in Finland are projected to nearly disappear in the southern and central parts of the country. Heavy snow loads > 30 kg m^–2 are becoming more common in southern and eastern Finland despite that the average cumulative 5-day snow loads decrease in these areas by 18 to 50%, respectively. As a result of the changes in the combined occurrence of wind, snow loading and soil frost, the risk of climatic conditions making conifers liable to uprooting are projected to increase in southern, central and eastern Finland. In the north, the risk of stem breakage is becoming more pronounced under snow loading > 20 kg m^–2. Despite some uncertainties related to this work, we assume that the findings can serve as valuable support for the risk assessment of wind and snow induced damages to Finnish forests and for forestry, in general.

Gregow, Finnish Meteorological Institute, Helsinki, Finland E-mail: hilppa.gregow@fmi.fi
Peltola, University of Eastern Finland, Faculty of Forest Sciences, Joensuu, Finland E-mail: heli.peltola@uef.fi
Laapas, Finnish Meteorological Institute, Helsinki, Finland E-mail: ml@nn.fi
Saku, Finnish Meteorological Institute, Helsinki, Finland E-mail: ss@nn.fi
Venäläinen, Finnish Meteorological Institute, Helsinki, Finland E-mail: av@nn.fi

article id 120, category Research article

Antti J. Lukkarinen, Seppo Ruotsalainen, Teijo Nikkanen, Heli Peltola. (2010). Survival, height growth and damages of Siberian (Larix sibirica Ledeb.) and Dahurian (Larix gmelinii Rupr.) larch provenances in field trials located in southern and northern Finland. Silva Fennica vol. 44 no. 5 article id 120. https://doi.org/10.14214/sf.120

Keywords: height growth; survival; larch; Larix; provenance; seedling damage

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The aim of this study was to analyse differences in the survival and height growth of, as well as damages to Siberian (Larix sibirica Ledeb.) and Dahurian (Larix gmelinii Rupr.) larch provenances over four growing seasons in field trials established in 2006 in southern (Punkaharju) and northern Finland (Kivalo). In this context, the study also investigated if the geographical and climatic conditions of the origin of the provenance could explain the differences between the provenances. The study material consisted of 20 Russian Siberian and Dahurian larch provenances and five seed sources from Finland (4) and Russia (1) as comparison lots. It was found that the Finnish seed sources of Siberian larch survived well in both the Kivalo and Punkaharju trials. Five northern latitude Russian provenances, of which one was Dahurian and the remainder were Siberian larches, had the highest survival in Kivalo. However, the differences observed in survival between provenances were only significant (p < 0.05) in Kivalo. Regardless of the trial, the differences, however, in height growth were significant and large between provenances. The southern Dahurian larches had a superior height growth in Punkaharju. The northern Dahurian larch provenance from Magadan (59°50′N, 150°40′E) had the largest height growth in Kivalo, among some northern Siberian larches. Damages were diverse, though Dahurian larches had less mammal damage than the Siberian larches. In general, the differences between provenances were not significant. Latitude and altitude best explained the differences between provenances, but also mean temperature, temperature sum and continentality index affected them (p < 0.05).

Lukkarinen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: antti.lukkarinen@pp.inet.fi
Ruotsalainen, Finnish Forest Research Institute, FI-58450 Punkaharju, Finland E-mail: sn@nn.fi
Nikkanen, Finnish Forest Research Institute, FI-58450 Punkaharju, Finland E-mail: tn@nn.fi
Peltola, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: hp@nn.fi

article id 455, category Research article

Seppo Kellomäki, Matti Maajärvi, Harri Strandman, Antti Kilpeläinen, Heli Peltola. (2010). Model computations on the climate change effects on snow cover, soil moisture and soil frost in the boreal conditions over Finland. Silva Fennica vol. 44 no. 2 article id 455. https://doi.org/10.14214/sf.455

Keywords: climate change; soil frost; precipitation; temperature; A2 climate scenario; snow accumulation; soil carrying capacity; soil moisture

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This study considered how climate change affects the accumulation of snow, the soil moisture and soil frost at sites without tree cover in boreal conditions in Finland (60°–70°N). An increase of 4.5 °C in annual mean temperature and 20 % in annual precipitation were assumed for Finland by the year 2100 according to A2 emission scenario. Along with climate, the soil type of the permanent inventory plots of the Finnish National Forest Inventory was used. Soil and climate data were combined by using a process-based ecosystem model. Calculations were done for four periods: current climate (1971–2000), near future (2001–2020), mid-term future (2021–2050) and long-term future (2071–2100). According to our simulations, the average monthly duration and depth of snow decreased over the simulation period. However, the increasing precipitation may locally increase the snow depths in the mid-term calculations. In the autumn and winter, the average volumetric soil moisture content slightly increased in southern Finland during the near future, but decreased towards the end of the century, but still remained on a higher level than presently. In northern Finland, the soil moisture in the autumn and winter increased by the end of this century. In the summertime soil moisture decreased slightly regardless of the region. Throughout Finland, the length and the depth of soil frost decreased by the end of the century. In the south, the reduction in the depth was largest in the autumn and spring, while in the mid-winter it remained relatively deep in the middle of the century. In the north, the depth tended to increase during the first two calculation periods, in some areas, even during the third calculation period (2071–2100) due to reduced insulation effects of snow during cold spells. The wintertime increase in soil moisture and reduced soil frost may be reflected to reduced carrying capacity of soil for timber harvesting.

Kellomäki, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: seppo.kellomaki@uef.fi
Maajärvi, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: mm@nn.fi
Strandman, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: hs@nn.fi
Kilpeläinen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: ak@nn.fi
Peltola, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: hp@nn.fi

article id 202, category Research article

Tuula Nuutinen, Antti Kilpeläinen, Hannu Hirvelä, Kari Härkönen, Veli-Pekka Ikonen, Reetta Lempinen, Heli Peltola, Lars Wilhelmsson, Seppo Kellomäki. (2009). Future wood and fibre sources – case North Karelia in eastern Finland. Silva Fennica vol. 43 no. 3 article id 202. https://doi.org/10.14214/sf.202

Keywords: National Forest Inventory; fibre length; wood density; proportion of latewood; forest scenario analysis

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Information on the potential wood supply is important for the wood industry. In this study, the future development of growing stock, cutting potential and wood properties corresponding to the regional scenario of North Karelian Forest Programme 2006–2010 was analysed. The simulations were performed by employing the Finnish MELA system together with the sample plot and tree data of the 9th Finnish National Forest Inventory (NFI9) as initial data for the simulations. Disc-based models for basic wood density, proportion of latewood and fibre length of Norway spruce and Scots pine in Sweden were calibrated and integrated into the MELA system. The wood properties at breast height of both harvested and standing trees were analysed in different strata (age, site type and cutting method) during the scenario period of 50 years (2002–2052). The average wood properties within the same strata varied only slightly over time. However, the results for different strata differed considerably. In general, wood density, fibre length and proportion of latewood increased, on average, as a function of tree age and along with a decrease in site fertility (excl. wood density and proportion of latewood in harvested Norway spruce in the first case and fibre length in the latter case for both species). For trees less than 80 years, properties in harvested trees were equal to or slightly greater than those of standing trees. The values for clear-cuttings were greater or equal to those of thinnings (excl. wood density and proportion of latewood in Norway spruce). The study demonstrates the value of model-based analyses utilising NFI tree measurements in regions that are considered to be sources of raw material.

Nuutinen, European Forest Institute, Torikatu 34, FI-80100 Joensuu, Finland E-mail: tuula.nuutinen@efi.int
Kilpeläinen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: ak@nn.fi
Hirvelä, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: hh@nn.fi
Härkönen, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: kh@nn.fi
Ikonen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: vpi@nn.fi
Lempinen, Finnish Forest Research Institute, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: rl@nn.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: hp@nn.fi
Wilhelmsson, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden E-mail: lw@nn.fi
Kellomäki, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: sk@nn.fi

article id 197, category Research article

Veli-Pekka Ikonen, Seppo Kellomäki, Heli Peltola. (2009). Sawn timber properties of Scots pine as affected by initial stand density, thinning and pruning: a simulation based approach. Silva Fennica vol. 43 no. 3 article id 197. https://doi.org/10.14214/sf.197

Keywords: three-dimensional modeling; sawing simulator; knots; Pinus sylvestris L.; shading

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The aim of this work was to analyze how different management schedules with varying initial stand density, thinning and artificial pruning of branches affect the quality, quantity and value of sawing yield in Scots pine (Pinus sylvestris L.). For this purpose, an integrated model system was employed and further developed to simulate: i) the three dimensional structure of the crown and stem of an average tree grown in a stand related to the changes in the within-stand light conditions as caused by the stand management, and ii) the sawing of logs into pieces and their quality grading based on the size and number of living and dead knots on the surfaces of sawn pieces. To maximize the quality of sawn timber, relatively dense stand is desired in the early phase of the rotation to reduce, especially in the lower part of stem, the growth of branches, and to increase the rate of dying and pruning-off of branches. In the later phase, a relatively sparse stand is desired to increase the self-pruning of branches and the occlusion of knots. However, in any case, artificial pruning is needed to maximize the knot-free zone of the stem. Also the value optimization of individual sawn pieces affects the quality and value of sawn timber. Because, only average tree was simulated, the differences between scenarios for stem volume were small. In the future, further model development is needed to analyze the development of crown and stem properties of trees with different status in a stand.

Ikonen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: veli-pekka.ikonen@joensuu.fi
Kellomäki, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: sk@nn.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: hp@nn.fi

article id 194, category Research article

Ane Zubizarreta Gerendiain, Heli Peltola, Pertti Pulkkinen. (2009). Growth and wood property traits in narrow crowned Norway spruce (Picea abies f. pendula) clones grown in southern Finland. Silva Fennica vol. 43 no. 3 article id 194. https://doi.org/10.14214/sf.194

Keywords: fibre length; stem volume; height; diameter; wood density; earlywood; latewood

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We investigated the growth, yield, wood density traits and fibre properties in 13 narrow crowned Norway spruce (Picea abies f. pendula) clones grown at a spacing of 2 m x 1.5 m (about 3300 seedlings/ha) in a field trial established in 1988 in southern Finland on a forest soil. For comparison, we used 3 normal crowned Norway spruce (Picea abies (L.) Karst.) genetic entries grown as a mixture in the same trial representing southern Finnish breeding regions. We found that wood density traits and fibre properties showed, on average, lower phenotypic variation than growth and yield traits regardless of crown type. Narrow crowned clones also had, on average, lower stem volume and fibre length, but higher overall wood density. More over, the phenotypic correlations between studied growth and wood properties ranged, on average, from moderate (normal crown) to high (narrow crown). These results were opposite to previous findings for narrow and normal crowned genetic entries grown in narrower spacing (1 m x 1 m) in southern Finland. Thus, this indicates lower plasticity of narrow crowned clones to the increasing growing space compared to normal crowned ones, so, they should be grown at denser spacing in order to fully utilise its space efficiency capacity. However, this field trial was established as a mixture of normal and narrow crown trees, so that 90% of genetic entries were narrow crowned ones, and therefore the crown competition would be much higher for normal crowned trees when the whole trial would consist of that entry alone. In the latter case, we could expect significantly lower productivity of normal crowned genetic entries with this spacing.

Zubizarreta Gerendiain, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: ane.zubizarreta@joensuu.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: hp@nn.fi
Pulkkinen, Finnish Forest Research Institute, Haapastensyrjä Breeding Station, FI-12600 Läyliäinen, Finland E-mail: pp@nn.fi

article id 193, category Research article

Jaume Gort, Ane Zubizarreta Gerendiain, Heli Peltola, Pertti Pulkkinen, Johanna Routa, Raimo Jaatinen. (2009). Differences in fibre properties in Scots pine (Pinus sylvestris L.) genetic entries grown at different spacing and sites. Silva Fennica vol. 43 no. 3 article id 193. https://doi.org/10.14214/sf.193

Keywords: fibre length; fibre width; genetic entry; growth; wood density; coarseness; spacing

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In forest breeding, stem volume growth and sawn timber quality indicators have been used as the most important selection traits for Scots pine, whereas less attention has been given to characteristics such as fibre properties. In the above context, we investigated the differences in fibre properties (i.e. fibre length, fibre width and coarseness) in 20 year old Scots pine (Pinus sylvestris L.) genetic entries as affected by spacing and site, but also the phenotypic correlations between fibre properties, yield and wood density. The study was based on materials harvested from 10 genetic entries grown in a spacing trial (site 1) in central Finland, with a current stand density of 2000 (spacing 1), 2000–2500 (spacing 2) and 4000 trees/ha (spacing 3). In order to study the effects of site, we harvested additional material (4 of 7 genetic entries same as on site 1) from a trial located in southern Finland with a corresponding stand density of 2000 trees/ha (site 2). On site 1, spacing 1 and 3, all average values for analysed fibre properties were similar. In spacing 2 average values were slightly higher. On site 2, the average values for different fibre properties were similar compared to the corresponding spacing 1 on site 1. Spacing affected (p < 0.05) all average fibre properties on site 1; as did also site, when comparing same genetic entries grown on both sites. Regardless of spacing and site, the phenotypic correlations between average fibre length, fibre width and coarseness showed, on average, moderate to strong correlation (p < 0.05). Fibre width showed, in general, low and positive phenotypic correlation with diameter at breast height, stem volume and wood density on site 1. However, as a whole, the ranking of genetic entries changed depending on the trait and spacing considered. Thus, no overall ranking between genetic entries was possible.

Gort, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: jaume.gort@joensuu.fi
Zubizarreta Gerendiain, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: azg@nn.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: hp@nn.fi
Pulkkinen, Finnish Forest Research Institute, Haapastensyrjä Breeding Station, Karkkilantie E-mail: pp@nn.fi
Routa, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: jr@nn.fi
Jaatinen, Finnish Forest Research Institute, Haapastensyrjä Breeding Station, Karkkilantie E-mail: rj@nn.fi

article id 192, category Research article

Heli Peltola, Jaume Gort, Pertti Pulkkinen, Ane Zubizarreta Gerendiain, Jouni Karppinen, Veli-Pekka Ikonen. (2009). Differences in growth and wood density traits in Scots pine (Pinus sylvestris L.) genetic entries grown at different spacing and sites. Silva Fennica vol. 43 no. 3 article id 192. https://doi.org/10.14214/sf.192

Keywords: genetic entry; stem volume; height; diameter; wood property traits; phenotypic correlation

Abstract | View details | Full text in PDF | Author Info

In forest breeding, stem volume has typically taken as the most important selection trait, whereas less attention has been given to wood density traits. In this work, we investigated the effects of spacing and genetic entry on the growth, yield and wood density traits in 20 year old Scots pines (Pinus sylvestris L.) based on 10 genetic entries harvested from a spacing trial (stand density range 2000–4000 trees/ha) in central Finland. In order to study also the site effects, we harvested additional material from a trial located in southern Finland (stand density of 2000 trees/ha). Compared to growth and yield properties, wood density traits showed a lower phenotypic variation. Phenotypic correlations among different traits were negative, and mostly moderate to high, suggesting that selection for one trait would simultaneously affect the others. In addition, moderate to strong phenotypic correlations were found among different wood density traits. Stem volume (V) and breast height diameter (DBH) were the largest in widest spacing, whereas in the densest one tree height (H) and latewood percentage were the highest. Genetic entry affected H and wood density traits regardless of spacing. When comparing two sites (with same stand density), genetic entry affected H, whereas site affected DBH and wood density traits. Ranking between genetic entries changed depending on the trait, spacing or site considered. Therefore, no overall ranking was possible. However, we could identify genetic entries having a high V and a relatively high wood density, showing potential for future forest regeneration material.

Peltola, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: heli.peltola@joensuu.fi
Gort, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: jg@nn.fi
Pulkkinen, Finnish Forest Research Institute, Haapastensyrjä Breeding Station, Karkkilantie 247, FI-12600 Läyliäinen, Finland E-mail: pp@nn.fi
Zubizarreta Gerendiain, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: azg@nn.fi
Karppinen, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: jk@nn.fi
Ikonen, University of Joensuu, Faculty of Forest Sciences, FI-80101 Joensuu, Finland E-mail: vpi@nn.fi

article id 215, category Research article

Antti J. Lukkarinen, Seppo Ruotsalainen, Teijo Nikkanen, Heli Peltola. (2009). The growth rhythm and height growth of seedlings of Siberian (Larix sibirica Ledeb.) and Dahurian (Larix gmelinii Rupr.) larch provenances in greenhouse conditions. Silva Fennica vol. 43 no. 1 article id 215. https://doi.org/10.14214/sf.215

Keywords: height growth; larch; Larix; provenance; growth rhythm

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The aim of this study was to determine whether the growth rhythm and height growth differ between various larch provenances grown in greenhouse conditions. We also investigated whether the geographic and climatic conditions at the origin of the provenance could explain the possible differences between the provenances. The study material consisted of 16 Russian Siberian (Larix sibirica Ledeb.) and Dahurian larch (Larix gmelinii Rupr.) provenances and four seed sources from Finland as comparison lots. The growth rhythm differences were clearest between the southern and northern provenances; the southern provenances grew for a longer period and the proportion of late summer height growth was larger. Autumn colouration also developed later in these provenances. In the Russian larch material the provenances with a longer growing period had greater height growth. In the whole material the relationship was not so linear due to the deviating behaviour of the comparison material. Several of the Russian larch provenances were taller than the Finnish comparison seed lots, although the difference was not statistically significant. However, the growth of these provenances must be followed for a much longer period in field trials before any conclusions can be drawn about their usability in practical forestry.

Lukkarinen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: antti.lukkarinen@pp.inet.fi
Ruotsalainen, Finnish Forest Research Institute, Punkaharju Research Unit, Finlandiantie 18, FI-58450 Punkaharju, Finland E-mail: sr@nn.fi
Nikkanen, Finnish Forest Research Institute, Punkaharju Research Unit, Finlandiantie 18, FI-58450 Punkaharju, Finland E-mail: tn@nn.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: hp@nn.fi

article id 231, category Research article

Hilppa Gregow, Ulla Puranen, Ari Venäläinen, Heli Peltola, Seppo Kellomäki, David Schultz. (2008). Temporal and spatial occurrence of strong winds and large snow load amounts in Finland during 1961-2000. Silva Fennica vol. 42 no. 4 article id 231. https://doi.org/10.14214/sf.231

Keywords: soil frost; coniferous forest; wind climate; precipitation; snow

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Information on the temporal and spatial occurrence of strong winds and snow loads on trees is important for the risk management of wind- and snow-induced damage. Meteorological measurements made at 19 locations across Finland during 1961–2000 are used to understand the temporal and spatial occurrence of strong winds and large snow loads. A Kriging interpolation method was used to produce a spatial analysis of wind-speed events above 11 m s–1, 14 m s–1, and greater or equal to 17 m s–1 and snowfall accumulation above 20 kg m–2 and 30 kg m–2. According to the analysis, wind speeds exceeded 14 m s–1 at least 155 times and reached 17 m s–1 only 5 times at inland locations during the 40 years. Large snowfall accumulations were more frequent in the higher-elevation inland areas than along the coast. The snow load on trees exceeded 20 kg m–2 about 65 times a year when averaged over all 40 years, but was as high as 150 times a year during the mild 1990s. The maximum number of heavy snow-load events occurred in 1994 in northern Finland, consistent with a forest inventory by the Finnish Forest Research Institute in 1992–1994. The findings of this study imply that the risk of wind-induced damage is highest in the late autumn when trees do not have the additional support of frozen soil. In contrast, the risk of snow-induced damage is highest at higher-elevations inland, especially in northern Finland.

* Erratum (23 Oct 2012): The authors have requested inclusion of an additional author. Author information should thus be as follows: Hilppa Gregow, Ulla Puranen, Ari Venäläinen, Heli Peltola, Seppo Kellomäki & David Schultz

Gregow, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: hilppa.gregow@fmi.fi
Puranen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: up@nn.fi
Venäläinen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: av@nn.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@uef.fi
Kellomäki, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: seppo.kellomaki@uef.fi
Schultz, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland E-mail: ds@nn.fi

article id 247, category Research article

Ane Zubizarreta Gerendiain, Heli Peltola, Pertti Pulkkinen, Veli-Pekka Ikonen, Raimo Jaatinen. (2008). Differences in growth and wood properties between narrow and normal crowned types of Norway spruce grown at narrow spacing in Southern Finland. Silva Fennica vol. 42 no. 3 article id 247. https://doi.org/10.14214/sf.247

Keywords: fibre length; stem volume; height; diameter; wood density; earlywood; latewood

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In recent years there has been increased interest in the so called narrow crowned Norway spruce (Picea abies f. pendula), which is a rare mutant of Norway spruce (Picea abies (L.) Karsten), as a suitable wood raw material source for pulp and paper production. This is because it is less sensitive to competition than the normal crowned Norway spruce, and thus, could be more productive especially at dense spacing. In the above context, we investigated how the growth and yield (such as height, diameter, stem volume and ring width) in addition to wood density traits and fibre properties (such as wood density, fibre length and width, cell wall thickness and fibre coarseness) were affected in trees from 9 full-sib families representing narrow crowned Norway spruce grown at narrow spacing of 1 m 1 m in Southern Finland. For comparison, we used normal crowned Norway spruce trees from 6 breeding regions. We found that, compared to growth and yield traits, wood density traits and fibre properties showed, on average, lower phenotypic variations. In addition, these variations were smaller for narrow crowned families than for normal crowned genetic entries. Narrow crowned families also showed, on average, higher growth and yield and fibre length, but lower wood density. Moreover, the phenotypic correlations between growth, yield, wood density traits and fibre properties, ranged, on average, from moderate (narrow crowned) to high (normal crowned). As a whole, the growth and wood properties of narrow crowned families were found to be less sensitive to tree competition than the normal crowned genetic entries used as a comparison.

Zubizarreta Gerendiain, University of Joensuu, Faculty of Forest Sciences, Joensuu, Finland E-mail: ane.zubizarreta@joensuu.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, Joensuu, Finland E-mail: hp@nn.fi
Pulkkinen, Finnish Forest Research Institute, Haapastensyrjä Breeding Station, Läyliäinen, Finland E-mail: pp@nn.fi
Ikonen, University of Joensuu, Faculty of Forest Sciences, Joensuu, Finland E-mail: vpi@nn.fi
Jaatinen, Finnish Forest Research Institute, Haapastensyrjä Breeding Station, Läyliäinen, Finland E-mail: rj@nn.fi

article id 285, category Research article

Heli Peltola, Antti Kilpeläinen, Kari Sauvala, Tommi Räisänen, Veli-Pekka Ikonen. (2007). Effects of early thinning regime and tree status on the radial growth and wood density of Scots pine. Silva Fennica vol. 41 no. 3 article id 285. https://doi.org/10.14214/sf.285

Keywords: thinning response; ring width; early wood; late wood; intra-ring wood density; X-ray densitometry

Abstract | View details | Full text in PDF | Author Info

Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@joensuu.fi
Kilpeläinen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: ak@nn.fi
Sauvala, Finnish Forest Research Institute, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ks@nn.fi
Räisänen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: tr@nn.fi
Ikonen, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: vpi@nn.fi

article id 299, category Research article

Hongcheng Zeng, Timo Pukkala, Heli Peltola, Seppo Kellomäki. (2007). Application of ant colony optimization for the risk management of wind damage in forest planning. Silva Fennica vol. 41 no. 2 article id 299. https://doi.org/10.14214/sf.299

Keywords: harvest scheduling; heuristics; genetic algorithms; simulated annealing; spatial optimization

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Ant colony optimization (ACO) is still quite a new technique and seldom used in the field of forest planning compared to other heuristics such as simulated annealing and genetic algorithms. This work was aimed at evaluating the suitability of ACO for optimizing the clear-cut patterns of a forest landscape when aiming at simultaneously minimizing the risk of wind damage and maintaining sustainable and even flow of periodical harvests. For this purpose, the ACO was first revised and the algorithm was coded using the Visual Basic Application of the ArcGIS software. Thereafter, the performance of the modified ACO was demonstrated in a forest located in central Finland using a 30-year planning period. Its performance was compared to simulated annealing and a genetic algorithm. The revised ACO performed logically since the objective function value was improving and the algorithm was converging during the optimization process. The solutions maintained a quite even periodical harvesting timber while minimizing the risk of wind damage. Implementing the solution would result in smooth landscape in terms of stand height after the 30-year planning period. The algorithm is quite sensitive to the parameters controlling pheromone updating and schedule selecting. It is comparable in solution quality to simulated annealing and genetic algorithms.

Zeng, University of Joensuu, Faculty of Forest Sciences, P. O. Box 111, FI-80101 Joensuu, Finland E-mail: hongcheng.zeng@joensuu.fi
Pukkala, University of Joensuu, Faculty of Forest Sciences, P. O. Box 111, FI-80101 Joensuu, Finland E-mail: tp@nn.fi
Peltola, University of Joensuu, Faculty of Forest Sciences, P. O. Box 111, FI-80101 Joensuu, Finland E-mail: hp@nn.fi
Kellomäki, University of Joensuu, Faculty of Forest Sciences, P. O. Box 111, FI-80101 Joensuu, Finland E-mail: sk@nn.fi

article id 523, category Research article

Heli Peltola, Jari Miina, Ismo Rouvinen, Seppo Kellomäki. (2002). Effect of early thinning on the diameter growth distribution along the stem of Scots pine. Silva Fennica vol. 36 no. 4 article id 523. https://doi.org/10.14214/sf.523

Keywords: Scots pine; early thinnings; thinning responses; diameter growth; growth distribution

Abstract | View details | Full text in PDF | Author Info

The absolute and relative effects of the first thinning on the diameter growth distribution along the stems were studied in 98 Scots pines (Pinus sylvestris L.) at heights of 1.3, 4, 6 and 8 m. The data cover one 3-year pre-thinning period and four 3-year post-thinning periods in plots with densities varying from 575 to 3400 stems ha–1. A shift in the point of maximum diameter growth down the bole was found during the first 3 years after thinning, with a shift back up the stem later. The thinning response over the whole 12-year post-thinning period was strongest the nearer the stem base and the heavier the thinning. The largest trees had the highest diameter growth after thinning in absolute terms, and the growth was greater the heavier the thinning. The absolute thinning response over the 12-year post-thinning period was highest in the medium tree size and in the largest trees, especially on the heavily thinned and lightly thinned plots. Whereas in the moderately thinned stand the smaller and larger trees responded more than did those of medium size on average. In relative sense, however, the small trees on heavily or moderately thinned plots responded more rapidly and more strongly than the medium-sized or large trees over the whole stem. The small trees on the lightly thinned plots responded only slightly to thinning. The results suggest that it is possible to affect the uniformity of wood properties (such as ring width) both within and between trees by thinning.

Peltola, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: heli.peltola@forest.joensuu.fi
Miina, Finnish Forest Research Institute, Joensuu Research Centre, P.O. Box 68, FIN-80101 Joensuu, Finland E-mail: jm@nn.fi
Rouvinen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: ir@nn.fi
Kellomäki, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: sk@nn.fi

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

Abstract | View details | Full text in PDF | Author Info

The 6th IUFRO Workshop on Connection between Forest Resources and Wood Quality: Modelling Approaches and Simulation Software.

Leban, E-mail: jml@nn.fr
Peltola, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: heli.peltola@uef.fi
Leinonen, E-mail: sl@nn.fi
Todoroki, E-mail: ct@nn.nz
D'Amours, E-mail: sda@nn.ca
Gardiner, E-mail: bg@nn.uk
Goudie, E-mail: jg@nn.ca
Lowell, E-mail: el@nn.us
Seifert, E-mail: ts@nn.de
Verkasalo, Finnish Forest Research Institute, Joensuu Unit, P.O. Box 68, FI-80101, Joensuu, Finland E-mail: erkki.verkasalo@metla.fi
Wilhelmsson, E-mail: lw@nn.se
Nuutinen, European Forest Institute, Torikatu 34, FI-80100 Joensuu, Finland E-mail: tuula.nuutinen@efi.int

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