Current issue: 52(3)

Under compilation: 52(4)

Impact factor 1.683
5-year impact factor 1.950
Silva Fennica 1926-1997
1990-1997
1980-1989
1970-1979
1960-1969
Acta Forestalia Fennica
1953-1968
1933-1952
1913-1932

Silva Fennica vol. 52 | 2018

Category: Research article

article id 10013, category Research article
Hardo Becker, Jürgen Aosaar, Mats Varik, Gunnar Morozov, Kristiina Aun, Ülo Mander, Kaido Soosaar, Veiko Uri. (2018). Annual net nitrogen mineralization and litter flux in well-drained downy birch, Norway spruce and Scots pine forest ecosystems. Silva Fennica vol. 52 no. 4 article id 10013. https://doi.org/10.14214/sf.10013
Highlights: The net nitrogen mineralization (NNM) flux in drained peat soils depends largely on the C/N ratio and tree species; The soil NNM process is affected by trees through organic litter input into soil; Pine stand in low-fertility drained transitional bog is dominated by net ammonification; Birch and spruce stands on the fertile drained peat soil with higher pH and N content are dominated by net nitrification.

The main aim of the current study was to estimate the annual net nitrogen mineralization (NNM) flux in stands of different tree species growing on drained peatlands, as well as to clarify the effect of tree species, soil properties and litter on annual NNM dynamics. Three study sites were set up in May 2014: a downy birch (Betula pubescens Ehrh.) stand and a Norway spruce (Picea abies (L.) Karst.) stand in Oxalis full-drained swamp (ODS) and a Scots pine (Pinus sylvestris L.) stand in Myrtillus full-drained swamp (MDS). The NNM flux was estimated using the in situ method with incubated polyethylene bags. The highest value of NNM was found in stands that were growing on fertile ODS: 127.5 kg N ha–1 yr–1 and 87.7 kg N ha–1 yr–1, in the downy birch stand and in the Norway spruce stand, respectively. A significantly lower annual NNM flux (11.8 kg N ha–1 yr–1) occurred in the Scots pine stand growing in MDS. Nitrification was highest at fertile ODS sites and ammonification was the highest at the low fertility MDS site. For all study sites, positive correlation was found between soil temperature and NNM intensity. The difference in annual NNM between the downy birch stand and the Norway spruce stand growing on similar drained fertile peatlands was due to litter quality. The annual N input into the soil through leaf litter was the highest at the downy birch site where also the C/N ratio of litter was the lowest. The second highest N input into the soil was found in the spruce stand and the lowest in the pine stand.

  • Becker, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia ORCID ID:E-mail: hardo.becker@emu.ee (email)
  • Aosaar, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia ORCID ID:E-mail: jyrgen.aosaar@emu.ee
  • Varik, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia ORCID ID:E-mail: mats.varik@emu.ee
  • Morozov, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia ORCID ID:E-mail: gunnar.morozov@emu.ee
  • Aun, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia ORCID ID:E-mail: kristiina.aun@emu.ee
  • Mander, Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia ORCID ID:E-mail: ulo.mander@ut.ee
  • Soosaar, Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, Ülikooli 18, 50090 Tartu, Estonia ORCID ID:E-mail: kaido.soosaar@ut.ee
  • Uri, Chair of Silviculture and Forest Ecology, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Friedrich Reinhold Kreutzwaldi 1, 51014 Tartu, Estonia ORCID ID:E-mail: veiko.uri@emu.ee
article id 9996, category Research article
Mulualem Tigabu, Mostafa Farhadi, Lars-Göran Stener, Per C. Odén. (2018). Visible + Near Infrared Spectroscopy as taxonomic tool for identifying birch species. Silva Fennica vol. 52 no. 4 article id 9996. https://doi.org/10.14214/sf.9996
Highlights: Multivariate modelling of visible + near infrared (NIR) reflectance spectra of single seeds distinguished Betula pubescens and B. pendula with 100% and 99% accuracy, respectively; The results demonstrate the feasibility of NIR spectroscopy as taxonomic tool for classification of species that have morphological resemblance.

The genus Betula L. is composed of several species, which are difficult to distinguish in the field on the basis of morphological traits. The aim of this study was to evaluate the taxonomic importance of using visible + near infrared (Vis + NIR) spectra of single seeds for differentiating Betula pendula Roth and Betula pubescens Ehrh. Seeds from several families (controlled crossings of known parent trees) of each species were used and Vis + NIR reflectance spectra were obtained from single seeds. Multivariate discriminant models were developed by Orthogonal Projections to Latent Structures – Discriminant Analysis (OPLS-DA). The OPLS-DA model fitted on Vis + NIR spectra recognized B. pubescens with 100% classification accuracy while the prediction accuracy of class membership for B. pendula was 99%. However, the discriminant models fitted on NIR spectra alone resulted in 100% classification accuracies for both species. Absorption bands accounted for distinguishing between birch species were attributed to differences in color and chemical composition, presumably polysaccharides, proteins and fatty acids, of the seeds. In conclusion, the results demonstrate the feasibility of NIR spectroscopy as taxonomic tool for classification of species that have morphological resemblance.

  • Tigabu, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Box 49, SE-230 52 Alnarp, Sweden ORCID ID:E-mail: mulualem.tigabu@slu.se (email)
  • Farhadi, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Box 49, SE-230 52 Alnarp, Sweden ORCID ID:E-mail: mostafa.farhadi@gmail.com
  • Stener, The Forestry Research Institute of Sweden, Ekebo 2250, SE-268 90 Svalöv, Sweden ORCID ID:E-mail: lars-goran.stener@skogforsk.se
  • Odén, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, Box 49, SE-230 52 Alnarp, Sweden ORCID ID:E-mail: per.christer.oden@slu.se
article id 7763, category Research article
Sergei Senko, Mikko Kurttila, Timo Karjalainen. (2018). Prospects for Nordic intensive forest management solutions in the Republic of Karelia. Silva Fennica vol. 52 no. 4 article id 7763. https://doi.org/10.14214/sf.7763
Highlights: SWOT (strengths, weaknesses, opportunities and threats) and multi-criteria decision support analysis were combined to examine the potential for Nordic intensive forest management solutions (NIFMS) in Karelia, Russia; NIFMS looks promising for Karelian forestry; Improving quality-and-value of timber and sustained yield are the highly prioritized strengths; Unprepared forestry regulations are the main threat that needs to be taken into account.

In this study, the prospects for future forest management in Republic of Karelia, Russia were analyzed. Forestry has an important role in the economy of Karelia. However, productivity and profitability in the forestry sector are extremely low, forest stand structure and quality are weak, the commercial forest land of coniferous species has declined and the wood processing industry struggles with a deficit of raw materials. The situation is typical to many forest regions in Russia with extensive forest management cited as one reason for the current situation. In contrast, the Nordic countries have significant experience in intensive and sustainable forest management and the results have been to a large extent positive. The transfer of Nordic intensive forest management solutions (NIFMS) could improve forestry in Karelia. SWOT analysis, combined with the multi-criteria decision support (MCDS) method was used to identify local operational environments and to assign priorities. Major threats included unprepared regulations, poor road infrastructure, insecure investments, low forestry productivity, forest degradation, high investment costs and a negative attitude to intensive forestry. The main opportunities are high forest resource potential in Karelia, favorable authority development programs, proven Nordic expertise, wood-based energy development and availability of new technology. Results also showed that the main weaknesses that might influence the NIFMS in Karelia are slow return on investments, low market demand for energy wood, high costs associated with young forest thinnings, high demand for skilled specialists and a lack of investment in research and development.

  • Senko, University of Eastern Finland (UEF), School of Forest Sciences, Yliopistokatu 7, FI-80111 Joensuu, Finland ORCID ID:E-mail: sergei.senko@uef.fi (email)
  • Kurttila, The Natural Resources Institute Finland (Luke), Bioeconomy and environment, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: mikko.kurttila@luke.fi
  • Karjalainen, † Deceased ORCID ID:E-mail:
article id 10006, category Research article
Matti Maltamo, Tomi Karjalainen, Jaakko Repola, Jari Vauhkonen. (2018). Incorporating tree- and stand-level information on crown base height into multivariate forest management inventories based on airborne laser scanning. Silva Fennica vol. 52 no. 3 article id 10006. https://doi.org/10.14214/sf.10006
Highlights: The most accurate tree-level alternative is to include crown base height (CBH) to nearest neighbour imputation; Also mixed-effects models can be applied to predict CBH using tree attributes and airborne laser scanning (ALS) metrics; CBH prediction can be included with an accuracy of 1–1.5 m to forest management inventory applications.

This study examines the alternatives to include crown base height (CBH) predictions in operational forest inventories based on airborne laser scanning (ALS) data. We studied 265 field sample plots in a strongly pine-dominated area in northeastern Finland. The CBH prediction alternatives used area-based metrics of sparse ALS data to produce this attribute by means of: 1) Tree-level imputation based on the k-nearest neighbor (k-nn) method and full field-measured tree lists including CBH observations as reference data; 2) Tree-level mixed-effects model (LME) prediction based on tree diameter (DBH) and height and ALS metrics as predictors of the models; 3) Plot-level prediction based on analyzing the computational geometry and topology of the ALS point clouds; and 4) Plot-level regression analysis using average CBH observations of the plots for model fitting. The results showed that all of the methods predicted CBH with an accuracy of 1–1.5 m. The plot-level regression model was the most accurate alternative, although alternatives producing tree-level information may be more interesting for inventories aiming at forest management planning. For this purpose, k-nn approach is promising and it only requires that field measurements of CBH is added to the tree lists used as reference data. Alternatively, the LME-approach produced good results especially in the case of dominant trees.

  • Maltamo, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: matti.maltamo@uef.fi (email)
  • Karjalainen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: tomimkarjalainen@gmail.com
  • Repola, Natural Resources Institute of Finland (Luke), Natural resources, Eteläranta 55, FI-96300 Rovaniemi, Finland ORCID ID:E-mail: jaakko.repola@luke.fi
  • Vauhkonen, Natural Resources Institute of Finland (Luke), Bioeconomy and environment, Yliopistokatu 6, 80100 Joensuu, Finland ORCID ID:E-mail: jari.vauhkonen@luke.fi
article id 9987, category Research article
Monika Dering, Katarzyna Sękiewicz, Grzegorz Iszkuło, Aleksandra Chojnacka, Dominik Tomaszewski, Emilia Pers-Kamczyc, Piotr Karolewski. (2018). Spatial genetic structure and clonal structure of Prunus serotina during invasive spread. Silva Fennica vol. 52 no. 3 article id 9987. https://doi.org/10.14214/sf.9987
Highlights: The spread of Prunus serotina in invaded forests is facilitated by high propagule pressure; The seed shadow overlap prevents strong spatial genetic structure; During colonization of isolated site, a strong spatial genetic structure is produced due to founder effect; Overall clonality in P. serotina was low but may efficiently support seedling bank thus contributing to species invasiveness.

Prunus serotina Ehrh. (black cherry) is one of the most important invaders in the European forests, but existing studies have given limited insight into demo-genetic factors underpinning the process of species invasion. Fine-scale genetic structure (FSGS) may deliver important knowledge on genetics of invasion contributing to efficient management of the alien species. Using eight microsatellites we investigated FSGS, clonal structure and relatedness in four black cherry populations which represented different stages of the invasive spread into Scots pine forests. Three populations were in a continuous forest complex and represented the colonization (Z_1) and established stages (Z_2 and Z_3). To investigate how colonization ability of the species is modified by landscape features, we analyzed an isolated population at colonization stage located in limited forest patch located in an agricultural landscape (R). Populations from continuous forest showed low yet significant positive FSGS with Sp = 0.0068 in Z_1, 0.0054 in Z_2, and 0.0066 in Z_3, while in R spatial structure was the strongest (0.0145). Considerable relatedness noted in population R suggests a dominance of within-population mating and recruitments, low immigration rate and limited seed dispersal, all of which led to the observed strong FSGS. Also, we presume that a founder effect likely involved during colonization of isolated forest patch R led to strong FSGS. In contrary, the seed shadow overlap in the populations from continuous forest prevented strong FSGS and facilitated colonization. Despite of low level of clonality, we argue that it may efficiently support black cherry seedling bank contributing to species invasiveness.

  • Dering, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland ORCID ID:E-mail: mdering@man.poznan.pl (email)
  • Sękiewicz, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland ORCID ID:E-mail: ksekiewicz@man.poznan.pl
  • Iszkuło, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland; Faculty of Biological Sciences, University of Zielona Góra, Prof. Z. Szafrana 1, 65-516 Zielona Góra, Poland ORCID ID:E-mail: iszkulo@man.poznan.pl
  • Chojnacka, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland ORCID ID:E-mail: jagoda900@gmail.com
  • Tomaszewski, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland ORCID ID:E-mail: dominito@man.poznan.pl
  • Pers-Kamczyc, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland ORCID ID:E-mail: epk@man.poznan.pl
  • Karolewski, Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland ORCID ID:E-mail: pkarolew@man.poznan.pl
article id 9983, category Research article
Mika Rekola, Jaakko Nippala, Päivi Tynjälä, Anne Virtanen. (2018). Modelling competences and anticipating the future competence needs in the forest sector. Silva Fennica vol. 52 no. 3 article id 9983. https://doi.org/10.14214/sf.9983
Highlights: The most frequently used practices of modelling competences in Finnish forest sector organisations were superior-subordinate review discussions and quantitative surveys; Competence modelling was used for several human resources functions but surprisingly not for hiring and compensation; The experts interviewed underlined the need for generic competences in the future, especially they highlighted the importance of information processing and personal self-management skills.

This explorative study examined practices of competence modelling in the forest sector organisations and how organisations anticipate changes in competence needs in the future. Semi-structured in-depth interviews (n=10) were conducted amongst forest sector experts in Finland and data was analysed by thematic analysis. The findings showed that the practices of modelling competences were diverse, most frequently used ones being superior-subordinate review discussions and quantitative competence surveys. In addition to these formal systems, informal modelling, especially on the team level and in smaller companies was also frequent. Organisations used competence modelling for several human resources functions, such as appraisal, motivation and promotion of employees. Surprisingly hiring and compensation functions were not mentioned. Perceptions related to competence modelling were generally speaking positive. The most important challenges were the lack of further actions and sometimes the extraordinary burden to the employees. When anticipating the future, the experts interviewed mentioned several commonly recognised trends, e.g., development of information technology, fragmentation of working life and structural changes in labour markets. All these require more generic competences related to information processing and personal self-management, especially respondents highlighted the importance of self-awareness skills. It is concluded that several useful practices for competence modelling already exist and that present study provides a basis for further quantitative further study.

  • Rekola, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: mika.rekola@helsinki.fi (email)
  • Nippala, Suomen Partiolaiset – Finlands Scouter ry, Töölönkatu 55, FI-00250 Helsinki, Finland ORCID ID:E-mail: jaakko.nippala@partio.fi
  • Tynjälä, Finnish Institute for Educational Research, P.O. Box 35, FI-40014 University of Jyväskylä, Finland ORCID ID:E-mail: paivi.a.tynjala@jyu.fi
  • Virtanen, Finnish Institute for Educational Research, P.O. Box 35, FI-40014 University of Jyväskylä, Finland ORCID ID:E-mail: anne.virtanen@jyu.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
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.

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 ORCID ID:E-mail: eino.levkoev@uef.fi (email)
  • Mehtätalo, University of Eastern Finland, Faculty of Science and Forestry, School of Computing, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID: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 ORCID ID:E-mail: katri.luostarinen@uef.fi
  • Pulkkinen,  Natural Resources Institute Finland (Luke), Production systems, Haapastensyrjä Breeding Station, FI-16200 Läyliäinen, Finland ORCID ID:E-mail: pertti.pulkkinen@luke.fi
  • Zhigunov, Saint-Petersburg State Forest Technical University, Forestry Faculty, RU-194021, Institutskiy per. 5, Saint-Petersburg, Russia ORCID ID: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 ORCID ID:E-mail: heli.peltola@uef.fi
article id 9948, category Research article
Juha Heiskanen, Ville Hallikainen, Jori Uusitalo, Hannu Ilvesniemi. (2018). Co-variation relations of physical soil properties and site characteristics of Finnish upland forests. Silva Fennica vol. 52 no. 3 article id 9948. https://doi.org/10.14214/sf.9948
Highlights: Atmospheric temperature sum is related to site index H100 as a covariate;Soil pH and water retention at field capacity (FC) are also closely related to H100;Fine fraction is related to water retention at FC, soil layer and site type;Fine fraction co-varies also with temperature sum, H100 and slope.

Physical soil properties have a marked influence on the quality of forest sites and on the preconditions for forest growth and management. In this study, water retention characteristics (WRC) and related physical soil properties in addition to vegetation coverage and tree stand data were studied at upland forest sites in Finland. Fixed and mixed models between soil and site characteristics were formed to estimate physical and hydrologic soil characteristics and the site quality with indirect co-varying variables. In the present data, the site quality index (H100) shows a high coefficient of determination in respect to the temperature sum. It is also related to soil fine fraction content, topsoil pH and water retention at field capacity. The thickness of the humus layer is predictable from the pH and cover of xeric and mesic plant species. The soil fine fraction content (clay + silt) is closely related to water retention at field capacity, the soil layer and site type, and without WRC to the temperature sum and site index and type, as well as the slope angle. The soil bulk density is related to organic matter, depth (layer) or alternatively to organic matter, slope and field estimated textural class (fine, medium, coarse). Water retention characteristics were found to be best determinable by the fine fraction content, depth and bulk density. Water content and air-filled porosity at field capacity are closely related to the fine fraction. This study provides novel models for further investigations that aim at improved prediction models for forest growth, hydrology and trafficability.

  • Heiskanen, Natural Resources Institute Finland (Luke), Soil ecosystems, Neulaniementie 5, FI-70100 Kuopio, Finland ORCID ID:E-mail: juha.heiskanen@luke.fi (email)
  • Hallikainen, Natural Resources Institute Finland (Luke), Applied statistical methods, Eteläranta 55, FI-96300 Rovaniemi, Finland ORCID ID:E-mail: ville.hallikainen@luke.fi
  • Uusitalo, Natural Resources Institute Finland (Luke), Forest technology and logistics, Korkeakoulunkatu 7, FI-33720 Tampere, Finland ORCID ID:E-mail: jori.uusitalo@luke.fi
  • Ilvesniemi, Natural Resources Institute Finland (Luke), Biorefinery and bioproducts, Tietotie 2, FI-02150 Espoo, Finland ORCID ID:E-mail: hannu.ilvesniemi@luke.fi
article id 9947, category Research article
Eric R. Labelle, Linus Huß. (2018). Creation of value through a harvester on-board bucking optimization system operated in a spruce stand. Silva Fennica vol. 52 no. 3 article id 9947. https://doi.org/10.14214/sf.9947
Highlights: Use of harvester on-board computer bucking optimization remains highly under-utilized in German forestry; Revenue per tree and harvesting productivity were both statistically higher with automatic bucking as compared to quality bucking during a thinning operation in a spruce dominated stand.

Tree bucking, defined as the process in which a stem is segmented into shorter logs of varying lengths, has a significant effect on the value adding potential of a forest enterprise. Because of its importance in terms of correct product and length combinations, improper bucking can lead to financial losses. In this study, two treatments (OFF: quality bucking performed by the operator while using hot keys and ON: automatic bucking using the optimized suggestions from the harvester on-board computer; OBC) were tested in a Norway spruce (Picea abies [L.] Karst.) dominated stand located in Germany. Both treatments had the aim to maximize the value of a stem. The research took place in an 80-year old spruce and beech stand under a regenerative cutting. Fully-mechanized harvesting was performed with an 8-wheel Ponsse Bear single-grip harvester equipped with a H8 harvesting head. Results indicated that the product recovery of the two treatments differed by 4% in undamaged trees (no broken tree-tops or stems) to the benefit of manual bucking. However, the revenue of trees subjected to optimized bucking were up to 4% higher (in average 3%) than those of the manual bucking once expressed on a per cubic meter basis. Moreover, the harvesting productivity of the ON treatment was at the maximum 17% higher compared to the OFF treatment. Based on the results from this case study, the use of an optimization software in Norway spruce dominated stands with the aim to maximize the value of single stems showed promising results.

  • Labelle, Assistant Professorship of Forest Operations, Department of Ecology and Ecosystem Management, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, D-85354 Freising, Germany ORCID ID:E-mail: eric.labelle@tum.de (email)
  • Huß, Assistant Professorship of Forest Operations, Department of Ecology and Ecosystem Management, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, D-85354 Freising, Germany ORCID ID:E-mail: linus.huss@gmx.de
article id 9946, category Research article
Frauke Fedderwitz, Niklas Björklund, Velemir Ninkovic, Göran Nordlander. (2018). Does the pine weevil (Hylobius abietis) prefer conifer seedlings over other main food sources? Silva Fennica vol. 52 no. 3 article id 9946. https://doi.org/10.14214/sf.9946
Highlights: Adult pine weevils feed on seedlings and mature conifers, but cause economic damage only on seedlings; Their feeding preferences for branches and roots over seedlings were tested in a laboratory experiment; The only clear preference was for Norway spruce roots; Results support new approaches of seedling protection attempting to redirect pine weevils from planted seedlings to other food sources.

Adult pine weevils (Hylobius abietis (L.)) feed on the tender bark of branches and roots of mature conifer trees and on the stem bark of conifer seedlings. Their feeding on mature trees does not cause any economic damage, but their feeding on planted seedlings is so devastating that the pine weevil is considered one of the most important forest pest insects in Europe. We asked whether the pine weevil prefers seedlings over other regularly utilized food sources. This question is of particular interest because new approaches to seedling protection are based on decreasing any preference for seedlings by using less palatable plants or by enhancing their defence (by genetic selection or by methyl jasmonate treatment). In a laboratory choice experiment we tested pine weevil feeding preferences for seedlings compared with branches and roots from mature trees (separately for Norway spruce and Scots pine). Pine weevils preferred roots, but not branches, of Norway spruce over seedlings of the same species. With Scots pine there were no clear preferences, but the weevils showed a tendency to prefer roots over seedlings. These results provide support for seedling protection approaches that attempt to redirect pine feeding from planted seedlings to other food sources.

  • Fedderwitz, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: frauke.fedderwitz@slu.se (email)
  • Björklund, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: niklas.bjorklund@slu.se
  • Ninkovic, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: velemir.ninkovic@slu.se
  • Nordlander, Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: goran.nordlander@slu.se
article id 9940, category Research article
Esteban Ceriani-Nakamurakare, Sergio Ramos, Carolina A. Robles, María V. Novas, María F. D´Jonsiles, Paola Gonzalez-Audino, Cecilia Carmarán. (2018). Metagenomic approach of associated fungi with Megaplatypus mutatus (Coleoptera: Platypodinae). Silva Fennica vol. 52 no. 3 article id 9940. https://doi.org/10.14214/sf.9940
Highlights: There were no significant effects of host plant and location on fungal richness; Two fungal species, belonging to Fusarium and Candida genera, were present in all the studied associations; Results suggest that host plant identity would not be crucial to determine the composition of fungal communities associated to Megaplatypus mutatus.

Megaplatypus mutatus is a major forest pest in Argentina and an emerging pest in Europe. In this study the multitrophic interactions between M. mutatus and associated fungi were assessed with a metagenomics approach (454-pyrosequencing). A total of 270 collection points from insect galleries from three locations in Argentina were pooled for pyrosequencing analyses. Two hosts, Populus deltoides and Casuarina cunninghamiana, were independently evaluated to characterize the fungal communities associated to M. mutatus; compare the culture-independent approach with previous culturing studies, in terms of data recovery related to the fungal community composition, and test the specificity of the fungal communities amongst locations and hosts. A Generalized Linear Mixed Model was performed to compare the fungal richness in each dataset, which showed no significant differences between taxa richness amongst locations. Principal Coordinates Analyses showed a separation between fungal communities within the same host, suggesting that host identity would not be crucial to determine the specificity in fungal communities. Candida insectalens and one Fusarium species, present in all hosts and locations, achieved 37.6% of the total relative frequency per taxa. These results complement the data from culturing methods previously reported, thus improving the accuracy and understanding of the fungal assemblages associated to M. mutatus.

  • Ceriani-Nakamurakare, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Depto. Biodiversidad y Biología Experimental. Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires. Instituto de Micología y Botánica (INMIBO). Buenos Aires, (C1428EHA) Argentina ORCID ID:E-mail: cerianinaka@gmail.com
  • Ramos, Instituto Nacional de Tecnología Agropecuaria. Estación Experimental Agropecuaria Concordia. Entre Ríos, (E3200) Argentina ORCID ID:E-mail: ramos.sergio@inta.gob.ar
  • Robles, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Depto. Biodiversidad y Biología Experimental. Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires. Instituto de Micología y Botánica (INMIBO). Buenos Aires, (C1428EHA) Argentina ORCID ID:E-mail: carorobles@bg.fcen.uba.ar
  • Novas, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Depto. Biodiversidad y Biología Experimental. Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires. Instituto de Micología y Botánica (INMIBO). Buenos Aires, (C1428EHA) Argentina ORCID ID:E-mail: vicnovas@bg.fcen.uba.ar
  • D´Jonsiles, Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Depto. Biodiversidad y Biología Experimental. Buenos Aires, Argentina; CONICET- Universidad de Buenos Aires. Instituto de Micología y Botánica (INMIBO). Buenos Aires, (C1428EHA) Argentina ORCID ID:E-mail: lalijonsi@gmail.com
  • Gonzalez-Audino, Centro de Investigaciones de Plagas e Insecticidas (CITEFA-CONICET). Buenos Aires, (B1603ALO) Argentina ORCID ID:E-mail: pgonzalezaudino@citedef.gob.ar
  • Carmarán, Centro de Investigaciones de Plagas e Insecticidas (CITEFA-CONICET). Buenos Aires, (B1603ALO) Argentina ORCID ID:E-mail: carmaran@bg.fcen.uba.ar (email)
article id 9905, category Research article
Mercedes M. Fernandez, Diana Bezos, Julio J. Diez. (2018). Fungi associated with necrotic galls of Dryocosmus kuriphilus (Hymenoptera: Cynipidae) in northern Spain. Silva Fennica vol. 52 no. 3 article id 9905. https://doi.org/10.14214/sf.9905
Highlights: Presence of Dryocosmus kuriphilus in Northern Spain; The mycobiota associated to necrotic galls was studied for the first time; 7 fungal species were identified; The entomopathogenic fungi found could be use as potential biological control agents; Gnomomiopsis smithogilvyi, Fusarium oxysporum and F. avenaceum known by their toxicity against the insect, were found.

The Asian chestnut gall wasp (ACGW), Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) is one of the most important pests in Castanea species worldwide. In 2012, it was found for the first time in Catalonia (Spain) and a year later, in the north of Spain (Cantabria). Today, it is present in 14 Spanish provinces. In search of biological control against the ACGW, several authors have previously found the relationship between the presence of some Fusarium Link species in necrotic galls and wasp mortality due to the production of different types of wall-degrading enzymes and entomopathogenic mycotoxins. The objective of this study was to investigate the mycobiota associated with necrotic galls to find interesting perspectives for biological control of the ACGW. For this purpose, in 2014, 119 necrotic galls of Castanea sativa Miller were plated to isolate and identify the associated fungi. The fungal isolates were identified by the morphology of the fruiting bodies and DNA analyses. From necrotic galls, 7 species of fungi were identified. Of these, we highlight three species of Fusarium Link as well as the presence of Gnomoniopsis smithogilvyi Shuttlew, Liew & Guest due to its toxic capacity. Further studies are required to verify the effectiveness of these fungal species as biocontrol agents against the ACGW.

  • Fernandez, Dpt. of Agroforestry Sciences, ETSIIAA, University of Valladolid, Av. Madrid 50, 34071 Palencia, Spain; Sustainable Forest Management Research Institute UVa-INIA, ETSIIAA, 34071 Palencia, Spain ORCID ID: http://orcid.org/0000-0002-1646-5027 E-mail: mffernan@agro.uva.es (email)
  • Bezos, Sustainable Forest Management Research Institute UVa-INIA, ETSIIAA, 34071 Palencia, Spain ORCID ID:E-mail: dianabezos@yahoo.es
  • Diez, Sustainable Forest Management Research Institute UVa-INIA, ETSIIAA, 34071 Palencia, Spain; Dpt. of Plant Production and Forest Resources, University of Valladolid, Av. Madrid 50, 34071 Palencia, Spain ORCID ID:E-mail: jdcasero@pvs.uva.es
article id 7710, category Research article
Pekka Hyvönen, Jaakko Heinonen. (2018). Estimating storm damage with the help of low-altitude photographs and different sampling designs and estimators. Silva Fennica vol. 52 no. 3 article id 7710. https://doi.org/10.14214/sf.7710
Highlights: Digital photographs taken from low altitudes are usable for monitoring storm damage; Simple random sampling and ratio estimators resulted in similar standard errors; Characteristics of the storm influence the optimal flight plan and which variance estimator should be used; The developed model for simulations can be modified and utilized with future storms.

Climate change has been estimated to increase the risk of storm damage in forests in Finland. There is a growing need for methods to obtain information on the extent and severity of storm damage after a storm occurrence. The first objective of this study was to test whether digital photographs taken from aircrafts flying at low-altitude can be utilized in locating storm-damaged areas and estimating the need for harvesting of wind-thrown trees. The second objective was to test the performance of selected estimators. Depending on distances between flight lines, plots on lines and the used estimator, the relative standard errors of storm area estimates varied between 7.7 and 48.7%. For the area for harvesting and volume of wind-thrown trees, the relative standard errors of estimates varied between 16.8 and 167.3%. Using forest area information from Multisource National Forest Inventory data improved the accuracy of the estimates. However, performance of a simple random sampling estimator and ratio estimator were quite similar. Lindeberg’s method for variance estimation based on adjacent lines was sensitive to line directions in relation to possible trends in storm-damaged area locations. Our results showed that the tested method could be used in estimating storm-damaged area provided that the network of flight lines and photographs on lines are sufficiently dense. The developed model for simulations can be utilized also with forthcoming storms as model’s parameters can be freely adjusted to meet, e.g., the intensity and extent of the storm.

  • Hyvönen, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: pekka.hyvonen@luke.fi (email)
  • Heinonen, ORCID ID:E-mail: jaakkoheinonen@gmail.com
article id 9938, category Research article
Jyrki Hytönen, Egbert Beuker, Anneli Viherä-Aarnio. (2018). Clonal variation in basic density, moisture content and heating value of wood, bark and branches in hybrid aspen. Silva Fennica vol. 52 no. 2 article id 9938. https://doi.org/10.14214/sf.9938
Highlights: Hybrid aspen clones differed in their moisture content, ash content, basic density and heating value; Stem wood had lower ash content, basic density and effective heating value than stem bark; There was significant vertical variation in wood and bark along the stem in moisture content and basic density.

Hybrid aspen (Populus tremula × P. tremuloides) is one of the fastest growing tree species in Finland. During the mid-1990s, a breeding programme was started with the aim of selecting clones that were superior in producing pulpwood. Hybrid aspen can also be grown as a short-rotation crop for bioenergy. To study clonal variation in wood and bark properties, seven clones were selected from a 12-year-old field trial located in southern Finland. From each clone, five trees were harvested and samples were taken from stem wood, stem bark and branches to determine basic density, effective heating value, moisture and ash content. Vertical within-tree variation in moisture content and basic density was also studied. The differences between clones were significant for almost all studied properties. For all studied properties there was a significant difference between wood and bark. Wood had lower ash content (0.5% vs. 3.9%), basic density (378 kg m–3 vs. 450 kg m–3) and effective heating value (18.26 MJ kg–1 vs. 19.24 MJ kg–1), but higher moisture content (55% vs. 49%) than bark. The values for branches were intermediate. These results suggest that the properties of hybrid aspen important for energy use could be improved by clonal selection. However, selecting clones based on fast growth only may be challenging since it may lead to a decrease in hybrid aspen wood density.

  • Hytönen, Natural Resources Institute Finland (Luke), Natural resources, Teknologiakatu 7, FI-67100 Kokkola, Finland ORCID ID:E-mail: jyrki.hytonen@luke.fi (email)
  • Beuker, Natural Resources Institute Finland (Luke), Production systems, Vipusenkuja 6, FI-57200 Savonlinna, Finland ORCID ID:E-mail: egbert.beuker@luke.fi
  • Viherä-Aarnio, Natural Resources Institute Finland (Luke), Production systems, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID ID:E-mail: anneli.vihera-aarnio@luke.fi
article id 9933, category Research article
Timo Saksa, Jari Miina, Hilkka Haatainen, Kauko Kärkkäinen. (2018). Quality of spot mounding performed by continuously advancing mounders. Silva Fennica vol. 52 no. 2 article id 9933. https://doi.org/10.14214/sf.9933
Highlights: The number and quality of mounds varied considerably according to the operating conditions;The main factors reducing the quality of spot mounding were steep terrain, a thick humus layer, fresh logging residues, stoniness and soil texture;With careful selection of timing and conditions for mounding, the quality obtained by continuously advancing mounders can be improved.

Operating conditions affecting the quality of spot mounding by Bracke continuously advancing mounders were investigated on 66 regeneration areas (124 ha) in eastern Finland. The quality of mounds was classified as suitable (good or acceptable after additional compression) or unsuitable for planting. Models were constructed for the number of suitable planting spots obtained per hectare (good and acceptable mounds), the probability of successful mounding (≥1600 planting spots ha–1) and the probability of creating a suitable mound as a function of terrain, site and soil characteristics, as well as slash conditions (removed, fresh or dry logging residues). The average number of mounds created was 1892 ± 290 mounds ha–1, of which 1398 ± 325 mounds ha–1 (74%) were classified as suitable for planting. The quality of spot mounding was reduced by steep terrain, a thick humus layer and fresh logging residues. Stoniness and soil texture also affected the number of planting spots created. Mounding after logging residues had dried increased the number of planting spots by 191 spots ha–1 compared with mounding in the presence of fresh residues. Removing residues did not significantly increase the number of planting spots compared with mounding amongst dry residues. A thick humus layer, very stony soil, steep slopes and valley terrain decreased the number of planting spots by 150–450 spots ha–1. The number and quality of mounds varied considerably according to the operating conditions, but with careful selection of timing and sites the quality obtained by a continuously advancing mounder can be improved.

  • Saksa, Natural Resources Institute Finland (Luke), Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: timo.saksa@luke.fi (email)
  • Miina, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: jari.miina@luke.fi
  • Haatainen, Faculty of Science and Forestry, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: hilkka.haatainen@storaenso.com
  • Kärkkäinen, Tornator Oyj, Muuntamontie 2, FI-80100 Joensuu, Finland ORCID ID:E-mail: kauko.karkkainen@tornator.fi
article id 9927, category Research article
Eva Dařenová, Richard A. Crabbe, Robert Knott, Barbora Uherková, Jan Kadavý. (2018). Effect of coppicing, thinning and throughfall reduction on soil water content and soil CO2 efflux in a sessile oak forest. Silva Fennica vol. 52 no. 2 article id 9927. https://doi.org/10.14214/sf.9927
Highlights: The coppice stand reached similar soil CO2 efflux rates eight years after harvest as the original stand; Thinning increased SWC but did not affect soil CO2 efflux; 30% throughfall reduction decreased soil CO2 efflux by 50.7%.

In this study we determined the effect of transformation of a mature sessile oak forest stand into a coppiced forest, and of thinning and throughfall reduction in a coppice stand on soil water content (SWC) and soil CO2 efflux. The precipitation reduction was induced by installing parallel drainage channels in both unthinned and thinned coppice stands. The driving factor for temporal dynamics of soil CO2 efflux in all plots was soil temperature. The other factor was soil water content but only up to about 15%. Above this threshold, there was no more effect on CO2 efflux. We found no clear difference in SWC or soil CO2 efflux between the mature and coppiced stand eight years after harvesting. On the other hand, thinning of the coppice stand resulted in increase in SWC up to 22% in proportion, which we assume to be a result of increased gap fraction of the canopy. However, no effect on soil CO2 efflux was observed two years after the thinning. Installation of the drainage channels in two plots covering 30% of the ground area resulted in decrease in SWC up to a proportional 30.5% and thus contributed up to 50.7% reduction in soil CO2 efflux.

  • Dařenová, Global Change Research Institute CAS, v.v.i., Belidla 4a, 603 00 Brno, Czech Republic ORCID ID:E-mail: darenova.e@czechglobe.cz (email)
  • Crabbe, Global Change Research Institute CAS, v.v.i., Belidla 4a, 603 00 Brno, Czech Republic ORCID ID:E-mail: crabbe.r@czechglobe.cz
  • Knott, Mendel University in Brno, Zemedelska 3, 613 00 Brno, Czech Republic ORCID ID:E-mail: robert.knott@mendelu.cz
  • Uherková, Mendel University in Brno, Zemedelska 3, 613 00 Brno, Czech Republic ORCID ID:E-mail: xfedorov@node.mendelu.cz
  • Kadavý, Mendel University in Brno, Zemedelska 3, 613 00 Brno, Czech Republic ORCID ID:E-mail: jan.kadavy@mendelu.cz
article id 9914, category Research article
Jun Tanabe, Futoshi Ishiguri, Akira Tamura, Yuya Takashima, Jyunichi Ohshima, Kazuya Iizuka, Shinso Yokota. (2018). Within-tree radial and among-family variations in wood density, microfibril angle, and mechanical properties in Picea glehnii. Silva Fennica vol. 52 no. 2 article id 9914. https://doi.org/10.14214/sf.9914
Highlights: The modulus of elasticity was affected by both microfibril angle and wood density, whereas the modulus of rupture was mainly affected by wood density in Picea glehnii; A larger degree of among-family variation in wood properties was detected in juvenile wood than in mature wood, indicating that genetic improvements in the mechanical properties may be more effective for juvenile wood.

Genetic improvements in the mechanical properties of wood are important in forestry species used for lumber, such as Picea. The within-tree radial and among-family variations for the modulus of elasticity (MOE), modulus of rupture (MOR), and their related traits [i.e., microfibril angle (MFA) of the S2 layer in latewood tracheid and air-dry density (AD)] were evaluated in nine open-pollinated families of Picea glehnii (F. Schmidt) Mast. The radial variation in MOR was mainly affected by AD, whereas MOE was affected by MFA and AD. Higher F-values obtained by analysis of variance and coefficient of variation were observed for all properties at the 6th–15th annual ring, except for AD at the 6th–10th annual ring. This result suggests that the contribution of genetic effect is larger in these highly variable regions. In addition, positive correlation coefficients were obtained between wood properties at the 6th–15th annual ring and mean values of these properties. Therefore, genetic improvements for MOE, MOR, and their related traits in P. glehnii is likely to be more effective in juvenile wood, specifically at the 6th–15th annual ring from the pith.

  • Tanabe, Faculty of Education, Chiba University, Chiba, 263-8522, Japan ORCID ID:E-mail: tanabe_j@chiba-u.jp (email)
  • Ishiguri, Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan ORCID ID:E-mail: ishiguri@cc.utsunomiya-u.ac.jp
  • Tamura, Forest Tree Breeding Center, Forestry and Forest Products Research Institute, Hitachi, 319-1301, Japan ORCID ID:E-mail: akirat@affrc.go.jp
  • Takashima, Forest Tree Breeding Center, Forestry and Forest Products Research Institute, Hitachi, 319-1301, Japan ORCID ID:E-mail: ytakashima@ffpri.affrc.go.jp
  • Ohshima, Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan ORCID ID:E-mail: joshima@cc.utsunomiya-u.ac.jp
  • Iizuka, Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan ORCID ID:E-mail: kiizuka@cc.utsunomiya-u.ac.jp
  • Yokota, Faculty of Agriculture, Utsunomiya University, Utsunomiya 321-8505, Japan ORCID ID:E-mail: yokotas@cc.utsunomiya-u.ac.jp
article id 9902, category Research article
Perttu Anttila, Vesa Nivala, Olli Salminen, Markus Hurskainen, Janne Kärki, Tomi J. Lindroos, Antti Asikainen. (2018). Regional balance of forest chip supply and demand in Finland in 2030. Silva Fennica vol. 52 no. 2 article id 9902. https://doi.org/10.14214/sf.9902
Highlights: The impact of increasing forest chip demand in 2030 was analyzed in Finland; Demand of small trees may exceed potential at the national level; Surplus potential will remain in logging residues and stumps; Hot spots of demand call for efficient logistical solutions.

According to the National Energy and Climate Strategy of Finland in 2016, the demand for forest chips, that is, wood chips made of forest biomass directly for energy use, could even double by 2030 compared to the present situation. A spatially explicit impact analysis of regional supply and demand balances for forest chips was carried out. The balances were calculated as the difference between technical harvesting potentials and demand. First, the technical potentials were estimated based on the national forest inventory data. Secondly, three demand scenarios were defined for 2030 and subsequently deducted from the potentials. The results suggested that there would be increasing competition for feedstock in southern and western Finland, whereas in eastern and northern Finland there would still be surplus potential. Moreover, due to the remarkable deficit of small trees in southern Finland, there might be pressure towards using more pulpwood-sized and/or imported wood in energy production. The results also showed that, in particular, large new plants consuming substantial amounts of forest chips could have a significant effect on the regional availability of forest chips. Moreover, with increasing transport distances, new logistical solutions will be needed.

  • Anttila, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID: http://orcid.org/0000-0002-6131-392X E-mail: perttu.anttila@luke.fi (email)
  • Nivala, Natural Resources Institute Finland (Luke), Eteläranta 55, FI-96300 Rovaniemi, Finland ORCID ID:E-mail: vesa.nivala@luke.fi
  • Salminen, Natural Resources Institute Finland (Luke), Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID ID:E-mail: olli.salminen@luke.fi
  • Hurskainen, VTT Technical Research Centre of Finland Ltd, Koivurannantie 1, FI-40400 Jyväskylä, Finland ORCID ID:E-mail: markus.hurskainen@vtt.fi
  • Kärki, VTT Technical Research Centre of Finland Ltd, Koivurannantie 1, FI-40400 Jyväskylä, Finland ORCID ID:E-mail: janne.karki@vtt.fi
  • Lindroos, VTT Technical Research Centre of Finland Ltd, Vuorimiehentie 3 (Espoo), P.O. Box 1000, FI-02044 VTT, Finland ORCID ID:E-mail: tomi.j.lindroos@vtt.fi
  • Asikainen, Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: antti.asikainen@luke.fi
article id 7830, category Research article
Jari Lindblad, Johanna Routa, Johanna Ruotsalainen, Marja Kolström, Ari Isokangas, Lauri Sikanen. (2018). Weather based moisture content modelling of harvesting residues in the stand. Silva Fennica vol. 52 no. 2 article id 7830. https://doi.org/10.14214/sf.7830
Highlights: Weather data used for estimating the moisture content of energy wood; The validation of the weather based models performed based on the field data.

Harvesting residues collected from the final cuttings of boreal forests are an important source of solid biofuel for energy production in Finland and Sweden. In the Finnish supply chain, the measurement of residues is performed by scales integrated in forwarders. The mass of residues is converted to volume by conversion factors. In this study, weather based models for defining the moisture content of residues were developed and validated. Models were also compared with the currently used fixed tables of conversion factors. The change of the moisture content of residues is complex, and an exact estimation was challenging. However, the model predicting moisture change for three hour periods was found to be the most accurate. The main improvement compared to fixed tables was the lack of a systematic error. It can be assumed that weather based models will give more reliable estimates for the moisture in varying climate conditions and the further development of models should be focused on obtaining more appropriate data from varying drying conditions in different geographical and microclimatological locations.

  • Lindblad, ORCID ID:E-mail: jari.lindblad@luke.fi (email)
  • Routa, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: johanna.routa@luke.fi
  • Ruotsalainen, Finnish Meteorological Institute, Aviation and Military Weather Services, P.O. Box 1627, FI-70211 Kuopio, Finland ORCID ID:E-mail: johanna.ruotsalainen@fmi.fi
  • Kolström, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: marja.kolstrom@uef.fi
  • Isokangas, University of Oulu, Control Engineering, P.O. Box 8000, FI-90014 University of Oulu, Finland ORCID ID:E-mail: ari.isokangas@oulu.fi
  • Sikanen, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: lauri.sikanen@luke.fi
article id 7816, category Research article
Pentti Niemistö, Harri Kilpeläinen, Eero Poutiainen. (2018). Effect of first thinning type and age on growth, stem quality and financial performance of a Scots pine stand in Finland. Silva Fennica vol. 52 no. 2 article id 7816. https://doi.org/10.14214/sf.7816
Highlights: Early commercial first thinning at the top height of 11 m with tree selection targeting high quality of remaining stems was more profitable in a Scots pine stand than thinning from below at similar time or delayed thinning 10 years later; After early first thinning only one intermediate thinning was needed, but a late thinning at age of 60 years was feasible in connection with increased amount of high quality butt logs after artificial pruning; The optimal rotation period for a Scots pine stand using a lower interest rate of 1% was 80–85 years depending on the thinning pattern. With a higher rate of 4%, the optimal rotation took only 60 years.

The objective of the study was to ascertain the effects of tree selection (thinning from below, from above and according to stem quality) and timing of first commercial thinning (early and delayed) on the growth, yield and quality of trees in a Scots pine (Pinus sylvestris L.) stand. A long-term field experiment (25 years) was measured in 5-year periods and the further development was simulated with growth and yield models to final cuttings using alternative rotation periods of 55–85 years. The measurements included also the exact location and type of technical defects detected on all trees in the experimental plots. The measured volume increment per unit area during the study period, 25 years after the early thinning stage was the lowest in the plots thinned from below, and the highest in the plots thinned from above or in the delayed thinning plots. However, the largest volume of saw logs during the whole rotation of 80 years was yielded after early first thinning according to the quality. The largest volume of very high-quality butt logs was produced by pruning connected with early thinning from above, and a smaller volume after early thinning according to stem quality but no after thinning from below or delayed first thinning. Without pruning an early quality thinning with one intermediate thinning was the most profitable thinning treatment in the Scots pine stand regardless the rotation length or the interest rate used. By interest rates of 1% and 2%, the optimal rotations were 80–85 years and 70 years respectively. A late thinning at the age of 60 year with long rotation was profitable only for the pruned pine stands with a low interest rate.

  • Niemistö, Natural Resources Institute Finland (Luke), Natural resources, Kampusranta 9 C, FI-60320 Seinäjoki, Finland ORCID ID:E-mail: pentti.niemisto@luke.fi (email)
  • Kilpeläinen, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: harri.kilpelainen@luke.fi
  • Poutiainen, Oulu ORCID ID:E-mail: eero1.poutiainen@dnainternet.net
article id 7813, category Research article
Jaana Luoranen. (2018). Autumn versus spring planting: the initiation of root growth and subsequent field performance of Scots pine and Norway spruce seedlings. Silva Fennica vol. 52 no. 2 article id 7813. https://doi.org/10.14214/sf.7813
Highlights: Conifer seedlings planted after mid-September generally have poor rooting, which causes poor root egress during the following spring; Although Scots pine and Norway spruce seedlings planted in late autumn may have a slightly reduced growth, it is possible to plant them if weather conditions are favorable in late-autumn, without increased mortality.

There is a need to extend the planting season of conifer regeneration into periods where the soil remains unfrozen due to a lack of available labor and the mechanization of planting. This study investigated how the summer- (August) and autumn-, especially late autumn (mid-September to mid-October) plantings affect the field performance of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) container seedlings. This study examined the timing of root growth just after planting, shoot flush and the start of root growth the following spring, and subsequent field performance. Seedlings of both species were planted in a nursery field trial, and in a clearcut reforestation site from August to October and the following May. The root growth of planted seedlings declined in September and ceased after mid-September. In the following spring, seedlings which were planted in early-autumn started their root growth faster than late-autumn-planted seedlings in both species. There was no difference in the timing of shoot flush for various planting dates. During the initial two years after planting, the shoot growth of spring-planted seedlings was lower, compared to autumn-planted seedlings. In conclusion, it is possible to plant conifer seedlings in the boreal forest zone up to October under non-limiting field conditions.

  • Luoranen, Natural Resources Institute Finland (Luke), Production systems, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: jaana.luoranen@luke.fi (email)
article id 7772, category Research article
Curt Almqvist. (2018). Improving floral initiation in potted Picea abies by supplemental light treatment. Silva Fennica vol. 52 no. 2 article id 7772. https://doi.org/10.14214/sf.7772
Highlights: Supplemental light treatment:
  • Increases the proportion of genotypes initiating reproductive buds.
  • Increases floral induction, especially of female floral buds.
  • Facilitates breeding programmes, and seed production of highly improved base material from new selections for vegetative production programmes, to be more efficient.

Light is an important environmental factor for all green plants. Its intensity, spectral composition and photoperiod can affect the regulatory pathways in plants that lead to floral initiation. In this report, results are presented from three experiments in which supplemental light with metal halide lamps (250 µmol m–2 s–1, 20 hours day–1, approx. 6 weeks) was tested as a complement to other flowering stimulation treatments (elevated temperature, treatment with gibberellin A4 and A 7 (GA4/7), restricted water supply) applied to potted Picea abies (L.) Karst. in the greenhouse. Flower stimulation in a greenhouse resulted in more floral initiation compared to flower stimulation outdoors. Supplemental light treatment increased floral initiation further, and to a larger extent in female than in male flowers. It also increased the proportion of trees and genotypes that induced reproductive buds. In a practical application of the supplemental light treatment to potted Picea abies breeding material, 90.6% of the clones produced either female or male flowers, or both. A subset of the same material kept outdoors, and thus subjected to natural light and temperatures, produced no flowers despite being treated with GA4/7 and receiving a restricted water supply. In conclusion, supplemental light treatment facilitates breeding programmes, and seed production of highly improved base material from new selections for vegetative production programmes, to be more efficient.

  • Almqvist, Skogforsk (The Forestry Research Institute of Sweden), Uppsala Science Park, 751 83 Uppsala, Sweden ORCID ID: http://orcid.org/0000-0001-5739-4854 E-mail: curt.almqvist@skogforsk.se (email)
article id 7740, category Research article
Jonas R. Coussement, Kathy Steppe, Peter Lootens, Isabel Roldán-Ruiz, Tom De Swaef. (2018). A flexible geometric model for leaf shape descriptions with high accuracy. Silva Fennica vol. 52 no. 2 article id 7740. https://doi.org/10.14214/sf.7740
Highlights: A method for assessing leaf shape for 3D plant models is proposed; The model is highly flexible and fits a large variety of shapes; It allows analysis of shape differences within and between leaf datasets.

Accurate assessment of canopy structure is crucial in studying plant-environment interactions. The advancement of functional-structural plant models (FSPM), which incorporate the 3D structure of individual plants, increases the need for a method for accurate mathematical descriptions of leaf shape. A model was developed as an improvement of an existing leaf shape algorithm to describe a large variety of leaf shapes. Modelling accuracy was evaluated using a spatial segmentation method and shape differences were assessed using principal component analysis (PCA) on the optimised parameters. Furthermore, a method is presented to calculate the mean shape of a dataset, intended for obtaining a representative shape for modelling purposes. The presented model is able to accurately capture a large range of single, entire leaf shapes. PCA illustrated the interpretability of the parameter values and allowed evaluation of shape differences. The model parameters allow straightforward digital reconstruction of leaf shapes for modelling purposes such as FSPMs.

  • Coussement, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium; Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium ORCID ID:E-mail: jonas.coussement@ilvo.vlaanderen.be
  • Steppe, Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium ORCID ID:E-mail: kathy.steppe@ugent.be
  • Lootens, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium ORCID ID:E-mail: peter.lootens@ilvo.vlaanderen.be
  • Roldán-Ruiz, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium; Department of Plant Biotechnology and Bioinformatics, Faculty of Sciences, Ghent University, Technologiepark Zwijnaarde 927, B-9052 Zwijnaarde, Belgium ORCID ID:E-mail: isabel.roldan-ruiz@ilvo.vlaanderen.be
  • De Swaef, Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Caritasstraat 39, B-9090 Melle, Belgium ORCID ID:E-mail: tom.deswaef@ilvo.vlaanderen.be (email)
article id 7738, category Research article
Samuel Egbäck, Bo Karlsson, Karl-Anders Högberg, Kenneth Nyström, Mateusz Liziniewicz, Urban Nilsson. (2018). Effects of phenotypic selection on height-diameter ratio of Norway spruce and Scots pine in Sweden. Silva Fennica vol. 52 no. 2 article id 7738. https://doi.org/10.14214/sf.7738
Highlights: Swedish plus-tree selection promoted less slender Norway spruce trees and more slender Scots pine trees compared to neighboring trees; Similar results were also found for progeny trials which indicated that genetics played a prominent role in phenotypic appearance.

Genetically improved Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) are extensively used in operational Swedish forestry plantations. However, relatively little is known about the stem slenderness (height-diameter ratio) of genetically improved material. Thus, in this study we investigated effects of plus-tree selection on stem slenderness of Norway spruce and Scots pine in Sweden by evaluating both the plus-tree selection and a large number of progeny trials. Species-specific models for predicting the height-diameter ratio were estimated using regression and mixed model approach. Our results show that phenotypic plus-tree selection promoted less slender Norway spruce trees and more slender Scots pine trees compared to neighboring trees. Similar results were also found for the progeny trials which indicated that genetics played a prominent role in the phenotypic appearance. Compared to the progeny of neighboring trees, Norway spruce plus-tree progenies had a 5.3% lower height-diameter ratio, while Scots pine plus-tree progenies had a 1.5% greater height-diameter ratio. The narrow sense heritability for height-diameter ratio was 0.19 for Norway spruce and 0.11 for Scots pine, indicating that it is possible to modify the height-diameter ratio by breeding. Correlation coefficients between breeding values for height-diameter ratio and diameter were negative for Scots pine (–0.71) and Norway spruce (–0.85), indicating that selection for diameter only would result in less slender stems of both species. Similar correlations were also found between breeding values for height-diameter ratio and height of Scots pine (–0.34) and Norway spruce (–0.74).

  • Egbäck, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 49, 230 53 Alnarp, Sweden ORCID ID:E-mail: samuel.egback@slu.se (email)
  • Karlsson, Skogforsk, Ekebo, 268 90 Svalöv, Sweden ORCID ID:E-mail: bo.karlsson@skogforsk.se
  • Högberg, Skogforsk, Ekebo, 268 90 Svalöv, Sweden ORCID ID:E-mail: karl-anders.hogberg@skogforsk.se
  • Nyström, Swedish University of Agricultural Sciences, Department of Forest Resource Management, Skogsmarksgränd, 901 83 Umeå, Sweden ORCID ID:E-mail: kenneth.nystrom@slu.se
  • Liziniewicz, Skogforsk, Ekebo, 268 90 Svalöv, Sweden ORCID ID:E-mail: Mateusz.Liziniewicz@skogforsk.se
  • Nilsson, Swedish University of Agricultural Sciences, Southern Swedish Forest Research Centre, P.O. Box 49, 230 53 Alnarp, Sweden ORCID ID:E-mail: urban.nilsson@slu.se
article id 7699, category Research article
Dalytė Matulevičiūtė, Jurga Motiejunaite, Domas Uogintas, Ričardas Taraškevičius, Mindaugas Dagys, Valerijus Rašomavičius. (2018). Decline of a protected coastal pine forest under impact of a colony of great cormorants and the rate of vegetation change under ornithogenic influence. Silva Fennica vol. 52 no. 2 article id 7699. https://doi.org/10.14214/sf.7699
Highlights: We studied vegetation and its changes in a pine forest affected by a colony of great cormorants; Vegetation in the colony varied according to the period of bird influence and the stand elevation above sea level; Considerable vegetation changes occur in several years after bird colony establishment; Pine forest ecosystem cease to exist following a decade of bird activity.

We investigated the impact of a colony of great cormorants on the vegetation of the old growth Pinus sylvestris L. forest on the Curonian Spit peninsula, Lithuania. We studied the characteristics and rates of plant cover changes under varying length and intensity of bird influence. Plant species numbers, as well as the coverage of plants with different ecological requirements, varied according to the period of bird influence, but the resulting vegetation also depended upon the stand elevation above sea level. In our study, the initial increase in plant species richness at the start of bird nesting was not obvious and was of a transient character, due to the weak invasion of non-forest species and the rapid decline of forest plants. The colony area showed obvious and rapid vegetation changes during the investigation period. According to the calculated colony expansion rates, after 6–7 years of impact from birds the tree layer decreased by about four fold; the shrub layer decreased by about two fold; the field layer decreased by about 15 fold; and the dwarf shrub and bottom layers disappeared. The coverage by oligotrophic species decreased by more than four fold, while the coverage by eutrophic species increased by more than 60 fold. After 9–10 years of ornithogenic impact, all the trees were dead, and the protected coniferous forest ecosystem, with its characteristic plant species, had ceased to exist as such.

  • Matulevičiūtė, Institute of Botany, Nature Research Centre, Žaliųjų ežerų Str. 49, LT-08406 Vilnius, Lithuania ORCID ID: http://orcid.org/0000-0001-7550-1860 E-mail: dalyte.matuleviciute@botanika.lt (email)
  • Motiejunaite, Institute of Botany, Nature Research Centre, Žaliųjų ežerų Str. 49, LT-08406 Vilnius, Lithuania ORCID ID: http://orcid.org/0000-0002-6949-1990 E-mail: jurga.motiejunaite@botanika.lt
  • Uogintas, Institute of Botany, Nature Research Centre, Žaliųjų ežerų Str. 49, LT-08406 Vilnius, Lithuania ORCID ID: http://orcid.org/0000-0002-3937-1218 E-mail: domas.uogintas@botanika.lt
  • Taraškevičius, Geology and Geography Institute, Nature Research Centre, Akademijos Str. 2, LT-08412 Vilnius, Lithuania ORCID ID: http://orcid.org/0000-0002-5110-6142 E-mail: taraskevicius@geo.lt
  • Dagys, Institute of Ecology, Nature Research Centre, Akademijos Str. 2, LT-08412 Vilnius, Lithuania ORCID ID: http://orcid.org/0000-0001-9342-3464 E-mail: dagys@ekoi.lt
  • Rašomavičius, Institute of Botany, Nature Research Centre, Žaliųjų ežerų Str. 49, LT-08406 Vilnius, Lithuania ORCID ID: http://orcid.org/0000-0003-1314-4356 E-mail: valerijus.rasomavicius@botanika.lt
article id 9923, category Research article
Annika Kangas, Terje Gobakken, Stefano Puliti, Marius Hauglin, Erik Naesset. (2018). Value of airborne laser scanning and digital aerial photogrammetry data in forest decision making. Silva Fennica vol. 52 no. 1 article id 9923. https://doi.org/10.14214/sf.9923
Highlights: Airborne laser scanning (ALS) and digital aerial photogrammetry (DAP) are nearly equally valuable for harvest scheduling decisions even though ALS data is more precise; Large underestimates of stand volume are most dangerous errors for forest owner because of missed cutting probabilities; Relative RMSE of stand volume and the mean volume in a test area explain 77% of the variation between the expected losses due to errors in the data in the published studies; Increasing the relative RMSE of volume by 1 unit, increased the losses in average by 4.4 € ha–1.

Airborne laser scanning (ALS) has been the main method for acquiring data for forest management planning in Finland and Norway in the last decade. Recently, digital aerial photogrammetry (DAP) has provided an interesting alternative, as the accuracy of stand-based estimates has been quite close to that of ALS while the costs are markedly smaller. Thus, it is important to know if the better accuracy of ALS is worth the higher costs for forest owners. In many recent studies, the value of forest inventory information in the harvest scheduling has been examined, for instance through cost-plus-loss analysis. Cost-plus-loss means that the quality of the data is accounted for in monetary terms through calculating the losses due to errors in the data in the forest management planning context. These costs are added to the inventory costs. In the current study, we compared the losses of ALS and DAP at plot level. According to the results, the data produced using DAP are as good as data produced using ALS from a decision making point of view, even though ALS is slightly more accurate. ALS is better than DAP only if the data will be used for more than 15 years before acquiring new data, and even then the difference is quite small. Thus, the increased errors in DAP do not significantly affect the results from a decision making point of view, and ALS and DAP data can be equally well recommended to the forest owners for management planning. The decision of which data to acquire, can thus be made based on the availability of the data on first hand and the costs of acquiring it on the second hand.

  • Kangas, Natural Resources Institute Finland (Luke), Bioeconomy and environment, P.O. Box 68, FI-80170 Joensuu, Finland ORCID ID:E-mail: annika.kangas@luke.fi (email)
  • Gobakken, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: terje.gobakken@nmbu.no
  • Puliti, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: stefano.puliti@nibio.no
  • Hauglin, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: marius.hauglin@nmbu.no
  • Naesset, Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: erik.naesset@nmbu.no
article id 7822, category Research article
Mulualem Tigabu, Annika M. Felton. (2018). Multivariate calibration of near infrared spectra for predicting nutrient concentrations of solid moose rumen contents. Silva Fennica vol. 52 no. 1 article id 7822. https://doi.org/10.14214/sf.7822
Highlights: Multivariate calibrations were established for predicting nutrient concentrations of solid moose rumen contents by near infrared spectroscopy (NIRS); Crude protein, available protein and ash contents were accurately predicted; Prediction of microbial nitrogen, ash, acid-detergent fiber, neutral detergent fiber and lignin were satisfactory; The results demonstrate that NIRS offers quick and inexpensive procedure to quantify nutrient concentrations of solid rumen contents.

This study aimed at establishing calibrations to predict nutrient concentrations of solid moose (Alces alces L.) rumen content using near infrared spectroscopy (NIRS), as an alternative to expensive chemical analyses. NIR reflectance spectra of 148 dry pulverized samples were recorded. The scanned samples were then analyzed for crude protein, available protein, microbial nitrogen (N), ash, acid-detergent fiber (ADF), neutral detergent fiber (NDF) and lignin contents following standard chemical analysis procedures. The calibration models were derived by Orthogonal Projection to Latent Structure (OPLS) and validated using external prediction sets. The calibration models accurately predicted crude protein, available protein and ash contents (R2 = 0.99, 0.96, and 0.92, prediction error = 0.39, 0.72 and 0.53% dry matter, respectively) while NDF (R2 = 0.92; prediction error = 2.23% dry matter) and ADF (R2 = 0.89; prediction error = 1.94% dry matter) were predicted with sufficient accuracy and that of microbial-N (R2 = 0.81; prediction error = 1.25 mg yeast-RNA g–1 dry matter) and lignin (R2 = 0.84; prediction error = 1.05% dry matter) were acceptable. The ratio of performance to deviation values were > 3.0 for crude protein and available protein, between 3.0 and 2.5 for ADF, NDF and lignin, and 2.32 for microbial-N; attesting the robustness of the calibration models. It can be concluded that NIR spectroscopy offers a quick and inexpensive procedure for prediction of nutrient concentrations of solid rumen contents in wild herbivores.

  • Tigabu, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Box 49, SE-230 53 Alnarp, Sweden ORCID ID: http://orcid.org/0000-0003-2471-1168 E-mail: mulualem.tigabu@slu.se (email)
  • Felton, Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Box 49, SE-230 53 Alnarp, Sweden ORCID ID:E-mail: annika.felton@slu.se
article id 7803, category Research article
Lingbo Dong, Pete Bettinger, Huiyan Qin, Zhaogang Liu. (2018). Reflections on the number of independent solutions for forest spatial harvest scheduling problems: a case of simulated annealing. Silva Fennica vol. 52 no. 1 article id 7803. https://doi.org/10.14214/sf.7803
Highlights: No one particular neighborhood search technique of simulated annealing was found to be universally acceptable; The optimal number of independent solutions necessary for addressing the area restriction harvest scheduling model was described with a negative logarithmic function that was related with the problem size. However, optimal number of independent solutions necessary was not sensitive to the problem size for non-spatial and unit restriction harvest scheduling model problems, which should be somewhat above 250 independent runs; The types of adjacency constraints have moderate effects on the number of independent solutions, but these effects are not significant.

To assess the quality of results obtained from heuristics through statistical procedures, a number of independently generated solutions to the same problem are required, however the knowledge of how many solutions are necessary for this purpose using a specific heuristic is still not clear. Therefore, the overall aims of this paper are to quantitatively evaluate the effects of the number of independent solutions generated on the forest planning objectives and on the performance of different neighborhood search techniques of simulated annealing (SA) in three increasing difficult forest spatial harvest scheduling problems, namely non-spatial model, area restriction model (ARM) and unit restriction model (URM). The tested neighborhood search techniques included the standard version of SA using the conventional 1-opt moves, SA using the combined strategy that oscillates between the conventional 1-opt moves and the exchange version of 2-opt moves, and SA using the change version of 2-opt moves. The obtained results indicated that the number of independent solutions generated had clear effects on the conclusions of the performances of different neighborhood search techniques of SA, which indicated that no one particular neighborhood search technique of SA was universally acceptable. The optimal number of independent solutions generated for all alternative neighborhood search techniques of SA for ARM problems could be estimated using a negative logarithmic function based on the problem size, however the relationships were not sensitive (i.e., 0.13 < p < 0.78) to the problem size for non-spatial and URM harvest scheduling problems, which should be somewhat above 250 independent runs. The types of adjacency constraints did moderately affect the number of independent solutions necessary, but not significantly. Therefore, determining an optimal number of independent solutions generated is a necessary process prior to employing heuristics in forest management planning practices.

  • Dong, College of Forestry, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: farrell0503@126.com
  • Bettinger, Warnell School of Forestry and Natural Resources, University of Georgia, Athens 30602, GA, USA ORCID ID:E-mail: pbettinger@warnell.uga.edu
  • Qin, College of Economic and Management, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: huiyanqin@hotmail.com
  • Liu, College of Forestry, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: lzg19700602@163.com (email)
article id 7791, category Research article
Tadeusz B. Splawinski, Sylvie Gauthier, Nicole J. Fenton, Daniel Houle, Yves Bergeron. (2018). The colonization of young fire initiated stands by the crustose lichen Trapeliopsis granulosa and its potential effect on conifer establishment and stand succession. Silva Fennica vol. 52 no. 1 article id 7791. https://doi.org/10.14214/sf.7791
Highlights: T. granulosa is a poor seedbed for jack pine establishment; The presence of extensive T. granulosa cover can limit ongoing tree recruitment, thereby maintaining open lichen woodland; Dry open conditions favor the establishment of T. granulosa; Stands with significant T. granulosa cover may be good candidates for afforestation initiatives due to lower evaporation potential and decreased water stress.

The resilience of closed-crown coniferous stands within the boreal forest of North America is highly dependent on successful re-establishment of tree species following fire. A shift from closed-crown forest to open lichen woodland is possible following poor natural regeneration during the initial establishment phase, followed by the development of extensive lichen cover, which may hinder ongoing recruitment. We examined the development of the crustose lichen Trapeliopsis granulosa (Hoffm.) 18 to 21 years following fire within six sites in the boreal forest of northwestern Quebec, and explored its potential to affect ongoing recruitment during early successional stages of stand development. Germination and survivorship trials were conducted within the laboratory to determine the establishment rate of Pinus banksiana Lamb. (jack pine) on T. granulosa, mineral soil, and burnt duff under two separate watering frequencies (observed and drought). Survival and establishment rates of jack pine were highest on burnt duff, and poor on both T. granulosa and mineral soil. Under the drought treatment, no seedlings survived on any substrates. In the field, T. granulosa cover had a positive relationship with mineral soil cover, and negative relationships with duff cover, ericaceous shrub cover, organic layer depth, other lichen cover, and Sphagnum moss cover. No discernable relationship was found between T. granulosa and tree density, rock cover, dead wood cover or other moss cover. The development of extensive T. granulosa cover in fire-initiated stands can impede ongoing recruitment of conifer species due to its poor seedbed quality, thereby maintaining open forests.

  • Splawinski, Institut de recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, 445, boul. de l’Université, Rouyn-Noranda, QC, J9X 5E4, Canada ORCID ID:E-mail: tsplawinski@gmail.com (email)
  • Gauthier, Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du PEPS, P.O. Box 10380, Stn Sainte Foy, QC, G1V 4C7, Canada ORCID ID:E-mail: sylvie.gauthier@rncan-nrcan.gc.ca
  • Fenton, Institut de recherche sur les forêts (IRF), Université du Québec en Abitibi-Témiscamingue, 445 boul. de l’Université, Rouyn-Noranda, QC, J9X 5E4, Canada ORCID ID:E-mail: nicole.fenton@uqat.ca
  • Houle, Ministère des Forêts, de la Faune et des Parcs, Direction de la recherché forestière, Québec, QC, G1P 3W8, Canada; Ouranos Climate Change Consortium, Montréal, QC, H3A 1B9, Canada ORCID ID:E-mail: daniel.houle@mffp.gouv.qc.ca
  • Bergeron, Centre d’étude sur la forêt and Chaire industrielle en aménagement forestier durable, Université du Québec à Montréal, CP 8888 Succursale A, Montréal, QC, H3C 3P8, Canada ORCID ID:E-mail: bergeron.yves@uqam.ca
article id 7003, category Research article
Poje Anton, Raffaele Spinelli, Natascia Magagnotti, Matevz Mihelic. (2018). The effect of feedstock, knife wear and work station on the exposure to noise and vibrations in wood chipping operations. Silva Fennica vol. 52 no. 1 article id 7003. https://doi.org/10.14214/sf.7003
Highlights: Exposure to noise and vibration is higher when chipping branches rather than logs; Noise levels are higher in the separate cab, especially at some frequencies; Vibration is higher for the Z axis in the separate cab, for the X axis in the truck; Noise is higher when working with blunt knives, rather than new knives; Knife wear has no significant effect on exposure to whole-body vibration.

Industrial chipping is becoming increasingly popular, as the result of a growing demand for woody biomass. Industrial chippers are large, powerful machines that generate much noise and vibration. This study explored some factors that may affect exposure to noise and vibration, namely: feedstock type (branches vs. logs), work station characteristics (truck cab vs. separate cab) and knife wear (new knives vs. blunt knives). Exposure to noise was significantly affected by all three factors, and it was higher for branch feedstock, separate cabs and blunt knives. The higher exposure levels recorded for the separate cab were especially insidious, because they were below and above the hearing threshold and would elude immediate perception. Exposure to whole-body vibration (WBV) was significantly higher for branch feedstock and for the separate cab. Knife wear seemed to determine an increase in WBV, but this effect had no statistical significance and the result could not be taken as conclusive. Among the three factors studied, work station characteristics had the strongest effect. Further studies may extend the comparison to a wider range of options, as well as explore the use of exposure variation for machine diagnostics.

  • Anton, University of Ljubljana, Dept. of Forestry and Renewable Resources, Večna pot 83, 1000 Ljubljana, Slovenia ORCID ID:E-mail: anton.poje@bf.uni-lj.si
  • Spinelli, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy; AFORA, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, Queensland, 4558 Australia ORCID ID: http://orcid.org/0000-0001-9545-1004 E-mail: spinelli@ivalsa.cnr.it (email)
  • Magagnotti, CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy; AFORA, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, Queensland, 4558 Australia ORCID ID:E-mail: magagnotti@ivalsa.cnr.it
  • Mihelic, University of Ljubljana, Dept. of Forestry and Renewable Resources, Večna pot 83, 1000 Ljubljana, Slovenia ORCID ID:E-mail: matevz.mihelic@bf.uni-lj.si
article id 6999, category Research article
Virginia Morales Olmos, Jacek P. Siry. (2018). The Law of One Price in global coniferous sawlog markets. Silva Fennica vol. 52 no. 1 article id 6999. https://doi.org/10.14214/sf.6999
Highlights: The Law of One Price did not hold for North American, European and South American sawlog markets between 1995–2012; There are long-term relationships between some of the analyzed sawlog prices in these markets; The Law of One Price may hold between sawlogs traded in Sweden and Norway, Norway and Finland, and Canada West and US Northwest.

With progressing globalization of forest production, roundwood prices in different countries may follow similar trends. The Law of One Price (LOP) postulates that the price of a similar product should be the same in different markets when expressed in the same currency. The objectives of this research were (1) to test the LOP in selected coniferous sawlog markets, and (2) to analyze whether a common market – the European Union – leads to the existence of a single sawlog market. The analysis included Brazil, Chile, Finland, Germany, Norway, Poland, Russia Northwest, Sweden, the US South, the US Northwest, Canada East, and Canada West. The results suggest that some of the coniferous sawlog markets were cointegrated which means that they shared a long-term relationship even if in the short-term they do not necessarily adjust to each other. The LOP may hold between coniferous sawlog markets in Sweden and Norway from 1995 through 2012 when sawlog prices were expressed in USD, and in Norway and Finland for 2001–2012 for prices in EUR. Furthermore, the LOP may hold for North American markets in the West for 2004–2012.

  • Morales Olmos, Universidad de la República-Sede Tacuarembó, Ruta 5. km, 386.200, Tacuarembó, CP 45000, Uruguay ORCID ID:E-mail: vmolmos@gmail.com (email)
  • Siry, Warnell School of Forestry and Natural Resources, University of Georgia, 180 E. Green Street, Athens, GA 30602-2152, USA ORCID ID:E-mail: jsiry@uga.edu
article id 1665, category Research article
Lauri Haataja, Ville Kankaanhuhta, Timo Saksa. (2018). Reliability of self-control method in the management of non-industrial private forests. Silva Fennica vol. 52 no. 1 article id 1665. https://doi.org/10.14214/sf.1665
Highlights: Self-control method was found reliable at the main stages of the forest regeneration process; Only slight overestimation was found in self-control results of soil preparation and planting and small underestimation in self-control of young stand management; Diverse utilizing of self-control data is possible in support of service providers operations.
This study seeks to determine the extent to which self-control data can be relied upon in the management of private forests. Self-control (SC) requires the forest workers to evaluate their own work quality to ensure the clients’ needs are met in terms of soil preparation, planting and young stand management. Self-control data were compared to an independent evaluation of the same worksites. Each dataset had a hierarchical structure (e.g., sample plot, regeneration area and contractor), and key quality indicators (i.e., number of prepared mounds, planted seedlings or crop trees) were measured for each plot.  Self-control and independent-assessments (IA) were analyzed by fitting a multi-level multivariate model containing explanatory variables. No significant differences were observed in terms of soil preparation (number of mounds) or young stand management (number of crop trees) between self-control and independent-assessments. However, the self-control planting data included a slight but significant overestimation of the number of planted seedlings. Discrepancies are discussed in terms of sampling error and other explanatory factors. According to overall results, self-control methods are reliable at every stage of the forest regeneration process. As such, the diverse utilizing of self-control data is possible in support of service providers operations.
  • Haataja, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: lauritapiohaataja@gmail.com (email)
  • Kankaanhuhta, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: ville.kankaanhuhta@luke.fi
  • Saksa, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: timo.saksa@luke.fi

Category: Review article

article id 7760, category Review article
Maria A. Huka, Manfred Gronalt. (2018). Log yard logistics. Silva Fennica vol. 52 no. 4 article id 7760. https://doi.org/10.14214/sf.7760
Highlights: Characteristics of log yard logistics; Classification into tactical structural and operational problems in the wood industry; Different solution methods such as optimisation, heuristics and simulations and their possible application within the log yard with an overview of existing literature which includes several different case studies with varying emphases, problem analysis and solution methods.

For sawmills, paper mills, particleboard, oriented strand board (OSB), fiberboard and other wood production factories, the log yard is the first step, where raw materials are sorted and stored before production begins. Due to the size of these production sites great potential exists for the optimisation of internal logistics. In this paper the different planning problems of the log yard are introduced and existing literature examined. Beginning with the tactical problems of structure, such as assessing material flow, planning facility layout and assigning storage areas, it continues with operational problems such as vehicle movement planning within the log yard, empty trip minimisation and the seasonality of raw material availability. Data derived from this study reveals a variety of possible solution methods, the applicability of which depends on the precise nature of the log yard operations. Additionally, several real life examples are provided which illustrate the potential for operational improvement.

  • Huka, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria ORCID ID:E-mail: maria.huka@boku.ac.at (email)
  • Gronalt, University of Natural Resources and Life Sciences, Institute of Production and Logistics, Feistmantelstraße 4, 1180 Vienna, Austria ORCID ID:E-mail: manfred.gronalt@boku.ac.at

Category: Research note

article id 10009, category Research note
Janis Donis, Mara Kitenberga, Guntars Snepsts, Edgars Dubrovskis, Aris Jansons. (2018). Factors affecting windstorm damage at the stand level in hemiboreal forests in Latvia: case study of 2005 winter storm. Silva Fennica vol. 52 no. 4 article id 10009. https://doi.org/10.14214/sf.10009
Highlights: In hemiboreal forests in Latvia, dominant tree species, admixture of spruce in canopy-layer, mean height, timing of thinnings, upwind forest edges and wind gusts had significant effect on windstorm damage occurrence at stand-level; Stands on peat soils were more damaged than stands on mineral soils; Tree species composition of canopy-layer was not statistically significant in the model.

In managed European hemiboreal forests, windstorms have a notable ecological and socio-economic impact. In this study, stand properties affecting windstorm damage occurrence at the stand-level were assessed using a Generalized Linear Mixed model. After 2005 windstorm, 5959 stands dominated by birch (Betula spp.), Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.), with mean height > 10 m were inventoried. Windstorm damage was positively associated with spruce and pine-dominated stands, increasing mean height, fresh forest edges, decreasing time since the last thinning and stronger wind gusts. Tree species composition – mixed or monodominant – was not statistically significant in the model; while, the admixture of spruce in the canopy layer was positively associated with higher windstorm damage. Stands on peat soils were more damaged than stands on mineral soils. Birch stands were more damaged than pine stands. This information could be used in forest management planning, selection of silvicultural treatments to increase forest resilience to natural disturbances.

  • Donis, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 ORCID ID:E-mail: janis.donis@silava.lv (email)
  • Kitenberga, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 ORCID ID:E-mail: mara.kitenberga@gmail.com
  • Snepsts, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 ORCID ID:E-mail: guntars.snepsts@silava.lv
  • Dubrovskis, Latvia University of Life Sciences and Technologies, Liela iela 2, Jelgava, Latvia, LV-3001 ORCID ID:E-mail: edgars.dubrovskis@llu.lv
  • Jansons, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 ORCID ID:E-mail: aris.jansons@silava.lv
article id 9986, category Research note
Ninni Saarinen, Joanne C. White, Michael A. Wulder, Annika Kangas, Sakari Tuominen, Ville Kankare, Markus Holopainen, Juha Hyyppä, Mikko Vastaranta. (2018). Landsat archive holdings for Finland: opportunities for forest monitoring. Silva Fennica vol. 52 no. 3 article id 9986. https://doi.org/10.14214/sf.9986
Highlights: The 45-year Landsat archive contained 30 076 images for Finland by December 31, 2017; 16.3% of these were acquired within ±30 days of August 1 (northern hemisphere summer), have <70% cloud cover, and a 30 m spatial resolution; Using time series analyses, these data provide unique information that complements other datasets available for forest monitoring and assessment in Finland.

There is growing interest in the use of Landsat data to enable forest monitoring over large areas. Free and open data access combined with high performance computing have enabled new approaches to Landsat data analysis that use the best observation for any given pixel to generate an annual, cloud-free, gap-free, surface reflectance image composite. Finland has a long history of incorporating Landsat data into its National Forest Inventory to produce forest information in the form of thematic maps and small area statistics on a variety of forest attributes. Herein we explore the spatial and temporal characteristics of the Landsat archive in the context of forest monitoring in Finland. The United States Geological Survey Landsat archive holds a total of 30 076 images (1972–2017) for 66 scenes (each 185 km by 185 km in size) representing the terrestrial area of Finland, of which 93.6% were acquired since 1984 with a spatial resolution of 30 m. Approximately 16.3% of the archived images have desired compositing characteristics (acquired within August 1 ±30 days, <70% cloud cover, 30 m spatial resolution). Data from the Landsat archive can augment forest monitoring efforts in Finland, provide new information for science and applications, and enable retrospective, systematic analyses to characterize the development of Finnish forests over the past three decades. The capacity to monitor trends based upon this multi-decadal record with the addition of new measurements is of benefit to multisource inventories and offers nationally comprehensive spatially-explicit datasets for a wide range of stakeholders and applications.

  • Saarinen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 University of Helsinki, Finland; School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID: https://orcid.org/0000-0003-2730-8892 E-mail: ninni.saarinen@helsinki.fi (email)
  • White, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 University of Helsinki, Finland; Canadian Forest Service, (Pacific Forestry Center), Natural Resources Canada, 506 West Burnside Road, Victoria, BC, V8Z 1M5, Canada ORCID ID: http://orcid.org/0000-0003-4674-0373 E-mail: joanne.white@canada.ca
  • Wulder, Canadian Forest Service, (Pacific Forestry Center), Natural Resources Canada, 506 West Burnside Road, Victoria, BC, V8Z 1M5, Canada ORCID ID: https://orcid.org/0000-0002-6942-1896 E-mail: mike.wulder@canada.ca
  • Kangas, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: annika.kangas@luke.fi
  • Tuominen, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID ID:E-mail: sakari.tuominen@luke.fi
  • Kankare, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: ville.kankare@helsinki.fi
  • Holopainen, Department of Forest Sciences, University of Helsinki, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: markus.holopainen@helsinki.fi
  • Hyyppä, Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute, National Land Survey of Finland, Geodeetinrinne 2, FI-02431 Masala, Finland ORCID ID:E-mail: juha.hyyppa@nls.fi
  • Vastaranta, School of Forest Sciences, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID: https://orcid.org/0000-0001-6552-9122 E-mail: mikko.vastaranta@uef.fi
article id 9911, category Research note
Tālis Gaitnieks, Indulis Brauners, Kristīne Kenigsvalde, Astra Zaļuma, Lauma Brūna, Jurģis Jansons, Natālija Burņeviča, Andis Lazdiņš, Rimvydas Vasaitis. (2018). Infection of pre-commercially cut stumps of Picea abies and Pinus sylvestris by Heterobasidion spp. – a comparative study. Silva Fennica vol. 52 no. 1 article id 9911. https://doi.org/10.14214/sf.9911
Highlights: In pre-commercial thinnings both Heterobasidion infection frequency and the extent of surface colonization correlated positively with stump diameter of both Norway spruce and Scots pine; Spruce stumps were significantly more often subjected to primary infections than pine stumps; The pathogen exhibited more extensive surface colonization of spruce stumps than of pine stumps.

The aim was to investigate relative susceptibility of stumps of spruce and pine to airborne infections by Heterobasidion following pre-commercial thinnings. The proportions of infected stumps and colonized stump surface areas were analysed in 16 forest stands. In total, 746 spruce and 1063 pine stumps were sampled, and 184 and 105 infected stumps, respectively, were analysed. In conclusion, the present study demonstrated that in the investigated area: i) both Heterobasidion infection frequency and the extent of surface colonization correlated positively with stump diameter of both spruce and pine; ii) spruce stumps were significantly more often subjected to primary infections than pine stumps; iii) the pathogen exhibited more extensive surface colonization of spruce stumps than of pine stumps.

  • Gaitnieks, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: talis.gaitnieks@silava.lv (email)
  • Brauners, JSC “Latvia’s State Forests”, 1 Vainodes str., Riga, LV-1004, Latvia ORCID ID:E-mail: i.brauners@lvm.lv
  • Kenigsvalde, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: kristine.kenigsvalde@silava.lv
  • Zaļuma, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: astra.zaluma@silava.lv
  • Brūna, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: lauma.bruna@silava.lv
  • Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: jurgis.jansons@silava.lv
  • Burņeviča, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: natalija.arhipova@silava.lv
  • Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: andis.lazdins@silava.lv
  • Vasaitis, Swedish University of Agricultural Sciences (SLU), P.O. Box 7026, SE-75007 Uppsala, Sweden ORCID ID:E-mail: Rimvys.Vasaitis@slu.se
article id 9901, category Research note
Ilze Matisone, Roberts Matisons, Māris Laiviņš, Tālis Gaitnieks. (2018). Statistics of ash dieback in Latvia. Silva Fennica vol. 52 no. 1 article id 9901. https://doi.org/10.14214/sf.9901
Highlights: Dynamics of ash dieback during 2005–2015 were summarized; The area of ash dominated stands decreased twofold; The number of mature ash trees and their standing volume decreased by 53.1 and 69.9%, compared to 2005, respectively; The mortality of trees was higher during the first part of the survey, the decrease of standing volume culminated later.

Dieback of the common ash (Fraxinus excelsior L.) has been spreading throughout Europe since the 1990s, causing severe ecological and economical consequences; however, detailed statistics on its dynamics have been published rarely. This paper presents the dynamics of mature ash-dominated stands in Latvia for the period 2005–2015. Data from the national forest inventory and a permanent sampling plot network were summarised. According to the official statistics, the dieback has caused a twofold decrease in area of the ash stands (from 21 891 to 13 011 ha, which respectively comprised ca. 0.8 to ca. 0.4% of the total forest area). The official statistics on standing volume appeared biased, as they did not account for increased mortality. According to the permanent sampling plots, standing volume and stand density have been affected even more, having decreased by 53.1 and 69.9%, respectively, compared to 2005 (the stand density and standing volume of ash in 2015 was 77 individuals ha–1 and 151 m3 ha–1, respectively). The mortality of the trees has not been stable. Stand density decreased faster during 2005–2009 compared to 2010–2015, with mortality rates of 9.6 and 8.2% year–1, respectively. In contrast, the decrease in standing volume in 2005–2009 was slower than in 2010–2015 (mortality rates were 4.7 and 7.7% year–1, respectively) because trees with smaller dimensions were more susceptible to the dieback. Nevertheless, the observed mortality rates clearly indicate negative prospects for ash stands in Latvia.

  • Matisone, Latvian State Forest Research Institute (LSFRI) Silava, Rigas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: ilze.matisone@silava.lv (email)
  • Matisons, Latvian State Forest Research Institute (LSFRI) Silava, Rigas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: robism@inbox.lv
  • Laiviņš, Latvian State Forest Research Institute (LSFRI) Silava, Rigas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: maris.laivins@silava.lv
  • Gaitnieks, Latvian State Forest Research Institute (LSFRI) Silava, Rigas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: talis.gaitnieks@silava.lv
article id 9899, category Research note
Linda Robalte, Diāna Jansone, Didzis Elferts, Roberts Matisons, Āris Jansons. (2018). Bilberry ramet dimensions in relation to stand age in oligotrophic conditions in Latvia. Silva Fennica vol. 52 no. 1 article id 9899. https://doi.org/10.14214/sf.9899
Highlights: Bilberry ramet dimensions (age, diameter, height) and their structural diversity, as well as cover, increased with stand age; Active rejuvenation of ramets was observed in younger stands; The oldest bilberry ramets (>10 years of age) occurred in stands older than 70 years.

Dwarf shrub layer is an important component of boreal and hemiboreal forest ecosystems that has received little attention, particularly regarding its structural diversity, which, however, could serve as an additional proxy for habitat quality. Dimensions of bilberry (Vaccinium myrtillus L.) ramets were assessed in two sites in Latvia covered by dry oligotrophic Scots pine (Pinus sylvestris L.) stands 10–230 years of age. In total, 20 sampling plots (10×10 m) with 156 subplots (1×1 m) were sampled and 630 bilberry ramets analysed. The dimensions of ramets (age, diameter, and height) and cover of bilberry increased with stand age. The age of the studied ramets ranged 2–13 years; 5–6 years-old ramets were most frequent in all stands. The skewness of the distribution of the ramet dimensions shifted with stand age, leaning towards the higher values. Lower structural diversity of ramets was observed in stands 50–100 years of age. The highest diversity of ramet age structure occurred in stands younger than 150 years, whereas the oldest and largest ramets mostly occurred in the older stands (>150 years). Considering structural diversity of ramets, recovery of bilberry after stand-replacing disturbance (e.g. clearcut) was a continuous process, similarly to that observed in tree layer.

  • Robalte, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: robalte.l@gmail.com (email)
  • Jansone, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia; University of Latvia, Faculty of Biology, Jelgavas Str. 1, LV 1004, Riga, Latvia ORCID ID:E-mail: diana.jansone13@gmail.com
  • Elferts, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia; University of Latvia, Faculty of Biology, Jelgavas Str. 1, LV 1004, Riga, Latvia ORCID ID:E-mail: didzis.elferts@lu.lv
  • Matisons, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: roberts.matisons@silava.lv
  • Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: aris.jansons@silava.lv
article id 7818, category Research note
Roberts Matisons, Guntars Šņepsts, Līga Puriņa, Jānis Donis, Āris Janosns. (2018). Dominant height growth of European beech at the northeasternmost stands in Europe. Silva Fennica vol. 52 no. 1 article id 7818. https://doi.org/10.14214/sf.7818
Highlights: The dominant height growth of the introduced European beech was modelled using the generalised algebraic difference approach; The Chapman-Richards and Sloboda models showed the best fit to the data; Height growth of the second generation trees exceeded the first generation trees; In the western part of Latvia, height growth of beech exceeded that in southern Sweden.

The height growth of trees influences the productivity of stands and the competitiveness of species, shaping the range of their distribution. Dominant height growth was assessed for European beech (Fagus sylvatica L.), growing outside of its natural distribution range in the western part of Latvia. In 10 neighbouring experimental stands, 20 dominant trees were felled for stem analysis. Height growth was modelled using the generalised algebraic difference approach, applying several non-linear equations and mixed procedures. The Chapman-Richards and Sloboda models showed the best fit to the data. Height growth of the second generation (younger) trees exceeded that of the first generation, and followed curve for a higher site index, suggesting sufficient adaptation and improving conditions. Height growth of the studied beech exceeded predictions for beech in southern Sweden, which is considered to be the northern limit of the species range, yet the growth pattern differed. In Latvia, slower height growth was estimated for site indices < 32 m (in 100 years) during the first 60 years, yet larger maximal height was predicted, suggesting a longer establishment period. Nevertheless, the improving height growth indicated increasing potential for the application of the species in commercial forestry, and an expansion of the species within the region even during the 21th century.

  • Matisons, Latvian State Forest Research Institute “Silava”, Rīgas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: robism@inbox.lv (email)
  • Šņepsts, Latvian State Forest Research Institute “Silava”, Rīgas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: guntars.snepsts@silava.lv
  • Puriņa, Latvian State Forest Research Institute “Silava”, Rīgas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: liga.purina@silava.lv
  • Donis, Latvian State Forest Research Institute “Silava”, Rīgas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: janis.donis@silava.lv
  • Janosns, Latvian State Forest Research Institute “Silava”, Rīgas str. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: aris.jansons@silava.lv
article id 7771, category Research note
Mara Kitenberga, Roberts Matisons, Aris Jansons, Janis Donis. (2018). Teleconnection between the Atlantic sea surface temperature and forest fires in Latvia and Estonia. Silva Fennica vol. 52 no. 1 article id 7771. https://doi.org/10.14214/sf.7771
Highlights: Forest fire activity in Latvia and Estonia was related to conditions in the Atlantic; Teleconnections differed regionally; Negative correlation between number of fires in Estonia and SST in the North Atlantic was detected; Area of forest fires in Estonia and activity of fires in Latvia were positively correlated with SST in the Baltic, North and Mediterranean Seas in summer.

Forest fire is one of the natural disturbances, which have important ecological and socioeconomical effect. Although fire activity is driven by weather conditions, during past two centuries forest fires have been strongly anthropogenically controlled. In this study, teleconnection between sea surface temperature (SST) in the Atlantic, which influences climate in Europe, and forest fire activity in Latvia and Estonia was assessed using “Climate explorer” web-tool. Factors affecting number and area of forest fires in Latvia and Estonia differed, suggesting regional specifics. In Estonia, the number of fires correlated with the SST in the North Atlantic in spring and summer, which affects the inflow of cool and dry air masses from the Arctic, hence the aridity and burnability. The area of fires in Estonia and in Latvia was associated with increased SST in Baltic Sea and near the European coast in summer, which likely were consequences of occurrence of warm high-pressure systems in summer, causing hot and dry conditions. Nevertheless, the observed teleconnections could be used to predict activity of forest fires in Latvia and Estonia.

  • Kitenberga, Latvian State Forest Research Institute ‘Silava’, Rigas st. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: mara.kitenberga@gmail.com (email)
  • Matisons, Latvian State Forest Research Institute ‘Silava’, Rigas st. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: robism@inbox.lv
  • Jansons, Latvian State Forest Research Institute ‘Silava’, Rigas st. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: aris.jansons@silava.lv
  • Donis, Latvian State Forest Research Institute ‘Silava’, Rigas st. 111, Salaspils, Latvia, LV2169 ORCID ID:E-mail: janis.donis@silava.lv

Register
Click this link to register for Silva Fennica submission and tracking system.
Log in
If you are a registered user, log in to save your selected articles for later access.
Contents alert
Sign up to receive alerts of new content
Your selected articles

Committee on Publication Ethics A Trusted Community-Governed Archive