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Silva Fennica vol. 55 no. 1 | 2021

Category: Editorial

article id 10542, category Editorial
Jussi Manner. (2021). What is (not) an operator effect in forest work science? Silva Fennica vol. 55 no. 1 article id 10542. https://doi.org/10.14214/sf.10542

Category: Research article

article id 10460, category Research article
Hanna Lundmark, Lars Östlund, Torbjörn Josefsson. (2021). Continuity forest or second-generation forest? Historic aerial photos provide evidence of early clear-cutting in northern Sweden. Silva Fennica vol. 55 no. 1 article id 10460. https://doi.org/10.14214/sf.10460
Highlights: In the early 1900s clear-cutting had been applied to 10% of the forest land in the study area situated in Västernorrland province, northern Sweden; By the end of the 1940s 40% of the study area had been clear-cut and constituted second-generation forest; 50–70 years is too short of a time frame for assessing the continuity of a forest in the study area.

Modern forestry, which mainly consists of clear-cutting, is one of the most important factors influencing today’s boreal forests. In Sweden, the breaking point for modern forestry is generally considered to be around 1950. Recently, our common knowledge of the implementation of clear-cutting in Sweden has increased, and new research indicates that clear-cutting systems were already applied before the 1950s. In this case study, we used aerial photographs from the 1940s to analyze the extent of contemporaneous clear-cuts and even-aged young forests in an area in northern Sweden. Our results show that almost 40% of the study area had already been clear-cut by the end of the 1940s, but also that clear-cutting had been applied to 10% of the forest land in the early 1900s. This implies that the historical development of forestry in northern Sweden is more complex than previously thought, and that certain proportions of the forest land were already second-generation forests in the 1950s. Our results have implications for the use of concepts such as “continuity forest”, suggesting that this concept should employ a time frame of at least 100 years.

  • Lundmark, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, S-901 83 Umeå, Sweden ORCID ID: https://orcid.org/0000-0001-8402-7152 E-mail: hanna.lundmark@slu.se
  • Östlund, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, S-901 83 Umeå, Sweden ORCID ID: https://orcid.org/0000-0002-7902-3672 E-mail: lars.ostlund@slu.se
  • Josefsson, Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, S-901 83 Umeå, Sweden ORCID ID: https://orcid.org/0000-0002-8734-5778 E-mail: torbjorn.josefsson@slu.se (email)
article id 10444, category Research article
Risto Kalliola, Timo Saarinen, Niko Tanski. (2021). Seasonal variations of foliar element distributions of silver birch in different habitats. Silva Fennica vol. 55 no. 1 article id 10444. https://doi.org/10.14214/sf.10444
Highlights: Detailed mapping using micro X-ray fluorescence showed element variations in a seasonal cohort of silver birch leaves in six different habitats; Seasonal changes occurred in most of the ten studied nutrient elements; Different habitats showed unique seasonal development patterns in specific elements; Element distributions within individual leaf blades were variable; Phenotypic plasticity of foliar nutrients supports adaptation to patchy environments.

Novel information on silver birch (Betula pendula Roth) foliar element contents and their seasonal, between-habitat and leaf level variations are provided by applying fine-scaled element mapping with micro X-ray fluorescence. In the monthly leaf samples collected from May to October from six different habitats, pairwise scatter plots and Spearman’s rank correlations showed statistically significant positive correlations between Si, Al and Fe, and covariations between also many other pairs of elements. Of the ten elements studied, seven showed statistically significant changes in their average levels between May and June. The contents of P, S and K decreased in most habitats during the later season, whereas Ca and in some habitats also Mn and Zn increased. Comparing habitats, trees in the limestone habitat had relatively low content of Mg, strongly increasing levels of P until the late season, and high content of Ca and Fe. Other habitats also revealed distinctive particularities in their foliar elements, such as a high relative content of S and a low content of Ca at the seashore. Mn was high in three habitats, possibly due to bedrock characteristics. Except for P, the contents of all elements diverged between the midrib and other leaf areas. Zn content was particularly high in the leaf veins. Mn levels were highest at the leaf margins, indicating a possible sequestration mechanism for this potentially harmful element. Si may help to alleviate the metallic toxicities of Al and Fe. Because the growing season studied was dry, some trees developed symptoms of drought stress. The injured leaf parts had reduced levels of P, S and K, suggesting translocation of these nutrients before permanent damage.

  • Kalliola, Department of geography and geology, University of Turku, FI-20014 Turku, Finland ORCID ID: https://orcid.org/0000-0003-2454-8217 E-mail: risto.kalliola@utu.fi (email)
  • Saarinen, Department of geography and geology, University of Turku, FI-20014 Turku, Finland ORCID ID:E-mail: tijusa@utu.fi
  • Tanski, Department of geography and geology, University of Turku, FI-20014 Turku, Finland ORCID ID:E-mail: niko.tanski@utu.fi
article id 10422, category Research article
Juha Kaitera, Jouni Karhu. (2021). Temperature range for germination of Thekopsora areolata aeciospores from Finnish Norway spruce seed orchards. Silva Fennica vol. 55 no. 1 article id 10422. https://doi.org/10.14214/sf.10422
Highlights: Cherry-spruce rust was able to germinate at very low temperature (6 °C) close to the temperature when thermal growth starts; Optimum spore germination occurred between 15–24 °C; High temperature of 30 °C drastically reduced germination; Temperature had the most significant effect on germination, while spore source had less significant effect and agar media a non-significant effect on germination in a Fixed Effects model.

Cherry-spruce rust caused by Thekopsora areolata (Fr.) Magnus is a serious cone pathogen of Norway spruce [Picea abies (L.) Karst.]. The rust causes great economical losses in seed orchards specialized in the production of high quality seeds. Germination range of T. areolata aeciospores from rust populations (spore sources) in seven Finnish Norway spruce seed orchards was tested on water agar and malt agar at nine temperatures varying between 6–30 °C. The temperature range of spore germination was high varying between 6 °C and 27 °C, while germination was retarded at 30 °C. The peak in germination rate of all spore sources occurred between 15–24 °C. In a model with fixed effects of agar media, temperature and spore source, temperature had the most significant effect on germination. Spore source had a less significant effect, while agar media had a non-significant effect on germination. The rust was able to germinate at low temperatures corresponding to temperatures when the thermal growing season starts at 5 °C in the spring. As spores from cones from both the spruce canopy and the ground showed very similar germination ranges, it indicated the great capacity of all spores of the rust to germinate early in the spring. Hot temperatures with over 30 °C drastically reduced germination of the rust.

  • Kaitera, Natural Resources Institute Finland (Luke), Natural resources and bioproduction, Paavo Havaksentie 3, FI-90014 University of Oulu, Finland ORCID ID:E-mail: juha.kaitera@luke.fi (email)
  • Karhu, Natural Resources Institute Finland (Luke), Natural resources and bioproduction, Paavo Havaksentie 3, FI-90014 University of Oulu, Finland ORCID ID:E-mail: jouni.karhu@luke.fi
article id 10420, category Research article
Eeva-Liisa Terhonen, Jumoke Babalola, Risto Kasanen, Risto Jalkanen, Kathrin Blumenstein. (2021). Sphaeropsis sapinea found as symptomless endophyte in Finland. Silva Fennica vol. 55 no. 1 article id 10420. https://doi.org/10.14214/sf.10420
Highlights: Sphaeropsis sapinea was found for the first time as an endophyte in healthy Scots pine in Finland; This finding confirms that S. sapinea can proliferate in a symptomless stage in Scots pine in Finland.

The aim of this study was to determine if the ascomycete fungus Sphaeropsis sapinea (Fr.) Dyko & B. Sutton (syn. Diplodia sapinea (Fr.) Fuckel) could be cultured from surface sterilized Scots pine twigs presenting the endophytic stage of this fungus. This fungus causes the disease called Diplodia tip blight in conifers. Symptoms become visible when trees have been weakened by abiotic stressors related to temperature, drought and hailstorms. The disease is rapidly increasing and is observed regularly in Scots pine (Pinus sylvestris L.) forests in Europe. Changes in climatic conditions will gradually increase the damage of this pathogen, because it is favored by elevated temperatures and additionally the host trees will be more susceptible due to related environmental stress. Diplodia tip blight is emerging towards Northern latitudes, thus, actions to monitor the spread of S. sapinea in pine-dominated forests should be undertaken in Finland. Our aim was to search for S. sapinea in Scots pine along a transect in Finland. Branch samples were collected from healthy Scots pine, fungal endophytes were isolated and morphologically identified. Sixteen S. sapinea strains were found from four Scots pine trees from two locations. This finding confirms that S. sapinea is found as an endophyte in healthy Scots pine in Finland.

  • Terhonen, Forest Pathology Research Group, Department of Forest Botany and Tree Physiology, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Büsgen-Institute, Büsgenweg 2, D-37077 Göttingen, Germany ORCID ID:E-mail: terhonen@uni-goettingen.de (email)
  • Babalola, Forest Pathology Research Group, Department of Forest Botany and Tree Physiology, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Büsgen-Institute, Büsgenweg 2, D-37077 Göttingen, Germany ORCID ID:E-mail: j.babalola@stud.uni-goettingen.de
  • Kasanen, Forest Pathology Lab, Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: risto.kasanen@helsinki.fi
  • Jalkanen, Rovaniemi Research Unit, Natural Resources Institute Finland (Luke), Eteläranta 55, FI-96300 Rovaniemi, Finland ORCID ID:E-mail: ristjal@gmail.com
  • Blumenstein, Forest Pathology Research Group, Department of Forest Botany and Tree Physiology, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Büsgen-Institute, Büsgenweg 2, D-37077 Göttingen, Germany ORCID ID:E-mail: kathrin.blumenstein@uni-goettingen.de
article id 10391, category Research article
Victoria A.M. Poljatschenko, Lauri T. Valsta. (2021). Carbon emissions displacement effect of Finnish mechanical wood products by dominant tree species in a set of wood use scenarios. Silva Fennica vol. 55 no. 1 article id 10391. https://doi.org/10.14214/sf.10391
Highlights: Wood product consumption patterns are combined with production-based displacement factors to estimate displacement factors for logs by tree species; The main tree species in Finland have somewhat unequal displacement factors; Historical and projected wood use scenarios show large variation in the levels of avoided emissions between individual years and scenarios.

The carbon emissions displacement effect of Finnish logs for mechanical wood products by dominant tree species (Scots pine, Pinus sylvestris L.; Norway spruce, Picea abies (L.) H. Karst.; Birch, Betula spp.) was assessed by combining information from previous studies of current consumption patterns with displacement factors (DF) for structural construction, non-structural construction, and energy usage. We did not conduct additional life cycle analyses compared to the current literature. Our aim was to identify the factors that most extensively influence the displacement effect and to estimate the overall climate effect of Finnish logs in light of current production levels of mechanical forest industry. The analyses were based on information from both statistics and proprietary sources. Contrary to previous studies, we provide DFs by main tree species in Finland, which has been an unidentified area of research to date. Additionally, we apply a more detailed classification of structural and non-structural wood products. This study did not include effects on the forest carbon sink, as they depend case-wise on forest resources and forest management. According to our results, with current production and consumption trends, the average displacement effects for domestic Scots pine, Norway spruce, and birch logs were 1.28, 1.16, and 1.43 Mg C/Mg C, respectively. The corresponding overall annual displacement effect caused by the current production of sawn wood and wood-based panels was 12.3 Tg CO2 for Finland for the BAU scenario and varied between 8.6 and 16.3 Tg CO2 depending on the wood use scenario.

  • Poljatschenko, Simosol Oy, Hämeenkatu 10, FI-11100 Riihimäki, Finland ORCID ID:E-mail: victoria.poljatschenko@simosol.fi (email)
  • Valsta, Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: lauri.valsta@helsinki.fi
article id 10371, category Research article
Katalin Waga, Jukka Malinen, Timo Tokola. (2021). Locally invariant analysis of forest road quality using two different pulse density airborne laser scanning datasets. Silva Fennica vol. 55 no. 1 article id 10371. https://doi.org/10.14214/sf.10371
Highlights: Airborne laser scanning is used to assess forest road quality; High-pulse data analysis classified roads with good performance; Two-step classification further improved the accuracy; A reference surface improved the classification results of the low pulse data; 66–75% of the roads were correctly classified using the reference surface.

Two different pulse density airborne laser scanning datasets were used to develop a quality assessment methodology to determine how airborne laser scanning derived variables with the use of reference surface can determine forest road quality. The concept of a reference DEM (Digital Elevation Model) was used to guarantee locally invariant topographic analysis of road roughness. Structural condition, surface wear and flatness were assessed at two test sites in Eastern Finland, calculating surface indices with and without the reference DEM. The high pulse density dataset (12 pulses m–2) gave better classification results (77% accuracy of the correctly classified road sections) than the low pulse density dataset (1 pulse m–2). The use of a reference DEM increased the precision of the road quality classification with the low pulse density dataset when the classification was performed in two-steps. Four interpolation techniques (Inverse Weighted Distance, Kriging, Natural Neighbour and Spline) were compared, and spline interpolation provided the best classification. The work shows that applying a spline reference DEM it is possible to identify 66% of the poor quality road sections and 78% of the good ones. Locating these roads is essential for road maintenance.

  • Waga, Faculty of Science and Forestry, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland ORCID ID: https://orcid.org/0000-0003-1496-7012 E-mail: katalin.waga@uef.fi (email)
  • Malinen, Faculty of Science and Forestry, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland; Metsäteho Ltd., Vernissakatu 1, FI-01300 Vantaa, Finland ORCID ID: https://orcid.org/0000-0002-5023-1056 E-mail: jukka.malinen@uef.fi
  • Tokola, Faculty of Science and Forestry, University of Eastern Finland, Yliopistokatu 7, FI-80100 Joensuu, Finland ORCID ID:E-mail: timo.tokola@uef.fi
article id 10360, category Research article
Mikko Kukkonen, Eetu Kotivuori, Matti Maltamo, Lauri Korhonen, Petteri Packalen. (2021). Volumes by tree species can be predicted using photogrammetric UAS data, Sentinel-2 images and prior field measurements. Silva Fennica vol. 55 no. 1 article id 10360. https://doi.org/10.14214/sf.10360
Highlights: A UAS-based species-specific forest inventory approach that avoids new field measurements is presented; Models were constructed using previously measured training plots and remotely sensed data; Bi-seasonal Sentinel-2 data were beneficial in the prediction of species-specific volumes; RMSE values associated with the prediction of volumes by tree species and total volume at the validation plot level were 33.4–62.6% and 9.0%, respectively.

Photogrammetric point clouds obtained with unmanned aircraft systems (UAS) have emerged as an alternative source of remotely sensed data for small area forest management inventories (FMI). Nonetheless, it is often overlooked that small area FMI require considerable field data in addition to UAS data, to support the modelling of forest attributes. In this study, we propose a method whereby tree volumes by species are predicted with photogrammetric UAS data and Sentinel-2 images, using models fitted with airborne laser scanning data. The study area is in a managed boreal forest area in Eastern Finland. First, we predicted total volume with UAS point cloud metrics using a prior regression model fitted in another area with ALS data. Tree species proportions were then predicted by k nearest neighbor (k-NN) imputation based on bi-seasonal Sentinel-2 images without measuring new field plot data. Species-specific volumes were then obtained by multiplying the total volume by species proportions. The relative root mean square error (RMSE) values for total and species-specific volume predictions at the validation plot level (30 m × 30 m) were 9.0%, and 33.4–62.6%, respectively. Our approach appears promising for species-specific small area FMI in Finland and in comparable forest conditions in which suitable field plots are available.

  • Kukkonen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: mikko.kukkonen@uef.fi (email)
  • Kotivuori, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: eetu.kotivuori@uef.fi
  • 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
  • Korhonen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: lauri.korhonen@uef.fi
  • Packalen, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: petteri.packalen@uef.fi

Category: Research note

article id 10491, category Research note
Atte Komonen, Ilkka Puumala, Gergely Várkonyi, Reijo Penttilä. (2021). Wood-decaying fungi in old-growth boreal forest fragments: extinctions and colonizations over 20 years. Silva Fennica vol. 55 no. 1 article id 10491. https://doi.org/10.14214/sf.10491
Highlights: Rare fungi can persist for decades in isolated old-growth forest fragments; The remaining old-growth forest fragments should be urgently protected, even if they are isolated from larger expanses of natural biotopes.

According to ecology theory, isolated habitat fragments cannot maintain populations of specialized species. Yet, empirical evidence based on monitoring of the same fragments over time is still limited. We studied the colonization–extinction dynamics of eight wood-decaying fungal species in 16 old-growth forest fragments (<14 ha) over a 20-year period (1997–2017). We observed 19 extinctions and 5 colonizations; yet, the distribution of extinctions and colonizations did not differ from the one expected by chance for any of the species. Twenty-six percent of the extinctions took place in two natural fragments amid large forest–peatland complexes. Phellinus nigrolimitatus (Romell) Bourdot and Galzin decreased and Phellinus ferrugineofuscus (P. Karst.) Bourdot increased in abundance (number of logs occupied). The volume of living spruce trees in the forest fragments correlated positively with the number of logs inhabited in five of the study species. Because fragment characteristics did not affect species turnover, it seems that stochastic processes governed colonizations and extinctions. Although the least abundant species in 1997 had declined, and the most abundant species had become more abundant, it appears that specialized wood-decaying fungi can persist for decades in isolated old-growth forest fragments, if suitable dead wood is continuously available.

  • Komonen, University of Jyväskylä, Department of Biological and Environmental Science, School of Resource Wisdom, P.O. Box 35, FI-40014 University of Jyväskylä, Finland ORCID ID:E-mail: atte.komonen@jyu.fi (email)
  • Puumala, University of Jyväskylä, Department of Biological and Environmental Science, School of Resource Wisdom, P.O. Box 35, FI-40014 University of Jyväskylä, Finland ORCID ID:E-mail: ilkka.puumala1@outlook.com
  • Várkonyi, Finnish Environment Institute, Friendship Park Research Centre, Lentiirantie 342 B, FI-88900 Kuhmo, Finland ORCID ID:E-mail: gergely.varkonyi@ymparisto.fi
  • Penttilä, Natural Resources Institute Finland, Natural resources, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID ID:E-mail: reijo.penttila@luke.fi

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