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Silva Fennica vol. 55 | 2021

Category: Editorial

article id 10604, category Editorial
Samuel F. Bartels. (2021). The deciduous confusion: it is time to get the contrast right. Silva Fennica vol. 55 no. 3 article id 10604. https://doi.org/10.14214/sf.10604
  • Bartels, Department of Ecosystem Science and Management, University of Norther British Columbia, 3333 University Way, Prince George, British Columbia, Canada V2N 4Z9 ORCID ID:E-mail: samuel.bartels@unbc.ca (email)
article id 10566, category Editorial
Henrik Heräjärvi. (2021). Science as a decision-support tool in forest policies. Silva Fennica vol. 55 no. 2 article id 10566. https://doi.org/10.14214/sf.10566
  • Heräjärvi, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: henrik.herajarvi@luke.fi (email)
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 10619, category Research article
Yrjö Nuutinen. (2021). Corrigendum: Comparing the characteristics of boom-corridor and selectively thinned stands of Scots pine and birch. Silva Fennica vol. 55 no. 4 article id 10619. https://doi.org/10.14214/sf.10619

Corrigendum

  • Nuutinen, Natural Resources Institute Finland (Luke), Production systems, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: yrjo.nuutinen@luke.fi (email)
article id 10580, category Research article
Tomi Kaakkurivaara, Nopparat Kaakkurivaara. (2021). Cost-efficiency and ergonomic study of two methods for planting Eucalyptus spp. seedlings in plantation forestry. Silva Fennica vol. 55 no. 4 article id 10580. https://doi.org/10.14214/sf.10580
Highlights: We present a first assessment of the planting stick method as used in Thailand for planting Eucalyptus spp. seedlings in plantations in terms of time, cost and ergonomic parameters; Parallel analysis shows that the planting tube method may be superior for planting Eucalyptus spp. seedlings

In Thailand and various other countries tree seedlings are generally planted using simple manual tools, often a ‘planting stick’, but the method requires time-consuming, labour-intensive teamwork. However, use of a ‘planting tube’ allows a single person to perform both the preparation and planting work. Thus, in a classical time study and ergonomic survey we compared the productivity, cost-effectiveness, and ergonomic impact of planting Eucalyptus spp. seedlings using the two tools at the same planting site in Western Thailand. The planting tube method proved to be more productive, more cost-efficient, and less burdensome than the planting stick method (with time and cost requirements of 21 s and €0.0061 per seedling, versus 16.6 s and €0.0463 per seedling, respectively). In conclusion, the planting tube method may be a viable alternative to reduce costs and increase productivity, while maintaining reasonable workloads for the workers, despite the higher purchase price of planting tubes.

  • Kaakkurivaara, Department of Forest Engineering, Faculty of Forestry, Kasetsart University, 50 Phahonyothin Rd, Lat Yao, Chatuchak, Bangkok 10900, Thailand ORCID ID:E-mail: tomi.kaakkurivaara@gmail.com (email)
  • Kaakkurivaara, Department of Forest Engineering, Faculty of Forestry, Kasetsart University, 50 Phahonyothin Rd, Lat Yao, Chatuchak, Bangkok 10900, Thailand ORCID ID:E-mail: ffornrm@ku.ac.th
article id 10539, category Research article
Jaakko Repola, Juha Heikkinen, Jari Lindblad. (2021). Pulpwood green density prediction models and sampling-based calibration. Silva Fennica vol. 55 no. 4 article id 10539. https://doi.org/10.14214/sf.10539
Highlights: The developed models provided a realistic description of the observed seasonal variation in pulpwood green density; The model predictions were more reliable than those obtained with current practices.

Pulpwood arriving at the mills is mainly measured by weighing. In the loading phase of forwarding and trucking, timber is weighed using scales mounted in the grapple loader. The measured weight of timber is converted into volume using a conversion factor defined as green density (kg m–3). At the mill, the green density factor is determined by sampling measurements, while in connection with weighing with grapple-mounted scales during transportation, fixed green density factors are used. In this study, we developed predictive regression models for the green density of pulpwood. The models were constructed separately by pulpwood assortments: pine (contains mainly Pinus sylvestris L); spruce (mainly Picea abies (L.) Karst.); decayed spruce; birch (mainly Betula pubescens Ehrh. and Betula pendula Roth); and aspen (mainly Populus tremula L.). Study material was composed of the sampling-based measurements at the mills between 2013–2019. The models were specified as linear mixed models with both fixed and random parameters. The fixed effect produced the expected value of green density as a function of delivery week, storage time, and meteorological conditions during storage. The random effects allowed the model calibration by utilizing the previous sampling weight measurements. The model validation showed that the model predictions faithfully reproduced the observed seasonal variation in green density. They were more reliable than those obtained with the current practices. Even the uncalibrated (fixed) predictions had lower relative root mean squared prediction errors than those obtained with the current practices.

  • Repola, Natural Resources Institute Finland (Luke), Natural resources, Ounasjoentie 6, 96200 Rovaniemi, Finland ORCID ID:E-mail: jaakko.repola@luke.fi (email)
  • Heikkinen, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail: juha.heikkinen@luke.fi
  • Lindblad, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, 00790 Helsinki, Finland ORCID ID:E-mail: jari.lindblad@luke.fi
article id 10528, category Research article
Jaana Luoranen, Heli Viiri. (2021). Comparison of the planting success and risks of pine weevil damage on mineral soil and drained peatland sites three years after planting. Silva Fennica vol. 55 no. 4 article id 10528. https://doi.org/10.14214/sf.10528
Highlights: The planting success was poorer on peatland sites than on mineral soil; Dense ground vegetation cover is more probable on peatland than on mineral soil; No differences in pine weevil feeding damage on mineral soil and peatland were found; Cultivated mineral soil reduced the vegetation cover, feeding damage and seedling mortality.

Over 20% of regeneration operations will be on drained peatland in the next decade in Finland. There are only a few studies comparing the planting success and the risk of pine weevil (Hylobius abetis (L.) feeding damage on mineral soil and drained peatland. Thirty sites planted with Norway spruce (Picea abies (L.) H. Karst.) container seedlings in 2009 in Southern and Central Finland were inventoried three growing seasons after planting. Prediction models for the probability of survival, pine weevil damage and the presence of ground vegetation cover were done separately for peatland and mineral soil sites. The planting success was 17% lower on peatland sites (1379 surviving seedlings ha–1) than on mineral soil (1654 seedlings ha–1). The factors explaining the survival were the ground vegetation cover and type of the planting spot on the peatland, and the ground vegetation cover on mineral soil. On mineral soil, 76% of the planting spots were on cultivated mineral soil while on peatland only 28% of the seedlings were planted on similar spots. There were also fewer seedlings that were surrounded by dense ground vegetation on mineral soil (4%) than on peatland (14%). Pine weevil feeding damage did not differ significantly on peatland (23%) or mineral soil (18%). The more time there was from clear-cutting, the more the probability of pine weevil feeding damage was reduced on both soil classes. Additionally, cover vegetation in the vicinity of the seedlings increased on mineral soil. Cultivated planting spots, especially those covered by mineral soil, prevented pine weevil feeding and reduced the harmful effects of vegetation on the seedlings both on mineral soil and peatland.

article id 10515, category Research article
Alwin A. Hardenbol, Anton Kuzmin, Lauri Korhonen, Pasi Korpelainen, Timo Kumpula, Matti Maltamo, Jari Kouki. (2021). Detection of aspen in conifer-dominated boreal forests with seasonal multispectral drone image point clouds. Silva Fennica vol. 55 no. 4 article id 10515. https://doi.org/10.14214/sf.10515
Highlights: Four boreal tree species (Scots pine, Norway spruce, birches and European aspen) classified with an overall accuracy of 95%; Presence of European aspen detected with excellent accuracy (UA: 97%, PA: 96%); Late spring is the best time for species classification by remote sensing; Best time to separate aspen from birch was when birch had leaves, but aspen did not.

Current remote sensing methods can provide detailed tree species classification in boreal forests. However, classification studies have so far focused on the dominant tree species, with few studies on less frequent but ecologically important species. We aimed to separate European aspen (Populus tremula L.), a biodiversity-supporting tree species, from the more common species in European boreal forests (Pinus sylvestris L., Picea abies [L.] Karst., Betula spp.). Using multispectral drone images collected on five dates throughout one thermal growing season (May–September), we tested the optimal season for the acquisition of mono-temporal data. These images were collected from a mature, unmanaged forest. After conversion into photogrammetric point clouds, we segmented crowns manually and automatically and classified the species by linear discriminant analysis. The highest overall classification accuracy (95%) for the four species as well as the highest classification accuracy for aspen specifically (user’s accuracy of 97% and a producer’s accuracy of 96%) were obtained at the beginning of the thermal growing season (13 May) by manual segmentation. On 13 May, aspen had no leaves yet, unlike birches. In contrast, the lowest classification accuracy was achieved on 27 September during the autumn senescence period. This is potentially caused by high intraspecific variation in aspen autumn coloration but may also be related to our date of acquisition. Our findings indicate that multispectral drone images collected in spring can be used to locate and classify less frequent tree species highly accurately. The temporal variation in leaf and canopy appearance can alter the detection accuracy considerably.

  • Hardenbol, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID: https://orcid.org/0000-0002-0615-505X E-mail: alwin.hardenbol@uef.fi (email)
  • Kuzmin, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland; University of Eastern Finland, Department of Geographical and Historical Studies, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: anton.kuzmin@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
  • Korpelainen, University of Eastern Finland, Department of Geographical and Historical Studies, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: pasi.korpelainen@uef.fi
  • Kumpula, University of Eastern Finland, Department of Geographical and Historical Studies, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: timo.kumpula@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
  • Kouki, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: jari.kouki@uef.fi
article id 10507, category Research article
Karri Uotila, Timo Saksa. (2021). Cost-efficient pre-commercial thinning: effects of method and season of early cleaning. Silva Fennica vol. 55 no. 4 article id 10507. https://doi.org/10.14214/sf.10507
Highlights: The first stage of multistage pre-commercial thinning, early cleaning, took 27–30% less time when carried out in the spring instead of the summer; The two stage pre-commercial thinning program was 11% less expensive to apply when early cleaning had been applied in the spring instead of the summer.

This study’s aim was to identify how the application season and the method of early cleaning (EC), the first stage of multistage pre-commercial thinning (PCT), affected the time consumption in EC and in the subsequent second PCT operation. The worktime in EC was recorded in the spring, summer, and autumn in 22 sites, which were either totally cleaned or point cleaned. Later, these sites were measured at the time of the second PCT. Time consumption was estimated in PCT, based on the removal of the sites. The time consumption in EC was 5.3 productive work hours (pwh) ha–1, 7.3 pwh ha–1, and 6.2 pwh ha–1 respectively in the spring, summer, and autumn. EC in the spring instead of the summer saved 27–30% of working time, depending on the cleaning method. Point cleaning was 0.8 pwh ha–1 quicker than total cleaning, but the difference was statistically insignificant. The second stage, PCT, was 1 pwh ha–1 slower to conduct in sites which had been early cleaned in the spring instead of the summer. However, at the entire management program level, EC applied in the spring or autumn instead of the summer saved 11% or 5% respectively of the total discounted costs (3% interest rate) of multistage pre-commercial thinning. Today, the commonest time to conduct EC is in the summer, which was the most expensive of the analyzed management alternatives here. We can expect savings in juvenile stand management in forestry throughout boreal conifer forests by rethinking the seasonal workforce allocation.

  • Uotila, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: karri.uotila@luke.fi (email)
  • Saksa, Natural Resources Institute Finland (Luke), Natural resources, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: timo.saksa@luke.fi
article id 10485, category Research article
Felicia Dahlgren Lidman, Emma Holmström, Tomas Lundmark, Nils Fahlvik. (2021). Management of spontaneously regenerated mixed stands of birch and Norway spruce in Sweden. Silva Fennica vol. 55 no. 4 article id 10485. https://doi.org/10.14214/sf.10485
Highlights: The absence of forest management does not always mean economic loss; With dense spontaneous regeneration of birch and Norway spruce, the first competition release can have a high impact on future stem development; Significantly different effects on stand volume production and diameter development of Norway spruce can be expected with different biomass harvest strategies.

Timber production and profitability were evaluated for spontaneously-regenerated mixtures on two formerly clearcut areas. The abandoned areas developed into birch-dominated (Betula pendula Roth and Betula pubescens Ehrh.) stands with successional ingrowth of Norway spruce (Picea abies (L.) H. Karst.). An experiment with randomized treatments within blocks was established, using three management strategies and one unthinned control, resulting in variation in optimal rotation age, merchantable volume and species composition. The management strategies were evaluated based on total production (volume) by using measured growth data 42 years after clearcutting and the modelled future stand development. The long-term effects of spontaneous regeneration and management strategies were evaluated based on land expectation value (LEV) and compared with a fifth management strategy using artificial regeneration and intense thinnings. 12 years after treatment, at a stand age of 42 years, the unthinned control had produced the highest total stem volume. At interest rates of 2% or higher, the unmanaged forest was an economically viable strategy, even compared to an intensive management strategy with a preferred merchantable timber species. Interest rates clearly impacted the profitability of the different management strategies. This study shows that when spontaneous regeneration is successful and dense, the first competition release can have a high impact on the development of future crop trees and on the species mixture.

article id 10441, category Research article
Dipak Mahatara, Amul K. Acharya, Bishnu P. Dhakal, Dipesh K. Sharma, Sunita Ulak, Prashant Paudel. (2021). Maxent modelling for habitat suitability of vulnerable tree Dalbergia latifolia in Nepal. Silva Fennica vol. 55 no. 4 article id 10441. https://doi.org/10.14214/sf.10441
Highlights: Dalbergia latifolia is a vulnerable species of Nepal with very few conservation priorities; Habitat suitability modelling for this species is essential to endorse different conservation interventions; 43 presence locations and different environmental variables were retained for model prediction in Maxent; Province 2 was found most suitable habitat for the growth of D. latifolia, with western most province as unsuitable.

Dalbergia latifolia Roxb., commonly known as rosewood, is one of the highly valuable tropical timber species of Nepal. The tree species was widely distributed in the past, however, over-exploitation of natural habitat, deforestation, forest conversion for agriculture, illegal logging and the invasion of alien species resulted in the classification of this species as vulnerable by the IUCN (International Union for Conservation of Nature) category. So, the prediction of habitat suitability and potential distribution of the species is required to develop restoration mechanisms and conservation interventions. In this study, we modelled the suitable habitat of D. latifolia over the entire possible range of Nepal using a Maxent model. We compiled 23 environmental variables (19 bioclimatic, 3 topographic and a vegetative layer), however, only 12 least correlated variables along with 43 spatially representative presence locations were retained for model prediction. We used a receiver operating characteristic (ROC) curve to assess the model’s performance and a Jackknife procedure to evaluate the relative importance of predictor variables. The model was statistically significant with an area under the curve (AUC) value of 0.969. The internal Jackknife test indicated that elevation was the most important variable for the model prediction with 71.3% contribution followed by mean temperature of driest quarter (9.8%). The most (>0.6) suitable habitat for the D. latifolia was 235 484 hectares with large sections of area in two provinces whereas, the western most provinces were not suitable for D. latifolia as per Maxent model. The information presented here can provide a framework for nature conservation planning, monitoring and habitat management of this rare and endangered species.

  • Mahatara, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: honeystar73@gmail.com (email)
  • Acharya, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: acharya.amulkumar@gmail.com
  • Dhakal, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: dhakalbp.shorea@gmail.com
  • Sharma, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: dipeshsharmadiyu2015@gmail.com
  • Ulak, Forest Research and Training Centre, Government of Nepal, P.O. Box 3339, Babarmahal, Kathmandu 44600, Nepal ORCID ID:E-mail: sunitaulak@gmail.com
  • Paudel, Agriculture Forestry University, P.O. Box 13712 Rampur, Chitwan, Nepal ORCID ID:E-mail: prashant.paudel88@gmail.com
article id 10244, category Research article
Hans Ole Ørka, Endre H. Hansen, Michele Dalponte, Terje Gobakken, Erik Næsset. (2021). Large-area inventory of species composition using airborne laser scanning and hyperspectral data. Silva Fennica vol. 55 no. 4 article id 10244. https://doi.org/10.14214/sf.10244
Highlights: A methodology for using hyperspectral data in the area-based approach is presented; Hyperspectral data produced satisfactory results for species composition in 90% of the cases; Parametric Dirichlet regression is an applicable method to predicting species proportions; Normalization and a tree-based selection of pixels provided the overall best results; Both visible to near-infrared and shortwave-infrared sensors gave acceptable results.

Tree species composition is an essential attribute in stand-level forest management inventories and remotely sensed data might be useful for its estimation. Previous studies on this topic have had several operational drawbacks, e.g., performance studied at a small scale and at a single tree-level with large fieldwork costs. The current study presents the results from a large-area inventory providing species composition following an operational area-based approach. The study utilizes a combination of airborne laser scanning and hyperspectral data and 97 field sample plots of 250 m2 collected over 350 km2 of productive forest in Norway. The results show that, with the availability of hyperspectral data, species-specific volume proportions can be provided in operational forest management inventories with acceptable results in 90% of the cases at the plot level. Dominant species were classified with an overall accuracy of 91% and a kappa-value of 0.73. Species-specific volumes were estimated with relative root mean square differences of 34%, 87%, and 102% for Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and deciduous species, respectively. A novel tree-based approach for selecting pixels improved the results compared to a traditional approach based on the normalized difference vegetation index.

  • Ørka, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID: https://orcid.org/0000-0002-7492-8608 E-mail: hans-ole.orka@nmbu.no (email)
  • Hansen, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway; Norwegian Forest Extension Institute, Honnevegen 60, NO-2836 Biri, Norway ORCID ID: https://orcid.org/0000-0001-5174-4497 E-mail: eh@skogkurs.no
  • Dalponte, Department of Sustainable Agro-ecosystems and Bioresources, Research and Innovation Centre, Fondazione E. Mach, Via E. Mach 1, 38010 San Michele all’Adige, TN, Italy ORCID ID: https://orcid.org/0000-0001-9850-8985 E-mail: michele.dalponte@fmach.it
  • Gobakken, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID: https://orcid.org/0000-0001-5534-049X E-mail: terje.gobakken@nmbu.no
  • Næsset, Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: erik.naesset@nmbu.no
article id 10555, category Research article
Ferréol Berendt, Felix Wolfgramm, Tobias Cremer. (2021). Reliability of photo-optical measurements of log stack gross volume. Silva Fennica vol. 55 no. 3 article id 10555. https://doi.org/10.14214/sf.10555
Highlights: Gross volume estimations of larger log stacks showed a smaller deviation compared to those of piles with smaller volumes; Log stack quality affects estimation accuracy; The deviations between the manual section-wise estimations were of similar amplitude as those for the photo-optical estimations.

In terms of assessing economic impact, one of the most important elements in the wood supply chain is the measurement of round wood. Besides the one-by-one measurement of logs, logs are often measured when stacked at the forest road. The gross stacked volume includes the volume of the wood, bark and airspace and is widely used for industrial wood assortments. The increasing international attention given to photo-optical measurement systems for portable devices is due to their simplicity of use and efficiency. The aim of this study was to compare the gross volumes of hardwood log stacks measured using one widespread photo-optical app with two manual section-wise volume estimations of log stacks based on the German framework agreement for timber trade (RVR). The manual volume estimations were done starting from the left (RVRleft) and right (RVRright) sides of the log stacks. The results showed an average deviation of the photo-optical gross volume estimation in comparison to the manual estimation of –2.09% (RVRleft) and –3.66% (RVRright) while the deviation between RVRleft and RVRright was +2.54%. However, the log stack gross volume had a highly significant effect on the deviation and better accuracy with smaller deviation were reached for larger log stacks. Moreover, results indicated that the gross volume estimations of higher quality log stacks were closer for the three analyzed methods compared to estimations of poor-quality log stacks.

  • Berendt, Department of Forest Utilization and Timber Markets, Eberswalde University for Sustainable Development, 16225 Eberswalde, Germany ORCID ID: https://orcid.org/0000-0002-6285-7590 E-mail: ferreol.berendt@hnee.de (email)
  • Wolfgramm, Landesforst MV Anstalt des öffentlichen Rechts, Forstamt Billenhagen, 18182 Blankenhagen, Germany ORCID ID:E-mail: felixwolfgramm@yahoo.de
  • Cremer, Department of Forest Utilization and Timber Markets, Eberswalde University for Sustainable Development, 16225 Eberswalde, Germany ORCID ID:E-mail: tobias.cremer@hnee.de
article id 10545, category Research article
Karol Tomczak, Tomczak Arkadiusz, Bartłomiej Naskrent, Tomasz Jelonek. (2021). The radial gradient of moisture content of silver birch wood in different seasons. Silva Fennica vol. 55 no. 3 article id 10545. https://doi.org/10.14214/sf.10545
Highlights: Seasonal variation in moisture content is significant, the greatest moisture content of wood was recorded in winter, and the lowest in summer; The greatest moisture content on cross-section was observed near to the pith, and lower values near to the bark; From environmental perspective results of this study may have an impact for log transport planning, weight-scaling systems, lumber drying.

Silver birch (Betula pendula Roth) is classified in diffuse-porous wood category. In this case structure of wood tissue is quite similar across whole cross-sectional area. The aim of this study was to analyse cross-section variability of moisture content (MC) of growing silver birch wood, significant hardwood species in Polish forests. Investigations were performed on 120 model trees. In the trunk of each model tree, an increment core was collected at breast height. Samples were collected of 30 different trees in four different seasons. The greatest MC was observed during winter, lowest MC in summer. Differences in MC were statistically significant only between winter versus spring, summer, and autumn. Distribution of MC on cross-section was similar in each season. The greatest average value was observed close to pith, then it was decreasing in bark direction. The greatest difference between observed in spring – 19.51% (p < 0.05) and lowest in autumn – 4.66%. Distribution of green density (GD) on cross section was inverse proportional to MC value. Variations in GD and MC are relevant for log transport planning, weight-scaling systems, lumber drying and dynamic assessment of stiffness. Therefore, from an environmental loss perspective, it is important to determine changes in MC and GD across the year.

  • Tomczak, Department of Forest Utilization, Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, Wojska Polskiego 71A, 60-625 Poznań, Poland ORCID ID: https://orcid.org/0000-0001-5192-0294 E-mail: karol.tomczak@up.poznan.pl (email)
  • Arkadiusz, Department of Forest Utilization, Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, Wojska Polskiego 71A, 60-625 Poznań, Poland ORCID ID: https://orcid.org/0000-0003-1140-8282 E-mail: arkadiusz.tomczak@up.poznan.pl
  • Naskrent, Department of Forest Utilization, Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, Wojska Polskiego 71A, 60-625 Poznań, Poland ORCID ID: https://orcid.org/0000-0002-0756-4162 E-mail: bartlomiej.naskrent@up.poznan.pl
  • Jelonek, Department of Forest Utilization, Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, Wojska Polskiego 71A, 60-625 Poznań, Poland ORCID ID: https://orcid.org/0000-0001-9558-9951 E-mail: tomasz.jelonek@up.poznan.pl
article id 10509, category Research article
Chuan Xie, Tianfeng Liu, Song Guo, Jian Peng, Zailiu Li. (2021). Effects of ultra-dry storage on seed germination and seedling growth of Handeliondendron bodinieri. Silva Fennica vol. 55 no. 3 article id 10509. https://doi.org/10.14214/sf.10509
Highlights: By reducing the moisture content of the seeds, Handeliodendron bodinieri seeds showed a strong tolerance; PEG played a protective role in the process of re-wetting ultra-dry seeds; Ultra-dry storage could promote Handeliodendron bodinieri seedling growth and root development.

Handeliodendron bodinieri (H. Lév.) Rehder is a rare, endangered, and therefore, protected tree species native to China. However, there are serious limitations to the effective protection of the species, including a low seed germination-rate and difficult storage due to a high seed oil-content. Here, we evaluated the feasibility of ultra-dry seed storage and its effects on seedling growth. We used the silica gel method to prepare ultra-dry seeds with different moisture contents to find an optimal moisture content range (2.54%–4.77%). Ultra-dry treatment improved storability of H. bodinieri seeds. Furthermore, seeds with a moisture content of 4.77% stored at room temperature, and seeds with a moisture content of 3.97% stored at 4 °C yielded the best results. Priming with an appropriate concentration of polyethylene glycol had a certain repairing effect on ultra-dry stored seeds and improved seed vigor, with a two-day priming treatment with 20% polyethylene glycol having the best effect. Finally, compared with sand storage at 4 °C, ultra-dry storage promoted seedling growth and root development; furthermore, it alleviated storage damage to H. bodinieri seeds, promoted soluble sugar and soluble protein accumulation, and increased seedling nitrogen, phosphorus, and potassium uptake. Therefore, ultra-dry storage can be effectively used to preserve H. bodinieri seeds. Specifically, low-temperature storage of ultra-dry seeds with a moisture content of 3.97% enhanced H. bodinieri seed vigor, and seedling growth and development.

  • Xie, Forestry College, Guangxi University, Daxue E Rd., Xiangtang District, Nanning 530004, Guangxi, China; Huanggang forestry research institute, Huanggang 438000, Hubei, China ORCID ID:E-mail: sherman99c@163.com
  • Liu, Forestry College, Guangxi University, Daxue E Rd., Xiangtang District, Nanning 530004, Guangxi, China ORCID ID:E-mail: ltfltfll@163.com
  • Guo, Forestry College, Guangxi University, Daxue E Rd., Xiangtang District, Nanning 530004, Guangxi, China ORCID ID:E-mail: guosong@gxu.edu.cn
  • Peng, Sanmengjiang forest farm of Guangxi, Liuzhou 545001, Guangxi, China ORCID ID:E-mail: pj75481425@126.com
  • Li, Forestry College, Guangxi University, Daxue E Rd., Xiangtang District, Nanning 530004, Guangxi, China ORCID ID:E-mail: lizailiu666@163.com (email)
article id 10506, category Research article
Mikko Tikkinen, Terhi Latvala, Tuija Aronen. (2021). Interest in vegetatively propagated Norway spruce materials – a survey among Finnish forest owners and professionals. Silva Fennica vol. 55 no. 3 article id 10506. https://doi.org/10.14214/sf.10506
Highlights: Survey among forest owners and professionals’ perceptions towards tree breeding and vegetative propagation yielded over 3000 responses; Most valued features in reforestation material were: improved resilience in changing climate, improved pest and pathogen resistance, and securing the species’ gene pool; Majority of respondents accepted reforestation with vegetatively propagated material to some extent; Willingness to pay for improved features was indicated.

Forests and forestry will encounter several changes of unknown magnitude within the coming decades. In the Nordic, long rotations complicate any anticipation to the upcoming changes. Tree breeding can contribute to coping with these changes. The time span of implementing breeding results in practice may be shortened through vegetative propagation. Introducing vegetative propagation to forest regeneration may phase several challenges before adopted by the industry, some of which are related to perceptions about new technology. Firstly, private forest owners are in a key role in implementing the technology in practice; although they do not represent the overall public, they are the decision makers in their own estates regarding forestry and forest regeneration. Secondly, the professionals related to the production of forest regeneration material and plants from forest species are in a key role when it comes to practically introducing the new technology to the forest owners. In this survey, perceptions of forest owners and professionals towards tree breeding and vegetative propagation were investigated. Additionally, the respondents were asked which traits they considered important to be improved by breeding, and their willingness to pay for these improved traits. The respondents valued the most: improved pest and pathogen resistance, improved resilience of forest in changing climate, and securing the species’ gene pool. Responses indicated that forest owners would be willing to pay more for the improved traits in forest regeneration material. The current novel study provides a foundation to concern public awareness regarding tree breeding and vegetative propagation in the future.

  • Tikkinen, Natural Resources Institute Finland ORCID ID: https://orcid.org/0000-0002-2368-8042 E-mail: mikko.tikkinen@luke.fi (email)
  • Latvala, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, FI-00790 Helsinki, Finland ORCID ID:E-mail: terhi.latvala@luke.fi
  • Aronen, Natural Resources Institute Finland (Luke), Production systems, Vipusenkuja 5, FI-57200 Savonlinna, Finland ORCID ID:E-mail: tuija.aronen@luke.fi
article id 10494, category Research article
Hannu Hökkä, Ari Laurén, Leena Stenberg, Samuli Launiainen, Kersti Leppä, Mika Nieminen. (2021). Defining guidelines for ditch depth in drained Scots pine dominated peatland forests. Silva Fennica vol. 55 no. 3 article id 10494. https://doi.org/10.14214/sf.10494
Highlights: Process-based hydrological model was applied to drained peatland forests representing a wide range of conditions in Finland; Ditch depth keeping the median July–August water table below 0.35 m was defined; Ditch depth depended on climatic conditions, stand volume, peat properties, and ditch spacing; Shallower ditches than recommended in practice proved to be sufficient in most situations.

We used a process-based hydrological model SUSI to improve guidelines for ditch network maintenance (DNM) operations on drained peatland forests. SUSI takes daily weather data, ditch depth, strip width, peat properties, and forest stand characteristics as input and calculates daily water table depth (WTD) at different distances from ditch. The study focuses on Scots pine (Pinus sylvestris L.) dominated stands which are the most common subjects of DNM. Based on a literature survey, and consideration of the tradeoffs between forest growth and detrimental environmental impacts, long term median July–August WTD of 0.35 m was chosen as a target WTD. The results showed that ditch depths required to reach such WTD depends strongly on climatic locations, stand volume, ditch spacing, and peat thickness and type. In typical ditch cleaning areas in Finland with parallel ditches placed about 40 m apart and tree stand volumes exceeding 45 m3 ha–1, 0.3–0.8 m deep ditches were generally sufficient to lower WTD to the targeted depth of 0.35 m. These are significantly shallower ditch depths than generally recommended in operational forestry. The main collector ditch should be naturally somewhat deeper to permit water outflow. Our study brings a firmer basis on environmentally sound forestry on drained peatlands.

  • Hökkä, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland ORCID ID:E-mail: hannu.hokka@luke.fi (email)
  • Laurén, 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: ari.lauren@uef.fi
  • Stenberg, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland ORCID ID:E-mail: leena.stenberg@luke.fi
  • Launiainen, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland ORCID ID:E-mail: samuli.launiainen@luke.fi
  • Leppä, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland ORCID ID:E-mail: kersti.leppa@luke.fi
  • Nieminen, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00791 Helsinki, Finland ORCID ID:E-mail: mika.nieminen@luke.fi
article id 10468, category Research article
Arto Haara, Juho Matala, Markus Melin, Janne Miettinen, Kari T. Korhonen, Tuula Packalen, Jari Varjo. (2021). Economic effects of grouse-friendly forest management. Silva Fennica vol. 55 no. 3 article id 10468. https://doi.org/10.14214/sf.10468
Highlights: The economic effects of grouse friendly forest management were evaluated by simulating alternative forest management approaches on four large forest holdings in different parts of Finland; The grouse-friendly management of forest holdings was possible with minor effects on the economics in most cases: only in one case was the reduction of NPV more than 5% during a 30-year simulation period; The interest rates had an impact on the differences between the economic effects of the forest management approaches.

Traditional timber production may have negative effects on other ecosystem services. Therefore, new forest management guidelines have been developed in order to enhance a habitat suitable for wildlife. In Finland, a recent example of this is grouse-friendly forest management (GFFM) which emphasises the preservation of grouse species (Tetronidae) habitats. This study aimed to analyse the economic effects of these guidelines. An analysis was made on how the application of GFFM affected the Net Present Value (NPV) in a 30-year simulation of forest management of four large forest holdings located from south to north in Finland. In the simulations, traditional forest management practices were compared to two levels of GFFM. Five levels of interest rate were used, namely 1, 2, 3, 4, and 5%. In most of the simulations, the NPV was reduced by about 1% or less due to the application of GFFM in comparison to the traditional reference forest management. Only in one case with more intensive GFFM, was the reduction of NPV more than 5%. The interest rates had an impact on the differences between the management approaches. For example, a low interest rate resulted in a higher thinning intensity in GFFM in comparison to traditional forest management, which lead to a higher NPV in GFFM. To sum up, it seems that it would be possible to manage forest holdings in a grouse-friendly manner with minor effects on the economics.

  • Haara, LUKE ORCID ID: https://orcid.org/0000-0002-6895-5300 E-mail: arto.haara@luke.fi (email)
  • Matala, Natural Resources Institute Finland, (Luke), Natural resources, Yliopistokatu 6B, FI-80100 Joensuu, Finland ORCID ID:E-mail: juho.matala@luke.fi
  • Melin, Natural Resources Institute Finland, (Luke), Bioeconomy and environment, Yli opistokatu 6B, FI-80100 Joensuu, Finland ORCID ID:E-mail: markus.melin@luke.fi
  • Miettinen, Finnish Wildlife Agency, Ratatie 41, FI-91501 Muhos, Finland ORCID ID:E-mail: janne.miettinen@riista.fi
  • Korhonen, Natural Resources Institute Finland, (Luke), Bioeconomy and environment, Yli opistokatu 6B, FI-80100 Joensuu, Finland ORCID ID:E-mail: kari.t.korhonen@luke.fi
  • Packalen, Ministry of Agriculture and Forestry, P.O. Box 30, FI-00023 GOVERNMENT, Finland ORCID ID:E-mail: tuula.packalen@mmm.fi
  • Varjo, Finnish Wildlife Agency, Sompiontie 1, FI-00730 Helsinki, Finland ORCID ID:E-mail: jari.varjo@riista.fi
article id 10462, category Research article
Yrjö Nuutinen, Jari Miina, Timo Saksa, Dan Bergström, Johanna Routa. (2021). Comparing the characteristics of boom-corridor and selectively thinned stands of Scots pine and birch. Silva Fennica vol. 55 no. 3 article id 10462. https://doi.org/10.14214/sf.10462
Highlights: After boom-corridor thinning (BCT), the number of stems per hectare was higher than that after selective thinning. The number of future crop trees was at the same level; The removal of the simulated intermediate thinnings and clearcutting in BCT treatments was 10–18% higher than in selective thinning. The saw log volumes were at the same level in both treatments.

Young, dense forest in Finland and Sweden urgently need to receive first thinning. In such stands, conventional selective thinning methods make the harvester work time consuming and, thus, costly. To make small-sized trees economically competitive as raw material for bioenergy and biorefining, new harvesting technologies and/or thinning methods need to be developed. A potential solution is boom-corridor thinning (BCT), rendering effective cutting work. The aim of this study was to describe and compare the stand structure of two Scots pine stands (Pinus sylvestris L.) and one birch-dominated (Betula pendula Roth with natural downy birch, B. pubescens Ehrh.) stand after BCT and selective thinning at the first thinning phase. Furthermore, simulations were conducted to predict the future stand development after the first thinning treatments. The density of the growing stock was 16–46% higher after BCT treatment than after selective thinning because BCT stands included more small and supressed trees with a dbh < 100 mm. However, the numbers of future crop trees with a dbh > 140 mm per hectare were at the same level in both treatments. The stem volume removal per hectare did not differ between treatments. However, simulation of stand development and intermediate thinning and clearcutting revealed that the total removal volume was 10–18% higher in BCT stands compared to selectively thinned ones. The saw log volumes harvested did, however, not differ between treatments. This study shows that BCT generates stands with higher biodiversity compared to conventional thinning as higher levels of biomass removal can be reached throughout stand rotations.

  • Nuutinen, Natural Resources Institute Finland (Luke), Production systems, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: yrjo.nuutinen@luke.fi (email)
  • Miina, Natural Resources Institute Finland (Luke), Natural resources, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: jari.miina@luke.fi
  • Saksa, Natural Resources Institute Finland (Luke), Natural resources, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: timo.saksa@luke.fi
  • Bergström, Swedish University of Agricultural Sciences (SLU), Dept of Forest Biomaterials and Technology, Section of Forest Operations, SE-90183 Umeå, Sweden ORCID ID:E-mail: dan.bergstrom@slu.se
  • Routa, Natural Resources Institute Finland (Luke), Production systems, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: johanna.routa@luke.fi
article id 10503, category Research article
Katja Lähtinen, Liina Häyrinen, Anders Roos, Anne Toppinen, Francisco X. Aguilar Cabezas, Bo J. Thorsen, Teppo Hujala, Anders Q. Nyrud, Hans F. Hoen. (2021). Consumer housing values and prejudices against living in wooden homes in the Nordic region. Silva Fennica vol. 55 no. 2 article id 10503. https://doi.org/10.14214/sf.10503
Highlights: Consumers in the Nordic region are similar in their housing value expectations and prejudices against building with wood; Physical properties of houses seem to be less important as constituents of housing value for the consumers compared to intangible factors related to lifestyles and milieus; Urban consumers are the most prejudiced against wood building, and thus supply of homes meeting their value expectations is of a critical importance for sustainable urbanization.

So far, consumer housing values have not been addressed as factors affecting the market diffusion potential of multi-storey wood building (MSWB). To fill the void, this study addresses different types of consumer housing values in Denmark, Finland, Norway, and Sweden (i.e., Nordic region), and whether they affect the likelihood of prejudices against building with wood in the housing markets. The data collected in 2018 from 2191 consumers in the Nordic region were analyzed with exploratory factor analysis and logistic binary regression analysis. According to the results, consumers’ perceptions on ecological sustainability, material usage and urban lifestyle were similar in all countries, while country-specific differences were detected for perceptions on aesthetics and natural milieus. In all countries, appreciating urban lifestyle and living in attractive neighborhoods with good reputation increased the likelihood of prejudices against wood building, while appreciation of aesthetics and natural milieus decreased the likelihood of prejudices. In strengthening the demand for MSWB and sustainable urbanization through actions in businesses (e.g., branding) and via public policy support (e.g., land zoning), few messages derive from the results. In all, abreast with the already existing knowledge on the supply side factors (e.g., wood building innovations), more customized information is needed on the consumer-driven issues affecting the demand potential of MSWB in the housing markets. This would enable, e.g., both enhancing the supply of wooden homes for consumers appreciating urban lifestyle and neighborhoods and fortifying positive image of wood among consumers especially appreciating good architecture and pleasant environmental milieus.

  • Lähtinen, Vaasan yliopisto/Seinäjoen yliopistokeskus ORCID ID:E-mail: katja.lahtinen@luke.fi (email)
  • Häyrinen, Natural Resources Institute Finland (Luke), Bioeconomy and Environment Unit, P.O. Box 2, FI-00790 Helsinki, Finland ORCID ID:E-mail: liina.hayrinen@luke.fi
  • Roos, Sveriges lantbruksuniversitet (SLU), Department of Forest Economics, Box 7060, SE-750 07 Uppsala, Sweden ORCID ID:E-mail: anders.roos@slu.se
  • Toppinen, University of Helsinki, Department of Forest Sciences/Helsinki Institute of Sustainability Science (HELSUS), P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: anne.toppinen@helsinki.fi
  • Aguilar Cabezas, Sveriges lantbruksuniversitet (SLU), Department of Forest Economics, SE-901 83 Umeå, Sweden ORCID ID:E-mail: francisco.aguilar@slu.se
  • Thorsen, University of Copenhagen, Department of Food and Resource Economics, Rolighedsvej 23, DK-1958 Frederiksberg C, DenmarkBo Jellesmark Thorsen ORCID ID:E-mail: bjt@ifro.ku.dk
  • Hujala, University of Eastern Finland (UEF), Faculty of Science and Forestry, School of Forest Sciences, P.O. Box 111, 80101 FI-Joensuu, Finland ORCID ID:E-mail: teppo.hujala@uef.fi
  • Nyrud, Norwegian University of Life Sciences (NMBU), Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: anders.qvale.nyrud@nmbu.no
  • Hoen, Norwegian University of Life Sciences (NMBU), Faculty of Environmental Sciences and Natural Resource Management, P.O. Box 5003, NO-1432 Ås, Norway ORCID ID:E-mail: hans.hoen@nmbu.no
article id 10496, category Research article
Jouni Siipilehto, Harri Mäkinen, Kjell Andreassen, Mikko Peltoniemi. (2021). Models for integrating and identifying the effect of senescence on individual tree survival probability for Norway spruce. Silva Fennica vol. 55 no. 2 article id 10496. https://doi.org/10.14214/sf.10496
Highlights: The effect of senescence was integrated into an individual tree survival model; The best model showed good fit for managed, unmanaged and old-growth stands; The probability for a large tree to survive decreased with increasing stand age; The best performed model included an interaction term between stem diameter and stand age and also stand age as a separate independent variable.

Ageing and competition reduce trees’ ability to capture resources, which predisposes them to death. In this study, the effect of senescence on the survival probability of Norway spruce (Picea abies (L.) Karst.) was analysed by fitting alternative survival probability models. Different model formulations were compared in the dataset, which comprised managed and unmanaged plots in long-term forest experiments in Finland and Norway, as well as old-growth stands in Finland. Stand total age ranged from 19 to 290 years. Two models were formulated without an age variable, such that the negative coefficient for the squared stem diameter described a decreasing survival probability for the largest trees. One of the models included stand age as a separate independent variable, and three models included an interaction term between stem diameter and stand age. According to the model including stand age and its interaction with stem diameter, the survival probability curves could intersect each other in stands with a similar structure but a different mean age. Models that did not include stand age underestimated the survival rate of the largest trees in the managed stands and overestimated their survival rate in the old-growth stands. Models that included stand age produced more plausible predictions, especially for the largest trees. The results supported the hypothesis that the stand age and senescence of trees decreases the survival probability of trees, and that the ageing effect improves survival probability models for Norway spruce.

  • Siipilehto, Natural Resources Institute Finland (Luke), Natural resources, Latokartanonkaari 9, P.O. Box 2, FI-00790 Helsinki, Finland ORCID ID:E-mail: jouni.siipilehto@luke.fi (email)
  • Mäkinen, Natural Resources Institute Finland (Luke), Production systems, Latokartanonkaari 9, P.O. Box 2, FI-00790 Helsinki, Finland ORCID ID: https://orcid.org/0000-0002-1820-6264 E-mail: harri.makinen@luke.fi
  • Andreassen, Norwegian Institute of Bioeconomy Research (NIBIO), NO-1431 Ås, Norway ORCID ID:E-mail: kjellandreassen@gmail.com
  • Peltoniemi, Natural Resources Institute Finland (Luke), Bioeconomy and environment, Latokartanonkaari 9, P.O. Box 2, FI-00790 Helsinki, Finland ORCID ID: https://orcid.org/0000-0003-2028-6969 E-mail: mikko.peltoniemi@luke.fi
article id 10483, category Research article
Māra Kitenberga, Guntars Šņepsts, Jānis Vuguls, Didzis Elferts, Ieva Jaunslaviete, Āris Jansons. (2021). Tree- and stand-scale factors shape the probability of wind damage to birch in hemiboreal forests. Silva Fennica vol. 55 no. 2 article id 10483. https://doi.org/10.14214/sf.10483
Highlights: Prior stem and root damage significantly increased the probability of birch being wind-damaged; Trees with a high slenderness ratio had a lower relative snapping height; The snapping height was significantly negatively affected by the prior stem and root damage.

Strong wind is the major natural disturbance in European forests, that periodically causes tremendous damages to forestry. Yet, factors that affect the probability of wind damage for birch (Betula pendula Roth and B. pubescens Ehrh.), the most common deciduous tree species in hemiboreal forests, are studied scarcely. This study aimed to assess the effects of several tree- and stand-scale variables on the probability of wind damage to birch using data from the Latvian National Forest Inventory (2004–2018), and determine individual tree characteristics that affect the height of the stem breakage. The data analysis was done using the Bayesian binary logistic generalized linear mixed-effects model and a linear mixed-effects model. The probability of wind damage significantly increased by stand age, basal area, and slenderness ratio. Trees with prior damage had a significantly higher probability (odds ratio 4.32) for wind damage. For wind-damaged trees, the snapping height was significantly decreased by an increase in the slenderness ratio (p = 0.03) and prior damage (p = 0.003). Previously damaged trees were more frequently (73%) snapped in the lowest 40% of tree height than trees without prior damage (54%). The probability of wind damage is largely set by factors related to the selection of site, species composition, and rotation. The damage probability could be decreased by management measures that lower competition within the stand with particular regard to preserving intact remaining trees during these manipulations. Factors that reduce the probability of the damage simultaneously increase the snapping height, emphasizing their relevance for mitigation of the wind damages.

  • Kitenberga, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia ORCID ID: https://orcid.org/0000-0002-6192-988X E-mail: mara.kitenberga@silava.lv
  • Šņepsts, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia ORCID ID:E-mail: guntars.snepsts@silava.lv
  • Vuguls, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia ORCID ID:E-mail: janis.vuguls@silava.lv
  • Elferts, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia; Faculty of Biology, University of Latvia, Jelgavas Street 1, LV–1004, Rīga, Latvia ORCID ID: https://orcid.org/0000-0002-9401-1231 E-mail: didzis.elferts@lu.lv
  • Jaunslaviete, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia ORCID ID:E-mail: ieva.jaunslaviete@silava.lv
  • Jansons, Latvian State Forest Research Institute ‘Silava’, Rigas Street 111, LV–2169, Salaspils, Latvia ORCID ID: https://orcid.org/0000-0001-7981-4346 E-mail: aris.jansons@silava.lv (email)
article id 10447, category Research article
Marian Schönauer, Stephan Hoffmann, Martin Nolte, Dirk Jaeger. (2021). Evaluation of a new pruning and tending system for young stands of Douglas fir. Silva Fennica vol. 55 no. 2 article id 10447. https://doi.org/10.14214/sf.10447
Highlights: Electric pruning shears combined with workflow re-organization reduced time demand for pruning; Thinning by chainsaw was more productive than using the clearing saw Husqvarna 535FBX, which on the other hand showed lower physical workload; Overall cost savings through the use of the new system were quantified at 6%.

In Germany, management restrictions for Norway spruce (Picea abies (L.) H. Karst.) due to climate change lead to increasing interest in Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) as a potential substituting species. However, Douglas fir requires cost-intensive silvicultural treatments, such as periodic thinnings and, in particular, pruning. In order to improve the efficiency of such treatments, a new tending system with an adapted two-step work system was analyzed. The new system, using electric pruning shears and the backpack clearing saw Husqvarna 535FBX ‘Spacer’, was compared to the conventional three-step work system, using handsaw and chainsaw and characterized by tree selection previously conducted as an independent work step. Time and motion studies to determine productivity and costs, as well as ergonomic analysis through heart rate measurements and posture analysis were conducted. Overall, the new system was found to be more productive and to have lower costs, with 8.9 trees per scheduled system hour (4.17 € tree–1), compared to the conventional system with 8.1 trees per scheduled system hour (4.44 € tree–1). Ergonomic improvements with the new system could be mainly observed during the felling of competing trees, when the level of heart rate reserve was reduced by 9.3 percent points, compared to the conventional system. However, significant advantages in reducing unfavorable body postures expected for the ‘Spacer’ could not be confirmed. Since time savings within the new system were mainly attributed to the adaptation of workflow and the use of the electric shears during pruning, it should be considered to replace the ‘Spacer’ within the new system by light chainsaws for best results under the conditions investigated.

  • Schönauer, Department of Forest Work Science and Engineering, University of Göttingen, Göttingen/Germany ORCID ID:E-mail: marian.schoenauer@uni-goettingen.de (email)
  • Hoffmann, Department of Forest Work Science and Engineering, University of Göttingen, Göttingen/Germany; School of Forestry, University of Canterbury, Christchurch/New Zealand ORCID ID: https://orcid.org/0000-0002-8077-967X E-mail: stephan.hoffmann@uni-goettingen.de
  • Nolte, Forest Education Center FBZ / State Enterprise Forestry and Timber NRW, Arnsberg/Germany ORCID ID:E-mail: Martin.Nolte@wald-und-holz.nrw.de
  • Jaeger, Department of Forest Work Science and Engineering, University of Göttingen, Göttingen/Germany ORCID ID:E-mail: dirk.jaeger@uni-goettingen.de
article id 10446, category Research article
Juha Kaitera, Tuomas Kauppila, Jarkko Hantula. (2021). Assessment of the potential of Norway-spruce-seed-orchard associated plants to serve as alternate hosts of Thekopsora areolata. Silva Fennica vol. 55 no. 2 article id 10446. https://doi.org/10.14214/sf.10446
Highlights: Prunus is the only alternate host of cherry-spruce rust identified in this study; Cherry-spruce rust does not infect plants that belong to common ground vegetation flora in Finnish Norway spruce seed orchards; Spores from different Finnish cherry-spruce rust populations are similarly pathogenic on Prunus; Disease control should be focused only on Prunus in seed orchards.

The alternate host range of cherry-spruce rust is poorly studied although such information could be important in protecting spruce seed orchards from infections. Pathogenicity of cherry-spruce rust, Thekopsora areolata (Fr.) Magnus, was investigated on potential alternate host species in a greenhouse and in a laboratory in Finland. Five common species of Ericaceae, Vaccinium myrtillus L., V. uliginosum L., V. vitis-idaea L., Empetrum nigrum L. and Arctostaphylos uva-ursi (L.) Spreng, were inoculated in the greenhouse using aeciospores from seven Norway spruce [Picea abies (L.) H. Karst.] seed orchards suffering from T. areolata in 2018. In addition, young detached leaves of Vaccinium spp. and 17 other plant species of ground vegetation from eight Norway spruce seed orchards were inoculated with aeciospores from six seed orchards in the laboratory in 2019. Also, young leaves of Prunus padus L. trees growing within the seed orchards or close to them were inoculated as controls. None of the inoculated leaves of the potential alternate hosts formed uredinia either in the greenhouse or in the laboratory. In contrast, leaves of P. padus from the seed orchards were infected by the six spore sources from six seed orchards and produced uredinia. As T. areolata spores were able to infect only P. padus, but not the other tested species belonging to ground flora, it was concluded that T. areolata disperses only via Prunus spp. in Finnish seed orchards.

  • Kaitera, Natural Resources Institute Finland (Luke), Natural Resources, FI-90570 Oulu, Finland ORCID ID:E-mail: juha.kaitera@luke.fi (email)
  • Kauppila, Botanical Gardens, University of Oulu, FI-90014 Oulu, Finland ORCID ID:E-mail: tuomas.kauppila@oulu.fi
  • Hantula, Natural Resources Institute Finland (Luke), Natural Resources, FI-00790 Helsinki, Finland ORCID ID:E-mail: jarkko.hantula@luke.fi
article id 10415, category Research article
Lele Lu, Sophan Chhin, Jianguo Zhang, Xiongqing Zhang. (2021). Modelling tree height-diameter allometry of Chinese fir in relation to stand and climate variables through Bayesian model averaging approach. Silva Fennica vol. 55 no. 2 article id 10415. https://doi.org/10.14214/sf.10415
Highlights: Bayesian model averaging (BMA) and stepwise regression (SR) were compared for modelling tree height-diameter allometry; The model acquired by SR was equal to the model with the third highest posterior probability of the BMA models; BMA produced estimates of the model parameters with slightly narrower ranges around the estimate of the population parameter; Temperature was the dominant climate variable shaping the allometry.

Tree height-diameter allometry reflects the response of specific species to above and belowground resource allocation patterns. However, traditional methods (e.g. stepwise regression (SR)) may ignore model uncertainty during the variable selection process. In this study, 450 trees of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) grown at five spacings were used. We explored the height-diameter allometry in relation to stand and climate variables through Bayesian model averaging (BMA) and identifying the contributions of these variables to the allometry, as well as comparing with the SR method. Results showed the SR model was equal to the model with the third highest posterior probability of the BMA models. Although parameter estimates from the SR method were similar to BMA, BMA produced estimates with slightly narrower 95% intervals. Heights increased with increasing planting density, dominant height, and mean annual temperature, but decreased with increasing stand basal area and summer mean maximum temperature. The results indicated that temperature was the dominant climate variable shaping the height-diameter allometry for Chinese fir plantations. While the SR model included the mean coldest month temperature and winter mean minimum temperature, these variables were excluded in BMA, which indicated that redundant variables can be removed through BMA.

  • Lu, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, P. R. China; Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, P. R. China ORCID ID:E-mail: 18556439861@163.com
  • Chhin, Division of Forestry and Natural Resources, West Virginia University, 322 Percival Hall, 1145 Evansdale Dr, Morgantown, West Virginia, 26506, USA ORCID ID:E-mail: steve.chhin@mail.wvu.edu
  • Zhang, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, P. R. China ORCID ID:E-mail: xqzhang85@caf.ac.cn
  • Zhang, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, P. R. China; Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, P. R. China ORCID ID:E-mail: xqzhang85@yahoo.com (email)
article id 10409, category Research article
Noé Dumas, Mathieu Dassot, Jonathan Pitaud, Jérôme Piat, Lucie Arnaudet, Claudine Richter, Catherine Collet. (2021). Four-year-performance of oak and pine seedlings following mechanical site preparation with lightweight excavators. Silva Fennica vol. 55 no. 2 article id 10409. https://doi.org/10.14214/sf.10409
Highlights: Mechanical site preparation (MSP) with lightweight excavators controls highly competitive plant species (Molinia caerulea, Pteridium aquilinum) much more efficiently than MSP with conventional methods; This MSP approach improves four-year survival and growth of pine seedlings, but it is less evident for oak seedlings.

Mechanical site preparation methods that used tools mounted on lightweight excavators and that provided localised intensive preparation were tested in eight experimental sites across France where the vegetation was dominated either by Molinia caerulea (L.) Moench or Pteridium aquilinum (L.) Kuhn. Two lightweight tools (Deep Scarifier: DS; Deep Scarifier followed by Multifunction Subsoiler: DS+MS) were tested in pine (Pinus sylvestris L., Pinus nigra var. corsicana (Loudon) Hyl. or Pinus pinaster Aiton) and oak (Quercus petraea (Matt.) Liebl. or Quercus robur L.) plantations. Regional methods commonly used locally (herbicide, disk harrow, mouldboard plow) and experimental methods (repeated herbicide application; untreated control) were used as references in the experiments. Neighbouring vegetation cover, seedling survival, height and basal diameter were assessed over three to five years after plantation. For pines growing in M. caerulea, seedling diameter after four years was 37% and 98% greater in DS and DS+MS, respectively, than in the untreated control. For pines growing in P. aquilinum, it was 62% and 107% greater in the same treatments. For oak, diameter was only 4% and 15% greater in M. caerulea, and 13% and 25% greater in P. aquilinum, in the same treatments. For pines, the survival rate after four years was 26% and 32% higher in M. caerulea and 64% and 70% higher in P. aquilinum, in the same treatments. For oak, it was 3% and 29% higher in M. caerulea and 37% and 31% higher in P. aquilinum. Herbicide, when applied for three or four years after planting, provided the best growth performances for pines growing in M. caerulea and P. aquilinum and for oaks growing in P. aquilinum. For these species and site combinations, DS+MS and DS treatments reduced the neighbouring vegetation cover for one to four years following site preparation.

  • Dumas, Université de Lorraine, AgroParisTech, INRAE, UMR Silva, 54000 Nancy, France ORCID ID:E-mail: noe.dumas@inrae.fr
  • Dassot, EcoSustain, Environmental Engineering Office, Research and Development, 31, rue de Volmerange, 57330 Kanfen, France; Institut National de l’Information Géographique et Forestière, 1 rue des Blanches Terres, 54250 Champigneulles, France ORCID ID:E-mail: mathieu.dassot@ign.fr
  • Pitaud, Office National des Forêts, Département Recherche Développement et Innovation, route d’Amance, 54280 Champenoux, France ORCID ID:E-mail: jonathan.pitaud@onf.fr
  • Piat, Office National des Forêts, Département Recherche Développement et Innovation, 3 rue du petit château, 60200 Compiègne, France ORCID ID:E-mail: jerome.piat@onf.fr
  • Arnaudet, Office National des Forêts, Département Recherche Développement et Innovation, 100 boulevard de la Salle, 45760 Boigny-sur-Bionne, France ORCID ID:E-mail: lucie.arnaudet@onf.fr
  • Richter, Office National des Forêts, Département Recherche Développement et Innovation, Boulevard de Constance, 77300 Fontainebleau, France ORCID ID:E-mail: claudine.richter@onf.fr
  • Collet, Université de Lorraine, AgroParisTech, INRAE, UMR Silva, 54000 Nancy, France ORCID ID: https://orcid.org/0000-0003-0861-7796 E-mail: catherine.collet@inrae.fr (email)
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: Review article

article id 10516, category Review article
Faujiah N. Ritonga, Jacob N. Ngatia, Run X. Song, Umar Farooq, Sonia Somadona, Andi T. Lestari, Su Chen. (2021). Abiotic stresses induced physiological, biochemical, and molecular changes in Betula platyphylla: a review. Silva Fennica vol. 55 no. 3 article id 10516. https://doi.org/10.14214/sf.10516
Highlights: Abiotic stress influence Betula platyphylla growth, development, and yield production by impairing physiological, biochemical, and molecular functions; Overexpression or RNAi line of transcription factors enhance the abiotic stress tolerance of B. platyphylla; MYB and AP2/ERF are the most frequently transcription factor family that has been explored over the last two decades in B. platyphylla under abiotic stress.

Abiotic stress is one of the major factors in reducing plant growth, development, and yield production by interfering with various physiological, biochemical, and molecular functions. In particular, abiotic stress such as salt, low temperature, heat, drought, UV-radiation, elevated CO2, ozone, and heavy metals stress is the most frequent study in Betula platyphylla Sukaczev. Betula platyphylla is one of the most valuable tree species in East Asia facing abiotic stress during its life cycle. Using transgenic plants is a powerful tool to increase the B. platyphylla abiotic stress tolerance. Generally, abiotic stress reduces leaves water content, plant height, fresh and dry weight, and enhances shed leaves as well. In the physiological aspect, salt, heavy metal, and osmotic stress disturbs seed germination, stomatal conductance, chlorophyll content, and photosynthesis. In the biochemical aspect, salt, drought, cold, heat, osmotic, UV-B radiation, and heavy metal stress increases the ROS production of B. platyphylla cells, resulting in the enhancement of enzymatic antioxidant (SOD and POD) and non-enzymatic antioxidant (proline and AsA) to reduce the ROS accumulation. Meanwhile, B. platyphylla upregulates various genes, as well as proteins to participate in abiotic stress tolerance. Based on recent studies, several transcription factors contribute to increasing abiotic stress tolerance in B. platyphylla, including BplMYB46, BpMYB102, BpERF13, BpERF2, BpHOX2, BpHMG6, BpHSP9, BpUVR8, BpBZR1, BplERD15, and BpNACs. These transcription factors bind to different cis-acting elements to upregulate abiotic stress-related genes, resulting in the enhancement of salt, drought, cold, heat, osmotic, UV-B radiation, and heavy metal tolerance. These genes along with phytohormones mitigate the abiotic stress. This review also highlights the candidate genes from another Betulacea family member that might be contributing to increasing B. platyphylla abiotic stress tolerance.

  • Ritonga, State Key Laboratory of Tree Genetics and Breeding, Forestry College, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: ritongafaujiah@ymail.com
  • Ngatia, College of Wildlife and Protected Areas, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: jacob.ngatia3@gmail.com
  • Song, State Key Laboratory of Tree Genetics and Breeding, Forestry College, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: 13359850710@163.com
  • Farooq, College of Life Science, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail:
  • Somadona, College of Agriculture, Riau University, Pekanbaru 28293, Indonesia ORCID ID:E-mail: sonia_hut@yahoo.co.id
  • Lestari, Forestry Major, College of Agriculture, Mataram University, Mataram 83125, Indonesia ORCID ID:E-mail: atlestari@unram.ac.id
  • Chen, State Key Laboratory of Tree Genetics and Breeding, Forestry College, Northeast Forestry University, Harbin 150040, China ORCID ID:E-mail: chensu@nefu.edu.cn (email)

Category: Research note

article id 10533, category Research note
Daniel Schraik, Aarne Hovi, Miina Rautiainen. (2021). Estimating cover fraction from TLS return intensity in coniferous and broadleaved tree shoots. Silva Fennica vol. 55 no. 4 article id 10533. https://doi.org/10.14214/sf.10533
Highlights: We developed a method to obtain the fraction of TLS pulses’ footprint area covered by a target’s projection area; We tested our method with shoots of Norway spruce, Scots pine and silver birch; We provide a physically-based framework related to unmeasured variables, and provide a robust statistical framework to deal with uncertainty.

Terrestrial laser scanning (TLS) provides a unique opportunity to study forest canopy structure and its spatial patterns such as foliage quantity and dispersal. Using TLS point clouds for estimating leaf area density with voxel-based methods is biased by the physical dimensions of laser beams, which violates the common assumption of beams being infinitely thin. Real laser beams have a footprint size larger than several millimeters. This leads to difficulties in estimating leaf area density from light detection and ranging (LiDAR) in vegetation, where the target objects can be of similar or even smaller size than the beam footprint. To compensate for this bias, we propose a method to estimate the per-pulse cover fraction, defined as the fraction of laser beams’ footprint area that is covered by vegetation targets, using the LiDAR return intensity and an experimental calibration measurement. We applied this method to a Leica P40 single-return instrument, and report our experimental results. We found that conifer foliage had a lower average per-pulse cover fraction than broadleaved foliage, indicating an increased number of partial hits in conifer foliage. We further discuss limitations of our method that stem from unknown target properties that influence the LiDAR return intensity and highlight potential ways to overcome the limitations and manage the remaining uncertainty. Our method’s output, the per-beam cover fraction, may be useful in a weight function for methods that estimate leaf area density from LiDAR point clouds.

  • Schraik, Aalto University, School of Engineering, Department of Built Environment, P.O. Box 14100, FI-00076 Aalto, Finland; ORCID ID: https://orcid.org/0000-0002-7794-3918 E-mail: daniel.schraik@aalto.fi (email)
  • Hovi, Aalto University, School of Engineering, Department of Built Environment, P.O. Box 14100, FI-00076 Aalto, Finland; ORCID ID: https://orcid.org/0000-0002-4384-5279 E-mail: aarne.hovi@aalto.fi
  • Rautiainen, Aalto University, School of Engineering, Department of Built Environment, P.O. Box 14100, FI-00076 Aalto, Finland; Aalto University, School of Electrical Engineering, Department of Electronics and Nanoengineering, P.O. Box 14100, FI-00076 Aalto, Finland ORCID ID: https://orcid.org/0000-0002-6568-3258 E-mail: miina.a.rautiainen@aalto.fi
article id 10524, category Research note
Arnis Gailis, Pauls Zeltiņš, Roberts Matisons, Andis Purviņš, Juris Augustovs, Valts Vīndedzis, Āris Jansons. (2021). Local adaptation of phenotypic stem traits distinguishes two provenance regions of silver birch in Latvia. Silva Fennica vol. 55 no. 2 article id 10524. https://doi.org/10.14214/sf.10524
Highlights: Two provenance subregions in Latvia – coastal and inland – were distinguished; Silver birch populations in inland region possessed better growth, higher heritability, and phenotypic plasticity; Moderate to high heritability for stem quality was estimated in both regions; Silver birch from inland region possesses higher potential for improvement of adaptability.

Populations of tree species with a wide geographic range, such as silver birch (Betula pendula Roth), show genetic specialization to native environments, while maintaining high phenotypical plasticity. Accordingly, assessment of local specialization is essential for adaptive management. The aim of the study was to detect geographic patterns of local adaptation of growth and stem quality based on two open-pollinated progeny trials in Latvia testing local material. Two provenance regions differing by continentality were distinguished, which also differed in genetic control of growth traits, likely originating from the post-glacial recolonization of vegetation and subsequent natural adaptation. Heritability of the traits was estimated for each of the distinguished regions, indicating differing patterns of genetic adaptation and potential for future selection. Trees from the more continental inland showed superior growth and possessed higher heritability. The coastal provenance region showed slower growth and intermediate heritability of the respective traits. Moderate to high heritability for stem quality traits was estimated irrespectively of region. Overall, better growth and higher heritability suggests that anthropogenic selection within the best inland provenances may constitute better performing and adaptable breeding population compared to the coastal one. Still, overlapping phenotypical variation and heritability of quality traits implies improved stemwood quality for plywood regardless of the provenance region. High adaptive capacity of silver birch genotypes suggests ability to cope with climatic changes, highlighting its potential for climate-smart forestry.

  • Gailis, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID:E-mail: arnis.gailis@silava.lv
  • Zeltiņš, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID:E-mail: pauls.zeltins@silava.lv (email)
  • Matisons, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID: https://orcid.org/0000-0002-4042-0689 E-mail: roberts.matisons@silava.lv
  • Purviņš, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID:E-mail: andis.purvins@silava.lv
  • Augustovs, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID:E-mail: juris.augustovs@silava.lv
  • Vīndedzis, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID:E-mail: valts.vindedzis@silava.lv
  • Jansons, Latvian State Forest Research Institute Silava, 111 Rigas street, LV-2169, Salaspils, Latvia ORCID ID: https://orcid.org/0000-0001-7981-4346 E-mail: aris.jansons@silava.lv
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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