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Silva Fennica 1926-1997
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Acta Forestalia Fennica
1953-1968
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Articles containing the keyword 'frost'.

Category: Research article

article id 7731, category Research article
Anneli Viherä-Aarnio, Pirkko Velling. (2017). Growth, wood density and bark thickness of silver birch originating from the Baltic countries and Finland in two Finnish provenance trials. Silva Fennica vol. 51 no. 4 article id 7731. https://doi.org/10.14214/sf.7731
Highlights: Baltic origins of silver birch had significantly thicker bark than the Finnish ones; In terms of wood density, no consistent difference was detected between the Baltic and Finnish origins; Incidence of darkened core wood increased with increasing seed origin latitude; Frost cracks were most common in south Latvian origins grown in central Finland.

Silver birch (Betula pendula Roth) seed origins from the Baltic countries and from Finland were compared in terms of growth, wood density, bark thickness and the incidence of darkened core wood, frost cracks and decay, and the effect of seed origin latitude was examined in two Finnish provenance trials. The material consisted of 21 stand and single tree origins ranging from latitudes 54° to 63°N from the Baltic countries and Finland. The trials, measured at the age of 22 years, were located at Tuusula (60°21´N), southern Finland and at Viitasaari (63°11´N), central Finland. The Baltic origins were superior to the Finnish ones in the southern trial regarding height, whereas in central Finland the Finnish origins grew better. There was no consistent difference between the Baltic and the Finnish group of origins in wood density. Bark thickness decreased with increasing seed origin latitude. The Baltic origins had significantly thicker bark than the Finnish origins. A moderate positive correlation was detected between the seed origin latitude and the incidence of darkened core wood in the southern trial, where the darkened core wood was more common in the Finnish origins than in the Baltic ones. The highest proportion of trees with frost cracks was detected in the south-western Latvian origins growing in central Finland. Seed transfers from the Baltic would have an increasing effect on the bark thickness of birch logs, but no or only minor effects on wood density. Based on our results, there is no reason to recommend the use of non-native Baltic seed origins in Finland instead of the native locally adapted seed sources.

  • Viherä-Aarnio, Natural Resources Institute Finland (Luke), Green technology, P.O. Box 2, FI-00791 Helsinki, Finland ORCID ID:E-mail: anneli.vihera-aarnio@luke.fi (email)
  • Velling, ORCID ID:E-mail: pike.velling@phnet.fi
article id 1560, category Research article
Marina Gurskaya, Pavel Moiseev, Martin Wilmking. (2016). Does slope exposure affect frost ring formation in Picea obovata growing at treeline in the Southern Urals? Silva Fennica vol. 50 no. 3 article id 1560. https://doi.org/10.14214/sf.1560
Highlights: Frost ring formation was ubiquitous from continuous forest cover to treeline, but, surprisingly, was not affected by slope exposure; Late frosts in spring were the main cause for frost ring formation; While mainly young trees (< 30 years) recorded frost events, at the climatically harshest site (highest elevation, northeastern exposure), frost events were recorded also in trees older than 70 years.

Topographic complexity in mountainous ecosystems strongly influences plant growth and as such also wood formation. This wood formation can possibly be used to understand topographic variation of the main climatic drivers, e.g. by modulating frost events. Here we test the influence of different slope exposures on the spatio-temporal distribution of frost rings in Siberian spruce (Picea obovata Ledeb.) in the Southern Urals, Russia. We sampled on two opposite slopes, northeast (NE) and southwest (SW), on three elevation levels from the highest single trees to closed canopy forest and analysed frost ring occurrence and their seasonal timing. Frost ring formation at all exposure-elevation combinations was common and mainly concentrated in the early part of the growing season. The age until trees record frost rings was equally similar (until about 35 years) on both slopes and different elevational levels with the exception of the climatically harshest site, the highest elevation on the NE slope. While we could not deduce a direct, easily identifiable climatic driver for the formation of frost rings, our analysis shows high potential to disentangle the complex interplay between climate, site condition and tree growth in mountainous ecosystems.

  • Gurskaya, Institute of Plant and Animal Ecology (IPAE), Ural Branch of Russian Academy of Sciences , 8 Marta St. 202, 620144 Ekaterinburg, Russia ORCID ID:E-mail: mgurskaya@yandex.ru (email)
  • Moiseev, Institute of Plant and Animal Ecology (IPAE), Ural Branch of Russian Academy of Sciences , 8 Marta St. 202, 620144 Ekaterinburg, Russia ORCID ID:E-mail: moiseev@ipae.uran.ru
  • Wilmking, Institute of Botany and Landscape Ecology, Soldmanstrasse 15, Ernst-Moritz-Arndt-University Greifswald, 17487 Greifswald, Germany ORCID ID:E-mail: wilmking@uni-greifswald.de
article id 45, category Research article
Guolei Li, Yong Liu, Yan Zhu, Qing Mei Li, R. Karsten Dumroese. (2012). Effect of fall-applied nitrogen on growth, nitrogen storage and frost hardiness of bareroot Larix olgensis seedlings. Silva Fennica vol. 46 no. 3 article id 45. https://doi.org/10.14214/sf.45
Nursery response of evergreen trees to fall fertilization has been studied widely, but little attention has been given to deciduous trees. Bareroot Olga Bay larch (Larix olgensis Henry) seedlings were fertilized in the nursery with urea at four rates (0, 30, 60, 90 kg N ha–1), with half of each rate applied on two dates (September 16 and October 1, 2009). The seedlings were excavated for evaluation on October 15. In the unfertilized (control) treatment, root and shoot dry mass increased by 100% and 57% respectively, while N concentration in the roots and shoots increased by 43% and 40% during the 30 day period. This indicated that substantial biomass growth during this period did not lead to internal nutrient dilution. Root dry mass increased when fall fertilization rates were ≥ 60 kg N ha–1. Fall fertilization increased N concentrations in root tissue by 48–73%. Compared with the control, shoot tissues of fall fertilized seedlings had slightly higher N concentration and content and significantly higher frost hardiness.
  • Li, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing 100083, China ORCID ID:E-mail:
  • Liu, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing 100083, China ORCID ID:E-mail: lyong@bjfu.edu.cn (email)
  • Zhu, Key Laboratory for Silviculture and Conservation, Ministry of Education, Beijing 100083, China ORCID ID:E-mail:
  • Li, Research Institute of Forestry, Chinese Academy of Forestry; Key Laboratory of Forest Silviculture of State Forestry Administration, Beijing 100091, China ORCID ID:E-mail:
  • Dumroese, US Department of Agriculture, Forest Service, Rocky Mountain Research Station, Moscow, ID, USA ORCID ID:E-mail:
article id 30, category Research article
Hilppa Gregow, Heli Peltola, Mikko Laapas, Seppo Saku, Ari Venäläinen. (2011). Combined occurrence of wind, snow loading and soil frost with implications for risks to forestry in Finland under the current and changing climatic conditions. Silva Fennica vol. 45 no. 1 article id 30. https://doi.org/10.14214/sf.30
This work focuses on the combined occurrence of wind, snow loading and soil frost with implications for risks to forestry in Finland under the current and changing climatic conditions. For this purpose, we employ meteorological datasets, available for the period of 1971–2009 and global climate model (GCM) simulations for the current climate 1971–2000, and periods 2046–65 and 2081–2100 applying the A1B-climate change scenario. Based on our results, the wind and snow induced risks to Finnish forests are projected to increase in the future although the change in the occurrence of strong winds is small. This is because soil frost depths that support tree anchorage from late autumn to early spring in Finland are projected to nearly disappear in the southern and central parts of the country. Heavy snow loads > 30 kg m–2 are becoming more common in southern and eastern Finland despite that the average cumulative 5-day snow loads decrease in these areas by 18 to 50%, respectively. As a result of the changes in the combined occurrence of wind, snow loading and soil frost, the risk of climatic conditions making conifers liable to uprooting are projected to increase in southern, central and eastern Finland. In the north, the risk of stem breakage is becoming more pronounced under snow loading > 20 kg m–2. Despite some uncertainties related to this work, we assume that the findings can serve as valuable support for the risk assessment of wind and snow induced damages to Finnish forests and for forestry, in general.
  • Gregow, Finnish Meteorological Institute, Helsinki, Finland ORCID ID:E-mail: hilppa.gregow@fmi.fi (email)
  • Peltola, University of Eastern Finland, Faculty of Forest Sciences, Joensuu, Finland ORCID ID:E-mail: heli.peltola@uef.fi
  • Laapas, Finnish Meteorological Institute, Helsinki, Finland ORCID ID:E-mail:
  • Saku, Finnish Meteorological Institute, Helsinki, Finland ORCID ID:E-mail:
  • Venäläinen, Finnish Meteorological Institute, Helsinki, Finland ORCID ID:E-mail:
article id 455, category Research article
Seppo Kellomäki, Matti Maajärvi, Harri Strandman, Antti Kilpeläinen, Heli Peltola. (2010). Model computations on the climate change effects on snow cover, soil moisture and soil frost in the boreal conditions over Finland. Silva Fennica vol. 44 no. 2 article id 455. https://doi.org/10.14214/sf.455
This study considered how climate change affects the accumulation of snow, the soil moisture and soil frost at sites without tree cover in boreal conditions in Finland (60°–70°N). An increase of 4.5 °C in annual mean temperature and 20 % in annual precipitation were assumed for Finland by the year 2100 according to A2 emission scenario. Along with climate, the soil type of the permanent inventory plots of the Finnish National Forest Inventory was used. Soil and climate data were combined by using a process-based ecosystem model. Calculations were done for four periods: current climate (1971–2000), near future (2001–2020), mid-term future (2021–2050) and long-term future (2071–2100). According to our simulations, the average monthly duration and depth of snow decreased over the simulation period. However, the increasing precipitation may locally increase the snow depths in the mid-term calculations. In the autumn and winter, the average volumetric soil moisture content slightly increased in southern Finland during the near future, but decreased towards the end of the century, but still remained on a higher level than presently. In northern Finland, the soil moisture in the autumn and winter increased by the end of this century. In the summertime soil moisture decreased slightly regardless of the region. Throughout Finland, the length and the depth of soil frost decreased by the end of the century. In the south, the reduction in the depth was largest in the autumn and spring, while in the mid-winter it remained relatively deep in the middle of the century. In the north, the depth tended to increase during the first two calculation periods, in some areas, even during the third calculation period (2071–2100) due to reduced insulation effects of snow during cold spells. The wintertime increase in soil moisture and reduced soil frost may be reflected to reduced carrying capacity of soil for timber harvesting.
  • Kellomäki, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland ORCID ID:E-mail: seppo.kellomaki@uef.fi (email)
  • Maajärvi, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland ORCID ID:E-mail:
  • Strandman, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland ORCID ID:E-mail:
  • Kilpeläinen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland ORCID ID:E-mail:
  • Peltola, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland ORCID ID:E-mail:
article id 175, category Research article
Heikki Hänninen, Jaana Luoranen, Risto Rikala, Heikki Smolander. (2009). Late termination of freezer storage increases the risk of autumn frost damage to Norway spruce seedlings. Silva Fennica vol. 43 no. 5 article id 175. https://doi.org/10.14214/sf.175
Over the last few years it has become increasingly common in artificial forest regeneration to extend the planting period by using freezer-stored seedlings for early summer plantings. Developmentally, however, planted freezer-stored seedlings lag behind seedlings planted earlier in the spring. As freezer-stored seedlings also start hardening later, they are more susceptible to early autumn frosts, especially in years when the thermal growing season ends and the first autumn frosts come earlier than usual. By means of computer simulations with a simple temperature sum model and long-term air-temperature data from three locations in Finland, we examined the effect of the freezer-storage termination date on the risk of autumn frost damage to the seedlings. The long-term simulations revealed a drastic effect of year-to-year variation in the thermal conditions during the growing season on the occurrence of autumn frost damage. Such results provide crucial information complementary to those obtained in field experiments, which are always restricted to a relatively short time period. Together with earlier field data, the present results suggest that at an average regeneration site in central Finland, the planting of seedlings whose storage has terminated on 15 June and 22 June involve autumn frost damage every tenth and every fifth year, respectively. The sensitivity analysis revealed that the temperature sum requirement of maturation has a great effect on the risk of autumn frost damage, thus pinpointing the need for experimental studies addressing this ecophysiological trait of the seedlings.
  • Hänninen, Plant Ecophysiology and Climate Change Group (PECC), Department of Biological and Environmental Sciences, Box 65, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: heikki.hanninen@helsinki.fi (email)
  • Luoranen, Finnish Forest Research Institute, Suonenjoki Research Unit, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail:
  • Rikala, Finnish Forest Research Institute, Suonenjoki Research Unit, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail:
  • Smolander, Finnish Forest Research Institute, Suonenjoki Research Unit, Juntintie 154, FI-77600 Suonenjoki, Finland ORCID ID:E-mail:
article id 209, category Research article
Jaana Luoranen, Kyösti Konttinen, Risto Rikala. (2009). Frost hardening and risk of a second flush in Norway spruce seedlings after an early-season short-day treatment. Silva Fennica vol. 43 no. 2 article id 209. https://doi.org/10.14214/sf.209
There have been years in Finland when container seedlings of Norway spruce (Picea abies (L.) Karsten) planted in the summer have been damaged by early-autumn frosts. For August and September plantings, the seedlings can be hardened by means of short-day (SD) treatment, but little information is available about its usability for earlier plantings. We studied the effects of early-season SD treatment on the frost hardiness and risk of a second flush of Norway spruce seedlings. In three successive years, second-year seedlings were grown in a greenhouse or outdoors in the spring and early summer and then subjected to two or three-week SD treatment beginning on the second, third, or fourth week of June. We monitored the height growth cessation, bud formation, and frost hardiness of the seedlings in the nursery. All SD treatments made the height growth cease, but the risk of a second flush increased if the temperature sum was less than 300 d.d. before the beginning of the SD treatment or more than 450 d.d. between the end of the treatment and mid-August. Clearly, then, SD treatment reduced the risk of a second flush in seedlings that had been grown in a greenhouse in the spring. Early-season SD treatment increased the frost hardiness of both needles and stems for late July to early September in comparison with untreated seedlings. Later in the autumn, however, the differences disappeared. Before recommending the use of early-season SD-treated seedlings for summer planting, the method has to be tested in practical field conditions.
  • Luoranen, The Finnish Forest Research Institute, Suonenjoki Research Unit, FI-77600 Suonenjoki, Finland ORCID ID:E-mail: jaana.luoranen@metla.fi (email)
  • Konttinen, The Finnish Forest Research Institute, Suonenjoki Research Unit, FI-77600 Suonenjoki, Finland ORCID ID:E-mail:
  • Rikala, The Finnish Forest Research Institute, Suonenjoki Research Unit, FI-77600 Suonenjoki, Finland ORCID ID:E-mail:
article id 231, category Research article
Hilppa Gregow, Ulla Puranen, Ari Venäläinen, Heli Peltola, Seppo Kellomäki, David Schultz. (2008). Temporal and spatial occurrence of strong winds and large snow load amounts in Finland during 1961-2000. Silva Fennica vol. 42 no. 4 article id 231. https://doi.org/10.14214/sf.231
Information on the temporal and spatial occurrence of strong winds and snow loads on trees is important for the risk management of wind- and snow-induced damage. Meteorological measurements made at 19 locations across Finland during 1961–2000 are used to understand the temporal and spatial occurrence of strong winds and large snow loads. A Kriging interpolation method was used to produce a spatial analysis of wind-speed events above 11 m s–1, 14 m s–1, and greater or equal to 17 m s–1 and snowfall accumulation above 20 kg m–2 and 30 kg m–2. According to the analysis, wind speeds exceeded 14 m s–1 at least 155 times and reached 17 m s–1 only 5 times at inland locations during the 40 years. Large snowfall accumulations were more frequent in the higher-elevation inland areas than along the coast. The snow load on trees exceeded 20 kg m–2 about 65 times a year when averaged over all 40 years, but was as high as 150 times a year during the mild 1990s. The maximum number of heavy snow-load events occurred in 1994 in northern Finland, consistent with a forest inventory by the Finnish Forest Research Institute in 1992–1994. The findings of this study imply that the risk of wind-induced damage is highest in the late autumn when trees do not have the additional support of frozen soil. In contrast, the risk of snow-induced damage is highest at higher-elevations inland, especially in northern Finland.

* Erratum (23 Oct 2012): The authors have requested inclusion of an additional author. Author information should thus be as follows: Hilppa Gregow, Ulla Puranen, Ari Venäläinen, Heli Peltola, Seppo Kellomäki & David Schultz
  • Gregow, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland ORCID ID:E-mail: hilppa.gregow@fmi.fi (email)
  • Puranen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland ORCID ID:E-mail:
  • Venäläinen, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland ORCID ID:E-mail:
  • Peltola, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: heli.peltola@uef.fi
  • Kellomäki, University of Joensuu, Faculty of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: seppo.kellomaki@uef.fi
  • Schultz, Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland ORCID ID:E-mail:
article id 242, category Research article
Jyrki Hytönen, Paula Jylhä. (2008). Fifteen-year response of weed control intensity and seedling type on Norway spruce survival and growth on arable land. Silva Fennica vol. 42 no. 3 article id 242. https://doi.org/10.14214/sf.242
The effects of seedling type (2-year-old container seedlings vs. 4-year-old bare-rooted seedlings) and post-planting vegetation control intensity on the growth and survival of Norway spruce (Picea abies (L.) Karst.) seedlings were compared based on 15-year data from a field experiment established on arable land. Vegetation control treatments with terbuthylazine and glyphosate were carried out 1–3 times on successive years, either as overall or spot applications. The highest stand volumes were obtained with the combination of large bare-rooted seedlings and effective vegetation control. Volume of bare-rooted seedlings was greater than that of container seedlings in all treatments (e.g. on the control plots 9.5 m3/ha vs. 4.1 m3/ha). The best results were obtained with the most intensive weed control treatments (spot treatment repeated twice and overall application repeated three times). These treatments increased both bare-rooted and containerised seedlings’ survival by 33–40% units and their height, breast height diameter, and volume by 45–49%, 17–47%, and 249–279%, respectively. In terms of survival, the container seedlings, in due part to their smaller size, benefited from vegetation control more than the bare-rooted seedlings. Successive early summer frosts damaged the seedlings and significantly retarded their growth. The frequency of frost damage was not affected by vegetation control nor was it attributed to seedling type.
  • Hytönen, Finnish Forest Research Institute, Kannus Research Unit, P.O. Box 44, FI-69101, Kannus, Finland ORCID ID:E-mail: jyrki.hytonen@metla.fi (email)
  • Jylhä, Finnish Forest Research Institute, Kannus Research Unit, P.O. Box 44, FI-69101, Kannus, Finland ORCID ID:E-mail:

Category: Review article

article id 313, category Review article
Heikki Hänninen, Koen Kramer. (2007). A framework for modelling the annual cycle of trees in boreal and temperate regions. Silva Fennica vol. 41 no. 1 article id 313. https://doi.org/10.14214/sf.313
Models of the annual development cycle of trees in boreal and temperate regions were reviewed and classified on the basis of their ecophysiological assumptions. In our classification we discern two main categories of tree development: 1) fixed sequence development, which refers to irreversible ontogenetic development leading to visible phenological events such as bud burst or flowering, and 2) fluctuating development, which refers to reversible physiological phenomena such as the dynamics of frost hardiness during winter. As many of the physiological phenomena are partially reversible, we also describe integrated models, which include aspects of both fixed-sequence and fluctuating development. In our classification we further discern simple E-models, where the environmental response stays constant, and more comprehensive ES-models, where the environmental response changes according to the state of development. On the basis of this model classification, we have developed an operational modelling framework, in which we define an explicit state variable and a corresponding rate variable for each attribute of the annual cycle considered. We introduce a unifying notation, which we also use when presenting a selection of previously published models. To illustrate the various developmental phenomena and their modelling, we have carried out model simulations. Finally, we discuss the ecophysiological interpretation of the model variables, methodological aspects of the empirical development and testing of the models, the introduction of new aspects to the modelling, other closely related models, and applications of the models.
  • Hänninen, Plant Ecophysiology and Climate Change Group (PECC), Department of Biological and Environmental Sciences, Box 65, FI-00014 University of Helsinki, Finland ORCID ID:E-mail: heikki.hanninen@helsinki.fi (email)
  • Kramer, Alterra, P.O. Box 47, 6700 AA Wageningen, The Netherlands ORCID ID:E-mail:

Category: Research note

article id 534, category Research note
Ilkka Leinonen, Heikki Hänninen. (2002). Adaptation of the timing of bud burst of Norway spruce to temperate and boreal climates. Silva Fennica vol. 36 no. 3 article id 534. https://doi.org/10.14214/sf.534
The adaptation of the annual cycle of development of boreal and temperate trees to climatic conditions has been seen as a result of stabilizing selection caused by two opposite driving forces of natural selection, i.e. the tolerance of unfavorable conditions during the frost exposed season (survival adaptation) and the effective use of growth resources during the growing season (capacity adaptation). In this study, two theories of the effects of climate on the adaptation of the timing of bud burst of trees were evaluated. This was done with computer simulations by applying a temperature sum model for predicting the timing of bud burst of different Norway spruce genotypes on the basis of air temperature data from various climatic conditions. High geographical variation in the temperature response of bud burst, typical for Norway spruce, was included in the theoretical analyses. The average timing of bud burst and the corresponding risk of occurrence of damaging frost during the susceptible period after bud burst were calculated for each genotype in each climate. Two contrasting theories of the stabilizing selection were evaluated, i.e. the overall adaptedness of each genotype was evaluated either 1) by assuming a fixed threshold for the risk of frost damage, or 2) by assuming a tradeoff between the risk of frost damage and the length of the growing season. The tradeoff assumption produced predictions of between provenance variation in bud burst which correspond more closely with empirical observations available in literature, compared to the fixed threshold assumption.
  • Leinonen, University of Oklahoma, Department of Botany and Microbiology, Norman, OK 73019, USA ORCID ID:E-mail: leinonen@ou.edu (email)
  • Hänninen, University of Helsinki, Department of Ecology and Systematics, FIN-00014 Helsinki, Finland ORCID ID:E-mail:

Category: Article

article id 7159, category Article
Seppo E. Mustonen. (1965). Ilmasto- ja maastotekijöiden vaikutuksesta lumen vesiarvoon ja roudan syvyyteen. Acta Forestalia Fennica vol. 79 no. 1 article id 7159. https://doi.org/10.14214/aff.7159
English title: Effect of meteorological and terrain factors in water equivalent of snow cover and frost depth.

The aim of the investigation was to obtain by snow and soil frost observations sufficient material for determination of regional springtime snow and soil frost values, because the water equivalent of snow and the frost depth affect runoff. The present paper elaborates a method by which the observations along a survey line can be corrected to be valid for a basin. Along the line 50 measurement points were arranged at specific intervals. Snow depth was recorded at each point, and snow density and frost depth at every fifth point. The terrain was studied along the line and the terrain of the survey points were classified in eight classes depending on the vegetation. The classes ranged from cultivated lands and open bogs to wooded areas according to volume of the growing stock and tree species composition.

The mean snow depth was 51.9 cm and mean snow density 0.235 g/m2. Water equivalent of snow in class 4 terrain (forest with small growing stock) was 30% higher than in class 8 (forest with high growing stock). An ample stand increases evaporation in wintertime. The difference can be partly caused by the different accumulation of snow in the different types of stands.

Soil type was not found to have any distinct influence on the frost depth in the present material. On cultivated lands the soil frost clearly penetrates to greater depth than in the forest. The growing stock of wooded areas influences the snow depth

The PDF includes a summary in English.

  • Mustonen, ORCID ID:E-mail:
article id 7143, category Article
O. Meurman. (1963). Puutarhantutkimuslaitoksella Piikkiössä kokeilluista koristepuista ja -pensaista. Acta Forestalia Fennica vol. 76 no. 3 article id 7143. https://doi.org/10.14214/aff.7143
English title: Notes on ornamental trees and shrubs at the Department of horticulture (Piikkiö, Finland).

Trees and shrubs of foreign origin have been grown in Finland at least from the 1700th century. At the State Horticultural Institute in the neighbourhood of the town Turku in southwestern coast of the country, a number of ornamental trees and shrubs have been planted since 1927. During the first decade, weather conditions were quite favourable, but the winters in 1939–1940 were so severe, that only the hardiest plants survived.

It would be important to study hardiness and suitability of the various woody plants cultivated in the different parts of the country. This paper includes notes of the survival of the tree species and shrubs so far planted at the Institute.

The PDF includes a summary in English.

  • Meurman, ORCID ID:E-mail:
article id 7114, category Article
Paavo Yli-Vakkuri. (1960). Metsiköiden routa- ja lumisuhteista. Acta Forestalia Fennica vol. 71 no. 5 article id 7114. https://doi.org/10.14214/aff.7114
English title: Snow cover and ground frost in Finnish forests.

Snow cover and ground frost was studied in 29 forest stands in Southern and Central Finland in 1957–1959. The tree species influenced greatly accumulation of snow on the forest floor. Norway spruce (Picea abies (L.) Karst.) retains snow in its crown. In addition, snow and water falling from the branches compress the snow cover under the trees, and the ground freezes deeper because of the shallow snow cover. In the spring, the dense crown prevents rain and radiation reaching the ground, which remains cold longer. However, ground frost may protect spruce, which has a weak root system, from wind damages.

Scots pine (Pinus sylvestris L.) has similar, but milder, effects on snow cover within the forest. The crowns of pine seedlings and young trees pass snow easily, but later the crowns intercept it considerably. The lower branches are, however, high up and the snow is evenly spread on the ground. The deciduous trees intercept little snow and in the spring the snow smelts and the frozen soil thaws early. The snow conditions of deciduous forests are, however, changed by a spruce undergrowth.

It can be assumed that the unfavourable conditions in spruce forests can be alleviated by thinning. Also, mixture of pine and deciduous trees can transform the conditions more favourable in the spruce stands.

The PDF includes a summary in English.

  • Yli-Vakkuri, ORCID ID:E-mail:
article id 7377, category Article
S. E. Multamäki. (1942). Kuusen taimien paleltuminen ja sen vaikutus ojitettujen soiden metsittymiseen. Acta Forestalia Fennica vol. 51 no. 1 article id 7377. https://doi.org/10.14214/aff.7377
English title: Frost injuries of Norway spruce seedlings and their effect on afforestation of drained peatlands .

The aim of the investigation was to study natural regeneration of Norway spruce (Picea abies (L.) Karst.) in drained peatlands and frost injuries in seedlings, and to compare microclimates of the regeneration areas. The experiments included peatlands in Satakunta in Western Finland. Restocking of the areas with seedlings and their survival was followed in 1935-40 at sample plots that were mainly 1 are large.

Susceptibility to freezing was shown to be dependent on the stage of development of the shoots. Shoots that have just begun to grow contain little water, and withstand better freezing temperatures than shoots in later stages of growth. Damages to the seedlings were observed when the temperatures decreased to -2.8–-4.3 °C. The most severe damage to a seedling was caused by the death of the leading shoot by spring frost.

Norway spruce regenerates easily on moist peatlands, but peatlands with dry surface tend to have little or no seedlings. The species regenerated better in marshy sites than correspondingly fertile mineral soil sites. However, it needs shelter to avoid frost damage. On clear cut spruce swamp the undergrowth spruce seedlings that were left in the site got severe frost damage. If the site had birch (Betula sp.) coppice or undergrowth, spruce seedlings survived in their shelter depending on the height and density of the birch trees. To be effective, the protective forest should have relatively even crown cover. Young spruce seedlings could grow well even under relatively dense birch stand.

The PDF includes a summary in German.

  • Multamäki, ORCID ID:E-mail:
article id 7377, category Article
S. E. Multamäki. (1942). Kuusen taimien paleltuminen ja sen vaikutus ojitettujen soiden metsittymiseen. Acta Forestalia Fennica vol. 51 no. 1 article id 7377. https://doi.org/10.14214/aff.7377
English title: Frost injuries of Norway spruce seedlings and their effect on afforestation of drained peatlands .

The aim of the investigation was to study natural regeneration of Norway spruce (Picea abies (L.) Karst.) in drained peatlands and frost injuries in seedlings, and to compare microclimates of the regeneration areas. The experiments included peatlands in Satakunta in Western Finland. Restocking of the areas with seedlings and their survival was followed in 1935-40 at sample plots that were mainly 1 are large.

Susceptibility to freezing was shown to be dependent on the stage of development of the shoots. Shoots that have just begun to grow contain little water, and withstand better freezing temperatures than shoots in later stages of growth. Damages to the seedlings were observed when the temperatures decreased to -2.8–-4.3 °C. The most severe damage to a seedling was caused by the death of the leading shoot by spring frost.

Norway spruce regenerates easily on moist peatlands, but peatlands with dry surface tend to have little or no seedlings. The species regenerated better in marshy sites than correspondingly fertile mineral soil sites. However, it needs shelter to avoid frost damage. On clear cut spruce swamp the undergrowth spruce seedlings that were left in the site got severe frost damage. If the site had birch (Betula sp.) coppice or undergrowth, spruce seedlings survived in their shelter depending on the height and density of the birch trees. To be effective, the protective forest should have relatively even crown cover. Young spruce seedlings could grow well even under relatively dense birch stand.

The PDF includes a summary in German.

  • Multamäki, ORCID ID:E-mail:
article id 7377, category Article
S. E. Multamäki. (1942). Kuusen taimien paleltuminen ja sen vaikutus ojitettujen soiden metsittymiseen. Acta Forestalia Fennica vol. 51 no. 1 article id 7377. https://doi.org/10.14214/aff.7377
English title: Frost injuries of Norway spruce seedlings and their effect on afforestation of drained peatlands .

The aim of the investigation was to study natural regeneration of Norway spruce (Picea abies (L.) Karst.) in drained peatlands and frost injuries in seedlings, and to compare microclimates of the regeneration areas. The experiments included peatlands in Satakunta in Western Finland. Restocking of the areas with seedlings and their survival was followed in 1935-40 at sample plots that were mainly 1 are large.

Susceptibility to freezing was shown to be dependent on the stage of development of the shoots. Shoots that have just begun to grow contain little water, and withstand better freezing temperatures than shoots in later stages of growth. Damages to the seedlings were observed when the temperatures decreased to -2.8–-4.3 °C. The most severe damage to a seedling was caused by the death of the leading shoot by spring frost.

Norway spruce regenerates easily on moist peatlands, but peatlands with dry surface tend to have little or no seedlings. The species regenerated better in marshy sites than correspondingly fertile mineral soil sites. However, it needs shelter to avoid frost damage. On clear cut spruce swamp the undergrowth spruce seedlings that were left in the site got severe frost damage. If the site had birch (Betula sp.) coppice or undergrowth, spruce seedlings survived in their shelter depending on the height and density of the birch trees. To be effective, the protective forest should have relatively even crown cover. Young spruce seedlings could grow well even under relatively dense birch stand.

The PDF includes a summary in German.

  • Multamäki, ORCID ID:E-mail:
article id 7375, category Article
P. Kokkonen. (1942). Beobachtungen über den Bodenfrost des Winters 1941 - 1942. Acta Forestalia Fennica vol. 50 no. 22 article id 7375. https://doi.org/10.14214/aff.7375
English title: Observations on the soil frost of the winter 1941-1942.
Original keywords: Bodenfrost; Formation
English keywords: soil frost; formation

Soil frost from the winter 1941-1942 was of a special form. To create such a strong soil frost there need to be capillary soil form and long period of permanent and intense cold, meaning minus temperatures.  The frost layer was thicker than normally.

Such a frost causes many problems on the fields and roads when the soil rises because of the frost and then falls unevenly back when the frost melts.

The PDF contains a summary in Finnish.
  • Kokkonen, ORCID ID:E-mail:
article id 7375, category Article
P. Kokkonen. (1942). Beobachtungen über den Bodenfrost des Winters 1941 - 1942. Acta Forestalia Fennica vol. 50 no. 22 article id 7375. https://doi.org/10.14214/aff.7375
English title: Observations on the soil frost of the winter 1941-1942.
Original keywords: Bodenfrost; Formation
English keywords: soil frost; formation

Soil frost from the winter 1941-1942 was of a special form. To create such a strong soil frost there need to be capillary soil form and long period of permanent and intense cold, meaning minus temperatures.  The frost layer was thicker than normally.

Such a frost causes many problems on the fields and roads when the soil rises because of the frost and then falls unevenly back when the frost melts.

The PDF contains a summary in Finnish.
  • Kokkonen, ORCID ID:E-mail:
article id 7343, category Article
S. E. Multamäki. (1939). Kuusen kylvöstä ja istutuksesta metsitettävillä soilla. Acta Forestalia Fennica vol. 47 no. 3 article id 7343. https://doi.org/10.14214/aff.7343
English title: Sowing and planting of Norway spruce in drained peatlands in Finland.

The drained peatlands regenerate usually well, and artificial regeneration by sowing or planting has been rare. Field trials of Norway spruce (Picea abies (L.) H. Karst.) were established in northern Satakunta in Western Finland in three drained peatlands in 1934. Sowing trials of Norway spruce consisted of patch and broadcast sowed sample sites in treeless bogs and under protective forest. The seedlings of spruce were planted either under protective forest or in treeless peatland.

The results show that artificial regeneration of Norway spruce succeeds best under protective forest. The best tree species for upper storey is Betula sp. which grows fast and controls growth of ground vegetation. The peat is relatively decomposed on those peatlands that are suitable for spruce, and breaking of the surface of the peat is not recommended. In the sowing trials, breaking of the upper layer of the peat caused frost heaving, cracking of the dried surface and sticking of mud in the seedlings in the patch sown sample site. The shoot and root growth of seedlings of the broadcast sown site was better than seedlings of the patch sown site. The planted spruce seedlings seemed to be more susceptible for spring frost than the seedlings in the sown site. The plants of seed origin succeeded in general better than the planted seedlings.

The PDF includes a summary in German.

  • Multamäki, ORCID ID:E-mail:
article id 7198, category Article
P. Kokkonen. (1926). Beobachtungen über die Struktur des Bodenfrostes. Acta Forestalia Fennica vol. 30 no. 3 article id 7198. https://doi.org/10.14214/aff.7198
English title: Observations on the structure of soil frost.

The article presents some basic elements of soil frost and its occurrence.  The data contains observations from different regions and soil types in Finland. Different forms of soil frost and factors affecting its formulation are discussed. 

The article concludes with the factors effecting soil frost.  There are three issues. By the single grain soils the water content determines whether the frost becomes massive or layered. The structure of soil determines the occurrence of hollow formed frost. Within the soils with crumb structure both layered and hollow formed frost may occur. Layered frost may occur in soils with homogeneous crumb structure in which two kinds of ice layers occur: irregular and solid. The hollow-formed frost may occur in locker soils.
  • Kokkonen, ORCID ID:E-mail:
article id 7198, category Article
P. Kokkonen. (1926). Beobachtungen über die Struktur des Bodenfrostes. Acta Forestalia Fennica vol. 30 no. 3 article id 7198. https://doi.org/10.14214/aff.7198
English title: Observations on the structure of soil frost.

The article presents some basic elements of soil frost and its occurrence.  The data contains observations from different regions and soil types in Finland. Different forms of soil frost and factors affecting its formulation are discussed. 

The article concludes with the factors effecting soil frost.  There are three issues. By the single grain soils the water content determines whether the frost becomes massive or layered. The structure of soil determines the occurrence of hollow formed frost. Within the soils with crumb structure both layered and hollow formed frost may occur. Layered frost may occur in soils with homogeneous crumb structure in which two kinds of ice layers occur: irregular and solid. The hollow-formed frost may occur in locker soils.
  • Kokkonen, ORCID ID:E-mail:
article id 5590, category Article
Heikki Hänninen, Seppo Kellomäki, Ilkka Leinonen, Tapani Repo. (1996). Overwintering and productivity of Scots pine in a changing climate. Silva Fennica vol. 30 no. 2–3 article id 5590. https://doi.org/10.14214/sf.a9235

The productivity of Scots pine (Pinus sylvestris L.) under changing climatic conditions in the southern part of Finland was studied by scenario analysis with a gap-type forest ecosystem model. Standard simulations with the model predicted an increased rate of growth and hence increased productivity as a result of climatic warming. The gap-type model was refined by introducing an overwintering sub-model describing the annual growth cycle, frost hardiness, and frost damage of the trees. Simulations with the refined gap-type model produced results conflicting with those of the standard simulation, i.e., drastically decreased productivity caused by mortality and growth-reducing damage due to premature dehardening in the changing climate. The overwintering sub-model was tested with frost hardiness data from Scots pine saplings growing at their natural site 1) under natural conditions and 2) under elevated temperature condition, both in open-top chambers. The model predicted the frost hardiness dynamics quite accurately for the natural conditions while underestimating the frost hardiness of the saplings for the elevated temperature conditions. These findings show that 1) the overwintering sub-model requires further development, and 2) the possible reduction of productivity caused by frost damage in a changing climate is less drastic than predicted in the scenario analysis. The results as a whole demonstrated the need to consider the overwintering of trees in scenario analysis carried out with ecosystem model for boreal conditions. More generally, the results revealed a problem that exists in scenario analysis with ecological models: the accuracy of a model in predicting the ecosystem functioning under present climatic condition does not guarantee the realism of the model, nor for this reason the accuracy for predicting the ecosystem functioning under changing climatic conditions. This finding calls for the continuous rigorous experimental testing of ecological models used for assessing the ecological implications of climatic change.

  • Hänninen, ORCID ID:E-mail:
  • Kellomäki, ORCID ID:E-mail:
  • Leinonen, ORCID ID:E-mail:
  • Repo, ORCID ID:E-mail:
article id 5583, category Article
Ilkka Leinonen, Heikki Hänninen, Tapani Repo. (1996). Testing of frost hardiness models for Pinus sylvestris in natural conditions and in elevated temperature. Silva Fennica vol. 30 no. 2–3 article id 5583. https://doi.org/10.14214/sf.a9228

Two dynamic models predicting the development of frost hardiness of Finnish Scots pine (Pinus sylvestris L.) were tested with frost hardiness data obtained from trees growing in the natural conditions of Finland and from an experiment simulating the predicted climatic warming. The input variables were temperature in the first model, and temperature and night length in the second. The model parameters were fixed on the basis of previous independent studies. The results suggested that the model which included temperature and photoperiod as input variables was more accurate than the model using temperature as the only input variable to predict the development of frost hardiness in different environmental conditions. Further requirements for developing the frost hardiness models are discussed.

  • Leinonen, ORCID ID:E-mail:
  • Hänninen, ORCID ID:E-mail:
  • Repo, ORCID ID:E-mail:
article id 5536, category Article
Roar Skuterud, Jon Dietrichson. (1994). Budburst in detached birch shoots (Betula pendula) of different varieties winter-stored in darkness at three different temperatures. Silva Fennica vol. 28 no. 4 article id 5536. https://doi.org/10.14214/sf.a9176

Budburst timing and the relationship to storage temperature and duration were investigated in four varieties (entries) of 1–2 metres tall silver birch (Betula pendula Roth) trees. A total of 2,160 shoots were sampled, and the material stores in darkness at 0, 3 or 6 °C from November 29, 1993. When the shoots were placed in storage, they had been through a period of 29 days with temperatures below 0°C (since October 15). By that time the autumn dormancy was assumed already broken, and the trees were expected to respond to increased temperature by bud development. On January 4, 1994, and on four subsequent dates, January 19, February 1, March 4 and March 17, shoots were taken out of storage and set in growth chambers at 9, 12 or 15°C. The time to budburst was recorded.

Duration of storage, storage temperatures and varieties were all highly significant for budburst. The interaction terms were of less statistical importance. Based on the contrast between the three different growth chamber environments, three different methods were used to calculate the threshold temperatures for each entry. In spite of the pre-selection of variable budburst performers, the threshold values, varying between 0°C to -2°C, could not be shown to be statistically different. According to the results, the time of budburst changes in accordance with both winter and spring temperatures, being extremely early after a mild winter and warm spring, given sufficient autumn chilling. The similarities in the threshold temperatures indicate that the ranking in earliness between varieties will most likely be the same from year to year without regard to climate change.

  • Skuterud, ORCID ID:E-mail:
  • Dietrichson, ORCID ID:E-mail:
article id 5535, category Article
Mats Hannerz. (1994). Predicting the risk of frost occurrence after budburst of Norway spruce in Sweden. Silva Fennica vol. 28 no. 4 article id 5535. https://doi.org/10.14214/sf.a9175

Temperature sums required for budburst in various Norway spruce (Picea abies (L.) H. Karst.) provenances were determined, and weather statistics were then used to predict the risk of potentially damaging frosts at 11 locations in Sweden. Frost risk was quantified as the probability of a frost occurring within 100 day-degrees (two weeks) after budburst. The examples provided show that a spruce seedling from central Sweden has to sustain almost twice as many frost occassions as a seedling from Belorussia, when planted in southern and central Sweden. The method presented here can be used for mapping early summer frost risk in Sweden and for supporting provenance transfer guidelines.

  • Hannerz, ORCID ID:E-mail:
article id 5518, category Article
Heikki Hänninen, Seppo Kellomäki, Kaisa Laitinen, Brita Pajari, Tapani Repo. (1993). Effect of increased winter temperature on the onset of height growth of Scots pine: a field test of a phenological model. Silva Fennica vol. 27 no. 4 article id 5518. https://doi.org/10.14214/sf.a15679

According to a recently presented hypothesis, the predicted climatic warming will cause height growth onset of trees during mild spells in winter and heavy frost damage during subsequent periods of frost in northern conditions. The hypothesis was based on computer simulations involving a model employing air temperature as the only environmental factor influencing height growth onset. In the present study, the model was tested in the case of eastern Finnish Scots pine (Pinus sylvestris L.) saplings. Four experimental saplings growing on their natural site were surrounded by transparent chambers in autumn 1990. The air temperature in the chambers was raised during the winter to present an extremely warm winter under the predicted conditions of a double level of atmospheric carbon dioxide. The temperature treatment hastened height growth onset by two months as compared to the control saplings, but not as much as expected on the basis of the previous simulation study. This finding suggests that 1) the model used in the simulation study needs to be developed further, either by modifying the modelled effect of air temperature or by introducing other environmental factors, and 2) the predicted climatic warming will not increase the risk of frost damage in trees as much as suggested by the previous simulation study.

The PDF includes an abstract in Finnish.

  • Hänninen, ORCID ID:E-mail:
  • Kellomäki, ORCID ID:E-mail:
  • Laitinen, ORCID ID:E-mail:
  • Pajari, ORCID ID:E-mail:
  • Repo, ORCID ID:E-mail:
article id 5497, category Article
Pertti Pulkkinen. (1993). Frost hardiness development and lignification of young Norway spruce seedlings of southern and northern Finnish origin. Silva Fennica vol. 27 no. 1 article id 5497. https://doi.org/10.14214/sf.a15658

Seedlings from four Norway spruce (Picea abies (L.) H. Karst.) stands originating from areas with effective temperature sums ranging from 710 d.d. to 1,150 d.d. were raised under artificial light and temperature treatment. After a 10-week growing period the hardening process was started by subjecting the seedlings to +8°C night temperature and +15°C day temperature, and increasing the night length by 1.5 hour/week. Hardiness was measured by means of artificial freezing treatment (-10°C or -15°C), followed by visual estimation of the degree of needle injury. The stem height, lignification and bud development were measured before the freezing treatment. The amount of injury increased the more southern the origin of the tested material was. Furthermore, the proportion of non-lignified part of the seedling stem was negatively correlated with the latitude of the provenances. The proportion of seedlings with clearly visible buds was more than 90% in the northernmost entry and less than 1% in the southernmost one. The overall correlation coefficient between the needle injuries and the proportion of non-lignified part of the stem was rather high, but varied considerably from 0.3 in the northernmost material to over 0.6 in the southern provenances. According to the results, it seems to be possible to use growth characteristics as an indicator of frost hardiness at the provenance level.
The PDF includes an abstract in Finnish.

  • Pulkkinen, ORCID ID:E-mail:
article id 5437, category Article
Tapani Repo. (1991). Rehardening potential of Scots pine seedlings during dehardening. Silva Fennica vol. 25 no. 1 article id 5437. https://doi.org/10.14214/sf.a15591

The ability of one-year old Scots pine (Pinus sylvestris L.) seedlings to reharden during the dehardening period was studied. Naturally hardened quiescent seedlings were preconditioned at 0°C for ten days and then placed in chambers at different forcing temperatures with different light regimes. The forcing periods were followed by cool periods. Changes in frost hardiness were monitored at intervals using freeze tests of whole plants. Frost hardiness was assessed by three methods: impedance, survival and growth retardation. Dehardening seemed to be a partially reversible process, i.e. in some growing conditions slight rehardening was found.

The PDF includes an abstract in Finnish.

  • Repo, ORCID ID:E-mail:
article id 5433, category Article
Marja-Leena Valkonen, Heikki Hänninen, Paavo Pelkonen, Tapani Repo. (1990). Frost hardiness of Scots pine seedlings during dormancy. Silva Fennica vol. 24 no. 4 article id 5433. https://doi.org/10.14214/sf.a15587

The relationships between bud dormancy and frost hardiness were examined using two-year-old Pinus sylvestris L. seedlings. The chilling temperatures used were +4 and -2°C. To examine the dormancy release of the seedlings, a forcing technique was used. Frost hardiness was determined by artificial freezing treatments and measurements of electrical impedance. At the start of the experiment, the frost hardiness of the seedlings was about -25°C. After the rest break, the seedlings kept at +4°C dehardened until after eight weeks their frost hardiness reached -5°C. At the lower chilling temperature (-2°C) the frost hardiness remained at the original level. When moved from +4 to -2°C, seedlings were able to reharden only after the time required for bud burst in the forcing conditions had reached the minimum.

The PDF includes an abstract in Finnish

  • Valkonen, ORCID ID:E-mail:
  • Hänninen, ORCID ID:E-mail:
  • Pelkonen, ORCID ID:E-mail:
  • Repo, ORCID ID:E-mail:
article id 5407, category Article
Eero Kubin. (1990). Lumi-, routa- ja lämpöolot eri tavoin muokatussa metsämaassa Kuusamossa. Silva Fennica vol. 24 no. 1 article id 5407. https://doi.org/10.14214/sf.a15559
English title: The effect of site preparation on snow, soil frost and temperature conditions at a site near Kuusamo.

The winter 1986–87 was unusually cold; the snow cover remained thin and consequently the soil froze to a considerable depth. In spite of the severe frost, the lowest temperatures measured at the ground surface was -10.3°C and in the soil at the depth of 10 cm -5.8°C. The temperature sum of the following summer was unusually small and the soil frost melted more slowly than usual. The winter frosts did not have a decisive influence on the survival of planted seedlings.

The PDF includes an abstract in English.

  • Kubin, ORCID ID:E-mail:
article id 5369, category Article
Helen J. Jozefek. (1989). The effect of varying levels of potassium on the frost resistance of birch seedlings. Silva Fennica vol. 23 no. 1 article id 5369. https://doi.org/10.14214/sf.a15528

Seven hundred one-year-old Betula pendula Roth seedlings were given different concentrations of potassium fertilizer. Over the study period seedlings were subjected to artificial growing and dormant phases. Frost resistance of the seedlings was assessed by artificial freezing tests and electrical impedance measurements on stem cuttings. In general, high concentrations of potassium fertilizer reflected a low tolerance to frost. Pre-freezing impedance readings decreased with increasing potassium fertilizer dosages. Results from pre-freezing impedance measurements were found to be in broad agreement with the hypothesis that high impedance readings indicate a frost hardy tissue whereas low readings imply the opposite.

The PDF includes an abstract in Finnish.

  • Jozefek, ORCID ID:E-mail:
article id 5355, category Article
Halvor Rostad. (1988). Frost resistance during shoot elongation in Picea abies seedlings in relation to the growth environment of the previous growing period. Silva Fennica vol. 22 no. 3 article id 5355. https://doi.org/10.14214/sf.a15512

Frost resistance during shoot elongation in seedlings of Norway spruce (Picea abies (L.) H. Karst.) was studied in two experiments. The aim of the first study was to evaluate the effect of varying mineral nutrition. Except for potassium, only minor differences in mineral elements concentrations were established, presumably due to low levels of irradiance and thus a low rate of dry matter production. No significant differences in frost injuries were found between the treatments in the experimental series, but the control seedlings were significantly less injured. It is assumed that poor hardiness development at the end of one growth period resulting from low levels of irradiance may decrease the frost resistance during the next shoot elongation phase. Observations from the second experiment with Norway spruce nursery stocks representing different seedling ages and production systems, support this assumption.

The PDF includes an abstract in Finnish.

  • Rostad, ORCID ID:E-mail:
article id 5355, category Article
Halvor Rostad. (1988). Frost resistance during shoot elongation in Picea abies seedlings in relation to the growth environment of the previous growing period. Silva Fennica vol. 22 no. 3 article id 5355. https://doi.org/10.14214/sf.a15512

Frost resistance during shoot elongation in seedlings of Norway spruce (Picea abies (L.) H. Karst.) was studied in two experiments. The aim of the first study was to evaluate the effect of varying mineral nutrition. Except for potassium, only minor differences in mineral elements concentrations were established, presumably due to low levels of irradiance and thus a low rate of dry matter production. No significant differences in frost injuries were found between the treatments in the experimental series, but the control seedlings were significantly less injured. It is assumed that poor hardiness development at the end of one growth period resulting from low levels of irradiance may decrease the frost resistance during the next shoot elongation phase. Observations from the second experiment with Norway spruce nursery stocks representing different seedling ages and production systems, support this assumption.

The PDF includes an abstract in Finnish.

  • Rostad, ORCID ID:E-mail:
article id 5353, category Article
Øystein Johnsen, Inger Apeland. (1988). Screening early autumn frost hardiness among progenies from Norway spruce seed orchards. Silva Fennica vol. 22 no. 3 article id 5353. https://doi.org/10.14214/sf.a15510

Nursery grown Norway spruce (Picea abies (L.) H. Karst.) seedlings from 12 different seed orchards were tested for early autumn frost hardiness using artificial freezing tests. Seed orchards containing grafted parent clones originating from high altitudes produced seedlings showing higher damage than commercial control seed lots of the commercial controls. A seed orchard containing both German and Norwegian clones produced seedlings showing high damage. The correlation between bud-set and frost damage was high at the provenance level, but lower at the half- and full-sib-levels. Families with good growth capacity in progeny field tests showed large between-family variation in frost damage in the artificial freezing tests. This indicates the possibility to combine high growth rate with acceptable autumn frost hardiness in the selection of parent trees.

The PDF includes an abstract in Finnish.

  • Johnsen, ORCID ID:E-mail:
  • Apeland, ORCID ID:E-mail:
article id 5352, category Article
Lars Christersson, Heinrich A. von Fircks. (1988). Injuries to conifer seedlings caused by simulated summer frost and winter desiccation. Silva Fennica vol. 22 no. 3 article id 5352. https://doi.org/10.14214/sf.a15509

Visible frost damage to forest trees in Sweden seldom occurs in winter but is frequent in late spring, summer and early autumn. Frosts are frequent in all seasons in various parts of Sweden, even in the southernmost part (lat. 56°, N) and temperatures may be as low as -10°C even around mid-summer. Ice crystal formation within the tissues, which in most seedlings takes place at around -2°C, causes injury, not the sub-zero temperatures themselves.

The apical meristem, the elongated zone, and the needles of seedlings of Picea abies (L.) H. Karst. in a growing phase were damaged at about -3°C and those of Pinus sylvestris L. at about -6°C. Other species of the genus Pinus were tested and most were found to be damaged at about -6°C, with some variations. Picea species tested were damaged at about -3°C to -4°C.

A method has been designed to compare the response of different species to winter desiccation, which occurs under conditions of (1) low night temperature, (2) very high irradiation and increase in needle temperature during the photoperiod, (3) frozen soil, and (4) low wind speed. There were differences in response to winter desiccation between pine and spruce species. Seedlings of Pinus contorta tolerated these winter desiccation conditions much better than those of P. sylvestris or Picea abies. Picea mariana was the least tolerant of the species tested.

The PDF includes an abstract in Finnish.

  • Christersson, ORCID ID:E-mail:
  • Fircks, ORCID ID:E-mail:
article id 5352, category Article
Lars Christersson, Heinrich A. von Fircks. (1988). Injuries to conifer seedlings caused by simulated summer frost and winter desiccation. Silva Fennica vol. 22 no. 3 article id 5352. https://doi.org/10.14214/sf.a15509

Visible frost damage to forest trees in Sweden seldom occurs in winter but is frequent in late spring, summer and early autumn. Frosts are frequent in all seasons in various parts of Sweden, even in the southernmost part (lat. 56°, N) and temperatures may be as low as -10°C even around mid-summer. Ice crystal formation within the tissues, which in most seedlings takes place at around -2°C, causes injury, not the sub-zero temperatures themselves.

The apical meristem, the elongated zone, and the needles of seedlings of Picea abies (L.) H. Karst. in a growing phase were damaged at about -3°C and those of Pinus sylvestris L. at about -6°C. Other species of the genus Pinus were tested and most were found to be damaged at about -6°C, with some variations. Picea species tested were damaged at about -3°C to -4°C.

A method has been designed to compare the response of different species to winter desiccation, which occurs under conditions of (1) low night temperature, (2) very high irradiation and increase in needle temperature during the photoperiod, (3) frozen soil, and (4) low wind speed. There were differences in response to winter desiccation between pine and spruce species. Seedlings of Pinus contorta tolerated these winter desiccation conditions much better than those of P. sylvestris or Picea abies. Picea mariana was the least tolerant of the species tested.

The PDF includes an abstract in Finnish.

  • Christersson, ORCID ID:E-mail:
  • Fircks, ORCID ID:E-mail:
article id 5351, category Article
Tapani Repo. (1988). Physical and physiological aspects of impedance measurements in plants. Silva Fennica vol. 22 no. 3 article id 5351. https://doi.org/10.14214/sf.a15508

Electrical impedance characteristics of plant cells are dependent on such physiological factors as physiological condition, developmental stage, cell structure, nutrient status, water balance and temperature acclimation. In the measurements also such technical and physical factors as type of electrodes, frequency, geometry of the object, inter-electrode distance and temperature have an effect. These factors are discussed especially with respect to the impedance method in frost resistance studies of plants.

The PDF includes an abstract in Finnish.

  • Repo, ORCID ID:E-mail:
article id 5350, category Article
Heikki Hänninen, Paavo Pelkonen. (1988). Frost hardiness and over-wintering of forest trees. Silva Fennica vol. 22 no. 3 article id 5350. https://doi.org/10.14214/sf.a15507

This issue of Silva Fennica consists of eight articles, which are based on a co-nordic conference ”Frost hardiness and over-wintering in forest tree seedlings”, held in Joensuu, Finland, during December 1–3, 1986. The whole annual cycle of the trees is considered. Emphasis is given on methods for the study of frost hardiness, genetic variation in frost hardiness, nitrogen metabolism, bud dormancy release, and joint effect of natural and anthropogenic stress factors in the winter damage of forest trees. Practical implications for tree breeding and nursery management are discussed.

The PDF includes an abstract in Finnish.

  • Hänninen, ORCID ID:E-mail:
  • Pelkonen, ORCID ID:E-mail:
article id 5350, category Article
Heikki Hänninen, Paavo Pelkonen. (1988). Frost hardiness and over-wintering of forest trees. Silva Fennica vol. 22 no. 3 article id 5350. https://doi.org/10.14214/sf.a15507

This issue of Silva Fennica consists of eight articles, which are based on a co-nordic conference ”Frost hardiness and over-wintering in forest tree seedlings”, held in Joensuu, Finland, during December 1–3, 1986. The whole annual cycle of the trees is considered. Emphasis is given on methods for the study of frost hardiness, genetic variation in frost hardiness, nitrogen metabolism, bud dormancy release, and joint effect of natural and anthropogenic stress factors in the winter damage of forest trees. Practical implications for tree breeding and nursery management are discussed.

The PDF includes an abstract in Finnish.

  • Hänninen, ORCID ID:E-mail:
  • Pelkonen, ORCID ID:E-mail:
article id 5348, category Article
Risto Häkkinen, Pertti Hari. (1988). The efficiency of time and temperature driven regulation principles in plants at the beginning of the active period. Silva Fennica vol. 22 no. 2 article id 5348. https://doi.org/10.14214/sf.a15505

The distribution of the minimum temperatures after the beginning of the active period (one temperature for each spring) have been calculated for each principle using daily meteorological data collected during the years 1883–1980. The efficiency criterion is the variance of the minimum temperature distributions and the length of the active period. The most efficient regulation principle is found to be based on the temperature sum which includes a feedback component.

The PDF includes a summary in Finnish.

  • Häkkinen, ORCID ID:E-mail:
  • Hari, ORCID ID:E-mail:
article id 5233, category Article
Leo Heikurainen. (1985). Verhopuuston vaikutus kuusitaimikon kehitykseen. Silva Fennica vol. 19 no. 1 article id 5233. https://doi.org/10.14214/sf.a15412
English title: The influence of birch nurse crop (Betula pubescens) on the growth of Norway spruce (Picea abies) seedling stands on drained peatlands.

Young Norway spruce (Picea abies (L.) H. Karst.) are susceptible to early summer frost damage. Birch (Betula pubescens Ehrh.) naturally colonize rich or fairly rich drained peatlands after clear cutting, and can provide protection for developing seedlings. The report describes the development of spruce stands after various types of handing of the birch nurse crops.

Different proportions of birch and spruces did not have any influence on the spruce stand production. In cases where the nurse crop stand is removed when the spruce stand age was 20 years and height 4 m the spruce suffered badly but recovered with time, reaching the spruce stand growing under a nurse stand within the next 20 years. The height growth of spruce depends on the density of the nurse stand, especially on fertile sites. The development of diameter growth also depends on the density of the nurse trees. Removal of the nurse stand in spruce stands on the sites concerned should be done when the spruce stand is 20 years old and at the height of 4 m.

The PDF includes a summary in English.

  • Heikurainen, ORCID ID:E-mail:
article id 4921, category Article
Simo Hannelius. (1975). Ojitusalueiden kulkukelpoisuudesta puunkorjuussa. Silva Fennica vol. 9 no. 3 article id 4921. https://doi.org/10.14214/sf.a14763
English title: On the trafficability of drained peatlands in harvesting.

During the next decade there will be a marked increase in the allowable cut in drained peatlands. At the same time, the mechanization in logging proceeds, and in short-distance haulage the use of forwarders will increase. This study, based on literature and some observations, deals with logging conditions in drained peatlands with special reference to the suitability of heavy logging machines for use in such terrain. In addition, soil frost and the bearing capacity of the frozen peat soil were studied.

Freezing of the soil in a drained peatland area depends prevailingly on the weather conditions during early winter. The factors influencing soil freezing of a drained peatland are completely different from those regulating the freezing of natural peat soils. The frost penetrates in general deeper in the drained than virgin peatland. The topmost peat layer does not, however, freeze uniformly. Generally speaking, the bearing capacity of a drained peat soil is lower than that of undrained peat due to lower water content.

It is concluded that heavy logging machines are probably not fitted for use in drained areas on peatland even if the average soil frost values recorded would suggest it. Moreover, because of their extremely superficial root systems, peatland forests are exposed to damages by heavy machines in thinning operations.

The PDF includes a summary in English.

  • Hannelius, ORCID ID:E-mail:
article id 4881, category Article
Juhani Päivänen. (1973). Harvennuksen vaikutus lumi- ja routasuhteisiin nuoressa turvemaan männikössä. Silva Fennica vol. 7 no. 2 article id 4881. https://doi.org/10.14214/sf.a14717
English title: The effect of thinning on the snow cover and soil frost conditions in a young Scots pine stand on drained peatland.

The paper describes the results obtained from an investigation into the effect of thinning of different intensity and fertilization on the depth and water equivalent of the snow cover as well as on the depth of the soil frost in a young Scots pine (Pinus sylvestris L.) stand growing on drained peatland in Central Finland. Thinnings and fertilization was carried out in 1968, and the snow cover was followed in the winters 1970/71 and 1971/72.

Only extremely heavy thinnings (60% of the volume) seemed to increase the depth and water equivalent of the snow cover. The indirect effect of fertilization on the snow cover was insignificant. In the clear-cut sample plot of the study, soil frost was either not found at all or the depths of the frozen soil layer was smaller than in the other plots. When deciding the silvicultural measures to be taken in the case of tree stands growing on drained peatlands, there seems to be reason to avoid radical thinnings. Otherwise, the favourable influence of the trees on a site on its water relationships will be diminished.

The PDF includes a summary in English.

  • Päivänen, ORCID ID:E-mail:
article id 4840, category Article
Paavo Yli-Vakkuri. (1971). Havaintoja latvakasvainten pakkasvaurioista kuusen taimistoissa Itä-Savossa. Silva Fennica vol. 5 no. 2 article id 4840. https://doi.org/10.14214/sf.a14642
English title: Winter frost damages to the leaders of Norway spruce saplings in Eastern South-Finland.
Original keywords: Itä-Savo; kuusi; pakkasvauriot; pääverso

In the eastern parts of South-Finland the growing season of 1967 was highly favourable, which resulted in good height growth during the following year. During the summer 1968, temperature conditions were unfavourable, while the middle of summer was cold and the later part of the growing season unusually hot. The following winter had exceptionally cold spells from January to March, which caused Norway spruce (Picea abies (L.) H. Karst.) abundant winter frost damages such as dead shoots and buds, and destroyed needles.

These damages occurred particularly in stands with height of 0.5–3 m, and the occurrence of damages seemed to concentrate to the parts of saplings that had been immediately above the snow cover. Detailed observations on spruce plantations growing under a dense nurse stand of alder (Alnus sp.) indicated that explicitly the top shoots suffered from damages and not so much the laterals. When the needles of the leader suffered from minor damages, the shoot continued to grow normally. Still, sometimes a branch took over and became a new leader. If only the leader bud was killed, further stem development became dependent on one of the topmost lateral buds. When the upper part of the leaded died, one of the lateral shoots at its base usually became the new leader.

The PDF includes a summary in English.

  • Yli-Vakkuri, ORCID ID:E-mail:
article id 4784, category Article
Matti Leikola, Pentti Pylkkö. (1969). Verhopuuston tiheyden vaikutus metsikön minimilämpötiloihin hallaöinä. Silva Fennica vol. 3 no. 1 article id 4784. https://doi.org/10.14214/sf.a14570
English title: Influence of stand density on the minimum temperatures during frost nights.

The objective of this investigation was to study the influence of stand density of white birch (Betula pubescens Ehrl.) on the minimum temperatures in the stand during the growing season, and the actual minimum temperatures of the leading shoot of Norway spruce (Picea abies (L.) H. Karst.) seedlings growing in the open. The 40-year-old uniform white birch stand was situated in 142 m above the sea level in Southern Finland. The stand was treated with thinnings of three different densities in 1961.

Air temperature was recorded in four sample plots at heights of 0.1 m, 0.5 m, 1.0 m, 2 m and 4 m. In the stand of moderate density, temperatures were measured at heights of 6.0 m, and in the stand of full density at 6.0 m, 8.0 m and 10.0 m.

The temperature differences between stands of various densities proved to be rather small. Especially the thinnest stand differed very little from the open area. The soil surface has in all cases been warm compared with the higher air layers indicating meadow-fog-type by Geier (1965). On cloudy or windy weather all the temperature profiles in the various stands resembled each other. The difference between the air temperature and temperature of the spruce shoot was greatest at midnight and decreased steadily thereafter.

The problem in using shelter stands for spruce regeneration areas is that optimum shelter stand density is difficult to define. Already a thin shelter stand causes drawbacks to the young seedlings, but in order to be effective enough against early frosts, the shelter stand should be comparatively dense.

The PDF includes a summary in English.

  • Leikola, ORCID ID:E-mail:
  • Pylkkö, ORCID ID:E-mail:

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