Current issue: 53(1)

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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'growth and yield'.

Category: Research article

article id 7816, category Research article
Pentti Niemistö, Harri Kilpeläinen, Eero Poutiainen. (2018). Effect of first thinning type and age on growth, stem quality and financial performance of a Scots pine stand in Finland. Silva Fennica vol. 52 no. 2 article id 7816.
Highlights: Early commercial first thinning at the top height of 11 m with tree selection targeting high quality of remaining stems was more profitable in a Scots pine stand than thinning from below at similar time or delayed thinning 10 years later; After early first thinning only one intermediate thinning was needed, but a late thinning at age of 60 years was feasible in connection with increased amount of high quality butt logs after artificial pruning; The optimal rotation period for a Scots pine stand using a lower interest rate of 1% was 80–85 years depending on the thinning pattern. With a higher rate of 4%, the optimal rotation took only 60 years.

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

  • Niemistö, Natural Resources Institute Finland (Luke), Natural resources, Kampusranta 9 C, FI-60320 Seinäjoki, Finland ORCID ID:E-mail: (email)
  • Kilpeläinen, Natural Resources Institute Finland (Luke), Production systems, Yliopistokatu 6, FI-80100 Joensuu, Finland ORCID ID:E-mail:
  • Poutiainen, Oulu ORCID ID:E-mail:
article id 196, category Research article
Aaron R. Weiskittel, Laura S. Kenefic, Robert S. Seymour, Leah M. Phillips. (2009). Long-term effects of precommercial thinning on the stem dimensions, form and branch characteristics of red spruce and balsam fir crop trees in Maine, USA. Silva Fennica vol. 43 no. 3 article id 196.
The effects of precommercial thinning (PCT) on stem dimensions, form, volume, and branch attributes of red spruce [Picea rubens Sarg.] and balsam fir [Abies balsamea (L.) Mill.] crop trees were assessed 25 years after treatment in an even-aged northern conifer stand. Treatments were a uniform 2.4 x 2.4-m spacing and a control (no PCT). The PCT treatment significantly increased individual tree diameter at breast height (DBH), height growth, crown ratio, and crown width, while it reduced the tree height to DBH ratio. PCT also significantly increased stem taper and consequently, regional volume equations overpredicted observed stem volume by 2 to 15%, particularly for the spaced trees. PCT also increased the number and maximum size of branches on the lower bole. The sizes of knots on half of the sampled spruce crop trees in the spaced plots precluded them from being used as select structural lumber; there were no other effects on log grade. Our findings indicate that PCT can have a long-term influence on the structural attributes of individual trees, and that improved stem-volume prediction equations are needed in the Acadian region of North America.
  • Weiskittel, School of Forest Resources, University of Maine, Orono, ME 04469, USA ORCID ID:E-mail: (email)
  • Kenefic, U.S. Forest Service, Northern Research Station, Bradley, ME 04411, USA ORCID ID:E-mail:
  • Seymour, School of Forest Resources, University of Maine, Orono, ME 04469, USA ORCID ID:E-mail:
  • Phillips, School of Forest Resources, University of Maine, Orono, ME 04469, USA ORCID ID:E-mail:
article id 245, category Research article
Saija Huuskonen, Jari Hynynen, Risto Ojansuu. (2008). Stand characteristics and external quality of young Scots pine stands in Finland. Silva Fennica vol. 42 no. 3 article id 245.
The effects of silvicultural practices (regeneration method and young stand management) on the stand characteristics of young Scots pine (Pinus sylvestris (L.)) stands were studied. Stand density, mean diameter, crown ratio and external quality of young Scots pine stands were analysed on the basis of extensive inventory data. The study material consisted of 181 stands containing inventory growth plots, representing the most common site types for Scots pine and covering all the important wood production areas in Finland. Intensive management practices, i.e. artificial regeneration and precommercial thinning, clearly enhanced mean diameter development of the stand. The overall stand density of the crop trees was relatively low in the material (1925 trees ha–1). In more than one third of the stands, the stem number of crop trees was below 1500 trees ha–1. Stand density was not affected by forest management, but it was slightly higher in Southern than in Northern Finland. The geographical location, in terms of annual effective temperature sum, affected the average slenderness and crown ratio. At a given mean stand diameter, the dominant height of the stand was lower, and the mean crown ratio was higher, in Northern than in Southern Finland. The average external quality of the Scots pine trees was relatively low. The proportion of trees without any observed defects was 54%. The most common external defects were curved stems (23%) and branchiness (9%). Branchiness was more frequent among the largest trees, while curved stems were more common in smaller trees. Defects were the most frequent in planted stands, and in stands growing on fresh sites. The defects were more frequent in Northern Finland than in Southern Finland. The relatively low stand density and poor external quality of the young stands emphasize the importance of stem quality as a tree selection criterion in commercial thinnings of Scots pine stands, if the goal is to produce high quality timber.
  • Huuskonen, University of Helsinki, Department of Forest Ecology, Helsinki, Finland ORCID ID:E-mail: (email)
  • Hynynen, Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland ORCID ID:E-mail:
  • Ojansuu, Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland ORCID ID:E-mail:
article id 320, category Research article
Saija Huuskonen, Jari Hynynen. (2006). Timing and intensity of precommercial thinning and their effects on the first commercial thinning in Scots pine stands. Silva Fennica vol. 40 no. 4 article id 320.
The effects of the timing and intensity of precommercial thinning on the stand diameter development and wood production in Scots pine stands was addressed. A model was developed in order to assess the thinning response of the stand diameter development. The effect of precommercial and first commercial thinning on the stand volume and the thinning removal at first commercial thinning were also modelled. The models were developed to be applicable for forest management planning purposes. The results are based on Scots pine (Pinus sylvestris L.) trials (13 experiments and 169 plots) located in Southern and Central Finland. Precommercial thinning considerably enhanced the diameter development. Precommercial thinning (at Hdom 3 m to 2000 trees per hectare) increased the mean diameter by 15% at the first commercial thinning stage (Hdom 14 m) compared to the unthinned stand (3000 trees ha–1). Early and intensive precommercial thinning resulted in the strongest response in diameter development. Wide spacing also enhanced the diameter increment. In naturally regenerated stands the diameter development was ca 13% slower than that in seeded stands. The total volume at the time of first commercial thinning was affected by the timing of thinning and the stand structure. The volume of merchantable thinning removal depended on the timing and intensity of precommercial and first commercial thinnings. Delaying the first commercial thinning from 12 meters (Hdom) to 16 meters increased the volume of thinning removal by ca.70%. The early and light precommercial thinning (Hdom 3 m, to density of 3000 trees per hectare) increased the thinning removal by 40% compared to the late and intensive precommercial thinning (at 7 meters to the density of 2000 trees per hectare).
  • Huuskonen, University of Helsinki, Dept. of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Hynynen, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
article id 407, category Research article
Soili Kojola, Timo Penttilä, Raija Laiho. (2004). Impacts of different thinning regimes on the yield of uneven-structured Scots pine stands on drained peatland. Silva Fennica vol. 38 no. 4 article id 407.
Drained peatlands in northern Europe comprise more than 10 million ha of forestland and thus constitute a considerable production potential in forestry. Much of this area consists of stands dominated by Scots pine and close to maturity regarding commercial thinning. The trees within these stands typically vary in terms of age, size, and growth rate. The impacts of silvicultural cuttings on these uneven-structured stands are inadequately known. We simulated the impacts of a control regime with no thinnings, and three different thinning regimes, involving different thinning intensities, on the development of fifteen pine-dominated stands in Finland. The simulations started from the first thinnings and were continued until regeneration maturity. The predicted total yields ranged from 244 to 595 m3 ha–1, depending on site and thinning regime. The highest total yields were observed for the control regime in which 18–38% of the yield was, however, predicted to self-thin by the end of the simulation. Thus, the differences in the yields of merchantable wood were fairly small among the compared regimes. However, the regimes involving thinnings generally needed less time than the control regime to reach regeneration maturity. The mean annual increment of total stem volume was at its highest in the control regime. The highest mean annual increment of merchantable wood was obtained in the regime involving two moderate thinnings, but excluding the most low-productive sites where thinnings did not increase the yield of merchantable wood.
  • Kojola, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland ORCID ID:E-mail: (email)
  • Penttilä, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland ORCID ID:E-mail:
  • Laiho, University of Helsinki, Department of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland ORCID ID:E-mail:
article id 436, category Research article
Martti Varmola, Hannu Salminen, Mauri Timonen. (2004). Thinning response and growth trends of seeded Scots pine stands at the arctic timberline. Silva Fennica vol. 38 no. 1 article id 436.
Growth patterns and reactions of Scots pine (Pinus sylvestris L.) to thinning in extremely harsh climatic conditions were studied in two seeded Scots pine stands located on the arctic timberline. Coniferous trees usually do not form closed stands at the timberline, but occur only in scattered tree groups. The trial was established in two stands in 1985–1986 when the trees were at an age of 47 and 56 years and an average dominant height of 6.0–6.9 m. The trial was remeasured in 1998. The thinning treatments reduced the stem number for five different levels; final density of 300, 550, 800, 1050, and 1300 stems ha–1 and unthinned. The experiment had a randomised block design with four replications in each stand. The increased growing space provided by thinning accelerated diameter growth after a delay of 2–3 years. The differences between the radial growth of the thinning treatments were very clear during the whole 13- to 14-year observation period. Annual increment of the mean diameter was regularly the higher, the larger the spacing. Dominant diameter was less influenced by treatments. There were no significant differences in dominant height between any of the treatments. Both basal area and volume were regularly the greater the higher the stem number was. Even a relatively light thinning had a distinct positive effect on tree growth, i.e. not carrying out thinning resulted in a production loss of merchantable wood. According to the results, seeded stands on the arctic timberline can grow surprisingly well in favourable conditions and reach a dominant height of 12–14 m in 100 years and a mean annual increment of 1.0–1.5 m3 ha–1 y–1 over a rotation period of 130–160 years. Based on increment figures and thinning reactions, a spacing of ca. 1000 stems ha–1 can be recommended.
  • Varmola, The Finnish Forest Research Institute, Rovaniemi Research Station, P.O.Box 16, FIN-96301 Rovaniemi, Finland ORCID ID:E-mail: (email)
  • Salminen, The Finnish Forest Research Institute, Rovaniemi Research Station, P.O.Box 16, FIN-96301 Rovaniemi, Finland ORCID ID:E-mail:
  • Timonen, The Finnish Forest Research Institute, Rovaniemi Research Station, P.O.Box 16, FIN-96301 Rovaniemi, Finland ORCID ID:E-mail:

Category: Research note

article id 897, category Research note
Lars Lundqvist, Susanne Spreer, Christer Karlsson. (2013). Volume production in different silvicultural systems for 85 years in a mixed Picea abies–Pinus sylvestris forest in central Sweden. Silva Fennica vol. 47 no. 1 article id 897.
A long-term comparison of different silvicultural systems was established in 1923 in central Sweden, in an uneven-aged mixed Norway spruce–Scots pine forest (Picea abies (L.) Karst. – Pinus sylvestris L.) with about 85% spruce and 15% pine. The five treatments consisted of two examples of even-aged management 1) clear-cutting followed by planting, and 2) seed tree regeneration, one uneven-aged management 3) selection system, one exploiting treatment 4) diameter limit cut, and 5) one untreated control plot. Each treatment plot was 1 ha, 100 m × 100 m. The plots were measured and managed at irregular intervals, ranging from 7 to 15 years. In 2007–2008 the even-aged treatments and the diameter limit cut were repeated and a new rotation started. Mean annual volume increment during the whole observation period differed widely between the treatments, partly because of differences in species composition over time, with treatment clear-cutting followed by planting at the top, and the control at the bottom. Treatment selection system gave only about 60% of planting, but this was probably largely an effect of too small growing stock during the first roughly 50 years. When the growing stock was increased, periodic annual volume increment increased to about 80% of the mean annual volume increment in the even-aged, planted plot.
  • Lundqvist, Deparment of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden ORCID ID:E-mail: (email)
  • Spreer, Sveaskog Förvaltnings AB, Ljusdal, Sweden ORCID ID:E-mail:
  • Karlsson, Field Research Unit, Swedish University of Agricultural Sciences, Siljansfors, Sweden ORCID ID:E-mail:

Category: Article

article id 7041, category Article
Yrjö Ilvessalo. (1920). Tutkimuksia metsätyyppien taksatoorisesta merkityksestä nojautuen etupäässä kotimaiseen kasvutaulujen laatimistyöhön. Acta Forestalia Fennica vol. 15 no. 3 article id 7041.
English title: Studies on mensurational significance of forest site types as part of preparation of Finnish growth and yield tables.

New growth and yield tables were prepared for Southern Finland. To finalize the tables, it had to be determined whether the forest site types developed by Cajanus could be used in mensurational research.

Comparative study was performed in 1916-1919 to study the growth of the trees in different forest site types. Total of 467 sample sites were measured in Southern and Central Finland. All the forest site types were found to have a distinctive vegetation typical to the site. It can be concluded that the ground vegetation can be used to determine the forest site type. The growth of trees was different in different forest site types, yet similar within each site type. The forest site types are uniform, natural and easy to determine, and can thus be used to classify the forest stands and used in mensurational research and a basis to growth and yield tables.

The PDF includes a summary in German.

  • Ilvessalo, ORCID ID:E-mail:
article id 4652, category Article
Kullervo Kuusela. (1956). Hakkuilla käsiteltyjen koivikoiden rakenteesta ja kasvusta. Silva Fennica no. 90 article id 4652.
English title: On the structure and growth of birch stands treated with cutting.

The study is continuation of the earlier structure and growth studies of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) in Forest Research Institute. The material represents birch stands (Betula verrucosa, now B. pendula, and B. Pubescens L.) in Southern Finland. The stands were treated with different fellings, and in regard to their silvicultural condition classified as good, satisfactory and unsatisfactory. Height of the trees, height of living crown, volume, increment and volume increment and development of stem diameter series was measured.

The most characteristic difference between the silviculturally good and poor stands was that the the annual increment of the good stands concentrated into large size trees, and the increment of unsatisfactory stands into small and inferior trees.

It is concluded that if the aim of stand treatment is to produce large and high quality volume increment, the most favourable stand volume of  birch stands, compared with naturally normal stand volume, seems to be 90-85% at the age of 41-55 years, and 80-70% at the age of 56-65 years. If growth of large size trees is aimed at, the maximum number of the dominant trees per hectares cannot be more than 400 at the age of 50-60 years.

The article includes a summary in English.

  • Kuusela, ORCID ID:E-mail:
article id 4551, category Article
Yrjö Ilvessalo. (1939). Metsikön kasvun arvioiminen. Silva Fennica no. 52 article id 4551.
English title: Assessment of forest growth.

Silva Fennica issue 52 includes presentations held in professional development courses, arranged for foresters working in public administration in 1938. The presentations focus on practical issues in forest management and administration, especially in regional level. The education was arranged by Forest Service.

This presentation describes different methods of assessing tree growth.

  • Ilvessalo, ORCID ID:E-mail:
article id 4446, category Article
Yrjö Ilvessalo. (1927). Methods for preparing yield tables. Silva Fennica no. 5 article id 4446.

The article is a review on methods used in Central Europe and in Finland to construct growth and yield tables, and on their defects and advantages. One of the main defects of growth and yield tables prepared previously in Central Europe is that the site quality classes for different tree species have been formed independently and using different principles. Thus, the yields of different tree species on a similar site can’t be compared. In addition, the quality classes of this kind of growth and yield tables and growth series are artificial.

The Society of Forestry in Finland (now Finnish Society of Forest Sciences) started to prepare new yield tables for the most important tree species in Finland in 1916. The new yield tables aimed to improve the yield tables made in Central Europe in two aspects. Firstly, the quality of the site of each sample plot was assessed on the spot and independently from the standing crop. Thus the sample plots of each site class in setting up the growth series can be treated as independent groups. Consequently, the quality classes are be the same for all tree species. Secondly, mathematical-statistical methods were used to determine which of the stands that belong to the same quality class belong also to the same growth series.

The PDF includes a summary in Finnish.

  • Ilvessalo, ORCID ID:E-mail:
article id 4441, category Article
Yrjö Ilvessalo. (1927). Preparation of growth and yield tables. Silva Fennica no. 4 article id 4441.

One of the difficulties in constructing growth and yield tables has been to determine which of the sample plots growing the same tree species and belonging to the same forest site type, with reference to the quality of stands, have to be included in the same growth series.

New growth and yield tables for the most important tree species were constructed in Finland in 1916–1919, using new principles that aim at avoiding some of the common weaknesses. There were two main differences to the earlier work. First, the site quality class (forest site type) was determined for each sample plot when the sample plot was measured, independently of the stand occupying the site. In this way it was possible to treat the sample plots of each site as an independent group from the beginning, and so that the quality classes were the same for all the tree species. Second, mathematic-statistical methods were used to deduct the so-called stem frequency distribution series, when studying which of the sample plots of the same quality class belong to the same growth series. They represent the average number of stems of the different diameter classes. A more detailed description of the method used to create the growth and yield tables is published in Acta Forestalia Fennica no. 15.

In the PDF is included a summary in Finnish.

  • Ilvessalo, ORCID ID:E-mail:

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