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Articles containing the keyword 'thinnings'.

Category: Research article

article id 134, category Research article
Dan Bergström, Urban Bergsten, Tomas Nordfjell. (2010). Comparison of boom-corridor thinning and thinning from below harvesting methods in young dense Scots pine stands. Silva Fennica vol. 44 no. 4 article id 134. https://doi.org/10.14214/sf.134
At present, only a small proportion of the potential extractable bioenergy from young dense forests in Sweden is utilized. The conventional mechanized first thinning systems used in such stands suffer from low productivity, so the operation is only profitable in stands with bigger trees and high standing volumes. Conventional harvesters are used for this operation equipped with accumulating felling heads designed for handling several trees during each crane cycle. In thinning from below the felling and bunching work requires many time-consuming non-linear crane movements to avoid felling or damaging of future crop trees. However, higher productivity can be achieved when trees between strip roads are harvested in about 1 m-wide corridors with a length corresponding to the reach of the crane. We refer to this operation as boom-corridor thinning. The objective of this study was to compare felling and bunching productivity in young dense stands when employing thinning from below or boom-corridor thinning. Experiments were performed using a randomized block design involving between 4400 and 18 600 trees x ha-1 with a corresponding average tree size of 7.2 and 3.2 cm dbh, respectively. Based on the average tree being removed at a dbh of 5.7 cm, the productivity (ODt x PW-hour-1) was significant (almost 16%) higher for the boom-corridor thinning than for thinning from below treatment. At the same time, the time taken for the work element “Crane in-between” (the period between the loaded crane starting to move towards a tree and the felling head rapidly slowing down for positioning) was significantly reduced, by almost 17%. The positive results were achieved even though the operator was new to the method. To achieve a significantly higher efficiency during the felling and bunching operation, development of new harvesting equipment and operating techniques seems crucial.
  • Bergström, Swedish University of Agricultural Sciences, Dept of Forest Resource Management, Section of Planning and Operations Management, Umeå, Sweden ORCID ID:E-mail: dan.bergstrom@srh.slu.se (email)
  • Bergsten, Swedish University of Agricultural Sciences, Dept of Forest Resource Management, Section of Planning and Operations Management, Umeå, Sweden ORCID ID:E-mail:
  • Nordfjell, Swedish University of Agricultural Sciences, Dept of Forest Resource Management, Section of Planning and Operations Management, Umeå, Sweden ORCID ID:E-mail:
article id 134, category Research article
Dan Bergström, Urban Bergsten, Tomas Nordfjell. (2010). Comparison of boom-corridor thinning and thinning from below harvesting methods in young dense Scots pine stands. Silva Fennica vol. 44 no. 4 article id 134. https://doi.org/10.14214/sf.134
At present, only a small proportion of the potential extractable bioenergy from young dense forests in Sweden is utilized. The conventional mechanized first thinning systems used in such stands suffer from low productivity, so the operation is only profitable in stands with bigger trees and high standing volumes. Conventional harvesters are used for this operation equipped with accumulating felling heads designed for handling several trees during each crane cycle. In thinning from below the felling and bunching work requires many time-consuming non-linear crane movements to avoid felling or damaging of future crop trees. However, higher productivity can be achieved when trees between strip roads are harvested in about 1 m-wide corridors with a length corresponding to the reach of the crane. We refer to this operation as boom-corridor thinning. The objective of this study was to compare felling and bunching productivity in young dense stands when employing thinning from below or boom-corridor thinning. Experiments were performed using a randomized block design involving between 4400 and 18 600 trees x ha-1 with a corresponding average tree size of 7.2 and 3.2 cm dbh, respectively. Based on the average tree being removed at a dbh of 5.7 cm, the productivity (ODt x PW-hour-1) was significant (almost 16%) higher for the boom-corridor thinning than for thinning from below treatment. At the same time, the time taken for the work element “Crane in-between” (the period between the loaded crane starting to move towards a tree and the felling head rapidly slowing down for positioning) was significantly reduced, by almost 17%. The positive results were achieved even though the operator was new to the method. To achieve a significantly higher efficiency during the felling and bunching operation, development of new harvesting equipment and operating techniques seems crucial.
  • Bergström, Swedish University of Agricultural Sciences, Dept of Forest Resource Management, Section of Planning and Operations Management, Umeå, Sweden ORCID ID:E-mail: dan.bergstrom@srh.slu.se (email)
  • Bergsten, Swedish University of Agricultural Sciences, Dept of Forest Resource Management, Section of Planning and Operations Management, Umeå, Sweden ORCID ID:E-mail:
  • Nordfjell, Swedish University of Agricultural Sciences, Dept of Forest Resource Management, Section of Planning and Operations Management, Umeå, Sweden ORCID ID:E-mail:
article id 144, category Research article
Markku Oikari, Kalle Kärhä, Teijo Palander, Heikki Pajuoja, Heikki Ovaskainen. (2010). Analyzing the views of wood harvesting professionals related to the approaches for increasing the cost-efficiency of wood harvesting from young stands. Silva Fennica vol. 44 no. 3 article id 144. https://doi.org/10.14214/sf.144
A lot of viable guidelines are currently available for more cost-effective harvesting of energy wood and industrial roundwood (i.e. pulpwood) from young stands. The study ranked the proposed potential approaches for increasing the cost-efficiency of small-diameter (d1.3 < 10 cm) energy wood and industrial roundwood harvesting from early thinnings. Research data, based on a total of 40 personal interviews, was collected in early 2008. The interviewees were divided into four wood harvesting professional groups: 1) Managers in wood procurement organizations, 2) Forest machine contractors, 3) Forest machine manufacturers and vendors, and 4) Wood harvesting researchers. In the opinion of the respondents, there is great potential to increase the cost-efficiency of wood harvesting through improving harvesting conditions (i.e. effective tending of seedling stands, delaying harvesting operations, and pre-clearance of dense undergrowth). The interviewees also underlined that harvesting methods can be rationalized, e.g. multiple-tree handling in industrial roundwood cuttings, crane scale measurement, integrated wood harvesting, and careful selection of stands for harvesting. The strong message given by the interviewees was that the education of forest machine operators must be made more effective in the future. There would be significant possibilities for cost savings in young stands, if methods and techniques with the most potential were utilized completely in wood harvesting.
  • Oikari, Karelwood, Kontiolahti, Finland ORCID ID:E-mail: markku.oikari@karelwood.com (email)
  • Kärhä, Metsäteho Oy, Helsinki, Finland ORCID ID:E-mail:
  • Palander, University of Eastern Finland, Faculty of Science and Forestry, Joensuu, Finland ORCID ID:E-mail:
  • Pajuoja, Metsäteho Oy, Helsinki, Finland ORCID ID:E-mail:
  • Ovaskainen, University of Eastern Finland, Faculty of Science and Forestry, Joensuu, Finland ORCID ID:E-mail:
article id 143, category Research article
Juha Laitila, Jani Heikkilä, Perttu Anttila. (2010). Harvesting alternatives, accumulation and procurement cost of small-diameter thinning wood for fuel in Central Finland. Silva Fennica vol. 44 no. 3 article id 143. https://doi.org/10.14214/sf.143
This study compared harvesting alternatives, accumulation and procurement costs of small-diameter thinning wood chips for fuel, when trees were harvested either as delimbed stemwood or whole trees. The calculation was made for a hypothetical plant located in Central Finland and the radius of the procurement area was 100 km via the existing road network. Cutting was done with conventional harvester head equipped with multi-tree-handling (MTH) accessories, with the logged trees being chipped at the roadside storage. The cost of delimbed stemwood chips at heating plant was 24% higher compared to the cost of whole tree chips. The availability analysis attested that delimbing lowered the regional cutting removal by 42% compared to the whole tree harvesting, when the minimum accumulation for the fuel fraction at the stand was set at 25 m3/ha. Delimbing diminishes the recovery rate at the site, resulting in a diminishing number of potential recovery sites meeting the threshold volume. However, the study showed that the forest energy potential is increased and procurement costs are reduced, if delimbed stemwood is harvested from stands where the whole tree harvesting is not acceptable due to nutrient loss or for other ecological reasons. Intelligent selection of cutting methods for different stands enables minimization of transport distance and control of procurement cost.
  • Laitila, The Finnish Forest Research Institute, Joensuu, Finland ORCID ID:E-mail: juha.laitila@metla.fi (email)
  • Heikkilä, L&T Biowatti Oy, Seinäjoki, Finland ORCID ID:E-mail:
  • Anttila, The Finnish Forest Research Institute, Joensuu, Finland ORCID ID:E-mail:
article id 151, category Research article
Janne Miettinen, Pekka Helle, Ari Nikula, Pekka Niemelä. (2010). Capercaillie (Tetrao urogallus) habitat characteristics in north-boreal Finland. Silva Fennica vol. 44 no. 2 article id 151. https://doi.org/10.14214/sf.151
This study aimed to identify tools for taking capercaillie habitats into consideration in forest management. This would provide new alternatives for ecologically more sustainable forest management. Capercaillie summer and winter locations, from wildlife monitoring counts (1998–2004) in northern Finland, and reference, non-capercaillie locations were combined with forest planning data, and the area proportions of different landscape classes in an 800-m radius circle surrounding capercaillie and reference locations were compared. Thinning stands (in summer and winter) and spruce mires (in summer) were more abundant in capercaillie habitats than in reference landscapes, whereas e.g. seedling stands, mature stands and waste land areas were less abundant. The relative habitat use was highest in mean tree diameter (DBH) classes from 10.5 to 14.5 cm in summer habitats of adult capercaillie in heath forests, whereas in peatland forests, in brood habitats and in winter habitats it peaked in diameter classes 14.5 to 18.5 cm. The tree layer density was positively associated with the relative habitat use. A trend of lower habitat use was detected in the largest diameters (17–40 cm) in comparison to middle-sized diameters (10–16 cm) in heath forests, but not in peatland forests. Relatively young managed forests (age 30–40 years or more) can form suitable capercaillie habitats in north-boreal forests. However, this suitability is not necessarily permanent. Understorey management, longer rotations and multicohort forest management are suitable tools for capercaillie habitat management, because they can increase the available cover close to the ground, canopy cover, overall forest cover at the landscape scale and bilberry cover.
  • Miettinen, Finnish Game and Fisheries Research Institute, Finland ORCID ID:E-mail: janne.miettinen@rktl.fi (email)
  • Helle, Finnish Game and Fisheries Research Institute, Finland ORCID ID:E-mail:
  • Nikula, Finnish Forest Research Institute, Finland ORCID ID:E-mail:
  • Niemelä, University of Turku, Dept of Biology ORCID ID:E-mail:
article id 256, category Research article
Juha Laitila. (2008). Harvesting technology and the cost of fuel chips from early thinnings. Silva Fennica vol. 42 no. 2 article id 256. https://doi.org/10.14214/sf.256
This study compared and analyzed the procurement cost of whole tree chips when using supply chains based on comminution at the roadside landing or at the terminal. It also identified the bottlenecks of the most common logging systems used in Finland. The study was done by using existing and published productivity parameters and models. The procurement cost calculations were made for a stand where the forwarding distance was 200 metres, removal of whole trees was 60 m per hectare and the area of the stand was 2.0 hectares. The average size of the removed whole trees was 30 litres. The direct transport distance from the stand to the terminal or to the end use facility was 40 km while the secondary distance from the terminal to the end use facility was 10 km. A stumpage price for the harvested raw material was not included in this study. According to the study the cost of whole trees chips were 31.9–41.6 euros/m at the plant, or 14.9–19.4 euros/MWh when the moisture content of chips was estimated to be 40%. The two-machine system was found to be the most cost competitive logging system in pre-commercial thinnings thanks to both efficient cutting and, especially, forwarding work. In the manual worker based logging, the costs of felling bunching were the same as the mechanised system, whereas in forwarding the costs were almost double. Using the harwarder system the logging costs were found to be the highest, but in the larger tree volumes and removals the costs were almost equal to the manual worker based logging. The supply chain based on chipping at the roadside landing was more cost efficient compared to the chipping at the terminal system. The lower comminution cost at the terminal was not enough to cover the higher transportation cost of unprocessed material to the terminal, handling cost of chips at the terminal or the delivery cost to the end use facility.
  • Laitila, Finnish Forest Research Institute, Joensuu Research Unit, Joensuu, Finland ORCID ID:E-mail: juha.laitila@metla.fi (email)
article id 523, category Research article
Heli Peltola, Jari Miina, Ismo Rouvinen, Seppo Kellomäki. (2002). Effect of early thinning on the diameter growth distribution along the stem of Scots pine. Silva Fennica vol. 36 no. 4 article id 523. https://doi.org/10.14214/sf.523
The absolute and relative effects of the first thinning on the diameter growth distribution along the stems were studied in 98 Scots pines (Pinus sylvestris L.) at heights of 1.3, 4, 6 and 8 m. The data cover one 3-year pre-thinning period and four 3-year post-thinning periods in plots with densities varying from 575 to 3400 stems ha–1. A shift in the point of maximum diameter growth down the bole was found during the first 3 years after thinning, with a shift back up the stem later. The thinning response over the whole 12-year post-thinning period was strongest the nearer the stem base and the heavier the thinning. The largest trees had the highest diameter growth after thinning in absolute terms, and the growth was greater the heavier the thinning. The absolute thinning response over the 12-year post-thinning period was highest in the medium tree size and in the largest trees, especially on the heavily thinned and lightly thinned plots. Whereas in the moderately thinned stand the smaller and larger trees responded more than did those of medium size on average. In relative sense, however, the small trees on heavily or moderately thinned plots responded more rapidly and more strongly than the medium-sized or large trees over the whole stem. The small trees on the lightly thinned plots responded only slightly to thinning. The results suggest that it is possible to affect the uniformity of wood properties (such as ring width) both within and between trees by thinning.
  • Peltola, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland ORCID ID:E-mail: heli.peltola@forest.joensuu.fi (email)
  • Miina, Finnish Forest Research Institute, Joensuu Research Centre, P.O. Box 68, FIN-80101 Joensuu, Finland ORCID ID:E-mail:
  • Rouvinen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland ORCID ID:E-mail:
  • Kellomäki, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland ORCID ID:E-mail:

Category: Research note

article id 9911, category Research note
Tālis Gaitnieks, Indulis Brauners, Kristīne Kenigsvalde, Astra Zaļuma, Lauma Brūna, Jurģis Jansons, Natālija Burņeviča, Andis Lazdiņš, Rimvydas Vasaitis. (2018). Infection of pre-commercially cut stumps of Picea abies and Pinus sylvestris by Heterobasidion spp. – a comparative study. Silva Fennica vol. 52 no. 1 article id 9911. https://doi.org/10.14214/sf.9911
Highlights: In pre-commercial thinnings both Heterobasidion infection frequency and the extent of surface colonization correlated positively with stump diameter of both Norway spruce and Scots pine; Spruce stumps were significantly more often subjected to primary infections than pine stumps; The pathogen exhibited more extensive surface colonization of spruce stumps than of pine stumps.

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

  • Gaitnieks, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: talis.gaitnieks@silava.lv (email)
  • Brauners, JSC “Latvia’s State Forests”, 1 Vainodes str., Riga, LV-1004, Latvia ORCID ID:E-mail: i.brauners@lvm.lv
  • Kenigsvalde, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: kristine.kenigsvalde@silava.lv
  • Zaļuma, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: astra.zaluma@silava.lv
  • Brūna, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: lauma.bruna@silava.lv
  • Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: jurgis.jansons@silava.lv
  • Burņeviča, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: natalija.arhipova@silava.lv
  • Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: andis.lazdins@silava.lv
  • Vasaitis, Swedish University of Agricultural Sciences (SLU), P.O. Box 7026, SE-75007 Uppsala, Sweden ORCID ID:E-mail: Rimvys.Vasaitis@slu.se
article id 310, category Research note
Timo Tahvanainen, Kalle Kaartinen, Timo Pukkala, Matti Maltamo. (2007). Comparison of approaches to integrate energy wood estimation into the Finnish compartment inventory system. Silva Fennica vol. 41 no. 1 article id 310. https://doi.org/10.14214/sf.310
The harvesting of energy wood from young stands is increasing as the demand for renewable wood fuel is growing. Energy wood consists of stems, tree tops, branches and needles, depending on the size of the trees and the logging method used. The current forest inventory and planning systems used in private forests in Finland do not produce estimates of energy wood components. In stands typical for energy wood harvesting, a large share of energy wood consists of trees smaller than the minimum size for pulpwood. In this study, energy wood was included into the calculation system of compartment inventory, and a procedure for simulating the thinning treatments in young stands was developed. The results for six inventory alternatives and prediction of energy wood were compared with the use of inventory material from 37 young stands that have plenty of energy wood. The measurement of additional stand characteristics and the use of a calibration estimation method was tested, as well as the use of plot-level inventory data instead of stand level data. The results showed that the measurement of the number of trees per hectare, in addition to stand basal area and mean diameter, improved the energy wood estimates. The additional minimum and maximum diameters improved the precision of the estimates, but did not affect bias. The removal estimates were more precise when plot-level data was used, rather than stand-level data. The removal estimates were higher with plot-level data. The results suggest that, in heterogeneous young stands, plot by plot prediction would give more accurate removal estimates than the calculation of a corresponding prediction at the stand-level.
  • Tahvanainen, Finnish Forest Research Institute, P.O. Box 68, FI-80101 Joensuu, Finland ORCID ID:E-mail: timo.tahvanainen@metla.fi (email)
  • Kaartinen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuun yliopisto, Finland ORCID ID:E-mail:
  • Pukkala, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuun yliopisto, Finland ORCID ID:E-mail:
  • Maltamo, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuun yliopisto, Finland ORCID ID:E-mail:

Category: Article

article id 7175, category Article
Leo Heikurainen. (1967). Hakkuun vaikutus ojitettujen soiden vesitalouteen. Acta Forestalia Fennica vol. 82 no. 2 article id 7175. https://doi.org/10.14214/aff.7175
English title: Influence of cuttings on the water economy of drained peatlands.

The present investigation revealed that the influence of a forest cover on the water economy of the soil is very great in Finland. Cutting of the forest gave cause to a rise of the ground water table, which, when clear-cutting is in question, reached a magnitude of 20–40 cm. The water supplies of the soil increased 40–60 mm. In the winter, too, the ground water remaind at a lower level in the forest than in opening, however, the difference is rather small. Thinnings had same kind of effect as clear-cuttings, but the influence of even heavy thinnings was still relatively small.

The water supplies of the soil after felling decreased mainly due to the decrease in the interception in the canopy. When the water table is at the same level in the forest and in opening, evapotranspiration might be greater in the forest than in openings. However, when the water level is during the growing season considerably lower in the forest than in an opening, the evapotranspiration is strongly decreased in the forest, which means that more water is evaporated and transpirated from the opening than from the forest. Because the water table is at a higher level in the opening than in the forest, runoff from clear-cut areas has exceeded that from the forest. This means that the influence of felling on the water economy of the soil is actually even greater than indicated in this work.

The results mean that the influence of the forest cover makes up that of drainage. This affects the need for maintenance of ditches. On the other hand, the final cutting will rise the ground water strongly.

The PDF includes a summary in English.

  • Heikurainen, ORCID ID:E-mail:
article id 7411, category Article
Aarne Nyyssönen. (1954). Hakkauksilla käsiteltyjen männiköiden rakenteesta ja kehityksestä. Acta Forestalia Fennica vol. 60 no. 4 article id 7411. https://doi.org/10.14214/aff.7411
English title: Structure and development of Scots pine stands treated with different cuttings.

Permanent sample plots are considered to be the most reliable basis for investigations into structure and development of stands. Such sample plots, established since 1924 in Finland, have been used to study thinnings of varying intensity. These studies are yet too short to give comprehensive conclusions. It is also possible to base the studies on sample plots measured in managed forests and gain in this way information suitable for practical purposes. In this investigation development of stands treated by two different methods, repeated thinnings and repeated selection cutting were studied in pure, even-aged Scots pine (Pinus sylvestris L.) stands in Southern Finland, on three forest types.

The results show that volume increment level of naturally normal stands seem to have been reached easily by stands treated with repeated thinnings. With advancing age, the growing stock of thinned stands fall short from the natural stands. As thinnings have removed primarily the poorest trees, the increment is distributed over trees of a larger size more in thinned than in naturally normal stands.

When intensive cuttings have resulted in a relatively small growing stock, the decrease in volume increment leads to considerable decrease in volume. The size of the tree has no essential effect – within certain limits - on the volume increment of the stand, if the volume removed is similar. However, every intermediate thinning removing largest-sized trees may result in the prolonged rotation. Since the volume increment of an older stand is much smaller than earlier, intermediate thinnings removing largest-sized trees should be avoided if the aim is the greatest volume yield. The growing stock of middle-aged or older stands untreated or treated with slight cuttings only can as a rule be considerably reduced without volume increment declining.

The PDF includes a summary in English.

  • Nyyssönen, ORCID ID:E-mail:

Category: Special section

article id 289, category Special section
Thomas Wutzler, Martina Mund. (2007). Modelling mean above and below ground litter production based on yield tables. Silva Fennica vol. 41 no. 3 article id 289. https://doi.org/10.14214/sf.289
Estimates of litter production are a prerequisite for modeling soil carbon stocks and its changes at regional to national scale. However, the required data on biomass removal is often available only for the recent past. In this study we used yield tables as a source of probable past forest management to drive a single tree based stand growth model. Next, simulated growth and timber volume was converted to tree compartment carbon stocks and biomass turnover. The study explicitly accounted for differences in site quality between stands. In addition we performed a Monte Carlo uncertainty and sensitivity analysis. We exemplify the approach by calculating long-term means of past litter production for 10 species by using yield tables that have been applied in Central Germany during the last century. We found that litter production resulting from harvest residues was almost as large as the one from biomass turnover. Differences in site quality caused large differences in litter production. At a given site quality, the uncertainty in soil carbon inputs were 14%, 17%, and 25% for beech, spruce, and pine stands, respectively. The sensitivity analysis showed that the most influential parameters were associated with foliage biomass and turnover. We conclude that rates of mean past litter production and their uncertainties can reliably be modeled on the basis of yield tables if the model accounts for 1) full rotation length including thinning and final harvest, 2) differences in site quality, and 3) environmental dependency of foliage biomass and foliage turnover.
  • Wutzler, Max Planck Institute for Biogeochemistry, Jena, Germany ORCID ID:E-mail:
  • Mund, Max Planck Institute for Biogeochemistry, Jena, Germany ORCID ID:E-mail:

Category: Article

article id 5639, category Article
Dimitris Athanassiadis. (1997). Residual stand damage following cut-to-length harvesting operations with a farm tractor in two conifer stands. Silva Fennica vol. 31 no. 4 article id 5639. https://doi.org/10.14214/sf.a8541

The objectives of this study were to record residual stand damage during harvesting operations and evaluate the influence of factors such as distance of the tree from the strip road, machine parts, operational phase, on the occurrence of tree wounds. The machine was a farm tractor equipped with a crane mounted on the front axle and a single grip harvester head. The study was carried out in two stands located in Southeast Sweden. Stand 1 was a 30-year-old Norway spruce (Picea abies (L.) H. Karst.) plantation on an afforested pasture while stand 2 was a 90-year-old mixed stand of Norway spruce, Scots pine (Pinus sylvestris L.), birch (Betula pendula Roth) and aspen (Populus tremula L.).

The mean damage percentage was 6.3% for the first stand and 6.5% for the second stand. Sixty-five percent of the wounds were less than 50 cm2, with 91% of the damage occurring on the stem and 91% of the damage on or below the root collar. Sixty-six percent of the wounds produced by the stem under processing or by the harvesting head while only 10% of the wounds were produced by the tractor wheel. Damaged trees were distributed evenly in the crane reach zone. Significant differences were found between rut depths after one, two, four and six passes of the tractor in stand 1.

  • Athanassiadis, ORCID ID:E-mail:
article id 5559, category Article
Jari Hynynen. (1995). Predicting the growth response to thinning for Scots pine stands using individual-tree growth models. Silva Fennica vol. 29 no. 3 article id 5559. https://doi.org/10.14214/sf.a9210

Individual tree-growth models for diameter and height, and a model for the cylindrical stem form factor are presented. The aims of the study were to examine modelling methods in predicting growth response to thinning, and to develop individual-tree, distance-independent growth models for predicting the development of thinned and unthinned stands of Scots pine (Pinus sylvestris L.). The models were constructed to be applicable in simulation systems used in practical forest management planning. The models were based on data obtained from eleven permanent thinning experiments located in even-aged Scots pine stands in Southern and Central Finland.

Two alternative models were developed to predict tree diameter growth in thinned and unthinned stands. In the first model, the effect of stand density was described using stand basal area. In the alternative model, an explicit variable was incorporated referring to the relative growth response due to thinning. The magnitude of the growth response was expressed as a function of thinning intensity. The Weibull function was employed to describe the temporal distribution of the thinning response. Both models resulted in unbiased predictions in unthinned and in moderately thinned stands. An explicit thinning variable was needed for unbiased growth prediction in heavily thinned stands, and in order to correctly predict the dynamics of the growth response.

In the height growth model, no explicit thinnning variable referring thinning was necessary for growth prediction in thinned stands. The stem form factor was predicted using the model that included tree diameter and tree height as regressor variables. According to the results obtained, the information on the changes in the diameter/height ratio following the thinning is sufficient to predict the change in stem form.

  • Hynynen, ORCID ID:E-mail:
article id 5449, category Article
Timo Pukkala, Taneli Kolström. (1991). Effect of spatial pattern of trees on the growth of Norway spruce stand. Silva Fennica vol. 25 no. 3 article id 5449. https://doi.org/10.14214/sf.a15603

The simulation model consists of a method to generate theoretical Norway spruce (Picea abies (L.) H. Karst.) stands, and a spatial growth model to predict the growth of these stands. The stand generation procedure first predicts the tree diameters from a few stand characteristics and from tree locations. Tree age and height are predicted using spatial models. Spatial growth models were made for both diameter growth and basal area growth. Past growth was used as a predictor in one pair of models and omitted in another pair. The stand generation method and the growth models were utilized in studying the effect of tree arrangement and thinning method on the growth of a Norway spruce stand.

The PDF includes an abstract in Finnish.

  • Pukkala, ORCID ID:E-mail:
  • Kolström, ORCID ID:E-mail:
article id 5235, category Article
Pekka Kilkki, Tapani Pohjola, Eljas Pohtila. (1985). Puiden ryhmittäisyyden huomioonottaminen harvennusmalleissa. Silva Fennica vol. 19 no. 2 article id 5235. https://doi.org/10.14214/sf.a15414
English title: Use of the spatial distribution of trees in thinning models.

Thinning models are generally based on the density of the stand measured by the average basal area per hectare, for instance. These models are handicapped by the uneven structure of the stands. In uneven stands the averages are inadequate indicators for the need and amount of thinnings.

Small relascope plots were tested in the measurement of the spatial distribution of trees and in the determination of the need and amount of thinnings. The thinning quantity was determined as the difference between the actual distribution of the relascope plots into basal area classes and the ideal distribution after thinning. Sequential sampling was used in the derivation of the decision equations. A respective BASIC-program for a programmable pocket calculator is given.

The PDF includes a summary in English.

  • Kilkki, ORCID ID:E-mail:
  • Pohjola, ORCID ID:E-mail:
  • Pohtila, ORCID ID:E-mail:
article id 5179, category Article
Pertti Harstela, Antti Maukkonen. (1983). Tavanomainen ja kuormainprosessori varttuneissa harvennusmetsiköissä. Silva Fennica vol. 17 no. 2 article id 5179. https://doi.org/10.14214/sf.a15095
English title: A conventional and grapple loader processor in second and third thinnings. A simulator experiment.

Using literature and a simulator experiment, an ordinary processor and a grapple loader processor were compared in conditions corresponding to thinning later than the first commercial thinning. Visual bucking only was employed in the simulator experiment. The strip road spacing was 30 m and there was no preliminary skidding of the trees. The simulator experiment confirmed the view reached in the literature that work productivity of the grappler loader processor is 20–40 % greater than that of an ordinary processor provided that the stem size is under 0.2–0.4 m3.

The PDF includes a summary in English.

  • Harstela, ORCID ID:E-mail:
  • Maukkonen, ORCID ID:E-mail:
article id 4944, category Article
Eino Mälkönen. (1976). Effect of whole-tree harvesting on soil fertility. Silva Fennica vol. 10 no. 3 article id 4944. https://doi.org/10.14214/sf.a14790

This paper analyses the nutrient loses caused by whole-tree harvesting on the basis of the literature data. It has been considered that traditional stemwood harvesting does not lead to impoverishment of the soil because the nutrient content of the wood is quite low. The nutrient loss occurring in connection with heavy thinnings and whole-tree harvesting has been considered so great that it has to be compensated by fertilizer application. In comparison with harvesting unbarked stem timber, whole-tree harvesting has been found to increase the nutrient loss at the stage of final cutting as follows: N2 to 4 times, P 2 to 5 times, K 1.5 to 3.5 times and Ca 1.5 to 2.5 times. Depending on the conditions prevailing on the site, any one of these nutrients may be the limiting factor for tree growth during the next tree generation

The PDF includes a summary in Finnish.

  • Mälkönen, 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 4819, category Article
Matti Kärkkäinen. (1970). Hakkuutähteiden merkityksestä puuston vaurioitumisen ja raiteenmuodostuksen kannalta harvennusmetsissä. Silva Fennica vol. 4 no. 2 article id 4819. https://doi.org/10.14214/sf.a14608
English title: Significance of logging waste in thinnings as to scars and tracks in the terrain.

The purpose of this study was to explain whether it is possible to affect, in practical working site conditions, by means of logging waste on the strip road, the depth of the track which is formed in terrain transportation and the injuries of the growing stand. Five 20 m long investigation areas with logging waste and five similar areas without logging waste were arranged on one strip road at Teisko logging site in Southern Finland. The logging waste layer was mainly Norway spruce and 10–15 cm thick. A KL–836 B forwarder was used. The type of soil was loam.

The logging waste affected the depth of the track only by decreasing the wear of humus layer. Even decreasing effect of logging waste on the injuries in the growing stand was minor. At Kitee working site in Eastern Finland strip roads were studied. The type of soil was thick, rather mouldered peat. The thickness of logging waste was 3–4 times greater than in Teisko, mainly spruce. A Volvo Nalle SM 460 forwarder was used. The effect of the logging waste on the depth of the tracks was clearly to be noticed. On basis of the appearance of the tracks one could assume that the difference was due to different wear of the humus, and not so much due to the quantity of logging waste that improves the carrying capacity of terrain.

In some extent logging waste was also found to affect the amount and quality of tree injuries. In practical working conditions, the importance might be small, since in the experiments an unrealistically great amount of logging waste was used.

The PDF includes a summary in English.

  • Kärkkäinen, ORCID ID:E-mail:
article id 7544, category Article
Yrjö Vuokila. (1970). Harsintaperiaate kasvatushakkuissa. Acta Forestalia Fennica no. 110 article id 7544. https://doi.org/10.14214/aff.7544
English title: Selection from above in Intermediate cuttings.

This study is concerned with silvicultural selection from above. The material consists of 18 Scots pine (Pinus sylvestris L.) sample plots in the southern half of Finland in experimental forests. The method is motivated by the great difference between the stumpage prices of saw timber and pulpwood. The method suggested includes the removal of individuals belonging to the predominating canopy, to achieve high levels of income from the stand at an early stage. The method is applied at when the growing stock is attaining saw-timber size. Before that the stand is treated with thinnings from below. It is supposed that the volume of growing stock is maintained at a level as high as that in below-thinned stands, and that rotation is of normal length.

On the average, the increment in basal area, as well as volume increment, is greater in stands selectively cut from above than in those treated with low thinnings of the same degree. Initially, selection from above seems to exert a negative effect upon the development of dominant height; later, the dominant height reassumes the same rate of increment as in the below-thinned stands. Selection from above also means an increase in saw-timber production, although it involves a reduction in the mean size of saw timber. The investigation includes growth and yield tables for pine stands treated with silvicultural selection from above.

The results of the investigation prove that silvicultural selection from above is at least as profitable as low thinning. This provides freedom for stand treatment, and contributes to the application of a method most suitable for the owner in each individual case. It is further stressed that the maintenance of a high wood capital in the stand is far more important than the method of thinning applied.

The PDF includes a summary in English.

  • Vuokila, ORCID ID:E-mail:
article id 7613, category Article
Pekka Kilkki, Unto Väisänen. (1969). Determination of the optimum cutting policy for the forest stand by means of dynamic programming. Acta Forestalia Fennica no. 102 article id 7613. https://doi.org/10.14214/aff.7613

The purpose of this study was determining the optimum cutting program for forest stands by the application of dynamic programming. Calculations have been made for even-aged Scots pine (Pinus sylvestris L.) stands in Southern Finland, aged 50-100 years. Three logging cost levels, thinning from below and from above, and rates of interest of 1, 2, 3, 4, and 5% was applied. Both optimum routes and the economic results of different cutting programs was analysed.

According to the results, the higher the rate of interest is, the lower the density remains, and shorter the rotation is. The starting level of the growing stock may influence the treatment of the stand for tens of years. If logging costs change, so that harvesting small wood becomes relatively more expensive in the future, the density of growing stock will increase. However, heavy thinnings today are recommendable, to avoid expensive thinnings in the future.

The density of the growing stock should be higher if thinning from above is applied, instead of thinning from below. The growth of the stands thinned from below needs to be greater than the growth of stands thinned from above, to justify thinnings from below. Too high density often results in larger losses than do too low a density or the wrong rotation. Thinnings seem to be profitable even at much higher logging costs than those of today. The maturity of the stand is determined both by the age and the density of the growing stock. The stand may be mature because of great age, high density combined with a relatively high age, or because the growing stock is too low in density.

The PDF includes a summary in Finnish.

  • Kilkki, ORCID ID:E-mail:
  • Väisänen, ORCID ID:E-mail:
article id 4600, category Article
Aarne Nyyssönen. (1950). Vertailevia havaintoja hoidettujen ja luonnontilaisten männiköiden rakenteesta ja kehityksestä. Silva Fennica no. 68 article id 4600. https://doi.org/10.14214/sf.a9091
English title: Comparative study on structure and development of managed and natural Scots pine stands.

The Forest Research Institute of Finland has established permanent sample plots to survey the effect of thinnings on the stands. This study compares the development of tended and natural Scots pine (Pinus sylvestris L.) stands growing on three different forest types: Oxalis-Myrtillus, Vaccinium and Calluna site type. The effect of heavy thinning from below (Oxalis-Myrtillus and Vaccinium site types) and increment felling (Calluna site type) was assessed by dividing the trees of the stands in tree classification classes according to their crown storey and defects.

The results show that thinning from below and increment thinning increase the proportion of trees in the 1st crown storey, which is already large in the natural stands. Also the diameter distribution is more even and the mean diameter higher after the thinnings.

In Scots pine stands in natural state, volume increment per stem is highest in the 1st crown storey and diminishes strongly towards the lower crown storeys. Thinnings increased the increment. The study indicates that many of the objectives of the intermediate cuttings, including promoting the growth of the best trees and improving the quality of the stand, have in general been achieved. Consequently, the thinnings give means to achieve the most valuable yield in the stand.

The article includes a summary in English.

  • Nyyssönen, ORCID ID:E-mail:
article id 4569, category Article
Martti Tertti. (1939). Näkökohtia kuusimetsän hoidosta. Silva Fennica no. 52 article id 4569. https://doi.org/10.14214/sf.a13976
English title: Forest management of Norway spruce forests.

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 types of fellings in Norway spruce (Picea abies (L.) H. Karst.) forests in different forest site types. The use of thinning from below and above, clear cutting of Norway spruce stands, and thinning of mixed forests with birch (Betula sp.) are discussed.

  • Tertti, ORCID ID:E-mail:
article id 4533, category Article
Olli Heikinheimo. (1938). Harvennushakkauksista. Silva Fennica no. 46 article id 4533. https://doi.org/10.14214/sf.a13942
English title: Thinning of forest stands.

Silva Fennica issue 46 includes presentations held in professional development courses, arranged for foresters working in public administration in 1937. 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 principles of thinning of forest stands. 

  • Heikinheimo, ORCID ID:E-mail:

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