Current issue: 56(1)

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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'forwarder'.

Category: Research article

article id 2018, category Research article
Sima Mohtashami, Lars Eliasson, Gunnar Jansson, Johan Sonesson. (2017). Influence of soil type, cartographic depth-to-water, road reinforcement and traffic intensity on rut formation in logging operations: a survey study in Sweden. Silva Fennica vol. 51 no. 5 article id 2018.
Highlights: Soil type and traffic intensity had significant effects on rut formation; Further studies are required to identify all factors affecting rut formation, especially on soils with medium bearing capacity; The cartographic depth-to-water index (DTW) alone did not predict rut formation, but used in combination with other information, e.g. soil type, could be an interesting tool for delineating soil areas that are potentially vulnerable to rut formation in logging operations.

Rut formation caused by logging operations has been recognised as a challenge for Swedish forestry. Frequent traffic with heavy machines on extraction roads, together with a warmer climate, is one of the factors that increases the risk of rut formation in forests. One possible way to control this impact of logging operations is to design and apply decision support tools that enable operators to take sensitive areas into account when planning extraction roads. In this study, 16 different logging sites in south-eastern Sweden were surveyed after clear-cut. Information was collected about extraction roads (i.e. traffic intensity, whether the roads had been reinforced with slash) and ruts. Digital maps such as cartographic depth-to-water (DTW) index and soil type were also examined for any connection to rut positions. Soil type and traffic intensity were found to be significant factors in rut formation, while DTW and slash reinforcement were not. However, the DTW map combined with other information, such as soil type, could contribute to decision support tools that improve planning of extraction roads.

  • Mohtashami, The forestry research institute of Sweden, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden ORCID ID:E-mail: (email)
  • Eliasson, The forestry research institute of Sweden, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden ORCID ID: E-mail:
  • Jansson, The forestry research institute of Sweden, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden ORCID ID: E-mail:
  • Sonesson, The forestry research institute of Sweden, Skogforsk, Uppsala Science Park, SE-751 83 Uppsala, Sweden ORCID ID: E-mail:
article id 1030, category Research article
Jussi Manner, Tomas Nordfjell, Ola Lindroos. (2013). Effects of the number of assortments and log concentration on time consumption for forwarding. Silva Fennica vol. 47 no. 4 article id 1030.
Highlights: We analysed the effects of total and forwarded log concentrations (m3 (100 m)–1) and the number of loaded assortments on forwarding; The combination of the number of loaded assortments and their abundance (i.e. forwarded log concentration) affected time consumption most; This knowledge enables improved efficiency by optimizing number and assortment proportions in the various loads required to forward a stand.
Forwarding has been carried out for 50 years, but much is still unknown about this work. Its complexity comes from both stand features and essential decision-making. Forwarding time consumption is influenced by e.g. log concentrations and number of assortments. Traditionally, focus has been on the total log concentration (TLC), referring to all logs at the harvesting site. However, we focused on forwarded log concentration (FLC), the load-specific log concentration which depends on the assortment distribution at harvesting site and the load-specific number of assortments. To evaluate the effects of TLC, number of assortments in a load and FLC on the loading and unloading times, a standardized field experiment was carried out. Pile and load sizes were constant, while TLC and FLC were manipulated by varying the pile distribution on the test path. For all work elements, the time consumption per m3 was significantly affected by the number of assortments that were loaded, but only the “driving while loading” work element was also significantly influenced by TLC. However, when untangling the intercorrelation between tested factors, it was found that the time consumption for driving while loading significantly decreased as a function of FLC and was unaffected by the number of assortments in a load. That FLC influences the forwarding time consumption highlights the need to study the effects of combining various assortment proportions in a load. Such knowledge will enable analysis of the most efficient number and assortment proportions to combine in the various loads required to forward a given stand.
  • Manner, Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE-901 83 Umeå, Sweden ORCID ID:E-mail: (email)
  • Nordfjell, Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE-901 83 Umeå, Sweden ORCID ID:E-mail:
  • Lindroos, Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE-901 83 Umeå, Sweden ORCID ID:E-mail:
article id 346, category Research article
Tuomo Nurminen, Heikki Korpunen, Jori Uusitalo. (2006). Time consumption analysis of the mechanized cut-to-length harvesting system. Silva Fennica vol. 40 no. 2 article id 346.
The time consumption and productivity of harvesting are dependent on stand conditions, the operators’ skills, working techniques and the characteristics of the forestry machinery. Even if the basic methods and machine types of the cut-to-length harvesting system have not changed significantly in 10 to 15 years, improvements in the operators’ competence, technical solutions in forest machinery and changes in the working environment have undoubtedly taken place. In this study, the objective was to discover the special characteristics in the time consumption of mechanized cutting and forest haulage in Finnish conditions. The empirical time study was conducted with professional operators and medium-sized single-grip harvesters and forwarders in final fellings and thinnings in easy terrain in central Finland. The models for effective time consumption in the work phases and total productivity were formed. Stem size, tree species and bucking affected the cutting, whereas timber density on the strip road, the average driving distance, load capacity, wood assortment and the bunching result of the harvester operator had an effect on the forest haulage performance. The results may be used in simulations, cost calculations and education.
  • Nurminen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail: (email)
  • Korpunen, University of Joensuu, Faculty of Forestry, P.O. Box 111, FI-80101 Joensuu, Finland ORCID ID:E-mail:
  • Uusitalo, Finnish Forest Research Institute, Parkano Research Unit, Kaironiementie 54, FI-39700 Parkano, Finland ORCID ID:E-mail:
article id 428, category Research article
Jonny Andersson, Lars Eliasson. (2004). Effects of three harvesting work methods on Harwarder productivity in final felling. Silva Fennica vol. 38 no. 2 article id 428.
During the last ten years interest in the harwarder has increased, however, studies have concentrated on effects of technical improvements on machine productivity. It has been noted that there is a large potential to increase the productivity through development of suitable work methods. To find efficient work patterns for a harwarder with a turnable loading area, three different harvesting methods were studied in final felling. Three work methods were used. Method 1: the harwarder drove backwards into the stand making a strip road, strip road trees were felled and left on the ground, on the way out of the stand the harwarder cut and processed the trees on both sides of the machine directly into the loading area. Method 2: the harwarder drove forward along the edge of the cut, cutting and processing trees directly into the loading area. Method 3: the harwarder drove forward into the stand and cut and processed strip road trees and trees standing on both sides of the machine directly into the loading area. The most efficient work method was method 2 where the productivity was 13.0 m3 u.b. per E0h (cubic metre under bark per effective hour). The productivities for method 1 and 3 were 12.1 and 11.9 m3 u.b. per E0h, respectively. In addition to work method harwarder productivity was shown to be dependent on load volume, average tree size and hauling distance. The only work elements significantly affected by work methods were processing and movement during processing. The operator had only a few weeks to get used to the machine and even less time to practise on the work methods. Thus, it is probable that the productivity for the studied methods will increase with increasing work experience. Furthermore, as only three work methods were studied, there are still untested work methods. The potential to further improve harwarder work methods is considerable.
  • Andersson, Swedish University of Agricultural Sciences, Department of Silviculture, S-901 83 Umeå, Sweden ORCID ID:E-mail:
  • Eliasson, Swedish University of Agricultural Sciences, Department of Silviculture, S-901 83 Umeå, Sweden ORCID ID:E-mail: (email)

Category: Article

article id 4921, category Article
Simo Hannelius. (1975). Ojitusalueiden kulkukelpoisuudesta puunkorjuussa. Silva Fennica vol. 9 no. 3 article id 4921.
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 4843, category Article
Unto Silvennoinen, Rihko Haarlaa. (1971). Metsätraktoreiden liikkuvuus lumessa. Silva Fennica vol. 5 no. 2 article id 4843.
English title: The mobility of logging tractors on snow.

The mobility of logging tractors was tested in the winter 1969 on difficult snow conditions to gather information for planning of logging operations and for logging machinery design. The tractors tested were Clark Ranger 666, Timberjack C, Valmet Terra, Ford Brunett 5000, Fiskars 510, BM-Volvo SM 660, BM Volvo SM 661, Ford Country 6, MF-Robur I and BM-Boxer T-350.

According to the results, there is a preference of tracked vehicles in difficult snow conditions compared to wheeled tractors. Ford Country with long and bearing full-tracks proved to have the best mobility. On downhill grades it was found significant differences between three-quarter-track-tractors and skidders, although the performance on level ground and uphill grades was relatively similar. The tracked vehicles can easier move on the packed snow layer and reach a higher speed.

The driving speed does not increase significantly until the density of snow has entirely changed through getting wet. Wet top layer of snow affects positively on driving, because it increases packing of the snow. Increasing density of the snow improves especially the mobility of broad-tired wheeled tractors. To be able to predict the driving speed of a tractor in winter working conditions one must know the depth of the snow layer and the density of the snow and the grade of the slope. In addition, the passages on the same route and the packing of the snow must be regarded.

The PDF includes a summary in English.

  • Silvennoinen, ORCID ID:E-mail:
  • Haarlaa, ORCID ID:E-mail:
article id 4830, category Article
Matti Kärkkäinen. (1970). Optimaalisesta vinssausmatkasta. Silva Fennica vol. 4 no. 4 article id 4830.
English title: The optimum winching distance.

The goal of this study was to develop a mathematical model for determination of the optimal winching distance in different conditions as based on harvesting costs. In the thinned forest the strip roads are parallel and the winching routes perpendicularly to them. A directed felling of trees is used so that it is easy to make loads to be winched. The stems can also be prepared to timber assortments on the stump area and gathered to loads for skidding alongside the winching routes.

After winching the timber is transported using a forwarder mowing on the strip roads. If the stems have not been bucked in the forests, they are to be prepared to timber assortments before the following transportation, because the problem of turning whole stems in a thinned forest has not yet been solved.

In the mathematical model the formation of the costs was described using 18 variables of which 15 had an effect on the optimum winching distance. Some empirical values were estimated concerning these variables, and the corresponding optimum winching distance were computed. The optimum was mainly determined by the quantity of timber harvested per unit area, the size of the winching load, the regression coefficient of the times which were depended on the winching distance.

According to the model, the deviation from optimum winching distance does not cause a very great change in the analysed total costs. When the winching distance is longer, the increase of the costs is smaller than if it is shorter than optimum. In general, the increase of the costs was so small that in practice one obviously can be satisfied with rather approximate methods in determining the suitable winching distance.

The PDF includes a summary in English.

  • Kärkkäinen, ORCID ID:E-mail:

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