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Silva Fennica vol. 46 no. 2 | 2012

Category : Research article

article id 441, category Research article

Ane Zubizarreta-Gerendiain, Petri Pellikka, Jordi Garcia-Gonzalo, Veli-Pekka Ikonen, Heli Peltola. (2012). Factors affecting wind and snow damage of individual trees in a small management unit in Finland: assessment based on inventoried damage and mechanistic modelling. Silva Fennica vol. 46 no. 2 article id 441. https://doi.org/10.14214/sf.441

Keywords: Pinus sylvestris; Picea abies; Betula spp.; critical wind speed; snow loading; damage risk

Abstract | View details | Full text in PDF | Author Info

In this work, we assessed the factors affecting wind and snow damage of individual trees in a small management unit in western Finland. This was done based on inventoried damage and observed wind speeds and snow loading in storms Pyry and Janika in 2001 and Mielikki in 2002 together with mechanistic model. First, we studied which factors explain the observed damage in individual trees. Secondly, we studied how well the mechanistic model (HWIND) could predict the wind speed needed to uproot individual trees at the margins of permanent upwind edges. We found that Pyry storm caused 70% and Janika and Mielikki 18 and 12% of observed damage. In Janika storm, all trees uprooted. In other storms, both uprooting and stem breakage occurred. Scots pine suffered the most damage. Recently thinned stands on the upwind edges of open areas suffered the most damage. But, damage occurred also on soils with relatively shallow anchorage. HWIND predicted correctly damage for 69% of all uprooted trees. No-uprooting was correctly predicted for 45 and 19% of standing trees (all Scots pines), which were measured within and at the immediate upwind edge of same stands. HWIND model needs further validation at the permanent edges and/or on soils with shallow rooting to improve its prediction accuracy in such conditions.

Zubizarreta-Gerendiain, Technical University of Lisbon, School of Agriculture, Forest Research Centre, Lisbon, Portugal E-mail: azg@nn.po
Pellikka, University of Helsinki, Dept. of Geosciences and Geography, Helsinki, Finland E-mail: pp@nn.fi
Garcia-Gonzalo, Technical University of Lisbon, School of Agriculture, Forest Research Centre, Lisbon, Portugal E-mail: jgg@nn.po
Ikonen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: vpi@nn.fi
Peltola, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: heli.peltola@uef.fi

article id 58, category Research article

Ilona Suuriniemi, Jukka Matero, Harri Hänninen, Jussi Uusivuori. (2012). Factors affecting enlargement of family forest holdings. Silva Fennica vol. 46 no. 2 article id 58. https://doi.org/10.14214/sf.58

Keywords: economies of scale; structural change; forest ownership; non-industrial private forest owners; land policy; parcelization; consolidation

Abstract | View details | Full text in PDF | Author Info

This study contributes to the research of enlargement – a counterforce of parcelization – of forest holdings. To help planning policy measures aiming at increased average size of forest holdings, we study the characteristics of family forest owners who acquired additional forestland area during the years 2004–2008. Increases of forestland area due to purchases on the open market, purchases from parents or other relatives, inheritance or gift are studied. Survey data, containing information of 6318 forest owners, are analyzed with logistic regression analysis in order to establish a relationship between the probability of increasing the forestland area and the characteristics of landowners. The results indicate that young male owners, who appreciate economic values of the ownership and are active users of their forest estates, most often expand their forest property. This can be considered as an encouraging result from the point of view of the political objective to boost forest management activity through enlarging family forest holdings.

Suuriniemi, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: is@nn.fi
Matero, University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland E-mail: jukka.matero@uef.fi
Hänninen, Finnish Forest Research Institute, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: hh@nn.fi
Uusivuori, Finnish Forest Research Institute, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: ju@nn.fi

article id 57, category Research article

Corrado Costa, Paolo Menesatti, Raffaele Spinelli. (2012). Performance modelling in forest operations through partial least square regression. Silva Fennica vol. 46 no. 2 article id 57. https://doi.org/10.14214/sf.57

Keywords: chipping; productivity; harvesting; skidding

Abstract | View details | Full text in PDF | Author Info

Partial Least Square (PLS) regression is a recent soft-modelling technique that generalizes and combines features from principal component analysis (PCA) and multiple regression. It is particularly useful when predicting one or more dependent variables from a large set of independent variables, often collinear. The authors compared the potential of PLS regression and ordinary linear regression for accurate modelling of forest work, with special reference to wood chipping, wood extraction and the continuous harvesting of short rotation coppice. Compared to linear regression, PLS regression allowed producing models that better fit the original data. What is more, it allowed handling collinear variables, facilitating the extraction of sound models from large amounts of field data obtained from commercial forest operations. On the other hand, PLS regression analysis is not as easy to conduct, and produces models that are less user-friendly. By producing alternative models, PLS regression may provide additional – and not alternative – ways of reading the data. Ideally, a comprehensive data analysis could include both ordinary and PLS regression and proceed from their results in order to get a better understanding of the phenomenon under examination. Furthermore, the computational complexity of PLS regression may stimulate interdisciplinary team-building, to the greater benefit of scientific research within the field of forest operations.

Costa, CRA ING, Monterotondo Scalo (Roma), Italy E-mail: cc@nn.it
Menesatti, CRA ING, Monterotondo Scalo (Roma), Italy E-mail: pm@nn.it
Spinelli, CNR IVALSA, Sesto Fiorentino (FI), Italy E-mail: spinelli@ivalsa.cnr.it

article id 56, category Research article

Johan Holmgren, Andreas Barth, Henrik Larsson, Håkan Olsson. (2012). Prediction of stem attributes by combining airborne laser scanning and measurements from harvesters. Silva Fennica vol. 46 no. 2 article id 56. https://doi.org/10.14214/sf.56

Keywords: ALS data; pre-harvest inventory; tree detection

Abstract | View details | Full text in PDF | Author Info

In this study, a new method was validated for the first time that predicts stem attributes for a forest area without any manual measurements of tree stems by combining harvester measurements and Airborne Laser Scanning (ALS) data. A new algorithm for automatic segmentation of tree crowns from ALS data based on tree crown models was developed. The test site was located in boreal forest (64°06’N, 19°10’E) dominated by Norway spruce (Picea abies) and Scots Pine (Pinus sylvestris).The trees were harvested on field plots, and each harvested tree was linked to the nearest tree crown segment derived from ALS data. In this way, a reference database was created with both stem data from the harvester and ALS derived features for linked tree crowns. To estimate stem attributes for a tree crown segment in parts of the forest where trees not yet have been harvested, tree stems are imputed from the most similar crown segment in the reference database according to features extracted from ALS data. The imputation of harvester data was validated on a sub-stand-level, i.e. 2–4 aggregated 10 m radius plots, and the obtained RMSE of stem volume, mean tree height, mean stem diameter, and stem density (stems per ha) estimates were 11%, 8%, 12%, and 19%, respectively. The imputation of stem data collected by harvesters could in the future be used for bucking simulations of not yet harvested forest stands in order to predict wood assortments.

Holmgren, Swedish University of Agricultural Sciences, Forest Resource Management, Umeå, Sweden E-mail: johan.holmgren@slu.se
Barth, The Forestry Research Institute of Sweden, Uppsala, Sweden E-mail: ab@nn.se
Larsson, Swedish University of Agricultural Sciences, Forest Resource Management, Umeå, Sweden E-mail: hl@nn.se
Olsson, Swedish University of Agricultural Sciences, Forest Resource Management, Umeå, Sweden E-mail: ho@nn.se

article id 55, category Research article

Antti Mäkinen, Annika Kangas, Mikko Nurmi. (2012). Using cost-plus-loss analysis to define optimal forest inventory interval and forest inventory accuracy. Silva Fennica vol. 46 no. 2 article id 55. https://doi.org/10.14214/sf.55

Keywords: value of information; prediction error; inventory error

Abstract | View details | Full text in PDF | Author Info

In recent years, optimal inventory accuracy has been analyzed with a cost-plus-loss methodology, where the total costs of inventory include both the measurement costs and the losses from the decisions based on the collected information. Losses occur, when the inaccuracies in the data lead to sub-optimal decisions. In almost all cases, it has been assumed that the accuracy of the once collected data remains the same throughout the planning period, and the period has been from 10 up to 100 years. In reality, the quality of the data deteriorates in time, due to errors in the predicted growth. In this study, we carried out a cost-plus-loss analysis accounting for the errors in (stand-level) growth predictions of basal area and dominant height. In addition, we included the inventory errors of these two variables with several different levels of accuracy, and costs of inventory with several different assumptions of cost structure. Using the methodology presented in this study, we could calculate the optimal inventory interval (life-span of data) minimizing the total costs of inventory and losses through the 30-year planning period. When the inventory costs only to a small extent depended on the accuracy, the optimal inventory period was 5 years and optimal accuracy RMSE 0%. When the costs more and more heavily depended on the accuracy, the optimal interval turned out to be either 10 or 15 years, and the optimal accuracy reduced from RMSE 0% to RMSE 20%. By increasing the accuracy of the growth models, it was possible to reduce the inventory accuracy or lengthen the interval, i.e. obtain clear savings in inventory costs.

Mäkinen, Simosol Oy, Rautatietori 4, FI-11130 Riihimäki, Finland E-mail: antti.makinen@simosol.fi
Kangas, University of Helsinki, Department of Forest Sciences, Helsinki, Finland E-mail: ak@nn.fi
Nurmi, University of Helsinki, Department of Forest Sciences, Helsinki, Finland E-mail: mn@nn.fi

article id 54, category Research article

Urban Nilsson, Björn Elfving, Kjell Karlsson. (2012). Productivity of Norway spruce compared to Scots pine in the interior of northern Sweden. Silva Fennica vol. 46 no. 2 article id 54. https://doi.org/10.14214/sf.54

Keywords: Pinus sylvestris; current annual increment; mean annual increment; Picea abies; site index; yield

Abstract | View details | Full text in PDF | Author Info

Productivity of Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) was studied in 12 paired plots in the interior of northern Sweden. Stands were established between 1928 and 1959; yield plots were established between 1974 and 1983 during pre-commercial thinning of the stands. Gross stem-wood production was significantly higher for Scots pine than for Norway spruce, stem-wood production by Norway spruce being 29.4% that of Scots pine. The site index for Norway spruce was lower than for Scots pine at all sites except one; the average difference in site index was 4.8 m. The simulated maximum mean annual increment (MAI_max) during the rotation was 19% higher than the MAI_max estimated with the site index for Scots pine, whereas simulated MAI_max and MAI_max estimated from the site index was about the same for Norway spruce. The simulations also indicated that MAI peaked about 50 years later for Norway spruce than for Scots pine. More small trees were included in the diameter distribution of Norway spruce than of Scots pine resulting in a lower stem-wood volume for Norway spruce when stands with the same dominant height were compared. This study shows that the difference in growth and rotation length between Scots pine and Norway spruce has implications when choosing which species to grow in the interior of northern Sweden.

Nilsson, Swedish University of Agricultural Sciences (SLU), Southern Swedish Forest Research Centre, Alnarp, Sweden E-mail: urban.nilsson@slu.se
Elfving, SLU, Forest Ecology and Management, Umeå, Sweden E-mail: be@nn.se
Karlsson, SLU, Unit of Field Based Research, Asa, Sweden E-mail: kk@nn.se

article id 53, category Research article

Saana Kataja-aho, Aino Smolander, Hannu Fritze, Sini Norrgård, Jari Haimi. (2012). Responses of soil carbon and nitrogen transformations to stump removal. Silva Fennica vol. 46 no. 2 article id 53. https://doi.org/10.14214/sf.53

Keywords: biofuel; boreal forest; carbon; nitrogen; nutrient dynamics; stump removal

Abstract | View details | Full text in PDF | Author Info

We studied in central Finland whether stump harvesting after clear felling of coniferous forest poses further short-term changes in soil carbon and nitrogen dynamics when compared to the traditional site preparation method, mounding. Exposed mineral soil patches in Norway spruce (Picea abies) dominated clear-cut stands were sampled 1–5 years after the treatments. The extent of the exposed mineral soil surface was significantly larger at the stump removal sites when compared to the mounding sites. No differences were found in soil pH, organic matter content or total concentration of soil C between the treatments or treatment years. Total concentration of soil N was consistently higher and C:N ratio lower in the stump removal plots than in the mounded plots. Further, both net N mineralisation and nitrification were clearly increased in the stump removal plots one year after the treatments. Soil microbial activity (CO₂ production) was higher in the stump removal plots but similar difference was not found in sieved soil samples incubated in the laboratory. Fluxes of other important greenhouse gases (CH₄ and N₂O) did not seem to be affected by stump removal. The differences between the stump removal and mounding procedures were most obviously attributed to more substantial soil disturbance by stump pulling and/or differences in the microbial communities and quality of soil organic matter in the differently treated soil.

Kataja-aho, University of Jyväskylä, Dept. of Biological and Environmental Science, Jyväskylä, Finland E-mail: saana.m.kataja-aho@jyu.fi
Smolander, Finnish Forest Research Institute, Vantaa, Finland E-mail: as@nn.fi
Fritze, Finnish Forest Research Institute, Vantaa, Finland E-mail: hf@nn.fi
Norrgård, University of Jyväskylä, Dept. of Biological and Environmental Science, Jyväskylä, Finland E-mail: sn@nn.fi
Haimi, University of Jyväskylä, Dept. of Biological and Environmental Science, Jyväskylä, Finland E-mail: jh@nn.fi

Category : Research note

article id 442, category Research note

Emil Modig, Bo Magnusson, Erik Valinger, Jonas Cedergren, Lars Lundqvist. (2012). Damage to residual stand caused by mechanized selection harvest in uneven-aged Picea abies dominated stands. Silva Fennica vol. 46 no. 2 article id 442. https://doi.org/10.14214/sf.442

Keywords: selection cutting; logging damage; continuous cover management; residual stand; logging methods

Abstract | View details | Full text in PDF | Author Info

Permanent field plots were established in two uneven-aged Norway spruce (Picea abies (L.) Karst) dominated stands in west-central Sweden. The objective was to quantify level and type of damage caused by harvesting and to quantify the difference between two treatments: T20) only skid road harvest (20 m distance between ca. 4 m wide roads), and T40) skid road harvest (40 m distance between ca. 4 m wide roads) combined with thinning between the roads. In T40, the goal was to harvest approximately the same standing volume as in T20. After harvest, two circular sample plots (radius 18 m, i.e. 1018 m₂) were established at random locations within each treated area. All mechanical damage on the stem caused by harvest was measured and registered, including bark stripping larger than 15 cm₂, stem broken or split, and tearing of branches causing damage on the stem. About 70–90 per cent of the damaged trees were smaller than 15 cm dbh. Very few trees larger than 25 cm dbh were damaged. In T20, more than 50 per cent of the damaged trees were located less than 5 m from the skid road, compared to less than 25 per cent for T40, in which more than 50 per cent of the damaged trees were located 5–10 m from the skid road. Creating only half the number of skid roads caused no more damage, and was probably more profitable because mean stem volume was about 1.5 times larger than in T20.

Modig, Statens fastighetsverk, Jokkmokk, Sweden E-mail: em@nn.se
Magnusson, Skogsstyrelsen, Bräcke, Sweden E-mail: bm@nn.se
Valinger, Deparment of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden E-mail: ev@nn.se
Cedergren, Mariehamn, Åland E-mail: jc@nn.se
Lundqvist, Deparment of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden E-mail: lars.lundqvist@slu.se

article id 61, category Research note

Janine Schweier, Gero Becker. (2012). Harvesting of short rotation coppice – harvesting trials with a cut and storage system in Germany. Silva Fennica vol. 46 no. 2 article id 61. https://doi.org/10.14214/sf.61

Keywords: productivity; harvest operations; marginal sites; SRC; Stemster MK III

Abstract | View details | Full text in PDF | Author Info

Short rotation coppice (SRC) harvesting techniques are available in Germany, but broad experience and knowledge about machine performance and the related effective costs of harvesting operations are still missing. This information is crucial, as harvesting costs strongly influence the economic performance of the overall supply chain. Therefore, it was the aim of this study to collect and analyze productivity data of different harvesting systems for SRC. The combined cut and chip system on the one hand and the cut and storage system on the other hand were studied by literature review. Several studies analyze the combined cut and chip systems and the reported machine productivities showed great variations. The average was 30 green tons per scheduled machine hour (gt smh^–1). Few studies are analysing the cut and storage system. They report that machines still are under development and that further research is needed. Therefore, time studies of harvesting operations using the cut and storage system were carried out. Five trials were performed with the harvesting machine “Stemster MK III” developed by Nordic Biomass. The share of productive working time was 85% and the average productivity was 21 gt smh^–1. These results were compared with values from the literature. Resulting harvesting costs were calculated per oven dry ton (euros odt^–1). The advantages and disadvantages of both harvesting systems are highlighted.

Schweier, Albert-Ludwigs-University Freiburg, Institute of Forest Utilisation and Work Science, Freiburg, Germany E-mail: janine.schweier@fobawi.uni-freiburg.de
Becker, Albert-Ludwigs-University Freiburg, Institute of Forest Utilisation and Work Science, Freiburg, Germany E-mail: gb@nn.de

article id 60, category Research note

Dominik Röser, Blas Mola-Yudego, Robert Prinz, Beatrice Emer, Lauri Sikanen. (2012). Chipping operations and efficiency in different operational environments. Silva Fennica vol. 46 no. 2 article id 60. https://doi.org/10.14214/sf.60

Keywords: wood-fuel logistics; forest machinery; bioenergy supply

Abstract | View details | Full text in PDF | Author Info

This research analyses the productivity of energy wood chipping operations at several sites in Austria and Finland. The aim of the work is to examine the differences in productivity and the effects of the operational environment for the chipping of bioenergy at the roadside. Furthermore, the study quantifies the effects of different variables such as forest energy assortments, tree species, sieve size and machines on the overall productivity of chipping. The results revealed that there are significant differences in the chipping productivity in Austria and Finland which are largely based on the use of different sieve sizes. Furthermore, the different operational environments in both countries, as well as the characteristics of the raw material also seem to have an effect on productivity. In order to improve the chipping productivity, particularly in Central European conditions, all relevant stakeholders need to work jointly to find solutions that will allow a greater variation of chip size. Furthermore, in the future more consideration has to be given to the close interlinkage between the chipper, crane and grapple. As a result, investments costs can be optimized and operational costs and stress on the machines reduced.

Röser, Finnish Forest Research Institute, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: dominik.roser@metla.fi
Mola-Yudego, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: bmy@nn.fi
Prinz, Finnish Forest Research Institute, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: rp@nn.fi
Emer, University of Padova, Department of Land, Agriculture and Forest Systems, Legnaro (PD), Italy E-mail: be@nn.it
Sikanen, University of Eastern Finland, School of Forest Sciences, Joensuu, Finland E-mail: ls@nn.fi

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