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Silva Fennica vol. 34 no. 4 | 2000

Category : Research article

article id 623, category Research article

Anders Roos, Matti Flinkman, Armas Jäppinen, Mats Warensjö. (2000). Adoption of value-adding processes in Swedish sawmills. Silva Fennica vol. 34 no. 4 article id 623. https://doi.org/10.14214/sf.623

Keywords: sawmilling; production structure; technology adoption

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

Adding value to lumber by processing it after sawing and standard drying is one means for the sawmilling industry to increase market shares in competition with other materials, e.g. glass, steel, concrete, aluminium, and plastics. In this study the adoption patterns of value-adding processes used in Swedish softwood sawmills were analysed based on production data from 1995. About 90% of the sawmills applied a value-adding process after initial sawing and drying, and 72% of the sawmills applied two or more processes. The total share of processed sawnwood was about 40%. Important dimensions of value-adding processes are: extra drying and production of blanks for doors/windows and for furniture; surface-treatment, mainly planing, which is sometimes associated with preservation and painting; length trimming and pallet production; extra drying and production of edge-glued panels and laminated beams; and stress grading and production of building components. The association of different value-adding dimensions with location, ownership and production characteristics were investigated. The total share of value-added production were higher for private sawmills than for mills owned by forest companies or by forest owners’ associations, and it was higher for mills in southern Sweden than for sawmills in other parts of the country. Value-added share does not clearly correlate with mill size or with the dominating tree species being sawn.

Roos, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden E-mail: anders.roos@sh.slu.se
Flinkman, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden E-mail: mf@nn.se
Jäppinen, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden E-mail: aj@nn.se
Warensjö, Swedish University of Agricultural Sciences, Department of Forest Management and Products, P.O. Box 7060, SE-750 07 Uppsala, Sweden E-mail: mw@nn.se

article id 622, category Research article

Håkan Lindström. (2000). Intra-tree models of basic density in Norway spruce as an input to simulation software. Silva Fennica vol. 34 no. 4 article id 622. https://doi.org/10.14214/sf.622

Keywords: Picea abies; wood density; image analysis; basic density; growth conditions

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

Basic density is said to influence aspects of conversion, properties, and end-use of forest products. Consequently, it is argued that accurate models of basic density variation, within and between trees, could be used to improve the utilisation of wood as an industrial raw material. The objective of the present study was to develop basic density models based on Norway spruce trees, that could be used within a model system for conversion simulation studies. Nineteen stands of Norway spruce (Picea abies (L.) Karst.) were selected throughout Sweden. Based on dbh, two small, two moderate, and two large timber trees were taken from each stand. Dbh varied between 180–470 mm, tree height between 17–34 m, and total age between 51–152 years. Each selected tree was cross-cut into logs; discs were prepared from the butt end of each log and from the top end of the top log. Computed tomography scanning and image analysis were used to determine basic density and growth ring development on sampled discs. Basic density development in 20-mm segments from pith outwards was modelled in models based on ring width, tree and growth condition data. The resulting models had an adjusted R2 of 0.37–0.51 and a RMSE of 37–41 kg/m3.

Lindström, University of Canterbury, School of Forestry, Private Bag 4800, Christchurch, New Zealand E-mail: lindstromhakan@netscape.net

article id 621, category Research article

Jyrki Kangas, Pekka Leskinen, Timo Pukkala. (2000). Integrating timber price scenario modeling with tactical management planning of private forestry at forest holding level. Silva Fennica vol. 34 no. 4 article id 621. https://doi.org/10.14214/sf.621

Keywords: decision support; optimization; adaptive behaviour; non-industrial private forestry; tactical planning; timber price modelling

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

In forest management planning, deterministic timber prices are typically assumed. However, real-life timber prices vary in the course of time, and also price peaks, i.e. exceptionally high timber prices, might occur. If land-owners can utilise the price variation by selling timber with the high prices, they are able to increase their net revenues correspondingly. In this study, an approach is presented to study the timber price variation and its significance in the optimization of forest management. The approach utilizes stochastic timber price scenario modelling, simulation of forest development, and optimization of forest management. The approach is presented and illustrated by means of a case study. It is shown how the degree of uncertainty due to variation in timber prices can be analyzed in tactical forest planning of private forestry, and how the potential benefits of adaptive timber-selling behaviour for a forest landowner can be computed by using the approach. The effects of stochastic timber prices on the choice of forest plan are studied at the forest holding level considering also the spacing and type of cuttings and the optimal cutting order. A forest plan prepared under the assumption of constant timber price very seldom results in optimal forest management. Through studying the effects of stochastic timber prices, forest landowners and other decision makers obtain valuable information about the significance of adaptive timber selling behaviour. The presented methodology can also be used in analysing the land-owners’ economic risks as a function of time-price structure.

Kangas, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland E-mail: jyrki.kangas@metla.fi
Leskinen, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland E-mail: pl@nn.fi
Pukkala, University of Joensuu, Faculty of Forestry, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: tp@nn.fi

article id 620, category Research article

Annika Kangas, Matti Maltamo. (2000). Performance of percentile based diameter distribution prediction and Weibull method in independent data sets. Silva Fennica vol. 34 no. 4 article id 620. https://doi.org/10.14214/sf.620

Keywords: stand structure; calibration estimation; Weibull function; diameter distribution prediction; distribution-free method; nearest neighbour method

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

Diameter distribution is used in most forest management planning packages for predicting stand volume, timber volume and stand growth. The prediction of diameter distribution can be based on parametric distribution functions, distribution-free parametric prediction methods or purely non-parametric methods. In the first case, the distribution is obtained by predicting the parameters of some probability density function. In a distribution-free percentile method, the diameters at certain percentiles of the distribution are predicted with models. In non-parametric methods, the predicted distribution is a linear combination of similar measured stands. In this study, the percentile based diameter distribution is compared to the results obtained with the Weibull method in four independent data sets. In the case of Scots pine, the other methods are also compared to k-nearest neighbour method. The comparison was made with respect to the accuracy of predicted stand volume, saw timber volume and number of stems. The predicted percentile and Weibull distributions were calibrated using number of stems measured from the stand. The information of minimum and maximum diameters were also used, for re-scaling the percentile based distribution or for parameter recovery of Weibull parameters. The accuracy of the predicted stand characteristics were also compared for calibrated distributions. The most reliable results were obtained using the percentile method with the model set including number of stems as a predictor. Calibration improved the results in most cases. However, using the minimum and maximum diameters for parameter recovery proved to be inefficient.

Kangas, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland E-mail: annika.kangas@metla.fi
Maltamo, Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, FIN-80101 Joensuu, Finland E-mail: mm@nn.fi

article id 619, category Research article

Annika Kangas, Matti Maltamo. (2000). Percentile based basal area diameter distribution models for Scots pine, Norway spruce and birch species. Silva Fennica vol. 34 no. 4 article id 619. https://doi.org/10.14214/sf.619

Keywords: stand structure; diameter distribution prediction; distribution-free method; rational spline

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

Information about diameter distribution is used for predicting stand total volume, timber volume and stand growth for forest management planning. Often, the diameter distribution is obtained by predicting the parameters of some probability density function, using means and sums of tree characters as predictors. However, the results have not always been satisfactory: the predicted distributions practically always have a similar shape. Also, multimodal distributions cannot be obtained. However, diameter distribution can also be predicted using distribution-free methods. In the percentile method, the diameters at certain percentiles of the distribution are predicted with models. The empirical diameter distribution function is then obtained by interpolating between the predicted diameters. In this paper, models for diameters at 12 percentiles of stand basal area are presented for Scots pine, Norway spruce and birch species. Two sets of models are estimated: a set with and one without number of stems as a predictor. Including the number of stems as a predictor improved the volume and saw timber volume estimates for all species, but the improvements were especially high for number of stems estimates obtained from the predicted distribution. The use of number of stems as predictor in models is based on the possibility of including this characteristic to measured stand variables.

Kangas, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland E-mail: annika.kangas@metla.fi
Maltamo, Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, FIN-80101 Joensuu, Finland E-mail: mm@nn.fi

article id 618, category Research article

Steen Magnussen, Paul Boudewyn, Mike Wulder, David Seemann. (2000). Predictions of forest inventory cover type proportions using Landsat TM. Silva Fennica vol. 34 no. 4 article id 618. https://doi.org/10.14214/sf.618

Keywords: neural net; maximum likelihood classification; agreement of predictions

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

The feasibility of generating via Landsat TM data current estimates of cover type proportions for areas lacking this information in the national forest inventory was explored by a case study in New Brunswick. A recent forest management inventory covering 4196 km2 in south-eastern New Brunswick (the test area) and a coregistered Landsat TM scene was used to develop predictive models of 12 cover type proportions in an adjacent 4525 km2 region (the validation area). Four prediction models were considered, one using a maximum likelihood classifier (MLC), and three using the proportions of 30 TM clusters as predictors. The MLC was superior for non-vegetated cover types while a neural net or a prorating of cluster proportions was chosen for predicting vegetated cover types. Most predictions generated for national inventory photo-plots of 2 x 2 km were closer to the most recent inventory results than estimates extrapolated from the test area. Agreement between predictions and current inventory results varied considerably among cover types with model-based predictions outperforming, on average, the simple spatial extensions by about 14%. In this region, an 11-year-old forest inventory for the validation area provided estimates that in half the cases were closer to current inventory estimates than predictions using the optimal Landsat TM model. A strong temporal correlation of photo-plot-level cover type proportions made old-values more consistent than predictions using the optimal Landsat TM model in all but three cases. Prorating of cluster proportions holds promise for large-scale multi-sensor predictions of forest inventory cover types.

Magnussen, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: smagnussen@pfc.forestry.ca
Boudewyn, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: pb@nn.ca
Wulder, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: mw@nn.ca
Seemann, Canadian Forest Service, 506 West Burnside Road, Victoria B.C., Canada V8Z 1M5 E-mail: ds@nn.ca

article id 617, category Research article

Jouni Siipilehto. (2000). A comparison of two parameter prediction methods for stand structure in Finland. Silva Fennica vol. 34 no. 4 article id 617. https://doi.org/10.14214/sf.617

Keywords: Pinus sylvestris; Picea abies; parameter prediction; dbh and height distribution; Johnson’s SBB distribution; Näslund’s height curve

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

The objective of this paper was to predict a model for describing stand structure of tree heights (h) and diameters at breast height (dbh). The research material consisted of data collected from 64 stands of Norway spruce (Picea abies Karst.) and 91 stands of Scots pine (Pinus sylvestris L.) located in southern Finland. Both stand types contained birch (Betula pendula Roth and B. pubescent Ehrh.) admixtures. The traditional univariate approach (Model I) of using the dbh distribution (Johnson’s SB) together with a height curve (Näslund’s function) was compared against the bivariate approaches, Johnson’s SBB distribution (Model II) and Model Ie. In Model Ie within-dbh-class h-variation was included by transforming a normally distributed homogenous error of linearized Näslund’s function to concern real heights. Basal-area-weighted distributions were estimated using the maximum likelihood (ML) method. Species-specific prediction models were derived using linear regression analysis. The models were compared with Kolmogorov-Smirnov tests for marginal distributions, accuracy of stand variables and the dbh-h relationship of individual trees. The differences in the stand characteristics between the models were marginal. Model I gave a slightly better fit for spruce, but Model II was better for pine stands. The univariate Model I resulted in clearly too narrow marginal h-distribution for pine. It is recommended applying of a constrained ML method for reasonable dbh-h relationship instead of using a pure ML method when fitting the SBB model.

Siipilehto, Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland E-mail: jouni.siipilehto@metla.fi

article id 616, category Research article

Markus Lindholm, Hannu Lehtonen, Taneli Kolström, Jouko Meriläinen, Matti Eronen, Mauri Timonen. (2000). Climatic signals extracted from ring-width chronologies of Scots pines from the northern, middle and southern parts of the boreal forest belt in Finland. Silva Fennica vol. 34 no. 4 article id 616. https://doi.org/10.14214/sf.616

Keywords: boreal forest; Scots pine; tree-rings; ring-width chronologies; growth variability; growth responses; spectral analysis

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

Climatic signals were extracted from ring-width chronologies of Scots pines (Pinus sylvestris L.) from natural stands of the northern, middle, and southern parts of the boreal forest belt in Finland. The strength of the common growth signals (forcing factors) were quantified as a function of time. This was achieved by mean inter-series correlations, calculated over a moving 30-year window, both within and between the regional chronologies. Strong regional signals and also evidence for common forcings were found, especially between northern and central, central and eastern, as well as central/eastern and southern chronologies. Response function analyses revealed that growing season temperatures govern the growth rates of northern pines, while towards south, pine growth becomes less affected by temperatures, and more affected by e.g. precipitation. During some periods, growing conditions seem to have been favorable in the south, while they have been unfavorable in the north (growth inversions). Going from the north to the south, the variability of radial growth clearly decreases, and the variance of ring-width series becomes smaller. Growth variability in the four regions was compared during the common interval of the chronologies, from 1806 to 1991. The spectral densities of the northern, central, eastern and southern chronologies were also compared as functions of frequency, viz. cycles per year. The variance is much greater and there is more periodic behavior in the north than in the south in high, medium, as well as lower frequencies.

Lindholm, Saima Centre for Environmental Sciences, University of Joensuu, Linnankatu 11, FIN-57130 Savonlinna, Finland E-mail: ml@nn.fi
Lehtonen, Finnish Forest Research Institute, Joensuu Research Station, Box 68, FIN-80101 Joensuu, Finland E-mail: hl@nn.fi
Kolström, Finnish Forest Research Institute, Joensuu Research Station, Box 68, FIN-80101 Joensuu, Finland E-mail: tk@nn.fi
Meriläinen, Saima Centre for Environmental Sciences, University of Joensuu, Linnankatu 11, FIN-57130 Savonlinna, Finland E-mail: jm@nn.fi
Eronen, Department of Geology, Division of Geology and Palaeontology, Box 11, FIN-00014 University of Helsinki, Finland E-mail: me@nn.fi
Timonen, Finnish Forest Research Institute, Rovaniemi Research Station, Box 16, FIN-96301 Rovaniemi, Finland E-mail: mt@nn.fi

Category : Research note

article id 624, category Research note

Hashim Ali El Atta. (2000). Effect of diet and seed pretreatment on the biology of Bruchidius uberatus (Coleoptera, Bruchidae). Silva Fennica vol. 34 no. 4 article id 624. https://doi.org/10.14214/sf.624

Keywords: Bruchidius uberatus; Bruchidae; Acacia nilotica; seed borer biology

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

Diet significantly (P < 0.0001) affected fecundity of Bruchidius uberatus Fahraeus. Provision of 1% sugar solution increased fecundity from 15 eggs/female to 47. Furthermore, sugar solution prolonged significantly the oviposition period of B. uberatus from one week to two weeks. Diet also significantly (P < 0.0001) increased adult longevity. Mean adult longevity recorded was 3, 7 and 13 days in control, water and sugar treatments, respectively. Seed pretreatment had a highly significant impact on the various developmental stages of B. uberatus. Maximum egg hatchability occurred in non-husked Acacia nilotica (L.) Willd. ex Del. seeds (83%), moderate in de-husked seeds (74%) and least in seeds presoaked in concentrated sulphuric acid (42%). The frequency of larvae that developed successfully into pupae was greatest in non-husked seeds (72%), nevertheless in de-husked and acid pretreated seeds, absolutely no larvae developed into pupae and hence the adult stage was not reached in these two treatments. Thus, de-husking and acid pretreatment of A. nilotica seeds is highly recommended.

El Atta, University of Khartoum, Faculty of Forestry, Department of Forest Conservation and Protection, Shambat, Sudan E-mail: hashimelatta@yahoo.com

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