Category: Research article
article id 389, category Research article
The competitive position of the Nordic wood industry in Germany – intangible quality dimensions. Silva Fennica vol. 39 no. 2 article id 389. https://doi.org/10.14214/sf.389
This study examines the importance of various intangible product quality dimensions as perceived by wood-trading retailer and wholesaler companies in Germany. Using perceived importance and perceived performance, the study first examines the dimensionality of intangible product quality and then compares Nordic wood product suppliers with suppliers from other major supply regions. Data was collected from 76 German companies during 2000–2001. Results indicate that intangible product quality can be described in three dimensions, “Behaviour and Image”, “Serviceability and Environment”, and “Reliability”. Results also show that Nordic suppliers do not have a strong competitive position in Germany in terms of intangible product quality dimensions. Thus, Nordic suppliers could improve their competitive position by enhancing their service, logistics and other dimensions of the intangible product offering.
article id 388, category Research article
Repeatability in automatic sorting of curved Norway spruce saw logs. Silva Fennica vol. 39 no. 2 article id 388. https://doi.org/10.14214/sf.388
Sawn wood from curved logs is prone to have cross grain and contain compression wood, both of which affect the dimensional stability. Different types of curvature can, however, have different effects on both the sawing process and board quality, which is why a standard measure of bow height alone is not enough to sort logs or set the log quality. The aim of this study was to evaluate the repeatability when sorting curved saw logs using a 3D log scanner. In the study, 56 logs were categorized into five different curvature types and four different degrees of curvature severity. The logs were run through a Rema 3D log scanner four times, and the external geometry was recorded. From the geometry data, variables describing log shapes were calculated and used to develop models using linear discriminant analysis, which was used to classify the logs according to curvature type. The accuracy and repeatability were evaluated for the classifications with Cohen’s simple Kappa coefficient. The results of this study showed that it is possible to sort logs by curve type using a 3D log scanner, although sorting by curve type was largely dependent on curve severity. The repeatability test determined that the chance of a curved log being graded identically two consecutive times was 0.40, measured as kappa.
article id 387, category Research article
Evaluation of the multicriteria approval method for timber-harvesting group decision support. Silva Fennica vol. 39 no. 2 article id 387. https://doi.org/10.14214/sf.387
The decision support methods most often used in timber-harvesting planning are based on a single criterion. In this study, a voting-theory-based method called multicriteria approval (MA) is introduced to the group decision support of timber-harvesting. The use of voting methods alleviates the problems caused by the multitude of decision objectives involved in forestry decision-making and by the poor quality of information concerning both the preferences of decision-makers and the evaluation of decision alternatives with respect to the objectives often faced in practical timber-harvesting planning. In the case study, the tactical forest management plan of a forest holding jointly owned by three people was specified at the operative timber-harvesting level. The task was to find the best actual operative alternatives for the harvesting that had been proposed in the tactical plan. These timber-harvesting alternatives were combinations of treatment, timber-harvesting system and the timing of logging. Forest owners established multiple criteria under which the alternatives were evaluated. Two versions of MA were tested, one of them based on individual decision analyses and other one based on a composite analysis. The first was markedly modified from the original MA, combining properties of MA and Borda count voting. The other was an original MA with the order of importance for criteria estimated either using Borda count or cumulative voting. The results of the tested MA versions produced were very similar to each other. MA was found to be a useful tool for the group decision support of timber-harvesting.
article id 386, category Research article
Functions for estimating stem diameter and tree age using tree height, crown width and existing stand database information. Silva Fennica vol. 39 no. 2 article id 386. https://doi.org/10.14214/sf.386
The aim was to investigate the relations between diameter at breast height and maximum crown diameter, tree height and other possible independent variables available in stand databases. Altogether 76 models for estimating stem diameter at breast height and 60 models for tree age were formulated using height and maximum crown diameter as independent variables. These types of models can be utilized in modern remote sensing applications where tree crown dimensions and tree height are measured automatically. Data from Finnish national forest inventory sample plots located throughout the country were used to develop the models, and a separate test site was used to evaluate them. The RMSEs of the diameter models for the entire country varied between 7.3% and 14.9% from the mean diameter depending on the combination of independent variables and species. The RMSEs of the age models for entire country ranged from 9.2% to 12.8% from the mean age. The regional models were formulated from a data set in which the country was divided into four geographical areas. These regional models reduced local error and gave better results than the general models. The standard deviation of the dbh estimate for the separate test site was almost 5 cm when maximum crown width alone was the independent variable. The deviation was smallest for birch. When tree height was the only independent variable, the standard deviation was about 3 cm, and when both height and maximum crown width were included it was under 3 cm. In the latter case, the deviation was equally small (11%) for birch and Norway spruce and greatest (13%) for Scots pine.
article id 385, category Research article
Effect of thinning on stem form and wood characteristics of teak (Tectona grandis) in a humid tropical site in Costa Rica. Silva Fennica vol. 39 no. 2 article id 385. https://doi.org/10.14214/sf.385
The aim of the study was to evaluate the effects of thinning intensity on wood properties, such as heartwood proportion, wood basic density, and stem form of teak (Tectona grandis L.f.). The thinning trial was established on a teak plantation in a humid tropical site in northern Costa Rica. The moderate and heavy thinnings yielded the highest percentage of heartwood volume (25 to 30% of total stem volume). The differences between stem form factors under different treatments were not statistically significant after separating thinning effects from timing effects. Both the highest (> 0.65 g cm–3) and the lowest (< 0.50 g cm–3) wood density values were observed under light thinnings, making it difficult to establish a relationship. Large variations in wood properties found under different thinning regimes suggest that at early stages teak stands can be managed under different thinning programs without negatively affecting the quality of wood under humid tropical conditions.
article id 384, category Research article
Comparison of randomized branch sampling with and without replacement at the first stage. Silva Fennica vol. 39 no. 2 article id 384. https://doi.org/10.14214/sf.384
Randomized Branch Sampling (RBS) is a multistage sampling procedure using natural branching in order to select samples for the estimation of tree characteristics. Usually, sampling units are selected with unequal probabilities. Conventional RBS uses sampling with replacement (SWR) for repeated sampling on the first stage, and the sample size equals 1 on all subsequent stages, thus resulting in n so-called sample paths. When the sampling fraction is large multiple selections of first stage units are likely. Sampling without replacement (SWOR) at the first stage is an alternative that is expected to increase efficiency of the procedure. In this case, the second stage sample size m must be larger than 1 to enable unbiased variance estimation. In the present study, a theoretical and an empirical comparison of the conventional RBS and the SWOR variant was accomplished. Requiring a certain precision of the RBS estimation, the conventional RBS method is mostly more time-consuming than the variant with SWOR at the first stage. Only if m = 1 is chosen as second stage sample size for the SWOR RBS, this is often more time-consuming. In those cases, conventional RBS is up to 5% cheaper. In general, the larger m is, the more expensive is conventional RBS compared with the variant with swor at the first stage. The smaller the ratio of the variance between the primary units to the total variance of the estimate, the larger is the advantage of the SWOR variant. Generally, it can be shown that the gain of efficiency by SWOR is larger in case of weak correlations between auxiliary and target variable.
article id 383, category Research article
Biodiversity value of potential forest fertilisation stands, as assessed by red-listed and ‘signal’ bryophytes and lichens. Silva Fennica vol. 39 no. 2 article id 383. https://doi.org/10.14214/sf.383
In Sweden ca. 20 000 ha forestland is fertilised each year. By using red-listed and ‘signal’ bryophytes and lichens as indicators, we investigated whether forest stands planned for fertilisation have a biodiversity value, and thus if restrictions due to conservation aspects are motivated. Species occurrences were registered in detailed line-transect analysis, with a record size of 10 x 10 m, in 74 coniferous forest stands with a mean age of 57 years in East-Central Sweden. On the 230 ha totally surveyed, 10 red-listed and 37 signal species were found. The mean number of records ha–1 of red-listed bryophytes and lichens was 0.26 ha–1, which is considerably less than previously found in mature production stands and woodland key habitats. Red-listed species were found in 31% of the stands and signal species in 95%. More than 70% of all records of red-listed species and 30% of the records of the signal species were found in moist micro-sites. If rare bryophytes and lichens are to be preserved in fertilisation stands, improved instructions regarding avoidance of important micro-sites are needed.
article id 382, category Research article
Survival-time analysis of white spruce during spruce budworm defoliation. Silva Fennica vol. 39 no. 2 article id 382. https://doi.org/10.14214/sf.382
Mortality and defoliation (DF%) in 987 white spruce (Picea glauca (Moench) Voss) trees were followed from 1992 to 2003 during an outbreak of the spruce budworm Choristoneura fumiferana (Clem.) in 15 white-spruce-dominated uneven-aged stands in the Fort Nelson Forest District near Prince George, British Columbia. Four stands were aerially sprayed with Bacillus thuringiensis (Bt). Defoliation and mortality levels were elevated in non-sprayed stands. The relationship between defoliation and survival-times was captured in a Cox proportional hazard model with a defoliation stress index (DSI), diameter (DBH), crown class (CCL), a random stand effect, Bt-treatment, and number of years of exposure to stand-level defoliation (DYEAR) as predictors. The DSI, optimized for discrimination between survivors and non-survivors, is the discounted sum of five lagged DF% values. Survival probabilities were predicted with a maximum error of 0.02. Hazard rates increased by 0.06 for every one point increase in DSI. CCL and random stand effects were highly significant. Bt-treatment effects were fully captured by DSI, CCL, and DYEAR.
article id 381, category Research article
Allozyme variation in natural populations of Picea asperata. Silva Fennica vol. 39 no. 2 article id 381. https://doi.org/10.14214/sf.381
A survey of allozymic alleles and genetic diversity was conducted for ten natural populations of Picea asperata Mast. originating from the mountains of Southwest China. A total of twenty-seven alleles at seventeen loci were observed. Ten of the loci were found monomorphic. Our results showed that the populations sampled were characterized by low genetic diversity (mean He = 0.096) and a low level of inbreeding (mean Fis = 0.005). The UPGMA tree of genetic relationships indicated that there was significant differentiation among populations. The coefficient of genetic differentiation among populations, based on Fst, equaled 0.311. Such extensive inter-populational differentiation detected in P. asperata could have resulted from allele frequency divergence among populations, particularly, in one population. Introgression from another species, variation in environmental conditions, and differing selection pressures could be some of the factors attributing to significant differences among populations. In addition, our results showed that the geographic and genetic distances were not correlated in the populations of P. asperata. Based on the genetic information obtained, we concluded that monitoring appropriate genetic markers may be an effective means of identifying potential genetic changes occurring during forest tree evolution.
article id 380, category Research article
Measurement of the tree root growth using electrical impedance spectroscopy. Silva Fennica vol. 39 no. 2 article id 380. https://doi.org/10.14214/sf.380
The non-destructive evaluation of plant root growth is a challenge in root research. In the present study we aimed to develop electrical impedance spectroscopy (EIS) for that purpose. Willows (Salix myrsinifolia Salisb.) were grown from cuttings in a hydroponic culture in a growth chamber. Root growth was monitored at regular intervals by a displacement method and compared with the EIS parameters of the plants. To measure its impedance spectrum (IS) (frequency range from 40 Hz to 340 kHz) each plant was set in a measuring cell filled with a solution of the hydroponic culture. The IS was measured using a two-electrode measuring system. A silver needle electrode was connected to the stem immediately above the immersion level and a platinum wire was placed in the solution. The measurements were repeated twice weekly for a root growth period of one month. The IS of the entity consisting of a piece of stem, roots and culture solution were modelled by means of an electric circuit consisting of two ZARC-Cole elements, one constant-phase element, and a resistor. On the plant basis, an increase in root volume by growth correlated with a reduction in the sum of resistances in the ZARC-Cole elements (mean Pearson’s correlation coefficient r = –0.70).
Category: Review article
article id 390, category Review article
Ecology of species living on dead wood – lessons for dead wood management. Silva Fennica vol. 39 no. 2 article id 390. https://doi.org/10.14214/sf.390
Dead wood has been identified as a crucial component for forest biodiversity. Recent research has improved our understanding of habitat relations for many species associated with dead wood. However, the consequences for forest management are yet to be explored. In this review we build upon the growing volume of studies on dead wood dependent species, the dynamics of dead wood and ecological theory in order to identify the challenges for forest management at the landscape level. The review has a Fennoscandian focus, but the problems and challenges are similar in many forest ecosystems. We argue that it is necessary to 1) counteract the current shortage in availability of dead wood, 2) concentrate planning at the landscape level in order to minimize isolation and reduce edge effects, 3) create a variety of dead wood types, and 4) utilise available quantitative analytical tools. This calls for new approaches to management that to a large extent includes available knowledge, and to find platforms for planning forested landscapes with diverse holdings.