Franka Brüchert

The effect of wind exposure on the tree aerial architecture and biomechanics of Sitka spruce (Picea sitchensis, Pinaceae)

This paper reports on the effect of wind loading below damaging strength on tree mechanical and physical properties. In a wind-exposed Sitka spruce stand in western Scotland, 60 trees at four different levels of wind exposure (10 m, 30 m, 50 m, 90 m from edge) were characterized for stem and crown size and shape and mechanical properties, including structural Youngs modulus (E(struct)), natural frequency, and damping ratio. E(struct) increased from the stand edge to the mid-forest, but with a large inter-tree variation. Swaying frequency and damping ratio of the trees also increased with distance from edge. Wind-exposed edge trees grew shorter, but more tapered with an overall lower E(struct), allowing for greater flexural stiffness at the stem base due to the larger diameter and for higher flexibility in the crown region of the stem. The trees at the middle of the stand compensated for their increased slenderness with a higher E(struct). Thus, for the different requirements for wind-firmness at stand edge and mid-forest, an adapted combination of tree form and mechanical properties allows the best withstanding of wind loads. The results show the requirement to understand the different strategies of trees to adapt to environmental constraints and the heterogeneity of their growth reactions in response to these strategies.

Conducting sustainability impact assessments of forestry-wood chains: examples of ToSIA applications

Within the EFORWOOD project, new methodological approaches to assess the sustainability impacts of forestry-wood chains (FWC) were developed by using indicators of environmental, social and economic relevance. This paper introduces and discusses the developed approach and the two main products developed in the EFORWOOD project: the Database Client and the Tool for Sustainability Impact Assessment (ToSIA), which hold, calculate and integrate the extensive information and data collected. Sustainability impact assessment (SIA) of FWCs is based on measuring and analysing environmental, economic and social indicators for all of the production processes along the value chain. The adoption of the method varies between applications and depends on the specification of the FWC in the assessment and what questions are studied. ToSIA is very flexible and can apply forest-, product-, industry- and consumer-defined perspectives. Each perspective influences the focus of the analysis and affects system boundaries. ToSIA can assess forest value chains in different geographical regions covering local, regional, national and up to the continental scale. Potential issues and scenarios can be analysed with the tool including, for example, the impacts of different forest policies on the sustainability of an FWC. This paper presents how ToSIA can be applied to solve such diverse problems and underlines this with examples from different case studies. Differences in chain set-up, system boundaries and data requirements are highlighted and experiences with the implementation of the sustainability impact assessment methods are discussed. The EFORWOOD case studies offer valuable reference data for future sustainability assessments.

Towards assessing the sustainability of European logging operations

The forest-based sector has been at the forefront in operationally implementing the sustainability concept, its associated principles and indicators for sustainable forest management. Several methods have been developed to study environmental impacts of forestry activities, but none of the existing tools address all the dimensions of sustainability along the whole forest wood chain (FWC) in a balanced way. Consequently, the decision was made to develop a tool for sustainability impact assessment (ToSIA), the modelling framework for sustainability impact assessment of FWCs. The objective of the EU Project Eforwood was to develop ToSIA, a decision support tool. Within ToSIA, a FWC is modelled as a number of interconnected processes. For each process, a range of economic, environmental and social indicators and their respective values are calculated, thus representing the three pillars of sustainability. By this method, the multifunctionality of forests can be assessed and supply chains can be compared with respect to sustainability. Sensitivity analysis and scenario techniques can be applied to learn about the effect of expected changes to the structure of the chain, the material flows and the indicator values. In order to provide the tool with information about forest and logging operations, data were collected at two fundamental levels: (1) a regional level with case studies in Scandinavia, Iberia and Baden-Württemberg and (2) a European level with a case study that reflects conditions in the 27 countries of the European Union. This paper describes and details the harvesting and logging processes for the European countries. The results are displayed for each of the three regional case studies as well as aggregated to five principal areas in Europe: Eastern, Northern, Western, Central and Southwest Europe.

Economic, environmental and social impact of alternative forest management in Baden-Württemberg (Germany) and Västerbotten (Sweden)

The forest sector is important for the German Federal State of Baden-Württemberg (BW) and the Västerbotten (VB) County in Sweden. Their forestry wood chains (FWCs) are of similar magnitude and supply forest industries. This study provides a regional comparison of the performance of FWCs from roundwood harvesting, including hauling, to mill gate concerning the factors that impact sustainability and assess different sustainability indicators for alternative supply chains, in particular fully mechanized chains in comparison to motor-manual operations. The harvest volumes are similar but operational conditions differ. Analysis of sustainability indicators demonstrated that the total costs for roundwood to industry are similar. Higher harvesting costs in BW are compensated for by lower transport costs to the mills. Employment per unit is higher in BW because of the high share of labour in felling. Due to smaller machinery and shorter transport distances in BW, energy use and greenhouse gas emissions per unit are lower than in VB. Areas for improvement are the technologies for logging in BW and the logistics of timber transport in VB.

Classification of wood surfaces according to visual appearance by multivariate analysis of wood feature data

Its natural aesthetics make wood an attractive material for construction and design. However, there is no detailed understanding of the relationships between human perception of the appearance and measurable features of wood surfaces that could be used for controlling sawn timber production. This study investigated whether wood surfaces can be classified according to their visual appearance on the basis of wood feature measurements. Cluster analysis was used to discover a classification based on a set of feature pattern variables in a sample of 300 softwood floorboards. A finely graded visual appearance sorting provided a reference. Discriminant analysis was applied to identify the relevant variables from the tested set and to assess predictability of the classification. The results indicated that visual appearance sorting could be approximated quite well by the variable-based classification after pregrouping according to board position in the log. Ambivalent results were obtained for group prediction within the validation sample. While for boards from some groups prediction was mostly or entirely correct, boards from other groups were largely misclassified. An effect of the available sample was one of the surmised causes, making repetition of the analysis based on a larger sample a desirable focus of further research.

Effect of Knot Detection Errors When Using a Computed Tomography Log Scanner for Sawing Control

Abstract Roundwood scanners utilizing X-ray computed tomography (CT) provide the information required for individual log-sawing optimization. However, errors in the automated detection of quality-r...

Crack Detection in Computer Tomographic Scans of Softwood Tree Discs

Abstract Cracks in softwood are an important defect that reduces the quality of sawn timber for construction purposes. As with all other quality reducing features in wood, it is of significant interest to know about their number and position in a log before sawing. On one hand, cracks are relatively easy to distinguish from wood by means of computer tomographic (CT) scanning owing to the large differences in density. The fact that they tend to be irregular and very thin, however, complicates detection. This study describes a method for automated crack detection in single CT slices and evaluates its precision in terms of both detection rate and length measurement. Twenty tree discs were sampled from spruce (Picea abies) and silver fir (Abies alba) logs and scanned with a computer tomograph. The results of the automated detection are compared with data from manual reference measurements on the physical discs and with data from visual inspection of the CT images. Under optimal conditions, the detection rate ...

Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce

Abstract Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability, production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computed tomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect peoples visual perception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could be beneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) of knot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used in training PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis. Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according to the developed classification. Visual assessment of the grading results indicated that the classification was largely consistent with human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CT data, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield of a desired appearance grade, compared to conventional log positioning, was observed.

Klassifikation und Vermessung von Rissen in Nadelrund- und Nadelschnittholz

Classification and measurement of visible cracks in softwood logs and sawn timber Cracks as an attribute of logs are an important quality factor for the production of sawn timber. They can develop in the standing tree due to growth stresses or external influences, but also in felled trees due to tension releases or drying. The definitions for different types of cracks that can be found in standards and in literature lack consistancy and are not sufficient for scientific use. This paper proposes a classification scheme for cracks in logs and sawn timber that is based on existing definitions in literature but also includes newly drafted definitions. A method for the estimation of crack damaged volume in wood is presented, which is based on manual measurement of the crack features for scientific use. The results give detailed and, depending on the dimensions of the sawn timber, also precise information about type, size and position of cracks as well as the expected volume of reject.