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Wehrhausen M.,Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg DE | Sauter U.H.,Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg DE | Bruchert F.,Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg DE | Becker G.,Albert Ludwigs University of Freiburg
Schweizerische Zeitschrift fur Forstwesen | Year: 2012

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.


Nagel P.,Forstliche Versuchs Und Forschungsanstalt Baden Wurttemberg DE | Hercher W.,Forstliche Versuchs Und Forschungsanstalt Baden Wurttemberg DE | Hartebrodt C.,Forstliche Versuchs Und Forschungsanstalt Baden Wurttemberg DE
Schweizerische Zeitschrift fur Forstwesen | Year: 2013

The requirements and policies that affect the results of individual forest enterprises are numerous. To develop functioning management and advisory mechanisms, these individual circumstances should be taken into consideration. However, compliance with all the influencing factors is not feasible in practice, wherefore a reduction in the existing complexity is necessary. Multivariate statistical methods allow to use a variety of indicators as a basis for the formation of different types of forest enterprises. The goal to consider the individual operating conditions as completely as possible can be achieved with a multivariate typology. For the Swiss Forestry Holding Network (HDN), the question arises as to whether the results of such a typology can also be reproduced by the currently used biogeographic classification of forest zones. Sixty-six variables with information about structural properties and the business results of 208 Swiss holdings from the years 2008 to 2010 formed the basis of the study data. These variables were reduced to 19 key variables. With the help of principal component and cluster analyses the holdings were divided into four clusters based on these key variables. They differ from each other significantly in most of the key variables. The results of this multivariate typology can be mapped in part by the forest zones of Switzerland. It should be noted that the variable "forest zone" also acts as a multivariate criterion, reflecting the physical and structural requirements of the enterprises. Combined with certain additional information (e.g. timber growth), the results of the multivariate analysis can be even better understood.


Wehrhausen M.,Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg DE | Bruchert F.,Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg DE | Sauter U.H.,Forstliche Versuchs und Forschungsanstalt Baden Wurttemberg DE
Schweizerische Zeitschrift fur Forstwesen | Year: 2012

Cracks in timber of Abies alba Mill. and Picea abies (L.) Karst. are of high importance for the optical and mechanical quality of sawn timber products. A sample of 92 logs was assessed in detail before and after the sawing and drying process. The quantity, types and form of cracks were taken on both round wood and sawn product. Emphasis was put on the question, whether cracks take significant influence on the grading results of the sawn timber according to the grading standards DIN 4074-1:2003-06 and DIN EN 1611-1:1999+A1:2002. The assumption that the amount of cracks increases with the log diameter could not be proved. There is a difference between the two tree species as well as between fresh and dried wood. There were no strong correlations found between specific descriptors of cracks in roundwood and the actual amount of cracks in sawn timber.

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