Multivariate Analysis of the Brinell Hardness of Silver Birch (Betula pendula Roth.) Wood in Poland

An analysis was undertaken of the Brinell hardness of silver birch wood and its dependence on stand location, tree age, tree thickness and forest habitat type, and the interactions between these factors. Wood was obtained from 12 forest districts throughout Poland, from trees aged approximately 30, 50, and 70 years. A total of 51 study plots was established, from which 306 trees were taken. Hardness was measured on three surfaces (transverse, radial, and tangential sections) for 4777 samples, giving a total of 14,331 measurements. It was shown that the hardness of silver birch wood in Poland is significantly influenced by location, tree age, tree thickness, and habitat type, and by interactions between those factors. Habitat type was not shown to affect radial hardness, except in the case of Gizycko forest district. For the whole of the analysed material, the mean hardness on a transverse section was calculated as 66.26 MPa, corresponding to a very hard wood on Morath's scale, whereas the values for the longitudinal sections (radial 44.06 MPa, tangential 44.02 MPa) correspond to a soft wood.