Leśne Prace Badawcze, 2010, 71, 2: 135-147.

Wybrane wskaźniki jakości technicznej drewna brzozy brodawkowatej (Betula pendula Roth.) w północno-wschodniej Polsce
Selected indicators of technical quality of silver birch (Betula pendula Roth.) wood  in north-eastern Poland

Hubert Lachowicz
Instytut Badawczy Leśnictwa, Zakład Zarządzania Zasobami Leśnymi, Sękocin Stary, ul. Braci Leśnej 3, 05-090 Raszyn, Fax: +48 0227150313, e-mail: H.Lachowicz@ibles.waw.pl

Abstract. Wood resistance and structural parameters with the consideration of the geographical location and tree age were selected for the study of the variability in technical quality of silver birch wood. The study area covered the north-eastern part of the birch timber resource basis in Poland. Trees were sampled at aged 45 and 70 years, in the sites located in the fresh broadleaved forest.
The most important result of the paper is the confirmed significance of both geographical location and tree age for the mean width of annual wood rings. Another finding is the statistically significant effect of geographical location on birch wood density and its mechanical properties. No significant effect of tree age on wood density and mechanical properties of birch wood has been found.
The highest values of resistance to static bending as well as the elasticity coefficient obtained during static bending have been stated for the Sokołów Podlaski Forest District: 131.4 MPa and 14741 MPa, respectively; while the lowest values obtained for the Płońsk Forest District were 121.5 MPa and 13447 MPa, respectively (the differences reaching 8.1% and 9.6%). In the Forest Districts Sokołów Podlaski and Biała Podlaska, the following birch wood parameters had their maximum values: wood density, compression resistance along fibers, static bending and coefficient of elasticity during static bending.

Key words: Silver birch, wood structure