The Influence of Location, Tree Age and Forest Habitat Type on Basic Fuel Properties of the Wood of the Silver Birch (Betula pendula Roth.) in Poland

The most extensive study to be carried out in Poland, and one of only a few worldwide, regarding the influence of location, tree age and forest habitat type on the basic fuel properties of silver birch ( Betula pendula Roth.) wood was conducted in 12 Forestry Districts of the Polish State Forests. The field study included trees in three age groups of approximately 30, 50 and 70 years. The research was carried out in a fresh broadleaved forest (FBF) habitat type, where in Poland silver birch stands predominate in respect of coverage area and merchantable volume. Additionally, for five selected Forestry Districts, a comparative study was conducted in a fresh mixed broadleaved forest (FMBF), the second most important habitat of this tree species. A total of 306 test trees were examined. For every sample, calorific value and contents of ash, carbon, hydrogen, nitrogen, sulphur and chlorine were determined. The results indicated a statistically significant influence of location on the calorific value ( p = 0.0001) and on the contents of ash ( p