Wzory do określania pierśnicowej liczby kształtu mieszańców selekcyjnych topoli

Knowledge of diameter at the breast height (DBH), tree height and form factor allows to estimate tree volume, which is one of the most important measures in forestry. The paper presents empirical equations for the determination of DBH form factor of different species and hybrids of Populus sp. The study was set up on short−rotation plantation in Wichrowo Forest District (northern Poland). Four poplar hybrids at the age of six were taken into account: P. × generosa × P. trichocarpa, P. trichocarpa, P. maximowiczii × P. trichocarpa, Populus × canadensis. In total, 427 trees were felled and individually measured in one meter sections. The estimation equations are based on the relationships between form factor and one or some independent variables derived from diameter at breast height and height. We used determination coefficient as a goodness−of−fit measure. In addition, standard error of estimates from this dataset was calculated. The standard error values varied from 5.8 to 6.6% depending on the formulae and Populus hybrids. Th e equations proposed in this paper enable the determination of the discussed form factor for varied poplar cultivars and can be treated as a regional equations.