Equations for predicting age of black locust (Robinia pseudoacacia L.) based on the tree circumference

In Poland black locust grows generally in parks, gardens and along roads and in forests as well. During dendrological inventories specialists often need information about age of a tree. Simple noninvasive methods utilize mainly relation between age and size of a tree. One of such methods is mathematical formula describing relation between tree's diameter (or circumference) and its age. The main objectives of the presented paper is to elaborate such formulae for trees growing either in forests stands or in an open space (single tree, trees alley or small groups). Relations between tree's age and circumference were analyzed on the background of measured trees growing in forests administrated by the State Forests National Forest Holding from a whole territory of Poland. The formulae describing relation between tree's age and circumference were developed based on 20,302 database records for trees growing in forest stands and 6267 records for trees growing in an open space. In both cases power functions showed the best matching (tab. 1) in 95% confidence interval and which lead to construction of the age tables (tab. 2 and 3). Both elaborated formulae were tested and checked out with four series of measurement data. Three control series (1 – ‘Siemianice', 2 – ‘WPN' and 3 – ‘Zielonka') show compatibility with analysed formulae, while the fourth one (4 – ‘Poznan') differed substantially. The probable reason of such situation lies in the fact that this series represented trees growing in urban conditions and having completely different growth rate