Applicability of different regression models for estimation of merchantable wood volume of sessile oak (Quercus petraea (Matt.) Liebl.) in Bosnia and Herzegovina

Abstract

In Bosnia and Herzegovina, there are tariff tables used for estimating the volume of sessile oak trees in high forests, which were created on the basis of two-entry volume tables for oak trees from the area of Germany, authored by Schwappach in 1905. There are indications that the application of the aforementioned tariffs in forest management practice results in certain differences in the estimated amount of merchantable wood volume compared to the real situation. The material for creation of volume tables was the data concerning the measurement of 2,413 model trees in different habitat and stand conditions. A large number of widely used regression models was tested to equalize the volume of merchantable wood volume as a dependent variable in terms of the diameter at breast height and height of the tree as independent variables. Regression models such as Schumacher-Hall and Spurr II provide satisfactory accuracy, that is, they can be used to estimate the merchantable wood volume of sessile oak trees in high forests (pure and mixed) in the territory of Bosnia and Herzegovina, with a permissible deviation. By introducing the third variable into the model, diameter at seven meters height, the accuracy of the tree volume estimation increases significantly, but due to the significant increase in the volume of work on collecting the necessary data, this model is not suitable for use in forest inventories.