The variation of growth in diameter and its relationship with the height of pedunculated oak (Quercus Robur L.) trees in the provenance cultures

Abstract

In provenance cultures, studies were conducted on diameter growth dynamics in pedunculated oak (Quercus robur L.) trees and the height-diameter relationship was evaluated based on three data approximation models. The studies highlighted a signifi cant variation of the trunk diameter in trees of different origins and a similar growth reaction of oaks from four provenances (Hârjauca, Plaiul Fagului, Zloti, and Baimaclia) in relation to the environmental conditions of the common stand. In all the years of observation, the trees from Edineț had a rapid growth in diameter, thus demonstrating their ability to adapt through phenotypic plasticity. An uneven distribution of tree diameters was observed by provenance, indicating that dominant trees have an advantage in competition for light, slowing the growth of those with smaller diameters and causing a positive skew towards oaks with larger diameters. With the advancing age of the oaks, a tendency to decrease the values of the heritability coefficients for the trunk diameter was observed. At the age of 5 years, studies show a strong genetic control over the growth in diameter, a fact highlighted by the heritability coefficient value of 0,53 for this character. As the trees age, non-genetic factors such as environmental conditions become increasingly important in determining tree diameter growth. The comparative analysis of three statistical fitting models for data on pedunculate oak trees from different provenances, showed that the logarithmic model is the most appropriate to explain the relationship between their height and diameter.