Short-term changes in height–diameter relation of two maple species and European cornel of understory in an oak forest in Hungary on the basis of two-parameters model

Forest understory species such as shrub and herbaceous layer, have received little attention in long-term studies. Knowledge of the diameter and the height of trees are fundamental for developing growth and yield models in forest stands. Overstory composition of the Síkfőkút Project site was dominated by sessile oak–Turkey-oak forest (Quercetum petraeae-cerris Soó 1963). Similarly to other European countries an oak decline occurred in Hungary oak woodlands at the end of 1970’s and about 63% of the oak trees perished in our site. The potential for oak species regeneration was a very low over the period of 1982-2012. Four nonlinear height-diameter functions were fitted and evaluated for Síkfőkút site based on a data set consisting of 2025 individuals for three dominant woody species (Acer campestre L., Acer tataricum L. and Cornus mas L.) and detected any short-term changes in these equations following dieback of oak canopies. These height– diameter equations increase our knowledge of the growth of these species; therefore will enable us to improve management planning in oak forests