Investigation of Height-Diameter Models in Different Development Stages of Unmanaged Beech Forest (Case Study: Educational and research forest of Kheirud)

Height Measurement of all trees in a forest or forest stand is almost impractical. For this reason, today different researchers prefer to estimate the tree height by the relationship between the DBH and height of trees.

In this study, to fitting different statistical models in different stages of forest development, after field inspection, three one hectare sample plots located in different development stages in Beech forest of Kheirud forest, Natural Resources Faculty in Tehran University were selected. Then the DBH of 251 trees have been measured randomly and 80 percent of trees were used for modeling and 20 percent were used to validate 22 regression models. In order to determine the best model for each of development stages, R2, E, MBE and NMPE criteria were used.

The results of this study indicated the suitability of Rational Function and Weibull models in initial stage, Modified Exponential in optimal stage and Gompertz and Richard models in Decay stages.

Based on the results of this study it can be concluded that different regression models doesn’t have the same ability in fitting the data of DBH and height of different forest stands and the same model can’t be used to fit the data of DBH and height of different forest stands.