Development of height-diameter models for oriental beech stands in Tokat-Almus region

In this study, height-diameter models were developed for the oriental beech stands of the Tokat-Almus region. For this purpose, diameter and height measurements were performed on 2392 trees in 78 sample areas. The data were divided into two groups randomly. One of the groups was used to develop a model and the other group was used to test the models developed. Some well-known and commonly used height-diameter models were tested to determine the most suitable base height-diameter model by four different criteria, and the Gompertz model was found to be the most suitable height-diameter model for the natural oriental beech stands. In the second stage, some generalized height-diameter models were tested for the same dataset. In the third stage, the height-diameter model was developed by using the most successful simple height-diameter model utilizing mixed-effect modeling approach. In the fourth stage, height-diameter models were developed with the quantile regression approach based on 3 and 5 quantiles, again using the Gompertz model. In the last stage, the models developed in the third and fourth stages were calibrated by using 1 to 10 trees as preliminary information in each sample plot, and considering the inventory costs, it was evaluated that the most appropriate calibration alternative was obtained by using 5 trees in each sample plot. As a result of the study, it was concluded that the models developed using the mixed-effect modeling approach and the generalized height-diameter model can be used for reliable height estimations in the oriental beech stands of the Almus region.