Developing some diameter distribution models in Karşıkent Forest Management stands

This study aims to develop diameter distribution models for forest stands located within the boundaries of Amasya Forest Regional Directorate, Niksar Forest Management Directorate, and Karşıkent Forest Operation Chiefdom. In pure and mixed stands of various tree species, the diameter distributions are modeled using a three-parameter Weibull probability density function. Data from 706 sample plots containing 21,334 trees were utilized, and five different models based on the 25%, 31%, 50%, 63%, and 95% percentile values of diameter distributions were developed. Various parameter estimation methods for diameter distribution modeling were compared, and model performance was evaluated using statistical criteria such as Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Bias, R², Akaike Information Criterion (AIC), and Bayesian Information Criterion (BIC). The results indicate that the percentile method based on the 50% and 95% values is the most successful model compared to others. This model shows lower error, higher explanatory power, and better AIC/BIC values than the other models. The Mean Absolute Error (MAE) for this model is calculated as 37.34, the Root Mean Square Error (RMSE) is 73.91, and the Bias is -6.40. These values indicate that the model exhibits a very low level of error and that systematic bias is minimized. Additionally, the model's R² value is determined to be 0.818, meaning that approximately 81.8% of the variance in the dependent variable is explained by the independent variables. This percentage suggests that the model has a high level of explanatory power. The Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) values for the model are 17,869.44 and 20,743.38, respectively. The lower values of AIC and BIC, compared to other models, demonstrate that this model fits the data better and is less complex.