Şahin, Abdurrahman2025-09-302025-09-30202502827581https://hdl.handle.net/11494/5915Research on site quality, volume estimation, growth and yield analysis, and other related topics relies heavily on tree and stand height as a key metric. This study evaluates three types of 36 nonlinear height-diameter models, categorized as simple, fixed-effects and generalized mixed-effects for accurately predicting total tree height using independent data from even-aged natural stands of oriental beech in northeastern Türkiye. The dataset comprised 1,355 height-diameter measurement pairs, obtained from 33 randomly selected temporary plots. To examine variations in the height-diameter relationship across different zones (regions) and developmental ages of oriental beech, nonlinear mixed-effects (NLME) modeling was employed. The Crecente-Campo height-diameter model, which explained 90% of the variance in the height-diameter relationship, was identified as the most effective. A significant difference we observed between the predicted and actual tree heights in the height-diameter model developed using nonlinear regression modeling (NLRM). However, this discrepancy was reduced following the application of the NLME procedure to the model. The results indicated that the application of the NLME approach increased the FI value by 3%, while reducing the AAE, RMSE, and Bias by 16–54%.eninfo:eu-repo/semantics/embargoedAccessMixed-effects modelingOriental beechRandom effectsTree height-diameter modelsArticle10.1080/02827581.2025.25333782-s2.0-105012228928Q2WOS:001538940100001Q2