Basal area growth equations for poplar (Populus deltoides) in Somee Sara, Guilan province, Iran.

The basal area growth equations are directly linked to economic variables such as stand volume. Estimating the stand basal area is essential for economic computation and yield estimation. The main objective of this study is to estimate the basal area growth equations for economic studies. Tree’s diameter at breast height and height were measured in plantations of Populus deltoides Clone No.6955 for two successive years. Due to lack of information on poplar growth at high age, two plantations in Gisoom and Pilambara (with age 26 and 27 years) were also inventoried. Three popular dynamic equations (Korf, Hossfeld and Bertalanffy-Richards) were used for data analysis. Graphical analysis and different statistics (RMSE, R2 and AIC) were used to compare models and select the most appropriate model. Then, the basal area growth equations were validated. For this purpose, 30 percent of collected data were set aside and used to estimate RMSE. The Korf growth equations have been successfully estimated with R² =0.97 and RMSE =1.52 square meter per hectare. The result of validation showed that there is no statistical difference between two set of data in terms of RMSE.