Single tree volume modeling for even age Persian oak (Quercus brantii) coppice in Central Zagros (Case study: Chaharmahal VA Bakhtiari province, Ardal and Kiar district)

Abstract

The idea of this research is to select the appropriate model for the rapid estimation of volume in even-aged Persian oak coppice stands. For this purpose, 19 widely used univariate and bivariate models were used in volume estimation. Initially, actual volume data from 73 cut trees in different diameter classes in 12 forests of Ardal and Kiar cities were divided into two sets of 70% for modeling and 30% for validation. Then, the coefficients of the selected models were calculated using the weighted least squares method. Models with significant coefficients were ranked by the root mean square error and R-squared. Of the 19 models, nine models were selected. The fitting results of the selected models showed that the least amount of root mean square error (0.035) was related to the five-parameter model and the highest amount of R2 (0.979) was related to the four and five-parameter models. The results of validation showed that among the bivariate models, the four and five parameter models and among the univariate models, the power model were the most efficient. The obtained results can be used in growth and yield models, preparation of Tarif and standard volume tables.

Keywords

• bias
• persian oak
• yield table
• weighted linear regressions
• volume modeling
• coppice forest