Estimation Basal Area Growth of Oak by Stepwise Filtration Method of Climatic Variables

Thirty-five core samples were taken from 35 stems of oak (Quercus castaneafolia C.A. (Mey.)) in Noor Forest Park. Associations between tree-ring chronologies with 85 climatic variables, including precipitation, temperature, evapotranspiration and water balance were examined on an annual, monthly, three-seasonal and growth season basis. Simple linear and multiple regression models were run to evaluate and to estimate impacts of climatic variables in current, and first, second and third preceding years on the growth of oak. Filtration method was used to find the best. Statistical factors, such as coefficients of variations and determination, and residual sum of squares in different subsequence process were attained. The best model for evaluation of the growth of oak could explain total variance by 88 percent. The response of this species was different in different years. The filtration method helped identifying and using the best models in each step. Based on this method, it was understood that the oak's growth responds chiefly to the current climatic variables rather than those of previous years, though there was a correlation between growth and the variables in the last three years, but to a lower extent. The result of this study showed that Caspian oak favors warm weather in the growth season, and growth will be different depending whether climatic variables are favorable or not in the current year and the last three years. Based on the research, climatic conditions of the current year have a greater effect on the tree's growth as compared to the conditions of previous years.