Modeling the Diameter and Height Growth of Poplar Trees Based on Climatic Parameters1

Modeling is investigating the relation between variables and can be used to provide a dynamic system and predict variations. This study aimed at modeling the diameter and height growth in different species and clones of poplar according to some climatic parameters including: temperature, precipitation, and humidity. The 10-year average of height and diameter growth of poplar trees in the compatibility design of Isfahan province
was applied for modeling and the temperature, precipitation, and humidity data were used as predicting variables. Univariate and multivariate regression analyses were conducted using linear, square, cubic, and logarithmic models and Enter and Stepwise techniques. The results indicated that diameter growth in univariate analysis had a significant relation with all parameters but the coefficient of determination was higher for the temperature (R2= 0.34). The best model with respect to the coefficient of determination (R2) and standard error was the quadratic model. In multivariate analysis, R2 was reduced but the Enter technique was better than the Stepwise one. The height growth in univariate analysis had the highest R2 with temperature and the linear model had a better fit on the data. Multivariate model increased R2 coefficient reasonably but there was no difference between Enter and Stepwise techniques with respect to the power of estimation. Considering the obtained model, it was observed that the temperature and precipitation respectively had the highest and lowest R2. Generally speaking, a total of 30% of diameter and height growth in poplar trees relates to
the climatic parameters especially temperature. The remainder relates to other parameters including soil specifications, irrigation, maintenance operation, and pest control.