Decline modelling of Quercus brantii under effects of physiographic factors in Dalab forests of Ilam

In addition to investigate effects of physiography factors including of slope (3 classes), aspect (4 classes), height above sea level (3 classes) on decline of oak trees, the aim of this study was decline modelling of Quercus brantii under effects of physiographic factors in Dalab forests of Ilam province. For this purpose, 509 hectares of Dalab forests of Ilam province were selected. Based on systematic-random sampling method with 200 × 250m dimensions, 100 circular plots (2000 m2) were measured. In each sample, physiography factors and percentage of decline were measured. ANOVA and Duncan tests were used to compare of oak decline in different physiography factors. Logistic regression model was used for modelling of oak decline. Omnibus test, log-likelihood and pseudo r-square coefficients were used to evaluate the logistic regression model. The results of ANOVA test showed that physiography factors had a significant effects on the oak decline. Also the results showed that with increasing slope and altitude, decline of oak trees was increased. The results showed that the lowest and highest of tree decline were belong to east and south aspects respectively. The results of this study can conserved areas that have oak decline, to be effective.