عنوان مقاله [English]
The first sign of any stress in trees usually appears in the status and morphology of the crown. Therefore, the cause of disease symptoms or oak decline in Zagros forests could also be checked by the status of the crown. For this purpose, 223 oak tree (in four levels of healthy, low, moderate and severe declines) in Meleh Siah forest, Ilam province were randomly selected in 12 0.25 ha square plots in three random transects. Total height, crown dimensions such as two vertical crown diameters, crown height, crown density and crown dry branches, general health status, and level of contamination to pests and diseases of trees in each plot were recorded. Crown area (canopy), crown ratio (live crown length to tree height) and crown volume were also calculated. For data analysis, one way ANOVA and Duncan's test were applied by using SPSS software. The results showed that about 57% of the oak trees in the region have low to severe declines. Analysis of the data suggests that the relationship between the decline and the crown ratio is not significant. However, the parameters of the crown area, crown density, crown length and crown volume is significant at 99%, so that large crowns have shown more damage. Crown density index showed the highest correlation with the degree of decline, so that closed canopy has shown fewer declines. Thus sparseness of oak trees canopy could be considered as a good indicator for the risk of tree decline.