Stands structure under oak charcoal disease in Dalab Forests of Ilam, Iran

In the last two decades, the vast areas of Zagros forests especially in Ilam province have been infected by charcoal oak disease, which killed many Persian oak trees. This study aimed to recognize the structure of the infected stands and to address the relationships between structural features and the tree characteristics with the infection level to the symptoms of charcoal oak disease. For this purpose, a number of 20 sample plots was established along a 6 km transect in Dalab protected forest to collect data such as collar diameter, diameter at breast height, height, crown area, and tree drying degree were measured and recorded for each tree within the sample plots. The number of tree bases was 153 and the surface area was 14.6 m2/ha, indicating a relatively high density and inventory of forests. In general, 85.5% of the individuals had a sign of the charcoal disease and the rate of infection was higher in seed-originated trees, middle-aged and old trees than branching bases and young ones. Based on the results, tree characteristics including collar diameter, diameter at breast height, basal area, total height, and crown area were significantly different among different infection levels of the disease. To understand the dynamics of stands’ structure under the charcoal disease, continuous monitoring of the forests is necessary. Since the higher severity of the disease outbreak in middle-aged and old trees, pruning and shrinking the infected trees’ crown to adjust the crown to root ratio as well as cutting and removing the trees which are not restorable are among the proposed practical plans.