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Crown dieback is of the phenomena that mainly has affected Persian oak trees. In order to assess the crown dieback of trees in forest stands of oak trees and its relationship with the individual trees, tree origin and size of tree canopy, Shalam forested area in the northern half of the Ilam province was selected. After dividing the study area into topographic homogeneous units, the biggest unit was selected for assessing the research objectives. Within the selected unit, 6 parallel transects were laid and about relatively 60 healthy and dieback trees were recorded. Then crown dieback, position of tree in stand, origination of trees, minimum and maximum crown diameter and crown height were measured. Data analysis was performed by analysis of variance and linear regression. Results showed that individual trees had healthier crown than the rest of the trees. Standard trees showed less crown dieback than the coppice trees. Effect of crown size on crown dieback depended on the location of trees as single or group and tree form. Totally it can be concluded that oak trees would give different responses to drought in terms of their individual or social characteristics and also it was seen a range of crown dieback with different intensity/pattern within stand in individual to group trees.

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Persian oak (Quercus brantii Lindl.) has a wide distribution in central Zagros forests and it is the prevalent species in this region. Considering the high volume of demolition and the importance of safekeeping of this jungle, investigation and knowing the structure and the situation of this forest from the qunatitative and qualitative aspects is necessary. This study accomplished to investigate the condition of the Iranian oaks (Quercus brantii Lindl.) forests from the qunatitativeand qualitative aspects of Bazoft district of Kouhrang township of Chahar Mahal and Bakhtiaris province. In this respect, 60 numbers of plots with 400 meter distance  in a randomize systematic method established in the area. Then in the studding plots the quantitativecharacteristics of trees like: dbh, trees high, crown diameter measured and some characteristics like canopy percent and firewoods were estimated and registered. Also qunatitative marks from 1 to 4 were given to the trees and they were recorded and data were analyzed. The results shown that the jungle wasa non- coeval and it was sparse forest. Also, 81% of the region had 0-25% coverage. The most density and firewood volume was observedin northeast direction. Also,75% of the trees were inthe proper degrees of Succulence. The results of this study showed the average and a suitable situation of study area stands in comparison to the other regions of central Zagros forests.

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Oak decline is a complex phenomenon that oak forests are faced with it across the world and Iran. Shalam forested area located in north of Ilam province was selectedto determine the role of topographicand some edaphic factors in tree mortality happened in Persian oak forests. The study region was divided into 20 homogeneous topographic units. Within each homogeneousunit,three 0.1-haplots  were randomly-systematically established for measuring the rate of tree mortality and oneprofile was prepared for characterization ofsome  physical and chemical soil characteristics (texture, moisture content, TNV%, OC% and N for each soil layer, and soil depth). In each plot,diameter at breast height (DBH), maximum and minimum crown diameters, crown dieback percent, origination and form of trees and shrubs for all species and site variables weremeasured. Results showed that 15.7% of forest stock had reduced while 97.65% of it belonged to Persian oak species. The results of multiple linear regression and RDA showed that tree mortality was significantly affected by elevation and aspect, but not by slope. The highestrate of tree mortality was observedin high elevation and south and west aspects. Also the results of multiple linear regression and RDA showed that tree mortality was significantly affected by soil depth and texture. So, the highestrate of tree mortality was observed in soils with less depth, less sand% and more silt%. It was concluded that topography and soil have effective role in tree mortality and its expansion across Zagros forests. Identifying the critical conditions in terms of topography and soil in these forests can help and be useful in the management of tree dieback.