Investigation on the Amount of Mortality of Iranian Oak Trees (Quercus brantii Lindi) using Satellite Imagery (Case study: Dashtebarm forests of Fars Province)

In recent years, oak trees in the Zagros forests have suffered a lot of fatalities for unclear reasons. Determining the rate and severity of forest crown density changes is important for the investigation and management of these forests. This research was carried out with the aim of determining the amount of crown cover changes in the forest area of Dashtebarm in Fars province under the influence of oak drying phenomena using satellite data in three different periods. To this end, QuickBird satellite images dating back to 2005 (before the oak trees dying), images with high spatial resolution, derived from Google Earth 2011 (during oak tree decay) and 2014 (after oak trees dying) used. First, the images were matched using precise ground control and biometric sampling closest neighbors based on the 2011 image. The results of the geometric matching of the images showed that the image QuickBird (2005) with root mean square error of 0.25 and QuickBird image taken from Google Earth (2014) with root mean square error of 0.56, were corrected. Then, 1000 meter square circle pieces with a radius of 17.85 meters, were designed and installed on GIS software, and the crown cover was taken in the samples. The results of this study showed that the average percentage of crown cover of trees in pre-drying period of oak trees was 19.17%, at drying time, 13.33%, and 11.16% for the period after drying of trees. According to the results, it was found that the crown crowns of oak trees decreased from pre-drying to post-drying periods and there was a need for reduction operations in areas with reduced crown cover.