The Lebanon Oak (Quercus libani Oliv.) response to pollarding in northern Zagros

Background and objectives: The Iran’s Forest, Rangeland and Watershed Organization (FRWO) banned any utilization from these forests and considers them as preserved and protected ecosystem, however traditional uses (e.g. pollarding, fuel wood harvest, livestock grazing and agriculture in the forest floor) of these forests by local communities are still common. In order to adapt their livelihood to natural difficulties and limitations, local people have innovated Galazani (pollarding) of oak trees. In winter, dried leafy branches are used to feed livestock (especially goat and sheep).
Despite the severe and widespread uses of forests in Baneh, there are some stands located around cemeteries and holy places, which due to traditional believes and their holiness to local people, have been protected from human exploitation and interference, therefore their structure and vegetation have been rather intact. The area of these less disturbed stands differs from 0.5 to more than 10 hectares. These stands have been examined in this study as less disturbed (unpollarded) stands. Less disturbed stands still have most structural and ecological characteristics of virgin north Zagros forest stands, which unfortunately, cannot be found today. These stands can be used as a model to perform restoration and management planning for degraded Zagros forests. Unfortunately, nowadays the holiness and respect to less disturbed stands has been diminished between new generations and will face more encroachment and destruction. Due to higher palatability of Lebanon oak leaves than Persian oak and Gall oaks, this species is more suitable for pollarding in northen Zagros. The purpose of this study was to investigate the response of Lebanon oak trees to pollarding.
Materials and methods: An unpollarded stand (0.7 ha) and a pollarded stand (1 ha) with similar physiographical conditions were selected. Full Callipering was performed in both stands and tree species, collar diameter and crown diameter for all trees over 5 cm in collar diameter were recorded. Moreover, total height and trunk height were measured in Lebanon oak trees as well.
Results: The results showed that the average of total height, trunk height, crown height and crown area were significantly lower (p< 0.01) in pollarded stands. Crown height to total height ratio were significantly higher in pollarded stands.
Conclusion: Although pollarding tension can decrease most of the biometrical indices of Lebanon oaks, but increase in crown height to total height ratio and root/shoot ratio can be an important factor to increase oak trees resistance to drought stress in northern Zagros.