Response of Gall oak (Quercus infectoria Oliv.) to pollarding in northern Zagros

This study aimed to investigate the response of Gall oak (Quercus infectoria Oliv.) to pollarding. Therefore, a less-disturbed stand (1.4 ha) and a pollarded stand (1.7 ha) were selected. Five rectangular plots (20×30 m) were established in each selected stand by random sampling. In each plot, tree species, diameter at breast height (DBH), total height, trunk height and crown diameter for all trees (DBH ≥ 5 cm) were recorded. In addition, 18 tree samples were taken in each studied stands to assess the diameter increment of Gall oak. A pair of increment cores per sample tree was taken 50 cm above ground level, in which annual radial increment was measured and further multiplied by 2 to derive the annual diameter increment. Then, the diameter increment distribution of Gall oak trees in identical diameter classes was determined for the period of 1984-2010. The mean radial increment of two cores extracted from each sample tree was used in the calculations. The results showed that the average diameters, total height, trunk height, crown height and crown area were significantly lower (p < 0.01) in pollarded stands. Moreover, the averagee diameter increment in less disturbed and pollarded stands was estimated 1.32 and 2.08 mm per year, respectively. The results indicated that average diameter increment of Gall oak trees across he identical diameter classes during the studied period was significantly different between the examined stands