Impact assessment of pollarding on biometrical indices of Lebanon oak (Quercus libani Oliv.) in Belake Forests, Baneh

Pollarding of oak trees as a traditional practice has been done in northern Zagros forests and affects tree characteristics. In order to assess the effects of pollarding on biometrical indices of Q. libani, a less-disturbed stand with an area of 0.65 ha and a pollarded stand with an area of 2.5 ha, with similar physiographic conditions were selected in Belakeh Forests, Baneh city of Kurdistan province of Iran. In each stand, diameter at breast height, collar diameter, total height, stem height, crown length and crown area of all Quercus libani trees over five cm dbh were measured. Ninteen sample trees in pollarded coppice stand and 26 sample trees in less-disturbed coppice stand were randomly selected to measure the diameter increment. Pairs of increment cores were extracted from each tree at the height of 50 cm using increment borer. Current annual increment in the samples was measured and the average annual increments in diameter classes were determined. Normality test was done, using the Kolmogorov–Smirnov test. Comparison of biometrical indices was done by Independent-samples T test. The results showed that the mean biometrical indices of Quercus libani were significantly different (P < 0.01) between the two stands. The value of the studied quantitative variables was greater in the less-disturbed stand. Furthermore, pollarding significantly increased the average diameter increment in pollarded oak trees (P < 0.01). The averages diameter increment and diameter increment percentage in pollarded stand were 3.41 mm and %2.83, respectively. Different values of the average diameter increment and the diameter increment percentage were obtained in the less-disturbed stand (2.23 mm and %1.02).