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چکیده
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Pollarding is one of the oldest traditional utilization of the forests in the Zagros region, western Iran. The aim of this traditional management is to hoard the oak leaves to provide winter feed while the livestock were housed. The objectives of the present research were to evaluate changes in the biometric indices (i.e., diameter, total height, and crown area) of pollarded oak trees and to study the mortality rate of oak trees during a 13-year period (2005-2018). A number of 79 permanent circular plots (area: 0.1 hectare) which were established in 2005 using digital systematic inventory grid, were retrieved in 2018. In each sample plot, diameter at breast height (dbh) for all trees (dbh ≥ 5 cm), total height and crown diameter of two trees (i.e., nearest tree to the center of the plot and the largest tree in terms of dbh in the plot) were measured in 2018. The number of cuttings and dried-up trees was recorded in the 13-year period. The pattern of trees distribution in biometric indices classes (i.e., diameter at breast height, total height and crown area) at the beginning (2005) and the end of the period (2018) were compared. Results showed that the medians of diameter increment, height increment, and crown area growth of pollarded oak trees were 1.6 mm/year, 10 cm/year, and 0.8 m2/year, respectively. There was a significant difference between trees distribution patterns in total height and crown area classes at the beginning (2005) and the end of the period (2018). The difference between trees distribution patterns in diameter classes was not statistically significant. The mortality rate of oak trees during the 13-year period was 15 trees/ha. To analysis the effect of pollarding on biometric indices, studied pollarded stands were compared with a reference site (a non-pollarded stand). The comparison showed that pollarding (i.e., the main traditional practice in the study area) severely influences the height and crown of oak trees and total height and crown size in pollarded stands were less than reference site.
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