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چکیده
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In the Zagros region, one of the oldest utilizations of forests is the use of oak leaves to provide livestock forage. This type of usage affects the biometric indices of trees (total height, trunk height, crown area and crown shape) . This research was conducted to monitor changes in the biometric indices (diameter at breast height, total height and crown area) and to study the mortality rate of oak trees in an 11-year period (2005-2015). In order to achieve these goals, 66 permanent plots which were established in 2005, were retrieved in 2015. In sample plots, diameter at breast height (dbh) for all trees (dbh ≥ 5 cm), total height and crown area (for two trees in each plot: nearest tree to the center of the plot and the largest tree in terms of DBH in the plot) were measured in 2015 . The pattern of distribution of trees in biometric index classes (diameter at breast height, total height and crown area) was recorded and compared at the beginning (2005) and the end of the period (2015). The number of cuttings and dried-up trees was recorded in the 11-year period. The effect of aspect on each biometric index, their variations (growth) and distribution pattern of trees in biometric index classes were also investigated. Results showed that the median of diameter increment (all species) was 1.6 mm per year, the median of height increment was 10 cm per year, and the median of crown growth was 0.8 m2 per year. The results of tree distribution patterns showed a significant difference between the distribution pattern of trees in the total height and crown area at the beginning and the end of the period. The distribution rate of oak trees during the 11-year period was 15 trees per hectare. Results related to the effect of aspect on biometric indices, growth and distribution pattern of trees showed that aspect had no significant effect on the height and crown area (all species). There was a significant effect on the diameter growth of the trees (all species), however this effect was not significant for the crown area and the height growth of the trees. Aspect had a significant effect on the distribution pattern of trees in the biometric index classes.
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