jafar fathi

This research was conducted with the aim of measuring the hand-arm vibration of the chainsaw operator during the cutting and bucking operations of three tree species, including hornbeam, beech, and Persian ironwood, in the Patom section of Kheyrud Educational and Research Forest. In this research, three tree trunks of the mentioned species were measured simultaneously in three x, y and z directions of a chainsaw using a SVANTEK 106 vibration meter. The results showed that the average vibration equivalent to a chainsaw in all three axes in the Persian ironwood was higher than the other two species of hornbeam and beech. The amount of vibration of the whole chainsaw during the cutting of hornbeam, beech and Persian ironwood trees in the rear handle was significantly higher than the front handle. The results of the t-test showed that the total amount of vibration of the chainsaw during sawing of hornbeam, beech and Persian ironwood in the rear handle is significantly higher than the front handle. The results of Tukey's test showed that the average total chainsaw vibration in Persian ironwood and beech is significantly higher than hornbeam. The results showed that the vibration transmission coefficient in beech and Persian ironwood during cutting and bucking in the front and rear handles is significantly more than the measured amount of hornbeam. The results showed that the amount of daily exposure time in both two hours and three hours was significantly higher in Persian ironwood and beech species than hornbeam (both cutting and bucking stage). The results also showed that the predictive value of the duration of white hand disease in both two hours and three hours, in the Persian ironwood and beech species is significantly higher than hornbeam (both cutting and bucking stage).

The objective was to investigate if changes in annual, monthly, and seasonal precipitation are associated with emergence of declining oak trees in Iran. Daily precipitation data were obtained from 20 synoptic stations distributed over the Zagros area from 1988-2019. Non-parametric Mann-Kendall (MK) test and Sen's Slope estimator (Qmed value) were applied to identify significant trends in the precipitation data. ‘‘De Martonne’’ climate classification (i.e., De Martonne aridity index (IDM) was used for climate classification. Although most stations showed decreasing trends in annual precipitation during the studied period (1988-2019), these trends were statistically significant at only two stations. The mean number of events per year pre- and post- oak decline was not significantly different (68 events before against 71 events after decline). Most of the annual precipitation in the Zagros region falls in winter and spring (80% in total). However, this ratio decreased after the year 2000 by 6% (not significant) compared with before. The difference between the average annual precipitation, before (1988-2000) and after (2000-2019) the emergence of the oak decline phenomenon, were not statistically significant in any of the climate types (semi-arid: 406 mm vs. 378 mm), Mediterranean (530 mm vs. 489 mm), and humid (924 mm vs. 912 mm) as well as in whole Zagros region (537 mm vs. 508 mm). Although our data suggested insignificant trends in precipitation for most stations, future research should investigate if rising temperature in the Zagros area has resulted in higher evaporation and drier soil thereby accelerating the oak tree decline.

In order to investigate the factors affecting damage caused by early snow in the compartment no. 10 in Patom district of Kheyrud forest research station, the sampling was conducted on a random grid (100 × 100 m) with 46 m 1000 circular sample plots. In each plot, effective factors including slope gradient of the plot, aspect, altitude (elevation), soil depth, diameter at breast height, and height of all tree species greater than 7.5 cm were recorded. Damages to trees were classified into four types including uprooting (tree throw), trunk fracture, crown fracture, and bending. The results showed that 28.1% of the trees were damaged, with damage of 3, 4, 10 and 11% for each type including uprooting (tree throw), trunk fracture, crown fracture, and bending, respectively. The results showed that there was a significant difference between the types of tree damage and some factors including aspect, slope, elevation, and soil depth. The highest percentage of tree damage occurred in the northern aspect, slope less than 15%, altitude of 330-380 m, and shallow soils depth, and the lowest occurred in the southern aspect. The damage on the eastern and western slopes was approximately similar. The highest and the lowest percentages of damage were related to alder and maple tree species, respectively. Thinning treatments affected the horizontal and vertical structure of the stands by reducing the slenderness coefficient of trees, which has a key role in reducing the severity of snow damage on trees, and improves tree and stand stability.