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BIC: -26.68), respectively. The regression model yielded significant (p<0.01) results at 99% confidence level in both methods. The regression analysis results for the variables of diameter (X1), length (X2), volume (X3) and skidding distance (X4) are given in Figure 4. CONCLUSIONS ZAKLJUČCI Farm tractors equipped with winches have been widely used as effective equipment in small-scale forestry activities in many countries. In timber extraction with farm tractors in Turkey, the drum is often mounted on the back of the tractor. In this study, productivity of the farm tractor with front-mounted single drum winch was evaluated during whole-tree harvesting operations. In the field, fallen trees were first winched uphill from stump to the prebunching area by using single drum winch and then trees were transported backward to the landing area. The factors that affect the productivity of both working phases (winching and skidding) were evaluated. The average daily productivity of uphill winching and skidding whole-trees was at 103.84 m3/8-hours and 114.40 m3/8-hours, respectively. Besides, the average daily cost of uphill winching and skidding whole-trees was at 86.18 €/8-hours and 94.97 €/8-hours, respectively. According to the results, the average daily cost of skidding whole-trees was required 8.79 €/8-hours higher than the average daily cost of uphill winching. A single drum winch system mounted in front of farm tractor can be considered as a very efficient alternative equipment for uphill winching operations depending on the ability of the operator. The stable position of the tractor is ensured by a movable front protection blade prevents uncontrolled shifting of the tractor and ensures ergonomic and safe operations. The productivity of skidding operation on skid trail was relatively low comparing with the results of the relevant studies. The main reason behind this inefficiency was that operator had to drive the skidder backward on skid trail and control the back sight which increased the total time during skidding. Farm tractor logging can be also limited by some other factors such as the terrain conditions, ground slope, and timber volume. Thus, the capabilities of the farm tractors and functionalities of the additional attachments should be well understood before performing an effective farm tractor logging operations. To improve the efficiency, effective logging plan should be made to ensure physically feasible and economically viable operations. ACKNOWLEDGEMENTS ZAHVALA This paper includes data from Kahramanmaras Sutcu Imam University Scientific Research Project (No: 2016/3-72M). The author would like to thank Nihat Nurdoğan (Forest Enterprise Chief of Baskonus) and anonymous forest workers for their help in field work. REFERENCES LITERATURA Acar, H.H., 1997: An investigation on the extraction from compartment by tractors at the mountainous region, Turk J Agric For, 21: 299-306. Acar, H.H., S. Unver, 2012: Working efficiency during the controlled sliding of logs in the polyethylene chute by tractor power, SDU Faculty of Forestry Journal, 13(2): 97-102. Acar, H.H., 2013: Assessment of unit work time in logging operations the using of log pulling-sliding head during |