Evaluation of consecutive skylines yarding and gravity skidding systems in primary forest transportation on steep terrain

This investigation evaluates two primary forest transportation systems, consecutive skyline yarding system integrated with two different types of skyline yarding systems and the gravity skidding system, considering technical, economical and environmental aspects. The results indicated that the productivity of consecutive skyline yarding system was 4.97 m(3) hr(-1), while the productivity of the gravity skidding system was 0.74 m(3) hr(-1). The unit costs of these primary transportation systems were found to be $5.98 and $51.28 m(3), respectively. Besides, the gravity skidding system caused more damages on skidded logs, residual trees, and forest soil than that of consecutive skyline yarding system. It was also indicated that two different skyline yarding systems produced definite and different average yarding distances and technical capacities, which negatively affected the overall performance of the consecutive skyline yarding system. Therefore, different types of skyline yarding systems should not be integrated into the consecutive yarding systems.