DIGITALNA ARHIVA ŠUMARSKOG LISTA
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The selection of a harvesting system is mainly reflected by the supply and demand of forest products in the forest industry. Besides, there are natural factors such as topographical conditions and terrain types that effect the selection of mechanized harvesting equipment used in forestry (Visser and Berkertt 2015). In Eastern Black Sea region of Turkey where topographical conditions are favorable and wide range of industrial wood-based forest products are available (Ozturk and Senturk 2016), hi-tech harvesting machinery are used in forest operations (Sessions 2007; Visser and Harill 2017). In the investments made to the machinery used for forestry operations, the harvesting managers prefer mechanized equipment with high cost efficiency, production rate, mobility, and ergonomic features (Đuka et al. 2018; Kulak et all 2017; Moskalik et al. 2017; Ozturk 2010; Russell and Mortimer 2005;). In Turkey, the timber harvesting activities are mainly conducted by the forest villagers and forest development cooperatives. Due to limited economic conditions, high technology equipment is often out of reach and the most common harvesting methods are human-power based traditional methods with limited involvement of farm tractors. Farm tractors have been used in many other countries in the concept of small-scale forestry due to their affordability and adaptability (Akay 2005; Magagnotti and Spinelli 2011; Ozturk and Akay 2007). Especially modified farm tractors can perform several tasks in timber harvesting operations such as skidding, winching, cable yarding, forwarding, and loading (Acar and Unver 2012; Johansson 1996; 1997; Spinelli and Magagnotti 2011). Previous studies indicated that skidding with farm tractor usually requires the average slope of 15% and the skidding distances of 30 – 70 meters (Gilanipoor et al. 2012). The cable winching with farm tractors can be efficient at the skidding distances of 30 – 50 meters with an average terrain slope of 25% (Heinrich 1987). Spinelli et al. (2004) stated that the cost of using a farm tractor can be very high at the skidding distances between 150 and 500 meters. In Turkey, different types of farm tractors integrated with mounted winch system and skidding equipment have been |