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ŠUMARSKI LIST 9-10/2016 str. 60     <-- 60 -->        PDF

productivity of a stand’s soil and alter hydorology (Wang et al., 2004). Skidders, tractors, and other machines used in harvesting operations may affect forest soils considerably, mainly depending on terrain conditions, soil characteristics, soil moisture content, and vehicle types (Akay et al., 2007b). Besides, the gross weight of the vehicle, tire size and air pressure in the tires, travel speeds, and number of passes are the operational factors that affect severity of soil compaction (Greene and Stuart, 1985; Susnjar et al., 2006). Studies reported that one of the critical factors affecting the degree of soil compaction is the number of machine passes over a specific point (Majnounian and Jourgholami, 2013). Most compaction occurs during the first ten passes of a vehicle with the most occurring in the firt three passes. Subsequent passes generally have little additional effect (Ampoorter et al., 2007). The major soil disturbance usually occurs during the first passes of machinery and increases by the number of passes (Gayoso and Iroume, 1991). Most compaction occurred after the initial few passes (Matangaran and Kobayashi, 1999). Other studies reported that the most significant soil compaction occurs after 18 skidder passes (Lotfalian and Parsakhoo, 2009) and Naghdi et al. (2007) studied the soil compaction on two types of soils following the timber skidding and they found out that the critical change in the soil’s bulk density occurred at the 11th pass of the skidder (Muntenau and Apafaian, 2015).
Operation period and selected machinery can make a big difference in protecting the soil from potential damages (Sutherland, 2003). During periods when soil is wet, heavy harvesting machines with rubber-tires generate deep ruts over forest soil, which leads to several problems such as excessive delays in operations, serious impacts on physical properties of forest soil and damages on tree roots (Akay and Erdas, 2007). Rutting occurs when soil strength is not sufficient to support the applied load from vehicle traffic (Lotfalian and Parsakhoo, 2009).
In Turkey, timber extraction is mainly done by farm tractors. The farm tractors equipped with winch are widely used for skidding operations in mountainous regions (Ozturk, 2014; Melemez, 2010). This study aims to investigate soil displacement and rutting on the skid road caused by a rubber-tired tractor during timber skidding in maritime pine (Pinus pinaster A.) plantation forest of Istanbul, Turkey.
Study Area – Područje, mjesto istraživanja
Study area was located in Sile Forest Administration in northern Turkey, management unit Sahilkoy forest compartment 37 (Fig.1). The study area mainly lies on north aspect