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ŠUMARSKI LIST 3-4/2017 str. 58     <-- 58 -->        PDF

extensively and effectively for solving com­plex problems in forest areas, especially in developed countries (Akay 2003; Rogers 2005; Demir 2007) in recent years. Nowadays, concepts such as digital map, GIS and land informa­tion systems have gained importance in the design of road networks (Akay, 2003; Aruga, 2005; Gümüş, 2008; Çalışkan, 2013).
Timber harvesting, as a succession of interrelated and interdependent operations in timber production, includes tree conversion (felling and processing) and timber transport. Timber transport consists of two mutually dependent sub-phases: off-road (timber extraction or primary transsport) and on-road (further transport or secondary forest road network) (Bayoğlu, 1962; Seçkin, 1978; Conway, 1982; FAO, 1982; Erdaş, 1986; Haarlaa and Jurvelius, 1987; Acar, 1994; Berg and Schiess, 1996; Dykstra and Heinrich, 1996; Heinimann, 1999; Karaman, 2001; Rummer, 2002; Heinimann and Stampfer, 2003; Pentek et al., 2008). In recent studies, Abbas et al., (2014) analyzed the different operational matters, conditions, equipment and transportation use reported by logging firms. The study provided technical forest product operations, information and methods for assessing the capacity of logging firms and markets looking to expand their businesses. Visser and Stampfer (2015) reviewed developments, the main engineering considerations of cable-assist workings, as well as the advances in integrating equipment into harvesting systems. They also analyzed the operating guidelines that are either in use or being developed to help implement the timber extraction systems. Duka et al., (2016) concluded that extending the operating range of skidder on steeper slopes with heavier loads has the potential to decrease harvesting costs and increase productivity.
There are four principal means of off-road transportation: ground vehicles on natural terrain, ground vehicles on skid roads, carriages on cable structures and airships in the air (Heinimann, 1999). The necessity of the timber raw material in Turkey has been increasing (GDF, 2013). Transportation stage involves a rather difficult, expensive and time consuming activity in timber production activities. In this process, transport of forest yield from forest to the landing has been practiced in various forms. In particular, transporting forest yield with minimum loss in quality and quantity and with minimum damage to the environment seems to be an important problem to be solved.
Timber transportation on ground surfaces in forest lands causes erosion on soil, damage on saplings and leads to loss of quality and quantity on stand trees (Lubello, 2008). This is especially a problem that we are faced with when losses of forest value, particularly in mountainous regions are taken into consideration. GIS for assessing soil trafficability was initially deployed for military off-road planning after which these applications were introduced to forest and agricultural applications (Lubello, 2008). In some cases, terrain evaluation has been carried out based on economic considerations in order to optimize road models regarding financial values. Lubello (2008) suggested a rule-based spatial decision support system for planning of forest operations using GIS techniques.
Suvinen (2006) used a GIS-based simulation model to evaluate the interaction of terrain trafficability, vehicle mobility and terrain tractability that takes place through the machine wheel’s surface. Mohtashami (2011) conducted a case study in Sweden putting forward that the use of digital planning of the improvement of strip roads in order to avoid vulnerable terrains made forwarding of timber more profitable.
Forest harvesting operations are usually pursued either by the General Directorate of Forestry or the private sector. However, there is no standard for specific terrain or forest road network conditions; therefore the selection of a specific harvesting operation has been limited to the availability of machiner­ies and worker force.
Thus, the first objective of this study was to investigate the secondary forest road network with regard to forest road density, forest road spacing and to implement developed planning approach using Geographic Information Systems (GIS) in Anbardağ planning unit of Giresun Forest Enterprise, Turkey. Another important objective was to develop a model for timber extraction systems via GIS analysis taking into consideration the terrain morphology and secondary forest road network.
Study area – Promatrano područje
This study was carried out in the Anbardağ forest planning unit covering an area of approximately 5975.0 ha in the Giresun province in the northeastern Black Sea region of Turkey. The area was located between 400 42’ 47“ – 400 30’ 13“ North, and 380 01’ 49“ – 380 13’ 16“ East. The relief has a very irregular topography, and the elevation ranges from 700 to 3100 m. The mean annual precipitation is 1297 mm, with the lowest values being recorded in July and August. Dominant tree species used for production purposes are natural oriental spruce (Picea orientalis Link.) and oriental beech (Fagus orientalis Lipsky). Traditionally, cut-to-length harvesting method has been used in Turkish forestry. While skidding depends on the steep slope and presence of adequate road infrastructures, felling and delimbing operations were used to be carried out via chainsaws,. Debarking with axe and/or log wizard is mostly operated in stands and rarely on roadside (Eker and Acar, 2006). Agricultural and forest tractors are mostly represented as off-road machines and have been widely used. Aerial yarding is carried out by means of cable cranes based on sledge winch yarder and