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ŠUMARSKI LIST 7-8/2017 str. 54     <-- 54 -->        PDF

of logging operations among 13 models. However, only one objective as minimization of cost was selected and animal power besides sledge yarders were not considered in this study. Minimum cost was found to be 491,282 € with the losses of quantity were 2500 m3 in a 9764 ha study area in the same region. In another study, Eker and Acar (2006) developed an operational harvest planning methodology including both felling and timber extraction systems that was suitable for topographical and technical, acceptable for economic constraints, sensitive for forest ecosystems. Sledge yarders were not considered when compared to this study, however, plastic channels were taken into account. The developed model minimized the annual average unit cost from %4 to % 30. Pentek et al., (2008) tested a model for selecting an ecoefficient harvesting system for commercial forests based on three influencing factors as terrain slope, extraction distance and breast height diameter of trees. Felling and timber extraction systems were both determined for each forest sub compartment similar with this study. Skidder was the most frequently used timber extraction systems as 74% of the study area. That was followed by forwarder (14%), cable crane (11%), and helicopter (1%). Although mentioned studies conducted under different typographic, economic, efficiency and technical conditions, they provide us sound information for the comparison. In this study, cable systems (small size, medium size and sledge yarders) were the leading timber extraction system (35%), flowed by skidder (23%), animal power (19%) and man power (5%) when considering outputs of STR2 in terms of area. However, 8% of the study area was not assigned to a timber extraction system due to the typographic or technical limitations.
This study is out to combine harvest scheduling and operational planning approach with an attempt to enhance planning of timber extraction methods, according to terrain and management conditions. Six timber extraction methods were used: man power, animal power (oxen), skidder (MB Trac), small size cable crane, medium size cable crane and sledge yarder were integrated in an operational model using integer linear programming technique. The model that was presented here produced solutions for a selected mountainous forest in Black sea region of Turkey, with different alternatives, but all including environmental concerns, unlike the present conventional approach, time restrictions as well as economical parameters.
Parameters such as income, costs, total spent time, timber loss and stand damage were characterized quantitatively, according to different timber extraction systems. The data infrastructure was generated using GIS environment. Contrary to conventional methods, alternative operational planning strategies were developed and many options were presented to decision maker to make the best and accurate decisions. At the end of the production period, providing conditions such as spent time from certain extraction methods at target levels, maintaining time flow for selected cable systems and achieving maximum profit were satisfied. Thus, the developed model allowed us to handle multiple scenarios, each with different dimension sizes, that may prove extremely useful in gaining possible results before system implementation, and to of course compare the outputs and to decide of re-planning if it is required. This kind of differential planning has a positive effect because decision maker can obtain outputs from various scenarios in a »reasonable amount of time« and get workable solutions.
Approximately 68,728 m3 annual allowable cut was determined for the first period of planning horizon. Among the developed alternatives, STR2 was selected for maximizing total profit and including constraints less than 2,000 hours for cable cranes and sledge yarders due to the availability of the machineries, staff and economic conditions of the enterprise. If this strategy is to be implemented, 6,365,205 € could be earned, 19,055 hours could be spent, and 1,697.8 m3 timber could be lost, while 91.77 damage could occur.
Similar studies should be expanded with the preparation of timber extraction plans and should be integrated into forest management plans as well as silviculture plans. As multiple timber extraction systems are presented to forest enterprise, operational plans must be prepared with operations research techniques. Different data affecting the selection of timber extraction system should be brought together as well as environmental concerns such as soil conservation or biodiversity provided with different forestry disciplines, and those data should be digitized according to timber extraction systems and in this way, these values must be integrated to operational plans numerically.
In conclusion, modeling is an inevitable tool in accommodating both harvest scheduling and timber extraction systems in operational planning. Considering different parameters such as cost, income, consumption time, loss or damage of the wood, extraction systems can provide a wide range of opportunities to the forest managers.