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ŠUMARSKI LIST 1-2/2015 str. 45     <-- 45 -->        PDF

case and in the hypothesis of downhill timber extraction to the closest forest road and no uphill extraction.
This study reported kt values between 3.02 and 3.85 (Table 8), recommending kt is 3.40 for rough calculations. These values are similar to those reported by FAO (1974a) for hilly and mountainous regions (Table 9). In turn, they differ from the findings of Olteanu (1985) which reported higher values of kt (from 3.61 to 4.84) for forests located in hilly regions. This can be explained by the fact that when determining the kt, Olteanu (1985) also considered the fragmentation degree of the forest stands. This is the specific case of Romanian forests from hilly regions; due to the high degree of forest fragmentation, in order to serve more stands, forest roads are in general located outside the forest areas. The values of road efficiency factor a“ ranged between 6.34 (scenario FR3) and 8.10 (scenario FR1), similar to what FAO (1974b) reported for hilly areas and steep terrain (Table 9). Since in this study kt was determined based on SDe values computed with the raster method, it can be concluded that the raster method can be used for a sound determination of the real mean extraction distance.
4 Discussions and conclusions
Rasprava i zaključci
This study presented several methods for computing the mean extraction distance using spatial analyses and pro­cess automation in GIS. The correction factors (ks, kn and kt) for adjusting the theoretical models to the real cases were determined. They were comparable with the values reported in literature and they can be used by practitioners in forest areas similar to this study. This could be the case of forest areas where skidding and forwarding are most commonly used in timber extraction. The raster method is recommended for the computation of SDe, while the grid point method G100 and the buffer strip method are recommended