Optimization of wood skidding factor calculation in the area of FM „Prijedor“ Prijedor
Determination of skidding distance is very important for operational planning in forestry because it is an indicator of forest accessibility. Value of skidding distance can be obtained in several ways: measurement of distance in the field by skid trails, calculating by using the mathematical models and by using of Geographic Information System (GIS) software. Operational planning in forestry is done on the level of compartment. It is not rare that forest practitioners do not have data about skidding trails length or secondary openness for specific compartment and in that case it is used straight direction from compartment gravity center to the belonging forest landing site or forest road, to calculate skidding distance. It is assumed that wood is equally distributed over area. When position and length of the skidding trails are known, then real skidding distance is calculated. Research area in this study was placed in two FMU, “Prosara”, where 9 compartments were analyzed, and “Kozara-Mlječanica”, where 18 compartments were analyzed. Skidding trails network was recorded using of GPS. Main aims of this study were:
- determination of geometric skidding distance;
- determination of real skidding distance by trails;
- determination of skidding factor for conversion of geometric in to real distance;
- comparison of established skidding factor with other studies results.
Density of road network in FMU “Prosara” is 11.32 m/ha, and in FMU “Kozara-Mlječanica” 12.85 m/ha. In all investigated compartment skidding trails were measured and it was established that secondary openness (by trails) is 119.7 m/ha in FMU “Prosara” and 96.5 m/ha in FMU “Kozara- Mlječanica”. Geometric skidding distance is 208 m in FMU “Prosara and 307 m in FMU “Kozara- Mlječanica”. Spatial analysis based on DTM and GIS determined classification of altitudes and slopes in categories, than were used for distinguishing of three relief areas, lowland, hilly and low mountains. Skidding factor is 1.2 for lowland, 1.45 for hilly and 1.55 for low mountains relief area. Multiplying of skidding factor with share of each relief area in total surface gave total skidding factor, 1.51. Slopes are classified in five categories and to each category skidding factor was dedicated according to Jeličić (1978) (Sokolović & Bajrić, 2013). Based on surface share and skidding factor, total skidding factor is calculated, that is 1.22. Based on DTM analysis, skidding factor for FMU “Prosara” is 1.355 and for FMU “Kozara-Mlječanica” 1.37. Real skidding distance was calculate by multiplying of corresponding skidding factor with geometric distance. For FMU “Prosara” was obtained 324 m and for FMU “Kozara-Mlječanica” 417 m. Skidding factors were calculated according to gravity zones and average 1.84 for FMU “Prosara” and 1.85 for FMU “Kozara-Mlječanica” was obtained. Obtained skidding factors are 36% higher than theoretical. Considering skidding direction it was showed that in downhill skidding, factor is slightly higher than in uphill skidding.
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