We have determined the sensitivity of the soil to the driving of forestry machinery and the characteristics of skid trails. On unbuilt skid trails we have measured 62 profiles for five parameters: the depth of the ruts, the width and inclination of a skid trail, the amount of visible stone on the skid trail surface, and the presence of roots on the trail. We found that the average depth of the ruts was the highest in Logatec (20.4 cm), followed by Smrečje (18.8 cm), Vrhnika (13 cm) and Podlipa (10.1 cm). A significant impact of erosion onto the rut depth was established, while the presence of roots and stone had an insignificant effect onto the depth of the ruts. The inclination of the skid trail had a significant impact onto the depth of the ruts, as with the increase of inclination by 1% the depth of the ruts increases by 0.374 cm. The model of the rut depth shows that the integration of the object into the model is characteristic and necessary, as the objects differ greatly. The depth of the rut therefore increased the most due to the effect of the object (inclination –12,02 to –4,16) and the inclination of the skid trail (0.241), which are highly significant, while the presence of stone has no significant effect onto rut depth.
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