In the study, we examined the impact of the horizontal complexity of forest skid trails on damage to trees in their immediate vicinity. The research was conducted at two work sites (GGE Unec – Škocjan, compartment 30D11A; GGE Nanos – Hrušica, compartments 10A01A, 10A01B, 10A01D), where logging and timber extraction took place in the past year. At each site, we randomly selected one skid trail and recorded 250 trees within a 4 m strip from the skid trail axis. For each tree, we determined the tree species and measured the diameter at breast height, the distance of the tree from the skid trail axis, and the width of the skid trail at that location. For damaged trees, we additionally measured the size of the damage and determined its location and age. Using the software QGIS 3.40 LTS and RoadEng 11, we determined the position of each tree relative to the geometric element of the skid trail axis (curve, straight), and for trees located in curves we also determined the radius of the corresponding curve. We analysed the influence of these factors on damage occurrence and damage size. The average proportion of damaged trees was 39%. Statistically significantly more damaged trees were found in curves than on straight sections. The analysis also showed a significant relationship between the distance of the tree from the edge of the skid trail and the occurrence of damage. We found that diameter at breast height affects damage size and that significant relationships exist between damage size and tree group. Damage on the stem had, on average, a larger size than damage on the root collar. The results therefore indicate that the horizontal complexity of skid trails impacts tree damage primarily through the position of trees in curves and their distance from the edge of the skid trail.
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