The paper deals with problems of influence of terrain factors on log skidding effects with the frame steered skidder. The two methods, tree-length and assortment system have been applied in the lowland and hilly region, in mature stands of hardwood forests. In the stands the primary and secondary opening have been carried out. It turned out that terrain factors had no influence on fixed time spent, and the time used was shown as an average value per trip. The time of binding and unbinding of round timber was calculated as an average per piece for all working conditions, while the time per trip was calculated dependent on a number of pieces in a load. By means of the time spent in a travelling empty and in a travelling loaded per 1 cbm of volume of wood, on a skid trail and in felling area, with regards to terrain factors the terrain has been divided into four groups :
1) waterlogged terrain in the lowland,
2) waterlogged terrain in the hilly region,
3) wet ground in the lowland and hilly region,
4) dry ground in the lowland and hilly region.
At skidding distance of 0,1 km in felling area and 0,5 km on skid trail with the tree-length system the smallest effect was obtained on waterlogged terrain in the hilly region ; by 8 percent higher effect was obtained on waterlogged terrain in the lowland, 25 percent on wet terrain in the lowland and hilly region and 34 percent on dry terrain in the lowland and hilly region. With the tree-length system in the same working conditions, at skidding distance of 0,1 km in felling area and 0,1 km on skid trail, the effect was by 29 percent higher in comparison with the assortment system. At skidding distance of 0,1 km in felling area and 0,5 km on skid trail this increase with tree-length system amounted to 18 percent.
