Detailed Analysis of Residual Stand Damage Due to Winching on Steep Terrains

Abstract

Damage to the remaining stand on steep terrain can be quite severe and is usually difficult to control during winching. Timber skidding, especially by agricultural tractor, is a common solution in small-scale forestry. One of the factors influencing remaining stand damage is winching on steep terrain, although, to date, this has only been studied in general. Limiting stand damage is possible when the factors causing the damage are well-known. Therefore, the aim of this paper was to study in detail the impact of slope steepness on different types of damage in the stand after winching, focusing in particular on: (1) the share of trees with damage (including natural regeneration), (2) the size of the wound, (3) the number of wounds per tree, (4) wound intensity, and (5) the position of the wound on a tree. Field observations were carried out in three beech (two in Italy and one in Iran) and two pine stands (in Italy), in which four classes of slope steepness were selected for each stand. After timber harvesting, damage to the remaining stand as well as to any natural regeneration was recorded. It was found that the share of wounded trees was directly related to slope steepness, although this was less obvious in the natural regeneration. On steeper slopes, there were larger wounds and, on average, there were more wounds per tree. Wound intensity also depended on the gradient of the slope. The size, understood as diameter at breast height, of the remaining trees on the slopes also had an impact on the wound characteristics: on thicker trees, bigger wounds were detected and a higher number of them. However, thicker trees were less often wounded. Wound position on a tree did not depend on slope steepness but it may have been related to stand density and size of winched timber.

The Effect of Season of the Year on the Frequency and Degree of Damage during Commercial Thinning in Black Alder Stands in Poland

“…Both in summer and in winter a greater number of cases of damage were recorded in the phloem zone, with damaged bark and exposed phloem (80%), while the remainder were deep wounds reaching the xylem. A comparable percentage of bark removal (70%) in pine stands and a lower percentage in beech stands (30-40%) were reported by Picchio et al [46]. Those authors also recorded at least a 30% incidence of xylem damage in both types of stands.…”

“…Danilović et al [24] reported that in pure beech stands wounds with a surface area exceeding 200 cm 2 accounted for 52.6% of the total, while in mixed stands the figure was 43.4%. In turn, in a study by Picchio et al [46] wounds of 25-100 cm 2 predominated, and the share of larger wounds was also considerable.…”

Impact Assessment of Timber Harvesting Operations for Enhancing Sustainable Management in a Secondary Atlantic Forest

“…Despite the challenging situation in the steep stand A, no effect on the rates of damaged remnant trees became obvious with respect to terrain slope or stand characteristics. Surprisingly, the steep stand A presented the lowest degrees of damaged basal area and volume compared to stands B and C. Differently, Picchio et al [32] described that damage to the remaining stand on steep terrain can be quite severe and is usually difficult to control. These authors also showed that the share of wounded trees was directly related to slope steepness, with larger wounds on steeper slopes.…”

How and How Much, Do Harvesting Activities Affect Forest Soil, Regeneration and Stands?

“…A lower level of damage was observed after cable-skidding and ranged from 4.9 to 7.1% [18]. Stańczykiewicz et al [74] studied the damage of regeneration using two systems: (1) a tower cable system combined with farm tractor and (2) a skidder in a mature spruce stand. The damage of regeneration using the tower cable system (23.9%) was lower than using the skidder system (61.3%).…”

“…8. Alternatively, when possible and when financially acceptable, different forms of extraction should be used, for example, cable cranes or traction-winch-supported forwarders [74]. 9.…”