Speaker
Description
Winch-assisted harvesting technology is becoming increasingly common in Alpine countries and in forests on steep terrain. However, research into the impact of this technological system on forest soil and stands remains limited. In a study conducted at three different sites, we measured several parameters on sample profiles perpendicular to the skid trail, including rut depth and compaction, skid trail slope and width, number of machine passes, coverage of the trail with logging residues, residue thickness, and soil water content. The average rut depth of skid trails across all sites was 14.9 cm, with the average depth in Žetale at 23.1 cm, in Log at 14.9 cm, and on Pohorje at 13.1 cm. We found that rut depth increases statistically significantly with the number of machine passes, and that higher soil water content generally increases rut depth, although the effect is small. The slope of the skid trail has a significant effect in Žetale and Pohorje, as terrain slope increases, rut depth increases only in Pohorje, while it decreases at the other two sites. We also analysed stand damage on circular sample plots of 100 m², distributed systematically across the site. The proportion of damaged trees was highest in Pohorje (52.5%), followed by Log (51.7%), and lowest in Žetale (38.6%). The average size of damage was highest in Pohorje (230.2 cm²), 178.9 cm² in Žetale, and lowest in Log (172.3 cm²). Most damage occurred on the stems, with the least in the crowns of standing trees. We found that tree species and diameter at breast height significantly influence the occurrence of tree damage. Compared to non-assisted mechanised harvesting, winch-assist technology is reported to cause less damage to forest floors due to the use of a winch and smaller wheel ruts, although this depends on several factors. The results of our study, compared to others that also examined winch-assist harvesting, show that average wheel rut depths are greater in most cases. A comparison of studies on stand damage during mechanised harvesting without winch assistance with our results showed, that the proportion of damaged trees was higher, while the average size of damage was lower at our sites than in some other studies. As has been established, soil and stand damage is influenced by many different factors, so further studies at different research sites are needed to obtain a better assessment of the suitability of winch-assisted harvesting technology for specific working conditions.
| Keywords | Winch-assist-harvesting; rut-damages; stand-damages; steep-slopes |
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