(1) This study aims to define a simple and effective method to calculate skidding distances on steep karst terrain, rich in ground obstacles (stoniness and rockiness) to support decision planning of secondary and primary forest infrastructure network for timber extraction in productive selective cut forests. Variations between geometrical extraction distances and actual distances were highlighted on the operational planning level (i.e., compartment level) through GIS-related calculation models, focusing on cable skidder timber extraction. Automation in defining geometrical and real extraction distances, as well as relative forest openness were achieved by geo-processing workflows in GIS environment. Due to variation of extraction correction factors at the compartment level from a minimum of 1.19 to a maximum of 5.05 in the same management unit, it can be concluded that planning harvesting operations (timber extraction) at operational level should not include the use of correction factors previously obtained for entire terrain (topographical) categories, sub-categories or even management units.
This research was conducted to determine the cause, intensity and location of damage (stem, butt end, root collar, root) and the extent of damage to standing trees during felling and processing by an harvester and timber extraction by a forwarder (cut-to-length system). The research was conducted in the central part of the Republic of Croatia in the Management Unit (MU) “Bjelovarska Bilogora” during the thinning of Subcompartment 14b, area of 18.28 ha, in the stand of hornbeam (Carpino betuli—Quercetum roboris fagetosum Rauš 1975), age 70, and of Subcompartment 14c, area of 9.07 ha, in a stand of common beech (Carici pilosae—Fagetum Oberdorfer 1957) aged 79 years. The thinning intensity was 12.13% in Subcompartment 14b and 13.72% in Subcompartment 14c. Field measurements were carried out on sample plots—the first time in 2017 to determine the intensity and characteristics of the damage to standing trees with regard to the cause of the damage (harvester or forwarder), and the second time in 2018 to determine the overall intensity and features of the damage to standing trees after finishing harvesting operations. For all trees remaining in the stand after the harvesting operations, the following were determined: tree species, diameter at breast height (DBH), the position of the tree in the stand depending on the forest traffic infrastructure, and—if damaged—cause of damage, type of damage, the position of damage on the tree, and dimensions of damage. The intensity of the damage was expressed by the ratio of damaged and undamaged trees, with a detailed analysis of bark damage (squeezed-bark damage and peeled-bark injuries). The results of the research indicate the highest prevalence of peeled-bark injuries. In relation to the total number of standing trees, trees with peeled-bark injuries were more represented in Subcompartment 14c (39%) than in Subcompartment 14b (33%). In Subcompartment 14b, the harvester and the forwarder damaged an equal number of trees, while in Subcompartment 14c, the harvester damaged 59% of the damaged trees. In both subcompartments, an average of 83% of (peeled bark) injuries were up to 1.3 m above the ground. In both subcompartments, the most common (67%) were injuries up to 100 cm2 in size, for which many authors claim the tree can heal by itself. Given the increasing use of harvester-forwarder systems in deciduous stands and research results that indicate possible damage to standing trees, it is necessary to pay attention to all phases of planning and execution of timber harvesting operations, thus minimising negative effects.
The use of forestry vehicles in mechanised harvesting systems is still the most effective way of timber procurement, and forestry vehicles need to have high mobility to face various terrain conditions. This research gives boundaries of planning timber extraction on sloped terrain with a cable skidder, considering terrain parameters (slope, direction of skidding, cone index), vehicle technical characteristics and load size (5 different loads) relying on sustainability and eco-efficiency. Skidder mobility model was based on connecting two systems: vehicle-terrain (load distribution) and wheel-soil (skidder traction performance) with two mobility parameters: (1) maximal slope during uphill timber extraction by a cable skidder based on its traction performance (gradeability), and (2) maximal slope during downhill timber extraction by a cable skidder when thrust force is equal to zero. Results showed mobility ranges of an empty skidder for slopes between −50% and +80%, skidder with 1 tonne load between −26% and +63%, skidder with 2 tonne load between −30% and +51%, skidder with 3 tonne load between −34% and +39%, skidder with 4 tonne load between −35% and +30% and skidder with 5 tonne load between −41% and +11%.These results serve to improve our understanding of safer, more efficient timber extraction methods on sloped terrain.
Kvalitetno isplanirana i u šumski ekosustav optimalno uklopljena šumska prometna infrastruktura jedan je od osnovnih preduvjeta potrebnih za današnje racionalno gospodarenje šumskim ekosustavom. Ukupna količina šumskih prometnica, njihov razmještaj u prostoru te njihove propisane tehničke značajke moraju biti dostatne za što kvalitetnije upravljanje šumom. Ako je šumska prometna infrastruktura pravilno položena u prostoru, ona omogućuje izvođenje svih zadataka predviđenih šumskogospodarskim planovima na određenom šumskom području, uz minimalne troškove njihove izgradnje i održavanja uz maksimalan učinak. U ovom radu prikazano je sadašnje stanje primarne otvorenosti gospodarske jedinice Crno jezero – Marković rudine te su predložene smjernice njezina daljnjega otvaranja s ciljem dostizanja vrlo dobre primarne relativne otvorenosti. Terenski su podaci obrađeni u računalnim programima ArcGIS 10.4 i QGIS 2.18.20. Ustanovljeno je da klasična otvorenost šuma u toj gospodarskoj jedinici iznosi 13,66 km/1000 ha, što ne udovoljava ni minimalno propisanoj klasičnoj otvorenosti koja za gorsko-planinsko reljefno područje iznosi 15 km/1000 ha. Analizirajući rezultate primarne relativne otvorenosti, zatečeno je vrlo slično stanje kao i kod klasične otvorenosti: primarna relativna otvorenost iznosi 45,05 %, što se smatra nedovoljnom primarnom relativnom otvorenošću. Nadalje, analizirana je postojeća srednja geometrijska udaljenost privlačenja drva za svaki odsjek zasebno te je utvrđeno da taj parametar na razini gospodarske jedinice iznosi 258,74 m. Pomnim planiranjem projektirano je ukupno 53,05 km novih trasa šumskih cesta, što je u konačnici rezultiralo povećanjem klasične otvorenosti šuma na 22,82 km/1000 ha, primarne relativne otvorenosti na 75,8 % te smanjenjem srednje geometrijske udaljenosti privlačenja drva na 140,55 m.
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