Productivity and cost of a tractor-mounted processor in thinning operations under alpine condition

The level of forest mechanization in North-eastern Italian Alps is slowly but constantly increasing. It becomes useful then to quantify the effects of the application of advanced harvesting techniques in forest. The present work concerns the productivity and costs study of a tractor-mounted processor working in a typical thinning operation in coniferous stands. The machine consists of a Hypro 755 processor mounted on the three point hitch of a 4WD Lamborghini tractor (59 kW). Trees were felled motor-manually and skidded by two tractors to the landing site, where the processor was operating. For data collection and statistical analysis an established protocol has been adapted to the study. The following hypothesis has been assumed in order to obtain a productivity model for the processor: - time for tree processing = f (volume of the individual tree, length of the individual tree, number of logs obtained per individual tree) The single tree has been chosen as observation unit and all variables and times have been collected on a total of 537 trees. Statistical analyses produced two models which, combined, are able to explain the productivity (m3/PSH15) of the processor according to the volume of the individual tree and the number of logs cross-cut per individual tree. Productivity increases according to the increment of the volume of the processed tree up to a maximum of 14 – 16 m3/PSH15, but drops-off when the volume overcome 0,6 – 0,7 m3. This is mainly due to mechanical limits of the processor, which is designed to operate in first thinning, i.e. with small trees. Within these limits, the machine acquires a productivity up to 10 times higher than that one achievable by motor-manual operation. The productivity allows to obtain operative costs (€/m3) lower than those of delimbing and cross-cutting motor-manually performed. When employed in first thinning, the tractor-mounted processor is an efficient, reliable and economical equipment, which involves significantly advantages also from the point of view of ergonomics and work safety in the forest.