Esbosco in ambiente montano con cable-forwarder

Wood extraction on steep slopes is usually operated by cable crane, but recently a modified forwarder has made its appearance in Austria. It consists of a usual forwarder equipped with a winch; once the cable of the winch is anchored on a tree or a stump, the machine can drive slopes up to 70%. The present work concerns the analysis of productivity, costs and impact on the soil of a cable-forwarder, operating on a main felling in a coniferous stand. Trees were felled and crosscut by a tracked harvester; the cable-forwarder was covering the same corridors, hauling the logs to the forest road. For data collection and statistical analysis an established protocol has been adapted to the study. All variables and times have been collected on a total of 44 extraction cycles. Statistical analyses produced three models which have been combined in order to explain the productivity (m3/PSH15) of the cable-forwarder in relation to different variables. Productivity increases according to the increment of the average volume of the loaded log and to the increase of the total payload. Contrarily, a long covered distance while loading, a long transportation distance and a steep slope of the corridor are variables which depress the productivity of the machine. Considering average conditions, the cable-forwarder is able to extract about 13 m3/h, with a calculated operative cost around 6 €/m3, that is lower than the extraction cost when using a cable crane in comparable conditions.