Abstract
Productivity assessment studies are essential in forest operations, mainly because their results enable operational planning and rate setting, the development of equitable payment systems, the assessment of environmental performance, the assessment of improvements brought by technology development, and the optimization of larger forest-based systems. This study examines productive performance and fuel consumption in farm-tractor based skidding operations implemented in flat terrain oak harvesting by developing detailed statistics and predictive models on skidding performance. Two felling areas were selected to monitor the operations, and detailed statistics and predictive models were developed at two resolutions by an end-to-end assessment. Based on 56 observed work cycles, and for average values of the number of logs, payload volume, winching distance and extraction distance of 4.96, 1.81 m3, 14.43 m, 177.3 m, respectively, the net efficiency and productivity rates of skidding operations were estimated at 0.125 h/m3 and 8.03 m3/h, respectively. At the resolution of piece-by-piece winching, winching time depended only on the winching distance. At the resolution of overall skidding operations, the skidding time depended on the number of logs in a payload and average winching and extraction distances. The same predictors were relevant in explaining the fuel consumption in skidding operations, which accounted for 3.72 L/h or 0.46 L/m3, while there was a variation in fuel consumption induced by the type of operation. Both efficiency and productivity were found to be highly sensitive to the operational distances, as the main factors affecting them. Nevertheless, significant improvements in efficiency, productivity, and fuel consumption may be achieved when dealing with fewer logs per turn and higher volumes per piece, since the models indicated no effects brought in fuel and time consumption by the log size, and the technical limits of the used winched reached 8.5 tons.