Disc saw Feller-Buncher productivity analysis in a Holm-Oak (Quercus ilex) coppice biomass harvesting operation in central Spain

A disc saw John Deere 130 kW feller-buncher has been tried to perform a selective felling of a dense holm oak (Quercus ilex) coppice in Central Spain, with an average density of 5250 trees·ha-1, an average dbh around 6 cm and an average height of 4 m. The treatment consisted on leaving around a 10% of standards, performing a very strong thinning (as an average, 2/3 of basal area). A height-dbh equation and a dry weight table have been fitted for this Species' coppices. The productivity has been analyzed in average conditions and, as part of a factorial experiment, in 25x25 plots with different stand and treatment conditions. Average felling and bunching productivity is 3,2 odt per productive machine hour. A productivity equation has been fitted, being the main identified explicative variables the unit dry weight of the extracted trees and the percentage of extracted basal area. The rest of harvesting costs - whole trees forwarding, roadside chipping and chip transport - have also been analyzed. The final costs are ranging from 71 to 87 EUR/odt of chips delivered to the power plant, under the studied conditions, for a transport distance of 80 km and considering a 15% of indirect and fixed costs over the direct harvesting costs. Some possible improvements in operations efficiency and cost have been proposed.