Productivity, Efficiency and Environmental Effects of Whole-Tree Harvesting in Spanish Coppice Stands Using a Drive-to-Tree Disc Saw Feller-Buncher

Whole tree harvesting was conducted on two coppice stands with different tree composition (Q. ilex and Q. pyrenaica) in gentle terrain. Felling and bunching were performed by a drive-to-tree wheeled feller-buncher with disc saw head. Operations were analyzed on 17 plots 25x25 m2 in order to develop productivity models and to assess operational costs. The study also aimed at determining biomass collection efficiency and evaluating the impact of the new harvesting method on the soil, the remaining trees and stumps. The treatment consisted in a strong coppice thinning leaving standards. Productivity ranged from 2.8 to 4.6 odt/pmh in the Q. ilex coppice, and from 0.9 to 2.6 in the Q. pyrenaica stand. Tree species, dry weight per tree and percentage of removed basal area were the main independent variables affecting productivity. Approximately 50% of the standards showed damages. Most wounds were light, caused by the drive-to-tree work pattern, followed through GPS tracking. Soil damage was also light; in no plots, deep disturbances were found. However, most of the stumps were damaged. Forwarding and chipping productivity and cost were also evaluated. The slash left on the terrain averaged 3.0 and 1.5 odt/ha in Q. ilex and Q. pyrenaica, respectively, including scrub debris. As a conclusion, while this heavy feller-buncher can be useful in coppice heavy thinnings with larger trees, it would be a good option to try lighter disc saw felling heads mounted on the harvester boom tip, which probably would reach better productivity and reduce the frequency of stand damage.