Productivity and cost of CTL harvesting of Eucalyptus globulus stands using excavator-based harvesters

Time-motion studies were conducted to evaluate the productivity and cost of harvesting Eucalyptus globulus stands on flat and steep terrain, using excavator-based cut-to-length timber harvesters. The recorded data was comprised of 11 time elements of the harvester functions, including the following: machine movement and positioning of the harvesting head; cleaning or clearing of undergrowth and obstacles to tree felling or log processing; tree felling, handling, and bucking to 2 and 4 m logs; and the bunching of merchantable logs. It was found that the duration of the time elements is influenced by terrain conditions, operational layout, tree volume and form, lengths of the trees, and the resulting log assortments. Machine movement time was significantly longer when the harvester had to prepare the trails in the harvesting process. Bunching time significantly increased with the trail spacing, which indicates the need to minimize the bunching distance in harvesting operations. Delimbing and bucking time were mainly influenced by the log yield (number of logs per tree, expressed as the ratio of the tree lengths to the resulting log lengths), and the interaction of the linear components of tree volume and tree form. Pre-felling with a chain saw improved the work efficiency on steep terrain and in coppice (multi-stem) stands, by minimizing the time for handling. Harvester productivity ranged between 5 to 14 m³ per machine-hour (42 to 84 trees per man-hour). Harvester operation cost ranged from 4 to 13 $/m³, hence, it was estimated that excavator-based harvesters will operate profitably on stands with an average tree volume greater than 0.07 m³. For less-developed stands, it is suggested that harvesting operation should be deferred to allow for tree growth, or a whole-tree harvesting technique should be adopted to maximize wood recovery.