A comparison of excavator-based harvester productivity among different machine operators in a clear-cut Eucalyptus plantation forest, South Africa

Background: Recent studies have identified the machine operator as a potential bottleneck to increased machine productivity. Machine productivity variations between 20% and 40% have been observed among different machine operators engaged with wood harvesting under similar working conditions. Most factors (site, climate and terrain) affecting worker productivity have already been analysed and they are described in the existing literature. However, very little information is available regarding the impact of operator selection on the productivity of South African excavatorbased harvesters. Methods: Operator performance was assessed by analysing work study data collected from nine different harvester operators over a three-week period. The experimental conditions were approximately the same for each operator, since all crews worked in clonal Eucalyptus plantations clear-cut at the age of 6 to 7 years. Results: Mean cycle time, which was the time needed to fell, delimb, debark and crosscut one eucalypt tree, varied from 26 to 51 s. Tree size accounted for approximately 25% of the total variation in cycle time and operator proficiency for 40%. Conclusions: Significant operator variability can be found even within a relatively small pool of operators, and that variability is strong enough to emerge over the well-known dominant effect of tree size. Such variability might be reduced through pre-selection tests and training, both conducted in a simulated environment.