The Effect of New Silvicultural Trends on Mental Workload of Harvester Operators

Close-to-nature (CTN) forestry offers many advantages, but makes management more complex
and generally results in lower harvesting productivity and higher harvesting cost. While the
higher harvesting cost of CTN is widely acknowledged, few ever consider the potential impact
on operator workload, as the harvesting task becomes more complex. This study aimed to de
termine the mental workload of harvester operators under two silvicultural regimes: »pure
conifer« stand and »mixwood« stand. In total, 13 harvester operators with varying experience
levels were monitored for work performance and mental workload when operating a harvester
simulator in two virtual stands designed according to the above-mentioned silvicultural re
gimes. Mental workload was assessed using the NASA Task Load Index (NASA-TLX) inter
view method and heart rate variability measurements, during two 30-minute test sessions
performed in the »pure conifer« and the »mixwood« stand, respectively. As expected, operat
ing in a more diversified »mixwood« stand resulted in a marked productivity loss, estimated
between 40 and 57%. The study also confirmed the increased aggravation of mental demand,
effort and frustration experienced by the operators when passing from the »pure conifer« stand
to the »mixwood« stand. Such increase in mental workload was independent of the age and
experience of the operators. Results can be used to paint a more holistic picture of CTN for
estry and its implications for harvester operators. Besides increasing the number of subjects
being monitored, future studies should focus on live forest operations