Abstract
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 determine 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 regimes. Mental workload was assessed using the NASA Task Load Index (NASA-TLX) interview method and heart rate variability measurements, during two 30-minute test sessions performed in the »pure conifer« and the »mixwood« stand, respectively. As expected, operating 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 forestry and its implications for harvester operators. Besides increasing the number of subjects being monitored, future studies should focus on live forest operations.
Highlights
In the face of a changing climate, close-to-nature (CTN) forestry can contribute to increasing the resiliency of forest stands to natural disturbances such as pests, pathogens, windthrows, and drougths (Schütz et al 2006, Morrison et al 2014, Felton et al 2016, Schäfer et al 2017)
It is important to recall that this study addresses mental workload – not stress – and in that regard, the capacity of simulators to reflect real work techniques and demands has been demonstrated in the past (Ovaskainen 2005)
During tests in a controlled virtual environment, the mental workload of harvester operators was statistically higher when engaged in a diverse »mixwood« stand rather than in a more even »pure conifer« stand
Summary
In the face of a changing climate, close-to-nature (CTN) forestry can contribute to increasing the resiliency of forest stands to natural disturbances such as pests, pathogens, windthrows, and drougths (Schütz et al 2006, Morrison et al 2014, Felton et al 2016, Schäfer et al 2017). The popularity of CTN and continuous-cover forestry has been on the rise in German public forests and in several other European countries. In this context, the presence of multi-cohorts with varying stem diameter and height distributions in combination with mixed-species assortments offers strong ecological benefits that have been studied extensively. Despite the documented ecological benefits, mechanized forest operations in CTN forestry are generally more complex than in conventional conifer monoculture and often lead to lowered harvesting productivity. Decreased harvesting producti vity in mixed-species or deciduous stands is normally associated with a higher number of assortments to be processed, diverging stem architecture, the presence of more multi-stage regeneration and often a smaller mean stem size
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