The effect of hardwood component on grapple skidder and stroke delimber idle time and productivity – An agent based model

• We modeled the interaction between grapple skidder and stroke delimber.
• We developed an agent-based model using the NetLogo software.
• Hardwood component does not affect machine idle time under average conditions.
• Hardwood component has no effect on system productivity under average conditions.
• System productivity is most sensitive to bunch size and skidding distance.

The forest industry is a capital intensive business and therefore high efficiency in management and forest operations is a must. Maine has millions of acres of forest stands with tree diameters smaller than 30 cm. The harvest productivity in such stands is low compared to stands with larger diameter trees. A recent harvest productivity study in Maine identified operational constraints for whole tree harvest systems, but efforts to improve active operations would be expensive and time consuming. A common practice to reduce costs and time consumption is to develop simulation models and implement new ideas within them. We developed a production efficiency model that leverages an agent-based modeling approach. The model is based on the interaction of two common forest machines (grapple skidder and stroke delimber) and incorporates empirical cycle time estimates from research in Maine. Three scenarios have been developed to investigate baseline conditions, and two GPS and GIS aided communication improvements. The goal of this paper is to document a new agent based model and to investigate the effect of hardwood component on machine idle time and productivity. Results showed that system productivity was affected by skidding distance, bunch spacing, and removal intensity. An increase in hardwood component led to a decrease in stroke delimber idle time but did not affect grapple skidder idle time. Further, hardwood component did not affect system productivity, and none of the three single-skidder scenarios tested performed any better than another. We validated the model by conducting a sensitivity analysis to confirm previous research results. The modeled waiting times are well within the range of observed values and therefore suggest that this model is accurate and well calibrated. Our conclusions are that when operating under average harvesting conditions there is no loss in productivity due to a change in hardwood component and that a stroke delimber idle time of 40% or more is unavoidable unless the stroke delimber can work independently. Future applications of this model may target specific production forestry conditions.