Application of System Dynamics Simulation to Assess System Productivity of Forest Harvesting Systems: A Case Study from Japan

Most forest harvesting operations are performed using two or more forestry machines in combination; in the typical forest production system in steep terrain in Japan, there are four production processes: felling, yarding, processing, and forwarding. It is essential to evaluate the overall productivity of such combined production systems, but the calculation method that indicates the productivity has not been fully established. In this study, we built simulation models of serial, parallel, and sequential production systems by using system dynamics to evaluate their productivity regarding the combined machine productivity (CMP) and combined labor productivity (CLP) indices. Comparing the three types of forest harvesting systems in Japan, the parallel production system had the highest CMP, while the serial production system had the highest CLP; the sequential production system lay between the serial and parallel production systems in terms of CMP and CLP. The overall productivity of Japanese forest production systems was lower than that of Central Europe, where processor tower yarders (PTYs) are used. Thus, the CLP of Japanese forest production systems was improved by 12.8 to 26.5% by incorporating the concept of a PTY, and it can be further improved by eliminating the forwarding process.