Correlation of woody biomass demand with optimum rotation age and thinning regime in Northern Tochigi Prefecture, Japan

Abstract

We used a simulator, which can estimate profits of woodland owners from the management of individual forest stands based on numerous sets of forestry-related parameters such as log prices, to identify the most profitable clearcutting rotation age and thinning frequency. We analyzed the effects of rising demand for woody biomass for mainly power generation. The assumed stands are planted Sugi (Cryptomeria japonica) forests in northern Tochigi Prefecture, where ground-based logging systems are predominant. The results showed that soil expectation value (SEV) was negative under many sets of parameters, and long rotation age was preferred in order to postpone the payment of replantation costs after clearcutting. However, because of the assumption that relatively low-cost logging operation was available and the log demand of sawmills was high, there were many sets of parameters where moderate rotation age (e.g., 65 years) and assumed maximum thinning (three times) were chosen as the optimum practice. Assuming a price increase of logs for energy production, the optimum thinning frequency had been scarcely changed, and the optimum rotation age was mostly unchanged or shortened by 5-10 years. The effects of a rise in biomass demand on optimum rotation age and thinning frequency were limited, but the shortened rotation age may support the economic rationality of the recent implementation of clearcutting in this region.