Enhanced influence of soil type on cumulative wind damage risk: insights from tree-pulling experiments in Japanese larch forests of Hokkaido, Japan

Abstract Root resistance is a key factor in determining the risk of wind damage through uprooting. To date, the influence of soil type on root resistance has primarily been assessed using the critical turning moment derived from tree-pulling experiments. However, for effective forest risk management, this influence should be evaluated based on cumulative wind damage risk. In this study, we assessed the cumulative wind damage risk for Japanese larch [Larix kaempferi (Lamb.) Carrière] at two sites with different soil types—brown forest soil and andosol—in Hokkaido, northern Japan. Our approach combined pulling experiments, a mechanistic model, and exceedance probability calculations. The pulling experiments showed a 13% greater critical turning moment for brown forest soil than that for andosol. This difference translated to a critical wind speed difference of ~1 m/s (5.5%–6.4%), as indicated by the mechanistic model. In contrast, the exceedance probability calculations revealed a much larger disparity: the cumulative risk throughout the silvicultural cycle of Japanese larch was 2.7-fold higher for andosol than that for brown forest soil. These findings highlight that soil type effects are magnified when cumulative risk is estimated using the critical turning moment.