Typhoons are an increasingly important disturbance under climate change in temperate forests of Hokkaido, northern Japan, yet their long-term ecological consequences remain poorly quantified. On 8 September 2004, Typhoon Songda (Typhoon Number 18) caused widespread wind damage across Hokkaido, providing a natural experiment to examine the post-disturbance dynamics in forest structure and composition. This study analysed the responses of two mixed conifer-broadleaf forests, using long-term census data collected in Nopporo Forest Park (2000-2025) and Tomakomai National Forest (1996-2024). Census intervals were 5 years for Nopporo and 2-3 years for Tomakomai. The two forests shared many broadleaf species, but their conifer composition was entirely distinct, with Abies sachalinensis found only in Nopporo and Picea jezoensis restricted to Tomakomai. To evaluate the damage by wind disturbance and the recovery, this study quantified the changes in basal area, tree density and species composition. The post-disturbance recovery was analysed for individual species and for different size classes. Broadleaf species were divided into three classes of shade tolerance.

The two study forests exhibited different damage and recovery trajectories in basal area, tree density and species composition following the same typhoon disturbance. The Nopporo forest experienced less basal area loss immediately by the typhoon and the stand basal area was increasing over 25 years. This forest also showed a consistent decline in tree density likely driven by stand development with self-thinning. In Nopporo, the dominant broadleaf species poorly regenerated and the shade-tolerant conifer (A. sachalinensis) increased in basal area and tree density, indicating a shift toward higher conifer dominance.  In contrast, the Tomakomai forest experienced more severe initial damage but demonstrated a rapid recovery by compensatory growth and recruitment of broadleaf species, and basal area and tree density eventually exceeded the pre-disturbance levels. In Tomakomai, stand size structure remained relatively stable through the study period, indicating the long-term resilience. However, the shade-intolerant conifer (P. jezoensis) suffered substantial damage and was still recovering slowly.