Verification and complementing of historical landslide records using multi‑proxy tree‑ring analyses at the Kamitokitozawa landslide, Japan

Tree-ring series serve as an archive of past landslide movements. Dendrogeomorphological approach is a powerful method for estimating the timing of landslide events. This study applies a multi-proxy dendrogeomorphological approach—including abrupt growth changes-based growth disturbance, stem scar recovery, tree-ring eccentricity, and the establishment age of shade-intolerant trees—to evaluate and complement historical records of landslide activity at the Kamitokitozawa landslide in Akita Prefecture, Japan. Tree-ring analyses from 25 tree-ring cores, 18 disks, and 6 shade-intolerant trees revealed landslide signals during 1997–2022. The multi-proxy dataset also clarified spatial differences in slope deformation, with stem scar recovery, establishment age of shade-intolerant trees, and abrupt growth changes capturing discrete episodes of landslide scarp enlargement, while tree-ring eccentricity, stem scar recovery, and the establishment age of shade-intolerant trees highlighted enlargement internal landslide body movement. The estimated landslide signals were compared against a historical landslide chronology derived from geological surveys, mining records, and forest road construction data. The comparison showed that dendrogeomorphological proxies not only matched the timing of landslide activity documented in the historical chronology but also revealed additional periods of slope movement that were not recorded in existing archives. Moreover, the presence of older geomorphic features such as buried wood fragments suggests that landslide activity may have occurred prior to the dendrochronological window, possibly linked to volcanic and seismic events.