The 2018 Hokkaido Eastern Iburi Earthquake (Mj 6.7) caused 7092 sites and 4300 ha of landslides within a range of 466 km². Many landslides occurred in planted forests with gentle slopes (20–30°). Artificial reforestation and slope greening have been carried out immediately after the earthquake. In the recovery planning, the natural dispersal of plants in the landslide scars has been considered one of the possible methods for reforestation.
We surveyed natural recovery vegetation on landslide scars that had been planted forests prior to the earthquake. The survey in the fourth year after the earthquake results that among the woody plants, Larix kaempferi and Alnus inokumae, pioneer species planted before the earthquake, appeared at a high frequency and had a high plant cover rate. In contrast, the natural dispersal of native woody species that escaped landslides observed at a low frequency, and plant cover rate was also low in the landslide scars. For the herbaceous plant, we found high occurrence frequency in pioneer species with wind-dispersed seeds. In particular, Petasites japonicus subsp. giganteus had the highest plant cover owing to horizontal elongated underground stems in the landslide scars. The results suggest that among the pioneer species, the species that can contribute to initial vegetation recovery in landslide scars are woody plants planted before the landslide and herbaceous plants that can extend their underground stems horizontally after establishment.