Abstract
In 1954, the 15th typhoon (also known as the Tôyamaru typhoon) caused catastrophic windthrow to trees in the headwater region of the Ishikari River, Hokkaido, Japan. To monitor forest regeneration, the Hokkaido Research Center of the Forestry and Forest Products Research Institute began periodic surveys of vegetation and tree stem at six study sites in stands that had, prior to the typhoon, been near-climax conifer forest. To date, surveys have been conducted in the following years: 1957–1968, 1972, 1976, 1980, 1984, 1988, 2002, 2009, and 2017. For the surveys, belts 2 m wide and 30–50 m long were chosen in each plot, each divided into 2 × 2 m quadrats. In each quadrat, every plant species present was recorded and its coverage ranked (0–1%: +, 1–10%: 1, 10–25%: 2, 25–50%: 3,
50–75%: 4, 75–100%: 5) in each layer (canopy, subcanopy, shrub, herb, vine, and moss). Surveys of tree stems were
conducted in 1993, 1998, 2002, 2009, and 2017, with plot widths enlarged to 10 m. In each belt, height and diameter
at breast height were measured for all stems whose heights were ≥ 1.3 m. All the survey data have been organized in
machine-readable format and published under a Creative Commons Attribution 4.0 International license.
