2021 Volume 46 Issue 3 Pages 316-328
To clarify the causes of trees falling due to the tsunami triggered by the Great East Japan Earthquake, we investigated and compared the habitats and tree shapes of the pines that survived and the pines that fell over in a coastal forest struck by the tsunami. In the results of the investigation, compared with the pines that survived, the pines that fell over had grown in an environment that was at a lower elevation and had a shallower ground water level. The trees that fell over also had a lower tree height, narrower trunk circumference above ground and smaller root system. If we assume a tsunami with a maximum inundation height of 11.9 m, as occurred in this coastal forest, the tree form was shown as a target tree form to be grown for pines constituting a coastal forest that is resistant to falling damage. For the root system, in the form of multiple tap root and two-tiered horizontal root type, relational expression (giving 12 m3 for a girth at breast height of 120 cm) estimated from breast height trunk circumference as root system disk volume was shown, and tap root length over 1.5 m and horizontal root length over 4 m were shown. In addition, this paper also shows the shape of the aboveground part which supports the growth of this root system and the planting environment.
