Abstract
Currently there is limited information on the resilience of uprooted broadleaved trees after tsunami disasters in coastal forests. Therefore, studies must investigate the root distribution of broadleaved trees in coastal sand dunes. In this study, we measured the root morphology and three-dimensional distribution of Pinus thunbergii and several broadleaved tree species by excavation survey. The gathered data were then compared with previous root morphology studies at mountainous sites. Except for some excavated root samples, the roots of P. thunbergii, Quercus dentata, Zelkova serrata, and Tilia japonica generally showed similar morphology to mountainous tree roots as reported by Karizumi (1979). The roots of young Q. dentata and Z. serrata trees were concentrated in shallow soil layers (0–50 cm), probably due to a higher stand density with adjacent trees and buried plastic waste. We also hypothesized that root growth was not inhibited by groundwater and hard soil layers at coastal forests on sand dunes because no high groundwater layers in soil profiles were observed when root samples were excavated. At some excavation points, we observed hard soil pan layers, but roots had penetrated into these layers. Sandy soils exhibited considerable permeability due to their porous nature and were not tightened. These observations suggested that the root distribution of broadleaved trees in coastal sand dunes with low groundwater levels, sandy soils, no higher stand density with adjacent tree, and no buried objects were similar to the root distribution of broadleaved trees in mountainous sites.
