The coastal areas of the Sendai Plain have been constructed with embankments to promote the development of the root system of Pinus thunbergii, which is the main tree species planted in coastal forests, to strengthen their tsunami mitigation function. However, the planted black pine trees have suffered from poor growth probably due to some adverse soil conditions. This study established three quadrates in the 2014 planting area at a coastal forest restoration site in Natori City, Miyagi Prefecture. We conducted tree-by-tree and multi-point soil surveys to assess the growth condition of the planting bases. The tree-by-tree survey results showed a significant difference in the growth of P. thunbergii between the three-square sections, even though they were planted in the same planting year. The results of multi-point soil surveys showed completely different soil physical and chemical properties among three quadrates, and that the poor growing areas showed consolidated subsoil, high moisture content, low pH, and high EC. Spatial variation in soil parameters was large within the quadrate, suggesting that highly heterogeneous soil parameters affected the plant growth. Multiple regression analysis was conducted using the growth status of black pine as the objective variable, and significant multiple regression equations were obtained in all quadrates. Although statistically significant equations indicated effects of soil properties on the growth of black pines, direct concerns on the plant growth was not clear.

We compared the growth of one-year-old containerized sugi (Cryptomeria japonica) seedlings outplanted in early September (fall-planting) with those outplanted after nursing continued until early April of the following year (spring-planting). The height-diameter ratio of the fall-planting seedlings decreased from 113 ± 21 cm cm^-1 in early September to 67 ± 12 cm cm^-1 in early April of the following year. Compared to the spring-planting seedlings, the fall-planting seedlings showed vigorous height growth from April, with the annual growth of 56.1 ± 32.5 cm for the fall-planting seedlings being significantly greater than the 20.3 ± 13.2 cm for the spring-planting seedlings. The annual height growth of the seedlings varied greatly depending on the planting location within the planting trial site, but regardless of the planting location, the fall-planting seedlings tended to have a greater annual height growth than the spring-planting seedlings. We could suggest the expectation of vigorous height growth of containerized sugi seedlings whose height-diameter ratio were large from the following spring by fall-planting before growth stopped.