After the Great East Japan Earthquake, tree-planting areas on the artificial ground, such as tsunami evacuation hills and road embankments have expanded. Since the properties of the artificial ground would depend on several factors such as embankment materials and construction methods, these would cause the variation of growth of planted trees by sites. In this study, the relationship between the growth of planted broad-leaved trees and the several ground properties were investigated at tsunami evacuation hills and road embankments constructed in Iwanuma City, Miyagi Prefecture, to make clear the main tree growth differentiated factors. Growth of tree seedlings in five embankments differentiated in times of construction and planting were measured over several years and its ground properties such as hardness, texture, nutrient content, and pH, were compared. The growth differences among embankments were related to the properties of the embankment materials rather than ground hardness. The growth of evergreen tree species, such as Machilus thunbergii, Quercus myrsinifolia, Q. salicina, Q. glauca, Q. acuta, Camellia japonica, and Ilex integra, slowed down on the embankments with acidic or alkaline reformed soils that contain fewer clay particles, organic matter, and exchangeable Ca and Mg. It was also suggested that the ground hardness could explain partial growth differences within a site. Within an embankment with the same material, slow growth of planted trees tended to occur on extremely hard or soft grounds.

Non-crystalline minerals are formed through weathering processes from volcanic materials and strongly bind phosphorus (P), which may reduce the P availability for forest trees on volcanic soils. On the other hand, volcanic materials are a direct source of P and enhance soil total P. It has not been clarified how P availability and P cycling in forest ecosystems relate to non-crystalline minerals in volcanic soils. The objective of this study is to clarify the differences of soil nutrient availability and foliar nutrients of trees by comparing volcanic vs. non-volcanic soils. We selected eight secondary forests where Quercus serrata was dominant in Japan as study sites. We collected surface soils from three layers (0-5, 5-15, 15-30 cm depth) from each study site and canopy fresh leaves of Q. serrata. We measured the concentration of oxalate-extractable Al and Fe (Al_o and Fe_o), P fractions, and exchangeable-cations in soils and N and P in leaves. Both Al_o and Fe_o and soil nutrients (P fraction and exchangeable cations) were significantly higher in volcanic soils than in non-volcanic soils. Al_o + 1/2Fe_o was significantly correlated to NaOH-P (indicator of P bound to Al and Fe). Both plant available-P and NaOH-P were significantly positively correlated with foliar N and P concentrations. Estimated maximum heights of trees tended to be higher in volcanic soils. Our results indicated that the addition of volcanic ash directly increased soil P availability via increasing the pool of P and flux of P from recalcitrant and organic forms of P to available inorganic forms of P in soils.