We reconstructed past vegetation at the Tagajyo archeological site, northeastern Japan, from pollen and wooden remains profiles based on a high-resolution and robust chronology, for better understanding of the ancient deforestation and surface environment change. The profiles clearly indicated the vegetation history for hilly areas as follows: 1) before construction of the Tagajyo as documented in AD 724, a cool temperate deciduous broad-leaved forest consisting of Quercus sect. Prinus and Carpinus was naturally distributed; 2) after construction of the Tagajyo castle, spreading grasslands by deforestation; 3) in the late 8th century, increasing secondary forest of Pinus densiflora; 4) from early 9th century to 915 AD, secondary forest of Quercus serrata, Q. crispula and Fagus crenata due to mitigate deforestation. On the alluvial plain areas, large-scale rice paddy and upland cultivation started after the construction of the Tagajyo castle. The pollen results and historical documents may imply that Moraceae-Cannabaceae was cultivated around the study site. The excessive deforestation in hilly areas caused a decrease of vegetation cover and soil erosion, leading to development of landform in the coastline during the late Holocene.

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The authors investigated the spatial variation of topsoil salinity in rice fields damaged by the 2011 Tohoku Earthquake Tsunami. Four study locations were selected from the alluvial plain of the lower Natori River in the Sendai Plain. The results suggest that salinity is lower in inland areas but increases in coastal areas because of geographical factors such as distance from the coastline, artificial constructions, microrelief, and altitude. For about six months after the tsunami, salinity decreased remarkably, but not in seaside locations. For this reason, it was difficult to distinguish the fluctuation caused by sampling methods and the temporal variation.

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