δ¹⁸O of tree-rings cellulose in two species (spruce and oak) as proxies of precipitation amount and relative humidity in Northern Japan.

Abstract

Relationships between climate factors and d¹⁸O values of tree rings in two species with different root systems were investigated in the northern Hokkaido Island. In spruce (Picea jezoensis with a shallow root type, the d¹⁸O values are negatively correlated with precipitation in July and August. Thus the d¹⁸O value in spruce must be valuable as a proxy of summer precipitation in this area. On the other hand, d¹⁸O value in oak (Quercus crispula) with deeper root than spruce, is not very sensitive to summer precipitation but negatively correlated mainly with relative humidity in July and August. Thus the d¹⁸O value in oak must become a proxy of summer relative humidity in this area.