Dendroclimatic Reconstruction of Summer Temperature at the Akaishi Mountains since A.D. 1774

Abstract

 Ring width, maximum density, and δ¹⁸O chronologies of Tsuga diversifolia and Picea jezoensis var. hondoensis growing in a sub-alpine forest at Mt. Senjo in the Akaishi Mountains were developed. Ring width and maximum density were measured with X-ray densitometry. Tree-ring δ¹⁸O was measured using a mass spectrometer after cellulose extraction. The chronologies developed have significant positive correlations with monthly temperatures in July, August, and September, with the exception of the ring width of T. diversifolia. The transfer functions for July-September temperature were developed using the four chronologies and were verified statistically. The transfer functions reveal a high coefficient of determination, whereas statistical verifications were not successful with rather low RE, CE, and sign test. The estimated temperatures since 1774 partially agreed with reported climate changes based on historical records. The results indicate that estimated temperature is weak for reconstructing increasing trends and low-frequency variations of temperature, although it is potentially useful for higher frequency temperature changes in local areas.