Age-dating of the rings of yakusugi (Cryptomeria japonica) based on the racemization of amino acids

Abstract

The rings of Yakusugi {Cryptomeria japonica, about 1800 years old) on eight points yielding from 1084 to 1474 years which were determined their dates by counting one by one from the cortex into the heart were treated chemically to take out amino acids by washing, hydrolysis, ion-exchange clean-up, derivatization and analyzed enantiomeric mixtures by gas chromatography using Chirasil-Val glass capillary column. Then, ring ages were determined from the d/l ratio of aspartic acid (Asp) by two different methods making two corresponding calibration curves. Racemization was observed in alanine (Ala), valine (Val), Asp, and phenylalanine (Phe). As it was proceeded only a little in Val, irregular with ages in Ala and Phe, availability was found in Asp in a reasonable agreement with ages what we derived from. Ring age was calculated from the d/l ratio of Asp by next two methods and compared with the corresponding ring dated. (I) Calibration curve from one ring dated and racemization through analytical step. (II) Calibration curve from two rings dated 1084 and 1474 years. The dated ages of the rings by these two methods were closely related to the ring ages and, especially, relative error % was much more sufficient in the case of (II). The standard error estimated on (I) and (II) are 39.8 years and 29.6 years, respectively. It is suitable method that Asp racemization reaction could be determined of dating tree rings. © 1982, The Japan Society for Analytical Chemistry. All rights reserved.