9:00 AM - 9:23 AM
[SGL17-01] Achievements and challenges of oxygen isotopic dendrochronology
★Invited Papers
Keywords:dendrochronology, oxygen isotopic ratio, cellulose, climate variation
Dendrochronology is one of the most accurate dating methods and has been widely used for conifer materials with a large number of tree rings, but there are limits to its application to the wide variety of hardwood materials. The oxygen isotopic dendrochronology is a dating method that uses the oxygen isotope ratio of cellulose in tree rings instead of the tree ring width as the master chronology for determining the age of wood. Because of its high consistency in the inter-annual variations between different trees, it is possible to determine the age of wood with only 30 to 50 years of tree rings, and it can be applied to all tree species, including hardwoods. Therefore, the need to construct a master chronology of cellulose oxygen isotope ratios has been understood by many people concerned, and during the last 10 years, its master chronology has been developed for the past 5,000 years in Japan.
The reason behind the wide applicability of oxygen isotopic dendrochronology beyond tree species is the simplicity of the mechanism of variation in tree-ring cellulose oxygen isotope ratios. Cellulose is a polymer of glucose, originally produced within leaves, and its oxygen isotope ratio records variations in the leaf water oxygen isotope ratio. Since the leaf water oxygen isotope ratio is expressed as a linear function of two meteorological factors: precipitation isotope ratio and relative humidity, variations in the tree ring cellulose oxygen isotope ratio of all trees are consistent over a wide area, reflecting the climate variability there.
The tree-ring cellulose oxygen isotope ratio is widely used, especially in the Asian monsoon region, to reconstruct summer precipitation and temperature over the past hundreds to thousands of years. Research on the dating of wooden material is progressing simultaneously using the tree-ring cellulose oxygen isotope ratio, too. In this lecture, I will introduce in detail the current achievements and challenges of the two purposes of the oxygen isotopic dendrochronology: “climate reconstruction'' and “dating”.
The reason behind the wide applicability of oxygen isotopic dendrochronology beyond tree species is the simplicity of the mechanism of variation in tree-ring cellulose oxygen isotope ratios. Cellulose is a polymer of glucose, originally produced within leaves, and its oxygen isotope ratio records variations in the leaf water oxygen isotope ratio. Since the leaf water oxygen isotope ratio is expressed as a linear function of two meteorological factors: precipitation isotope ratio and relative humidity, variations in the tree ring cellulose oxygen isotope ratio of all trees are consistent over a wide area, reflecting the climate variability there.
The tree-ring cellulose oxygen isotope ratio is widely used, especially in the Asian monsoon region, to reconstruct summer precipitation and temperature over the past hundreds to thousands of years. Research on the dating of wooden material is progressing simultaneously using the tree-ring cellulose oxygen isotope ratio, too. In this lecture, I will introduce in detail the current achievements and challenges of the two purposes of the oxygen isotopic dendrochronology: “climate reconstruction'' and “dating”.