Chemotaxonomical identification of Holocenic bogwood recovered after 2007 Niigataken Chuestsu-oki Earthquake

Abstract

Abstract A Holocenic coniferous bogwood salvaged from the 70 to 100 m-deep seabed after the 2007 Niigataken Chuetsu-oki Earthquake was analyzed anatomically and chemically. The main anatomical features of the wood were the presence of (i) large window-like pits in cross field and (ii) smooth-walled cells of ray tracheid. Feature (i) allowed identification of the wood as genus Pinus. Feature (ii) is characteristic of section Quinquefoliae, but possible decay by the long burial (3400–3210 cal BP) left the identification inconclusive. Chemical analysis showed that the major volatile components of the bogwood were cadinane-type sesquiterpenes. In contrast, those of modern pine samples were longifolene and monoterpenes from Pinus densiflora and Pinus thunbergii, nerolidol from Pinus parviflora and P. parviflora var. pentaphylla, and monoterpenes from Pinus koraiensis. Thus, none of the modern pines contained cadinane-type sesquiterpenes as major components. As organic components of wood are known to undergo diagenetic transformation under geological conditions, recent samples were subjected to heat treatment at 180°C for 24 h to simulate the long burial time. As a result, nerolidol, the main component of P. parviflora and P. parviflora var. pentaphylla was converted to cadinane-type sesquiterpenes. Therefore, it is highly likely that the bogwood sample was P. parviflora or P. parviflora var. pentaphylla, section Quinquefoliae subsection Strobus, agreeing with the anatomical feature of section Quinquefoliae.