Inter-tree correlation and climatic response of tree-ring δ18O in Chinese fir: Implications for cross-dating and climatic reconstruction in Central East China

The availability of both ancient and modern wood samples enables the Chinese fir (Cunninghamia lanceolata) in Central East China to become a potential tree species for dendroclimatic reconstruction over the Common Era. However, the potential of using tree-ring alpha-cellulose oxygen isotope ratios (delta 18OTRC) in Chinese fir for the purposes of cross-dating and climatic reconstruction remains unexplored. Here we presented three delta 18OTRC chronologies (1954-2006 CE) for the whole-ring (delta 18OWR), earlywood (delta 18OEW), and latewood (delta 18OLW) in Chinese fir. The results indicated that the delta 18OWR had the highest correlation among individual trees. Using the delta 18OWR instead of the conventionally employed TRW can facilitate the cross-dating procedure. The delta 18OWR, delta 18OEW, and delta 18OLW exhibited the strongest relationships with the hydroclimate variables during the entire (June-September), early (June-July), and late (August-September) summer, respectively. The climate conditions preceding the growing season had a stronger influence on delta 18OEW than delta 18OLW. Using the delta 18OWR and delta 18OEW to reconstruct the hydroclimate variations may result in greater bias than the use of delta 18OLW. Our study demonstrated that the delta 18OTRC in Chinese fir from Central East China has the potential for cross-dating and summer hydroclimate reconstruction.