Regional hydroclimate and precipitation δ18O revealed in tree-ring cellulose δ18O from different tree species in semi-arid Northern China

Oxygen isotopic ratios (δ18O) of tree-ring cellulose, grown from 1954 to 2003 in semi-arid Northern China demonstrate a common inter-annual variability, despite coming from three different species in two distinct growth environments (an alpine meadow and a rocky ridge). The variability was significantly negative correlated with precipitation and relative humidity during the growing season. This suggests that the past summer hydroclimate can be inferred from tree-ring cellulose δ18O from various kinds of trees growing in semi-arid Northern China. In addition, we evaluated past changes in δ18O of precipitation from the tree-ring cellulose δ18O and relative humidity using the mechanistic model for tree-ring cellulose δ18O in Roden et al. (2000). By fixing the species-dependent exchange rate of oxygen between carbohydrate and xylem water for Larix principis-rupprechtii and Picea koraiensis, we could also reconstruct the variations in precipitation δ18O from the different tree species, which are similar to the observed δ18O of precipitation during 1985–2002. Although the reconstructed δ18O of precipitation does not have any significant relation to local temperature or precipitation during 1954–2003, its long-term variation pattern is similar to that of the Asian summer monsoon indices and δ18O of stalagmite in the Heshang cave (30°27′N, 110°25′E; Fig. 1), suggesting that δ18O of precipitation is not controlled by local meteorology but is influenced by large-scale atmospheric circulation.