现代环境研究室知识库

Oxygen isotopic ratios (delta(18)O) 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 delta(18)O from various kinds of trees growing in semi-arid Northern China. In addition, we evaluated past changes in delta(18)O of precipitation from the tree-ring cellulose delta(18)O and relative humidity using the mechanistic model for tree-ring cellulose delta(18)O 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 delta(18)O from the different tree species, which are similar to the observed delta(18)O of precipitation during 1985-2002. Although the reconstructed delta(18)O 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 delta(18)O of stalagmite in the Heshang cave (30 degrees 27'N, 110 degrees 25'E; Fig. 1), suggesting that delta(18)O of precipitation is not controlled by local meteorology but is influenced by large-scale atmospheric circulation.