| Summary: | Tree-ring stable oxygen isotope (δ18OTR) demonstrates the enormous potential for revealing hydrological climate changes and large-scale atmospheric circulations. Here, we established the 210-year δ18OTR chronology of Pinus tabulaeformis Carr. in Baotou, southwest Inner Mongolia, North China. The regional precipitation δ18O (δ18OP) and June-July-August relative humidity (RHJJA) were the two dominant environmental factors controlling the δ18OTR changes. Since the 1930s, the increasing δ18OTR values in the study region reflected the drying trend due to reducing precipitation and increasing temperature. The δ18OTR series in Baotou generally exhibited stronger correlations with three Indian summer monsoon (ISM) indexes than three East Asian summer monsoon (EASM) indexes during 1948–2009 AD. However, the δ18OTR record also significantly correlated with one EASM index. These results indicated that the Asian summer monsoon played an essential role in modifying the δ18OTR values, and the ISM possibly had more considerable influence compared with the EASM. We also found that the δ18OTR record had a higher correlation with the central-Pacific El Niño-Southern Oscillation (ENSO) than that with eastern-Pacific ENSO, probably because of the more substantial impact of the central-Pacific ENSO on the ISM.
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