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A profound consideration of stable oxygen isotope source water origins is a precondition for an unambiguous palaeoenvironmental interpretation of terrestrial δ O archives. To stress the influence of air mass origins on widely used δ O tree-ring chronologies, we conducted correlation analyses between six annually resolved δ O tree-ring cellulose ( $\delta ^{18}\textit {O}_{TC}$ ) chronologies and mean annual air package origins obtained from backward trajectory modeling. This novel approach has been tested for a transect at the southeastern Tibetan plateau (TP), where air masses with different isotopic composition overlap. Detailed examinations of daily precipitation amounts and monthly precipitation δ O values ( $\delta ^{18}\textit {O}_{P}$ ) were conducted with the ERA Interim and Laboratoire de Météorologie Dynamique General Circulation Model (LMDZiso) data, respectively. Particularly the southernmost study sites are influenced by a distinct amount effect. Here, air package origin $\delta ^{18}\textit {O}_{TC}$ relations are generally weaker in contrast to our northern located study sites. We found that tree-ring isotope signatures at dry sites with less rain days per year tend to be influenced stronger by air mass origin than tree-ring isotope values at semi-humid sites. That implies that the local hydroclimate history inferred from $\delta ^{18}\textit {O}_{TC}$ archives is better recorded at semi-humid sites. [ABSTRACT FROM AUTHOR]