This is just a short take on Figure 3 of Xu et al.’s (2011) “Potential linkages between the moisture variability in the northeastern Qaidam Basin, China, since 1800 and the East Asian summer monsoon as reflected by tree ring d18O” (http://dx.doi.org/10.1029/2010JD015053).
Figure 3a and 3b, which is also highlighted in the paper-related slide-show on the webpage for the Journal of Geophysical Research – Atmosphere, display a ring width index and tree-ring d18O. The interesting part is, that one can clearly distinguish different episodes. If one considers the dates of strong tropical volcanic eruptions (e.g. http://dx.doi.org/10.1029/2006GL027992) and performs some provisional wiggle matching, then one can infer that these eruptions (Tambora, Cosiguina, Krakatau, Santa Maria) had direct impacts on tree growth at the study site. Obviously I will not talk about the later 20th century as the figure is not as easily related to the climate fluctuations afterwards.