• August to July Precipitation from Tree Rings in the Forest-Steppe Zone of Central Siberia (Russia)

      Shah, S.K.; Touchan, R.; Babushkina, E.; Shishov, V.V.; Meko, D.M.; Abramenko, O.V.; Belokopytova, L.V.; Hordo, M.; Jevšenak, J.; Kędziora, W.; et al. (Tree Ring Society, 2015-01)
      The goal of this research report is to describe annual precipitation reconstruction from Pinus sylvestris trees on three sites in the Abakan region, located in the Minusinsk Depression, at the confluence of the Yenisei and Abakan Rivers, Russia. The study was performed during the 4th annual international summer course "Tree Rings, Climate, Natural Resources and Human Interaction" held in Abakan, 5-19 August 2013. The reconstruction, for the 12-month total precipitation ending in July of the growth year, is based on a reliable and replicable statistical relationship between precipitation and tree-ring growth, and shows climate variability on both interannual and interdecadal time scales. The regional tree-ring chronology accounts for 56% of the variance of observed annual precipitation in a linear regression model, with the strongest monthly precipitation signal concentrated in May and June of the current growing season. Composite 500 mb height-anomaly maps suggest that the tree-ring data from this site, supplemented by other regional tree-ring data, could yield information on long-term atmospheric circulation variability over the study area and surrounding region. © 2015 The Tree-Ring Society.
    • The Dendroclimatological Potential of Willamette Valley Quercus garryana

      Gildehaus, S.; Arabas, K.; Larson, E.; Copes-Gerbitz, K. (Tree Ring Society, 2015-01)
      We develop a 341-year Oregon white oak (Quercus garryana Dougl.) tree-ring chronology in Oregon's Willamette Valley to evaluate climate-growth relationships and determine the species' dendroclimatological potential at our site and in the surrounding region. The standardized and residual chronologies exhibit significant positive correlations with previous-year April and May temperatures, inverse correlations with previous-year spring precipitation and summer PDSI, a positive correlation with current-year July precipitation and summer PDSI, and inverse correlations with current-year June temperatures. The strength of these relationships varies over time. Significant shifts in the chronologies' mean and variance align with phase changes in the Pacific Decadal Oscillation (PDO), with lower and more variable growth during the warmer, drier positive phase of the PDO over the instrumental record. The absence of similar shifts prior to the 1900s, suggests a lack of temporal consistency in the expression of PDO variability at our site. The strong crossdating at our site reflects a cohesive climate signal, and the climate analysis illustrates the potential to develop proxy data over multiple centuries. Together, these results indicate a potential to expand the network of currently available climate proxy data by utilizing Q. garryana in dendroclimatological research. © 2015 The Tree-Ring Society.