A three-century record of precipitation and blue oak recruitment from the Tehachapi Mountains, Southern California, USA

A three-century tree-ring chronology from living and dead blue oak (Quercus douglasii Hook. and Arn.) was developed from the Tehachapi Mountains in Southern California in order to develop a long-term reconstruction of precipitation at the study site. The ring-width series is significantly correlated with late winter/spring (December-April) precipitation. Comparison with two geographically separate blue oak residual chronologies from Southern California and meteorological records suggests broad-scale tree growth and climate homogeneity within the developed chronology. Evaluation of ranked extreme single-year events indicates extreme wet and dry years occur disproportionately during the 20th century. A disproportionate number of protracted episodes of unusually high or low periods of precipitation also occur in the 20th century. The most extreme persistently dry period occurred in the late 1770s and lasted about one decade, while the 1790s rank as the most persistently extreme wet decade during the reconstruction. Dendrochronological techniques were also used to estimate the timing of establishment and mortality of blue oak at the site. The most recent blue oak recruitment occurred in the 1940s, and no tree recruitment occurred during the second half of the 20th century. The lack of recent blue oak recruitment recorded here is typical throughout California's blue oak woodlands.