Synchronicity and geographic variation in Oregon white oak acorn production in the Pacific Northwest

Abstract

We explored geographic patterns and synchrony of Oregon white oak (Quercus garryana) acorn production over 8 years from Vancouver Island, British Columbia to Medford, Oregon. We divided our data into geographic areas: Puget-Willamette Trough, Columbia Gorge-East Cascades (Eastside) xeric, Eastside mesic, Cascade Mountain foothills, Roseburg, and Medford to compare annual acorn production among areas. Correlogram analysis indicated significant acorn crop correlation throughout the Puget- Willamette Trough, but synchrony was higher over greater distances among stands than among trees. Relationships between acorn production and mean monthly temperature or precipitation were examined with correlation analyses for each month between floral initiation and acorn maturation over 8 years of observations. Acorn production in the Puget-Willamette Trough was negatively correlated with spring precipitation, possibly due to an effect on floral processes, and winter temperature, which might relate to bud chilling requirements. In Eastside uplands, June precipitation positively correlated with current acorn production, but negatively correlated with the following year's production suggesting a climatically mediated depression by one year's production on that in the following year. Eastside production negatively correlated with precipitation in March suggesting precipitation interferes with floral processes at that time. Oregon white oak masting is similar to that in other white oaks in terms of periodicity and the effects of spring weather, but is also influenced by other weather related factors following floral induction.

Citation

Peter, David H.; Harrington, Constance A. 2009. Synchronicity and geographic variation in Oregon white oak acorn production in the Pacific Northwest. Northwest Science. 83(2):117-130.