A tree-ring based reconstruction of early summer precipitation in southwestern Virginia (1750-1981)

Abstract

In a closed-canopy forest, stand dynamics play an important role in shaping the forest, and it has been hypothesized that dense forests are not sufficiently limited by climate to warrant climate reconstruction. We collected Quercus prinus tree-ring data from a dense forest in the Appalachians, and after removal of stand dynamics and age trends we found strong influence of early summer precipitation on annual tree growth. We used the new Q. prinus chronology in a nested principal component analysis (PCA) of southeastern US Q. prinus chronologies and further strengthened the early summer precipitation signal in the tree-growth proxy, with favorable assessment of reconstruction skill. Our reconstruction was modeled using Bayesian regression, which allowed uncertainty to be quantified. The May-June precipitation reconstruction covered the period 1750-1981 and extended the instrumental record by 150 yr. It showed key drought years identified by other regional reconstructions, as well as an 11 yr quasi-periodicity that may be related to solar variability. This reconstruction has established a baseline precipitation record that can be used to measure changes brought about by global climate change.