Quantifying seasonal precipitation using high-resolution carbon isotope analyses in evergreen wood

High-resolution natural abundance stable carbon isotope analyses across annual growth rings in evergreen trees reveal a cyclic increase and decrease in the measured carbon isotopic composition (delta C-13), but the causes of this pattern are poorly understood. We compiled new and published high-resolution delta C-13 data from across annual growth rings of 33 modern evergreen trees from 10 genera and 15 globally distributed sites to quantify the parameters that affect the observed delta C-13 pattern. Across a broad range of latitude, temperature, and precipitation regimes, we found that the average, measured seasonal change in delta C-13 (Delta delta C-13(meas), parts per thousand) within tree rings of evergreen species reflects changes in the carbon isotopic composition of atmospheric carbon dioxide (Delta delta C-13(CO2))and changes in seasonal precipitation (Delta P) according to the following equation: Delta delta C-13(meas) = Delta delta C-13(CO2)-0.82(Delta P) + 0.73; R-2 = 0.96. Seasonal changes in temperature, pCO(2), and light levels were not found to significantly affect Delta delta C-13(meas). We propose that this relationship can be used to quantify seasonal patterns in paleoprecipitation from intra-ring profiles of delta C-13 measured from non-permineralized, fossil wood. (C) 2011 Elsevier Ltd. All rights reserved.