Drivers of radial growth and carbon isotope discrimination of bur oak (Quercus macrocarpa Michx.) across continental gradients in precipitation,vapour pressure deficit and irradiance |
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Authors: | STEVEN L VOELKER FREDERICK C MEINZER BARBARA LACHENBRUCH J RENÉE BROOKS RICHARD P GUYETTE |
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Institution: | 1. Biology Department, Southern Oregon University, , Ashland, OR, 97520 USA;2. Forestry Sciences Laboratory, U.S.D.A. Forest Service, , Corvallis, OR, 97331 USA;3. Department of Wood Science & Engineering, Oregon State University, , Corvallis, OR, 97331 USA;4. National Health and Environmental Effects Research Laboratory (NHEERL), Western Ecology Division, U.S. Environmental Protection Agency, , Corvallis, OR, 97333 USA;5. University of Missouri, Department of Forestry, , Columbia, MO, 65211 USA |
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Abstract: | Tree‐ring characteristics are commonly used to reconstruct climate variables, but divergence from the assumption of a single biophysical control may reduce the accuracy of these reconstructions. Here, we present data from bur oaks (Quercus macrocarpa Michx.) sampled within and beyond the current species bioclimatic envelope to identify the primary environmental controls on ring‐width indices (RWIs) and carbon stable isotope discrimination (Δ13C) in tree‐ring cellulose. Variation in Δ13C and RWI was more strongly related to leaf‐to‐air vapour pressure deficit (VPD) at the centre and western edge of the range compared with the northern and wettest regions. Among regions, Δ13C of tree‐ring cellulose was closely predicted by VPD and light responses of canopy‐level Δ13C estimated using a model driven by eddy flux and meteorological measurements (R2 = 0.96, P = 0.003). RWI and Δ13C were positively correlated in the drier regions, while they were negatively correlated in the wettest region. The strength and direction of the correlations scaled with regional VPD or the ratio of precipitation to evapotranspiration. Therefore, the correlation strength between RWI and Δ13C may be used to infer past wetness or aridity from paleo wood by determining the degree to which carbon gain and growth have been more limited by moisture or light. |
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Keywords: | CO2 dendrochronology drought growth humidity light stable isotopes stomata |
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