Southwestern U.S. Drought Maps From Pinyon Tree-Ring Carbon Isotopes
EOS, Volume 88, Number 4, pp. 39-40, 23 January 2007.
Steven W. Leavitt1,2, Thomas N. Chase1, Balaji Rajagopalan1, Eungul Lee1,
Peter J. Lawrence1, Connie A. Woodhouse 3,4
1Cooperative Institute for Research in Environmental Sciences (CIRES),
The University of Colorado, Boulder, CO 80309
2 Permanent Address: Lab. of Tree-Ring Research, University of Arizona, Tucson, AZ 85721
3 NOAA National Climatic Data Center Paleoclimatology Branch, Boulder, CO 80305.
4 Now at: Department of Geography and Regional Development, University of Arizona, Tucson, AZ 85721
Analysis of short-term fluctuations in δ13C in tree rings indicates they are related to climate,
notably the moisture status of the plant. The mechanism for this relationship is related to low moisture promoting
stomatal closure (reduced stomatal conductance), reduced discrimination against δ13C in leaf photosynthesis,
and therefore higher δ13C values of the resulting photosynthate (and tree rings). This study utilizes 14 pinyon pine sites
collected across 6 states in the American Southwest to develop Drought Indices using δ13C analysis.
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