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DROUGHT INDICATED IN CARBON‐13/CARBON‐12 RATIOS OF SOUTHWESTERN TREE RINGS 1
Author(s) -
Leavitt Steven W.,
Long Austin
Publication year - 1989
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.1989.tb03070.x
Subject(s) - isotopes of carbon , δ13c , environmental science , dendrochronology , mathematics , climatology , atmospheric sciences , stable isotope ratio , total organic carbon , geology , chemistry , physics , environmental chemistry , quantum mechanics , paleontology
Stomatal closure during periods of moisture deficiency should theoretically lead to elevated 13 C/ 12 C ratios as reduction of available CO 2 leads to diminished photosynthetic discrimination against 13 C in favor of 12 C. Stable‐carbon isotope ratio chronologies developed from 5‐yr tree‐ring groups at 17 sites in six southwestern states were tested for a drought relationship by first fitting a spline curve to each chronology to remove the long‐term trend and calculating indices as the ratio of actual to spline curve value. The time series of “Del Indices” so developed are significantly correlated with 5‐yr mean Palmer Hydrological Drought Indices (post‐1930 period) and reconstructed July Palmer Drought Severity Indices from respective areas. Overall, in the period since 1790, the driest pentads were 1900–04 and 1960–64, whereas the wettest were 1980–84 and 1915–19. Maps of drought represented for two pentads seem to be reasonable representations, although spatial correlations of Del Indices with PHDI were generally not significant. These Del Index drought reconstructions may provide a useful measure of past physiological response to drought (stomatal closure), although the present cost of analysis would prevent this from being a routine method.