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Post‐drought growth responses of western Juniper ( Juniperus occidentals var. occidentalis ) in central Oregon
Author(s) -
Knapp Paul A.,
Soulé Peter T.,
GrissinoMayer Henri D.
Publication year - 2001
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl012365
Subject(s) - juniper , precipitation , environmental science , dendrochronology , climatology , zoology , physical geography , forestry , geography , biology , geology , meteorology , archaeology
Increased atmospheric CO 2 may affect the physiological response of natural trees to drought. We examined radial growth rates developed from five western juniper chronologies to determine if post‐drought growth responses have changed. Using prior year October to current year June precipitation from 1896–1998, we identified drought recovery years as having standardized scores (z‐scores) >0 and preceded by a year with a z‐score <−0.6. We defined our analysis by an early period, 1896–1930, when atmospheric CO 2 concentrations were close to preindustrial levels, and a late period, 1964–1998, when concentrations were substantially higher. Mean growth index values of recovery years between early and late periods were significantly greater (p<0.05) for four of the five sites, and for all sites combined. These results are consistent with the drought‐ameliorating effects of CO 2 shown by controlled laboratory studies and suggest that rising levels of atmospheric CO 2 may impact western juniper growth rates.