Post-drought Growth Response of Western Juniper (Juniperus occidentalis var. occidentalis) in Central Oregon

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Paul A. Knapp, Professor (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/

Abstract: Increased atmospheric CO2 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 CO2 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 CO2 shown by controlled laboratory studies and suggest that rising levels of atmospheric CO2 may impact western juniper growth rates.

Additional Information

Publication
Geophysical Research Letters
Language: English
Date: 2001
Keywords
Juniperus occidentals var. occidentalis, Western Juniper, Post-drought Response, Geography