Radial growth rate increases in naturally-occurring ponderosa pine trees: a late 20th century CO2 fertilization effect?

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: • The primary objective of this study was to determine if gradually increasing levels of atmospheric CO2, as opposed to ‘step’ increases commonly employed in controlled studies, have a positive impact on radial growth rates of ponderosa pine (Pinus ponderosa) in natural environments, and to determine the spatial extent and variability of this growth enhancement. • We developed a series of tree-ring chronologies from minimally disturbed sites across a spectrum of environmental conditions. A series of difference of means tests were used to compare radial growth post-1950, when the impacts of rising atmospheric CO2 are best expressed, with that pre-1950. Spearman’s correlation was used to relate site stress to growth-rate changes. • Significant increases in radial growth rates occurred post-1950, especially during drought years, with the greatest increases generally found at the most water-limited sites. Site harshness is positively related to enhanced radial growth rates. • Atmospheric CO2 fertilization is probably operative, having a positive effect on radial growth rates of ponderosa pine through increasing water-use efficiency. A CO2-driven growth enhancement may affect ponderosa pine growing under both natural and controlled conditions.

Additional Information

Publication
New Phytologist 171:379-390
Language: English
Date: 2006
Keywords
CO2 fertilization, ponderosa pine (Pinus ponderosa), site harshness, drought, interior Pacific Northwest