Using dendrochronology to detect and attribute CO2-induced growth increases in P. menziesii and P. ponderosa in western North America
Abstract
Increased atmospheric CO2 could increase photosynthetic rates and cause trees to use water more efficiently, thereby increasing overall growth rates relative to climatic limiting factors. CO2 fertilization has been found across a range of forest types; however results have been inconsistent and based on short-term studies. Long-term studies based on tree-rings have generally been restricted to a few sites and have produced conflicting results. An initial global analysis of tree-ring widths for evidence of increasing growth relative to drought suggested a small but highly significant proportion of trees exhibit increasing growth over the past 130 years. These growth increases could not be attributed to increasing water use efficiency, elevation effects, nitrogen deposition, or divergence. These results suggest that CO2 fertilization is occurring at some locations and may influence future forest dynamics but this does not appear to occur at all locations. The processes causing differential responses are the focus of this study. Here we illustrate response differences between Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa). Using multiple site chronologies from these species over western North America, we demonstrate several site-specific explanations for differential responses to CO2 fertilization, such as forest composition, density, slope, aspect, soil type, and position relative to range limits.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.B21A0289S
- Keywords:
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- 0426 BIOGEOSCIENCES / Biosphere/atmosphere interactions;
- 0428 BIOGEOSCIENCES / Carbon cycling;
- 0439 BIOGEOSCIENCES / Ecosystems;
- structure and dynamics