Paper No. 21
Presentation Time: 9:00 AM-6:00 PM
GLACIAL JUNIPERUS FROM THE LA BREA TAR PITS SHOW SIMILAR GROWTH PATTERNS AS MODERN JUNIPERUS DESPITE PHYSIOLOGICAL CONSTRAINTS OF LOW CO2
MO, Kris H., Biology Department, Johnson County Community College, 12345 College Blvd, Overland Park, KS 66210, GERHART, Laci, Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, 8028 Haworth Hall, Lawrence, KS 66049, WARD, Joy K., Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Ave, Room 2045, Lawrence, KS 66045 and HARRIS, John M., The Page Museum at the La Brea Tar Pitts, Natural History Museum of Los Angeles County, 5801 Wilshire Blvd, Los Angeles, CA 90036, kmo@stumail.jccc.edu
Since the Last Glacial Maximum, atmospheric CO
2 concentrations have risen over 200 ppm, resulting in a near doubling of modern levels over glacial conditions. Past research has shown that c
i/c
a ratios (inter-cellular [CO
2] to atmospheric [CO
2]) in
Juniperus resulting in glacial c
i values less than half that of modern trees, suggesting a severe carbon limitation with potentially significant effects on productivity. In order to understand how changing [CO
2] influenced the growth patterns of trees, we analyzed ring widths of individual tree rings from glacial
Juniperus specimens preserved in the Rancho La Brea tar pits in southern California (aged 14-49 kyr BP). Modern trees from the Los Angeles basin were also analyzed to compare effects of changing precipitation, temperature and atmospheric [CO
2] levels. For each specimen, raw width and standardized indices (calculated as raw width divided by a 20-year sliding mean) were calculated, then compared across individuals.
Both mean raw width and maximum raw width were not significantly different between glacial and modern Juniperus samples. Interannual variation in ring width index also did not show significant differences between glacial and modern trees, despite significant differences in variation of ci/ca and ci. Modern Juniperus trees showed wide variation in maximum raw growth, suggesting that microsite conditions and interannual variation in climate play major roles in modern growth trends. Taken together, these results suggest that glacial trees were adapted to maintain growth despite lower carbon availability. These adaptations may constrain the ability of modern trees to fully utilize increases in atmospheric [CO2], resulting in limited growth enhancements with rising CO2 in long-lived species. These results have significant implications for increasing our understanding of the adaptation of trees to changing [CO2] and the impacts such adaptations may have on responses of plants to future climatic change.
