© 1986 Heron Publishing—Victoria, Canada
Growth and physiological responses of Pinus ponderosa Dougl ex P. Laws. to long-term elevated CO2 concentrations
K. A. Surano (1), P. F. Daley (1), J. L. J. Houpis (2), J. H. Shinn (1), J. A. Helms (2), R. J. Palassou (1) and M. P. Costella (2)
1. Environmental Sciences Division, Lawrence Livermore National Laboratory, P.O. Box 5507, Livermore, CA 94550, USA / 2. Department of Foresty and Resources Management, University of California, Room 145, Mulford Hall, Berkeley, CA 94720, USA /
Summary
Seven-year-old ponderosa pine (Pinus ponderosa Dougl. ex P. Laws.) saplings and one- and two-year-old ponderosa pine seedlings of a Sierra Nevada and a Rocky Mountain seed
source, respectively, were exposed to CO2-enriched atmospheres in an outdoor open-top chamber facility for 2.5 years. Seedling growth (main stem diameter, height,
volume) increased with increasing CO2 concentration, though the two populations exhibited different patterns of response. By the beginning of the last growth season,
however, the trees under the highest CO2 concentrations showed signs of stress that included accelerated needle abscision, chlorosis, and apparent alteration of tolerance
to heat. The stress response is at least partly attributable to elevated foliar temperatures resulting from CO2-induced stomatal closure, which in turn lowered transpirational cooling of needles.
