Journal
GLOBAL CHANGE BIOLOGY
Volume 16, Issue 7, Pages 2089-2103Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2486.2009.02053.x
Keywords
elevated CO2; elevated temperature; loblolly pine; photosynthesis; water stress
Funding
- United States Department of Energy NICCR [07-SC-NICCR-1060]
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We investigated the effect of elevated [CO2] (700 mu mol mol-1), elevated temperature (+2 degrees C above ambient) and decreased soil water availability on net photosynthesis (A(net)) and water relations of one-year old potted loblolly pine (Pinus taeda L.) seedlings grown in treatment chambers with high fertility at three sites along a north-south transect covering a large portion of the species native range. At each location (Blairsville, Athens and Tifton, GA) we constructed four treatment chambers and randomly assigned each chamber one of four treatments: ambient [CO2] and ambient temperature, elevated [CO2] and ambient temperature, ambient [CO2] and elevated temperature, or elevated [CO2] and elevated temperature. Within each chamber half of the seedlings were well watered and half received much less water (1/4 that of the well watered). Measurements of net photosynthesis (A(net)), stomatal conductance (g(s)), leaf water potential and leaf fluorescence were made in June and September, 2008. We observed a significant increase in A(net) in response to elevated [CO2] regardless of site or temperature treatment in June and September. An increase in air temperature of over 2 degrees C had no significant effect on A(net) at any of the sites in June or September despite over a 6 degrees C difference in mean annual temperature between the sites. Decreased water availability significantly reduced A(net) in all treatments at each site in June. The effects of elevated [CO2] and temperature on g(s) followed a similar trend. The temperature, [CO2] and water treatments did not significantly affect leaf water potential or chlorophyll fluorescence. Our findings suggest that predicted increases in [CO2] will significantly increase A(net), while predicted increases in air temperature will have little effect on A(net) across the native range of loblolly pine. Potential decreases in precipitation will likely cause a significant reduction in A(net), though this may be mitigated by increased [CO2].
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