|Ainsworth, Elizabeth - Lisa|
|Leakey, Andrew d b|
Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 3/19/2009
Publication Date: 7/18/2009
Citation: Gray, S.B., McGrath, J.M., Dermody, O., Ainsworth, E.A., Leakey, A. 2009. Temperature and Precipitation Interactions Eliminate Benefits of Free-air CO2 Enrichment to Soybean Water Relations in Two Out of Five Years. Plant Biology Annual Meeting. Plant Biology 2009, July 18-22, 2009, Honolulu, HI. Interpretive Summary:
Technical Abstract: A key assumption in projections of future food supply and ecosystem function is that elevated [CO2], through reduced stomatal conductance (gs), results in lower water use, conservation of soil moisture and amelioration of losses in productivity due to drought stress. A 5-year dataset from the soybean Free Air CO2 Enrichment (soyFACE) facility in the Midwest U.S. demonstrates that soybean did not benefit from this mechanism in 2 out of 5 years. Interannual variability in the effects of elevated [CO2] (550 ppm) on photosynthesis (A) and leaf area index (LAI) drives this variation in soil moisture and this interannual variability was a function of precipitation and temperature. Soil moisture in elevated [CO2] was greater in 2004 (up to 60%), 2005 (up to 20%), and 2007(up to 25%). On average, this was associated with a ~27% reduction in midday gs, a ~21% stimulation in midday A, and a ~5% stimulation in peak LAI in elevated [CO2]. In 2006 and 2008 however, elevated [CO2] did not significantly affect soil moisture, despite reducing gs~25%. In 2006, high rainfall throughout the season resulted in soil moisture at or near field capacity, eliminating any benefits of decreased gs in elevated [CO2]. In 2008, an unusually wet spring delayed planting by one month, resulting in soybeans developing under higher temperatures than usual. This late planting and higher temperatures amplified the stimulation of LAI by elevated [CO2], offsetting reductions in gs and eliminating any improvement in soil moisture at elevated [CO2]. Consequently, during a drought in August, there was no stimulation of A at elevated [CO2]. This suggests that increasing temperature and drought will diminish the benefits of elevated [CO2] to plant productivity in the future more than currently predicted.