Title: Does the Response of Leaf Photosynthetic Productivity to Rising Atmospheric Temperature and CO2 Scale Up to the Canopy? Authors
Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2010
Publication Date: June 1, 2010
Citation: Rosenthal, D.M., Siebers, M.B., Bernacchi, C.J., Long, S.P., Ort, D.R. 2010. Does the Response of Leaf Photosynthetic Productivity to Rising Atmospheric Temperature and CO2 Scale Up to the Canopy? American Society of Plant Biologists Annual Meeting. Available: http://abstracts.aspb.org/pb2010/public/P15/P15021.html. Technical Abstract: Theory predicts that interacting increases in temperature and CO2 will synergistically enhance leaf photosynthesis but how this interaction will scale to affect canopy and ecosystem productivity is less clear. Numerous factors contribute to this uncertainty including higher canopy temperatures from lower stomatal conductance (gs) driven by elevated [CO2] and the response and possible acclimation of respiration to increasing temperature and [CO2]. The goal of this research was to quantify the effect of indirect temperature increases on canopy productivity and to estimate the response of soybean canopy assimilation and productivity to simulated increases in temperature and [CO2]. Leaf microclimate was estimated from leaf area index and meteorological data using an energy balance approach and input into a canopy model to estimate microclimate for each leaf layer at 10 min intervals. Photosynthesis for each leaf layer was calculated and canopy assimilation was estimated by summing all leaf layers. Model output was highly correlated with biomass collected for each of the four years (r2 ranged from 0.88 to 0.97). Consistent with theory the stimulatory effect of CO2 increased with maximum daytime temperature. Indirect temperature elevation caused a small (0.5 to 2%) but in some years significant decrease in canopy assimilation. Moreover, on average in years modeled here, we found that incremental increases in air temperature (+ 1, 2 or 3C) would reduce canopy assimilation by between 3% to 20% in ambient and 2% to 13 % in elevated CO2, also consistent with the notion that elevating CO2 enhances the photosynthetic optimum.