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How do elevated CO 2 and O 3 affect the interception and utilization of radiation by a soybean canopy?
Author(s) -
DERMODY ORLA,
LONG STEPHEN P.,
McCONNAUGHAY KELLY,
DeLUCIA EVAN H.
Publication year - 2008
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2007.01502.x
Subject(s) - interception , canopy , carbon dioxide , biomass (ecology) , photosynthesis , productivity , leaf area index , chemistry , ecosystem , primary production , agronomy , growing season , environmental science , horticulture , botany , biology , ecology , macroeconomics , organic chemistry , economics
Net productivity of vegetation is determined by the product of the efficiencies with which it intercepts light ( ɛ i ) and converts that intercepted energy into biomass ( ɛ c ). Elevated carbon dioxide (CO 2 ) increases photosynthesis and leaf area index (LAI) of soybeans and thus may increase ɛ i and ɛ c ; elevated O 3 may have the opposite effect. Knowing if elevated CO 2 and O 3 differentially affect physiological more than structural components of the ecosystem may reveal how these elements of global change will ultimately alter productivity. The effects of elevated CO 2 and O 3 on an intact soybean ecosystem were examined with Soybean Free Air Concentration Enrichment (SoyFACE) technology where large field plots (20‐m diameter) were exposed to elevated CO 2 (∼550 μmol mol −1 ) and elevated O 3 (1.2 × ambient) in a factorial design. Aboveground biomass, LAI and light interception were measured during the growing seasons of 2002, 2003 and 2004 to calculate ɛ i and ɛ c . A 15% increase in yield (averaged over 3 years) under elevated CO 2 was caused primarily by a 12% stimulation in ɛ c , as ɛ i increased by only 3%. Though accelerated canopy senescence under elevated O 3 caused a 3% decrease in ɛ i , the primary effect of O 3 on biomass was through an 11% reduction in ɛ c . When CO 2 and O 3 were elevated in combination, CO 2 partially reduced the negative effects of elevated O 3 . Knowing that changes in productivity in elevated CO 2 and O 3 were influenced strongly by the efficiency of conversion of light energy into energy in plant biomass will aid in optimizing soybean yields in the future. Future modeling efforts that rely on ɛ c for calculating regional and global plant productivity will need to accommodate the effects of global change on this important ecosystem attribute.