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Water vapour fluxes and their impact under elevated CO 2 in a C4‐tallgrass prairie
Author(s) -
OWENSBY CLENTON,
HAM JAY,
KNAPP ALAN,
BREMER DALE,
AUEN LISA
Publication year - 1997
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 - 10.1046/j.1365-2486.1997.00084.x
Subject(s) - stomatal conductance , canopy , evapotranspiration , xylem , environmental science , transpiration , vapour pressure deficit , canopy conductance , water flow , agronomy , photosynthesis , botany , biology , ecology , soil science
We measured leaf‐level stomatal conductance, xylem pressure potential, and stomate number and size as well as whole plant sap flow and canopy‐level water vapour fluxes in a C4‐tallgrass prairie in Kansas exposed to ambient and elevated CO 2 . Stomatal conductance was reduced by as much as 50% under elevated CO 2 compared to ambient. In addition, there was a reduction in stomate number of the C4 grass, Andropogon gerardii Vitman, and the C3 dicot herb, Salvia pitcheri Torr., under elevated CO 2 compared to ambient. The result was an improved water status for plants exposed to elevated CO 2 which was reflected by a less negative xylem pressure potential compared to plants exposed to ambient CO 2 . Sap flow rates were 20 to 30% lower for plants exposed to elevated CO 2 than for those exposed to ambient CO 2 . At the canopy level, evapotranspiration was reduced by 22% under elevated CO 2 . The reduced water use by the plant canopy under elevated CO 2 extended the photosynthetically‐active period when water became limiting in the ecosystem. The result was an increased above‐ and belowground biomass production in years when water stress was frequent.