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Effect of Elevated Atmospheric Carbon Dioxide and Open‐top Chambers on Transpiration in a Tallgrass Prairie
Author(s) -
Bremer Dale J.,
Ham Jay M.,
Owensby Clenton E.
Publication year - 1996
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1996.00472425002500040008x
Subject(s) - transpiration , stomatal conductance , carbon dioxide , environmental science , evapotranspiration , water use efficiency , agronomy , eddy covariance , chemistry , horticulture , ecosystem , photosynthesis , ecology , biology , irrigation , biochemistry , organic chemistry
Abstract Increasing concentrations of atmospheric carbon dioxide (CO 2 ) may influence plant‐water relations in natural and agricultural ecosystems. A tallgrass prairie near Manhattan, KS, was exposed to elevated atmospheric CO 2 using open‐top chambers (OTCs). Heat balance sap flow gauges were used to measure transpiration in ironweed [ Vernonia baldwini var. interior (Small) Schub.], a C 3 forb, and on individual grass culms of big bluestem ( Andropogon gerardii Vitman) and indiangrass [ Sorghastrum nutans (L.) Nash], both C 4 grasses, in each of three treatments: (i) CE (chamber enriched, 2× ambient CO 2 ); (ii) CA (chamber ambient, no CO 2 enrichment); and (iii) NC (no chamber, no CO 2 enrichment). Sap flow data were coupled with measurements of stomatal conductance, plant/canopy resistance, and whole‐chamber evapotranspiration (ET) to determine the effect of elevated CO 2 on water use at different scales. Because of frequent rainfall during the study, all data were collected under well‐watered conditions. Comparisons of CE and CA showed that sap flow was reduced by 33% in ironweed, 18% in big bluestem, and 22% in indiangrass under CO 2 enrichment. Whole‐chamber ET was reduced by 23 to 27% under CO 2 enrichment. Comparisons of CA and NC showed that the environmental effect of the OTCs caused a 21 to 24% reduction in transpiration. Stomatal conductance decreased from 7.9 to 3.6 mm s −1 in big bluestem and from 5.3 to 3.2 mm s −1 in indiangrass under CO 2 enrichment. Soil water was consistently highest under elevated CO 2 , reflecting the large reductions in transpiration. During sap flow measurements, whole‐plant stomatal resistance to water vapor flux in big bluestem increased from 103 to 194 s m −1 under elevated CO 2 .