C3–C4 composition and prior carbon dioxide treatment regulate the response of grassland carbon and water fluxes to carbon dioxide

Authors

H. W. Polley, USDA-ARS Grassland, Soil & Water Research LaboratoryFollow
W. A. Dugas, Blackland Research and Extension Center
P. C. Mielnick, Blackland Research and Extension Center
H. B. Johnson, USDA-ARS Grassland, Soil & Water Research Laboratory

Date of this Version

2007

Comments

Published in Functional Ecology (2007) 21, 11–18.

Abstract

During May, July and October 2000, we measured the effects of temporarily increasing or decreasing CO₂ concentration by 150–200 μmol mol⁻¹ on daytime net ecosystem CO₂ exchange (NEE) and water flux (evapotranspiration, ET) of C₃–C₄ grassland in central Texas, USA that had been exposed for three growing seasons to a CO₂ gradient from 200 to 560 μmol mol⁻¹. Grassland grown at subambient CO₂ (< 365 μmol mol⁻¹) was exposed for 2 days to an elevated CO₂ gradient (> 365 μmol mol⁻¹). Grassland grown at elevated CO₂ was exposed for 2 days to a subambient gradient. Our objective was to determine whether growth CO₂ affected the amount by which grassland NEE and ET responded to CO₂ switching (sensitivity to CO₂).