1. 18O composition of CO2 and H2O ecosystem pools and fluxes in a tallgrass prairie: Simulations and comparisons to measurements.
- Author
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Riley, William J., Still, Christopher J., Helliker, Brent R., Ribas-Carbo, Miguel, and Berry, Joseph A.
- Subjects
BIOTIC communities ,ECOLOGY ,PRAIRIES - Abstract
In this paper we describe measurements and modeling of
18 O in CO2 and H2 O pools and fluxes at a tallgrass prairie site in Oklahoma. We present measurements of the δ18 O value of leaf water, depth-resolved soil water, atmospheric water vapor, and Keeling plot δ18 O intercepts for net soil-surface CO2 and ecosystem CO2 and H2 O fluxes during three periods of the 2000 growing season. Daytime discrimination against C18 OO, as calculated from measured above-canopy CO2 and δ18 O gradients, is also presented. To interpret the isotope measurements, we applied an integrated land-surface and isotope model (ISOLSM) that simulates ecosystem H2 18 O and C18 OO stocks and fluxes. ISOLSM accurately predicted the measured isotopic composition of ecosystem water pools and the δ18 O value of net ecosystem CO2 and H2 O fluxes. Simulations indicate that incomplete equilibration between CO2 and H2 O within C4 plant leaves can have a substantial impact on ecosystem discrimination. Diurnal variations in the δ18 O value of above-canopy vapor had a small impact on the predicted δ18 O value of ecosystem water pools, although sustained differences had a large impact. Diurnal variations in the δ18 O value of above-canopy CO2 substantially affected the predicted ecosystem discrimination. Leaves dominate the ecosystem18 O-isoflux in CO2 during the growing season, while the soil contribution is relatively small and less variable. However, interpreting daytime measurements of ecosystem C18 OO fluxes requires accurate predictions of both soil and leaf18 O-isofluxes. [ABSTRACT FROM AUTHOR]- Published
- 2003
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