Premium
18 O composition of CO 2 and H 2 O ecosystem pools and fluxes in a tallgrass prairie: Simulations and comparisons to measurements
Author(s) -
Riley William J.,
Still Christopher J.,
Helliker Brent R.,
RibasCarbo Miguel,
Berry Joseph A.
Publication year - 2003
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.1365-2486.2003.00680.x
Subject(s) - ecosystem , environmental science , growing season , atmospheric sciences , canopy , daytime , soil water , flux (metallurgy) , eddy covariance , stable isotope ratio , environmental chemistry , hydrology (agriculture) , ecology , soil science , chemistry , geology , biology , geotechnical engineering , physics , organic chemistry , quantum mechanics
In this paper we describe measurements and modeling of 18 O in CO 2 and H 2 O pools and fluxes at a tallgrass prairie site in Oklahoma. We present measurements of the δ 18 O value of leaf water, depth‐resolved soil water, atmospheric water vapor, and Keeling plot δ 18 O intercepts for net soil‐surface CO 2 and ecosystem CO 2 and H 2 O fluxes during three periods of the 2000 growing season. Daytime discrimination against C 18 OO, as calculated from measured above‐canopy CO 2 and δ 18 O gradients, is also presented. To interpret the isotope measurements, we applied an integrated land‐surface and isotope model (ISOLSM) that simulates ecosystem H 2 18 O and C 18 OO stocks and fluxes. ISOLSM accurately predicted the measured isotopic composition of ecosystem water pools and the δ 18 O value of net ecosystem CO 2 and H 2 O fluxes. Simulations indicate that incomplete equilibration between CO 2 and H 2 O within C 4 plant leaves can have a substantial impact on ecosystem discrimination. Diurnal variations in the δ 18 O value of above‐canopy vapor had a small impact on the predicted δ 18 O value of ecosystem water pools, although sustained differences had a large impact. Diurnal variations in the δ 18 O value of above‐canopy CO 2 substantially affected the predicted ecosystem discrimination. Leaves dominate the ecosystem 18 O‐isoflux in CO 2 during the growing season, while the soil contribution is relatively small and less variable. However, interpreting daytime measurements of ecosystem C 18 OO fluxes requires accurate predictions of both soil and leaf 18 O‐isofluxes.