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ELEVATED ATMOSPHERIC CO 2 INCREASES WATER AVAILABILITY IN A WATER‐LIMITED GRASSLAND ECOSYSTEM 1
Author(s) -
Fredeen Arthur L.,
Randerson James T.,
Holbrook N. Michele,
Field Christopher B.
Publication year - 1997
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.1997.tb04122.x
Subject(s) - evapotranspiration , environmental science , soil water , transpiration , ecosystem , water content , hydrology (agriculture) , moisture , grassland , agronomy , soil science , ecology , geology , chemistry , photosynthesis , biology , biochemistry , geotechnical engineering , organic chemistry
Californian annual grassland on sandstone (moderately fertile) and serpentine (very infertile) soils at the Jasper Ridge Biological Preserve, Stanford, California, were exposed to ambient or elevated (ambient + 36 Pa CO 2 ) atmospheric CO 2 in open‐top chambers since December 1991. We measured ecosystem evapotranspiration with open gas‐exchange systems, and soil moisture with time‐domain reflectometry (TDR) over 0–15 cm (serpentine) and 0–30 cm (sandstone) depths, at times of peak above ground physiological activity. Evapotranspiration decreased by 12 to 63 percent under elevated CO 2 in three consecutive years in the sandstone ecosystem (p = 0.053, p = 0.162, p = 0.082 in 1992, 1993, and 1994, respectively). In correspondence with decreased evapotranspiration, late‐season soil moisture reserves in the sandstone were extended temporally by 10 ± 3 days in 1993 and by 28 ± 11 days in 1994. The effect of elevated CO 2 on soil moisture was greater in the drier spring of 1994 (419 mm annual rainfall) than in 1993 (905 mm annual rainfall). In the serpentine ecosystem, evapotranspiration and soil moisture reserves were not clearly affected by elevated CO 2 . Soil water may be conserved in drought‐affected ecosystems exposed to elevated CO 2 , but the amount of conservation appears to depend on the relative importance of transpiration and soil evaporation in controlling water flux.