Elevated Atmospheric CO sub(2) Does Not Conserve Soil Water in the Mojave Desert

• Published in: Ecology (Durham) Vol. 85; no. 1; pp. 93 - 99
• Main Authors: Nowak, R S, Zitzer, S F, Babcock, D, Smith-Longozo, V, Charlet, T N, Coleman, J S, Seemann, J R, Smith, S D
• Format: Journal Article
• Language: English
• Published: 01-01-2004
• ISSN: 0012-9658

Numerous studies, including those of desert plants, have shown reduced stomatal conductance under elevated atmospheric CO sub(2). As a consequence, soil water has been postulated to increase. Soil water was measured for >4 yr at the Nevada Desert Free Air CO sub(2) Enrichment (FACE) Facility to determine if elevated atmospheric CO sub(2) conserves soil water for a desert scrub community in the Mojave Desert. We measured soil water in the top 0.2 and 0.5 m of soil with time domain reflectometry and to 1.85 m with a neutron probe for the three treatments at Desert FACE: elevated CO sub(2) (550 mu mol/mol), blower control (ambient CO sub(2)), and non-ring treatments. The treatment main effect was not significant in any analyses of variance. Although the treatment x date interaction was significant for soil water in the top 0.5 m of soil, the expected greater soil water for elevated CO sub(2) vs. ambient CO sub(2) only occurred on one sampling date. In contrast, soil water for that same depth was significantly lower under elevated CO sub(2) on six dates. Thus, we infer that increased water use from increased primary productivity (and therefore leaf area) under elevated CO sub(2) offset the decreased water use from reduced stomatal conductance, and hence soil water was not conserved under elevated CO sub(2) in the Mojave Desert, unlike other ecosystems.