title: Stimulated N2O flux from intact grassland monoliths after two growing seasons under elevated atmospheric CO2.
abstract: Long-term exposure of native vegetation to elevated atmospheric CO2concentrations is expected to increase C inputs to the soil and, in ecosystems with seasonally dry periods, to increase soil moisture. We tested the hypothesis that these indirect effects of elevated CO2(600 μl l-1vs 350 μl l-1) would improve conditions for microbial activity and stimulate emissions of nitrous oxide (N2O), a very potent and long-lived greenhouse gas. After two growing seasons, the mean N2O efflux from monoliths of calcareous grassland maintained at elevated CO2was twice as high as that measured from monoliths maintained at current ambient CO2(70 ± 9 vs 37 ± 4 μg N2O m-2h-1in October, 27 ± 5 vs 13 ± 3 μg N2O m-2h-1in November after aboveground harvest). The higher N2O emission rates at elevated CO2were associated with increases in soil moisture, soil heterotrophic respiration, and plant biomass production, but appear to be mainly attributable to higher soil moisture. Our results suggest that rising atmospheric CO2may contribute more to the total greenhouse effect than is currently estimated because of its plant-mediated effects on soil processes which may ultimately lead to increased N2O emissions from native grasslands.
authors.affiliation: Department of Integrative Biology, University of Basel, Schönbeinstrasse 6, CH-4056 Basel, Switzerland e-mail: arnone@ubaclu.unibas.ch, Fax: +41 61 267-3504, , , , , , CH.
authors.forename: John A
authors.initials: JA
authors.lastname: Arnone Iii
authors.affiliation: Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, USA, , , , , , US.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Bohlen
keywords: Grassland microcosms; Key words Elevated carbon dioxide; Nitrous oxide flux; Soil microorganisms; Soil moisture