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Title: CO2, CH4, and N2O fluxes affected by elevated CO2, water availability and species composition: Results from a greenhouse study

Author
item Dijkstra, Feike
item Morgan, Jack
item Lecain, Daniel
item Follett, Ronald

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2008
Publication Date: 10/5/2008
Citation: Dijkstra, F.A., Morgan, J.A., Lecain, D.R., Follett, R.F. 2008. CO2, CH4, and N2O fluxes affected by elevated CO2, water availability and species composition: results from a greenhouse study. In: Joint annual meeting of the Geological Society of America, American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, and Gulf Coast Asso. of Geological Studiesk. October 2008. CDROM.

Interpretive Summary:

Technical Abstract: Rising atmospheric CO2 concentration alters C and N cycling in terrestrial ecosystems. These changes in C and N cycling are to a large extent caused by CO2 effects on water availability and plant species composition, but their separate and interactive effects have rarely been tested simultaneously. We studied the effects of atmospheric CO2 concentration (400 vs 800 ppm), water availability (15 vs 20% soil moisture), and species composition (the perennial grasses Bouteloua gracilis, Pascopyrum smithii, and Stipa comata; the sub-shrub Artemisia frigida; and the forb Linaria dalmatica grown in monoculture and all five species together) on CO2, CH4, and N2O fluxes in a full factorial designed greenhouse experiment. Plants were grown in PVC pots capped at the bottom. We also included pots without plants. On days 48, 69, and 83 after planting, we placed chambers on top of the pots, circulated air through the pot-chamber system, and measured changes in gas concentrations during a two-hour period. The CO2 flux significantly increased with elevated CO2 (by 11%), with increased water availability (17%), and differed significantly among species. Methane consumption was significantly higher under elevated CO2 (19%), particularly with low water availability (significant CO2*water availability interaction). Methane consumption did not differ among species, but CH4 consumption was significantly higher in planted pots than in the pots without plants (on average 98% higher). The N2O flux was not significantly affected by elevated CO2, but was significantly higher with high water availability (67%) and differed significantly among species. The N2O flux was particularly high in pots grown with S. comata in combination with high water availability (significant species*water availability interaction). Our results suggest that atmospheric CO2 directly alters greenhouse gas fluxes, but that the magnitude and direction of changes in these fluxes strongly depend on how atmospheric CO2 affects water availability and species composition. [GRACEnet Publication]