Microbially mediated CH₄ consumption and N₂O emission is affected by elevated CO₂, soil water content, and composition of semi-arid grassland species
2010
Dijkstra, Feike A. | Morgan, Jack A. | LeCain, Daniel R. | Follett, Ronald F.
Elevated CO₂ affects plant productivity, but also water availability and plant species composition in semi-arid grasslands, thereby potentially causing complex effects on CH₄ consumption and N₂O emission. We studied the effects of atmospheric CO₂ concentration (400 vs 780 μL L⁻¹), water content (15 vs 20% gravimetric soil moisture), and composition of semi-arid grassland species (perennial grasses Bouteloua gracilis, Hesperostipa comata, and Pascopyrum smithii; sub-shrub Artemisia frigida; invasive forb Linaria dalmatica grown in monoculture and all five species together) on CH₄ consumption and N₂O emission in a full factorial greenhouse experiment. We used a unique method where we measured microbial effects on CH₄ consumption and N₂O emission in isolation from effects of gas diffusivity. Microbially mediated CH₄ consumption was significantly higher under elevated CO₂ (by 20%), but was not affected by soil water content or plant species composition. Microbially mediated N₂O emission was not significantly affected by elevated CO₂, but was significantly higher with high water content (by 67%) and differed significantly among species. Treatment effects on CH₄ consumption and N₂O emission often could not be explained simply by differences in soil moisture, suggesting that treatment-induced changes in other soil and microbial properties played a role in causing these effects.
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