Sillen, W.M.A., and Dieleman, W.I.J. (2012) Effects of elevated CO₂ and N fertilization on plant and soil carbon pools of managed grasslands: a meta-analysis. Biogeosciences, 9. pp. 2247-2258.

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Abstract

Elevated atmospheric CO₂ levels and increasing nitrogen deposition both stimulate plant production in terrestrial ecosystems. Moreover, nitrogen deposition could alleviate an increasing nitrogen limitation experienced by plants exposed to elevated CO₂ concentrations. However, an increased rate of C flux through the soil compartment as a consequence of elevated CO₂ concentrations has been suggested to limit C sequestration in terrestrial ecosystems, questioning the potential for terrestrial C uptake to mitigate the increasing atmospheric CO₂ concentrations. Our study used data from 69 published studies to investigate whether CO₂ elevation and/or nitrogen fertilization could induce an increased carbon storage in grasslands, and considered the influence of management practices involving biomass removal or irrigation on the elevated CO₂ effects. Our results confirmed a positive effect of elevated CO₂ levels and nitrogen fertilization on plant growth, but revealed that N availability is essential for the increased C influx under elevated CO₂ to propagate into belowground C pools. However, moderate nutrient additions also promoted decomposition processes in elevated CO₂, reducing the potential for increased soil C storage. An important role in the soil carbon response to elevated CO₂ was attributed to the root response, since there was a lower potential for increases in soil C content when root biomass was more responsive to CO₂ elevation. Future elevated CO₂ concentrations and increasing N deposition might thus increase C storage in plant biomass, but the potential for increased soil C storage is limited.

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