Elevated CO₂ stimulates marsh elevation gain, counterbalancing sea-level rise

Tidal wetlands experiencing increased rates of sea-level rise (SLR) must increase rates of soil elevation gain to avoid permanent conversion to open water. The maximal rate of SLR that these ecosystems can tolerate depends partly on mineral sediment deposition, but the accumulation of organic matter...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2009-04, Vol.106 (15), p.6182-6186
Main Authors: Langley, J. Adam, McKee, Karen L, Cahoon, Donald R, Cherry, Julia A, Megonigal, J. Patrick
Format: Article
Language:English
Subjects:
altitude
Atmospherics
Biological Sciences
Biomass
Carbon dioxide
Carbon Dioxide - chemistry
dry matter accumulation
elevated atmospheric gases
flooded conditions
Greenhouse Effect
Marshes
Nitrogen
plant growth
Productivity
root growth
roots
salinity
Seawater
Sedimentary soils
Soil salinity
Topographical elevation
wetland plants
Wetland soils
Wetlands
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Summary:Tidal wetlands experiencing increased rates of sea-level rise (SLR) must increase rates of soil elevation gain to avoid permanent conversion to open water. The maximal rate of SLR that these ecosystems can tolerate depends partly on mineral sediment deposition, but the accumulation of organic matter is equally important for many wetlands. Plant productivity drives organic matter dynamics and is sensitive to global change factors, such as rising atmospheric CO₂ concentration. It remains unknown how global change will influence organic mechanisms that determine future tidal wetland viability. Here, we present experimental evidence that plant response to elevated atmospheric [CO₂] stimulates biogenic mechanisms of elevation gain in a brackish marsh. Elevated CO₂ (ambient + 340 ppm) accelerated soil elevation gain by 3.9 mm yr⁻¹ in this 2-year field study, an effect mediated by stimulation of below-ground plant productivity. Further, a companion greenhouse experiment revealed that the CO₂ effect was enhanced under salinity and flooding conditions likely to accompany future SLR. Our results indicate that by stimulating biogenic contributions to marsh elevation, increases in the greenhouse gas, CO₂, may paradoxically aid some coastal wetlands in counterbalancing rising seas.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0807695106