Large Greenhouse Gas Emissions from a Temperate Peatland Pasture

• Published in: Ecosystems (New York) 2011-03, Vol.14 (2), p.311-325
• Main Authors: Teh, Yit Arn, Silver, Whendee L, Sonnentag, Oliver, Detto, Matteo, Kelly, Maggi, Baldocchi, Dennis D
• Format: Article
• Language: English
• Subjects: administrative management; agricultural conversion; Agricultural ecology; Agricultural ecosystems; Agriculture; Air pollution; Air quality management; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomedical and Life Sciences; Carbon dioxide; Climate change; Climatology. Bioclimatology. Climate change; Covariance; Ditches; Drainage; Drainage ditches; drained temperate peatland; Earth, ocean, space; Ecology; Ecosystems; Emissions; Environmental Management; Exact sciences and technology; External geophysics; Farm buildings; Fluctuations; Forest soils; Fundamental and applied biological sciences. Psychology; General aspects; Geoecology/Natural Processes; Global warming; Global warming potential; Greenhouse gases; Heterogeneity; Hydrology/Water Resources; Landforms; Life Sciences; Meteorology; Methane; Nitrogen oxide; Nitrous oxide; Pasture; Pastures; Peat; Peat soils; Peat-bogs; Peatlands; Plant Sciences; Rangelands; Sacramento-San Joaquin Delta; Soil ecology; Soil moisture; Soil respiration; Soil water; Synecology; Tropical forests; Zoology
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-011-9411-4

Agricultural drainage is thought to alter greenhouse gas emissions from temperate peatlands, with CH₄ emissions reduced in favor of greater CO₂ losses. Attention has largely focussed on C trace gases, and less is known about the impacts of agricultural conversion on N₂O or global warming potential. We report greenhouse gas fluxes (CH₄, CO₂, N₂O) from a drained peatland in the Sacramento-San Joaquin River Delta, California, USA currently managed as a rangeland (that is, pasture). This ecosystem was a net source of CH₄ (25.8 ± 1.4 mg CH₄-C m⁻² d⁻¹) and N₂O (6.4 ± 0.4 mg N₂O-N m⁻² d⁻¹). Methane fluxes were comparable to those of other managed temperate peatlands, whereas N₂O fluxes were very high; equivalent to fluxes from heavily fertilized agroecosystems and tropical forests. Ecosystem scale CH₄ fluxes were driven by “hotspots” (drainage ditches) that accounted for less than 5% of the land area but more than 84% of emissions. Methane fluxes were unresponsive to seasonal fluctuations in climate and showed minimal temporal variability. Nitrous oxide fluxes were more homogeneously distributed throughout the landscape and responded to fluctuations in environmental variables, especially soil moisture. Elevated CH₄ and N₂O fluxes contributed to a high overall ecosystem global warming potential (531 g CO₂-C equivalents m⁻² y⁻¹), with non-CO₂ trace gas fluxes offsetting the atmospheric “cooling” effects of photoassimilation. These data suggest that managed Delta peatlands are potentially large regional sources of greenhouse gases, with spatial heterogeneity in soil moisture modulating the relative importance of each gas for ecosystem global warming potential.