Methane emissions from sheep pasture, measured with an open-path eddy covariance system

Dengel, Sigrid; Levy, Peter E. ORCID:; Grace, John; Jones, Stephanie K.; Skiba, Ute M. ORCID: 2011 Methane emissions from sheep pasture, measured with an open-path eddy covariance system. Global Change Biology, 17 (12). 3524-3533.

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Methane (CH(4)) is an important greenhouse gas, contributing 0.4-0.5 W m(-2) to global warming. Methane emissions originate from several sources, including wetlands, rice paddies, termites and ruminating animals. Previous measurements of methane flux from farm animals have been carried out on animals in unnatural conditions, in laboratory chambers or fitted with cumbersome masks. This study introduces eddy covariance measurements of CH(4), using the newly developed LI-COR LI-7700 open-path methane analyser, to measure field-scale fluxes from sheep grazing freely on pasture. Under summer conditions, fluxes of methane in the morning averaged 30 nmol m (2) s (1), whereas those in the afternoon were above 100 nmol m(-2) s(-1), and were roughly two orders of magnitude larger than the small methane emissions from the soil. Methane emissions showed no clear relationship with air temperature or photo-synthetically active radiation, but some diurnal pattern was apparent, probably linked to sheep grazing behaviour and metabolism. Over the measurement period (days 60-277, year 2010), cumulative methane fluxes were 0.34 mol CH(4) m(-2), equating to 134.3 g CO(2) equivalents m(-2). By comparison, a carbon dioxide (CO(2)) sink of 819 g CO(2) equivalents m(-2) was measured over the same period, but it is likely that much of this would be released back to the atmosphere during the winter or as off-site losses (through microbial and animal respiration). By dividing methane fluxes by the number of sheep in the field each day, we calculated CH(4) emissions per head of livestock as 7.4 kg CH(4) sheep(-1) yr(-1), close to the published IPCC emission factor of 8 kg CH(4) sheep(-1) yr(-1).

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 1 - Monitoring and Interpretation of Biogeochemical and Climate Changes > BGC - 1.1 - Monitor concentrations, fluxes, physico-chemical forms of current and emerging pollutants ...
UKCEH and CEH Sections/Science Areas: Billett (to November 2013)
ISSN: 1354-1013
Additional Keywords: agriculture, carbon sink, closed path, CO2 flux, global warming potential, grassland, grazing, grazing system, LI-7200, LI-7700
NORA Subject Terms: Agriculture and Soil Science
Ecology and Environment
Date made live: 21 Feb 2012 16:14 +0 (UTC)

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