Winter-grazing reduces methane uptake by soils of a typical semi-arid steppe in Inner Mongolia, China

Steppe ecosystems are regarded as an important sink of atmospheric methane (CH4) and grazing is hypothesized to reduce CH4 uptake. However, firm experimental evidence is required to prove this hypothesis. Using a fully automated, chamber-based measuring system, we conducted continuous high-frequency (at a 3-h interval) measurements of CH4 uptake in a Leymus chinensis steppe, which is a typical grassland ecosystem in Inner Mongolia, China. Two management regimes were investigated: ungrazed since 1999 (UG99) and winter-grazed since 2001 (WG01). Measurements were carried out continuously during the periods of June–September 2004, May–September 2005 and March–June 2006. During all of these periods, significantly lower mean CH4 uptake (±S.E.) at WG01 (28±0.7 μg C m−2 h−1) as compared to UG99 (56±1.0 μg C m−2 h−1) (