Winter-grazing reduces methane uptake by soils of a typical semi-arid steppe in Inner Mongolia,China |
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| Affiliation: | 1. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP-CAS), Beijing 100029, PR China;2. Institute for Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Karlsruhe Research Centre, Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany;3. Institute of Botany, Chinese Academy of Sciences (IB-CAS), Beijing 100093, PR China;4. Institute for Plant Nutrition and Soil Science, Christian Albrechts University Kiel, Ohlshausenstrasse 40, 24118 Kiel, Germany;5. Graduate University of the Chinese Academy of Sciences, Beijing 100039, PR China;1. Institute of Grassland Science, College of Animal Science and Technology, China Agricultural University, West Road 2 Yuan Ming Yuan, Beijing, MD 100193, China;2. College of Ecology and Environment, Inner Mongolia Agricultural University, Zhaowuda Road 306, Huhhot, MD 010019, China;3. College of Resources and Environmental Sciences, China Agricultural University, West Road 2 Yuan Ming Yuan, Beijing, MD 100193, China;4. Anhui Agricultural University, Hefei, MD 230036, China;1. Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB, Wageningen, the Netherlands;2. Leibniz Universität Hannover, Institute of Microbiology, Herrenhäuserstr. 2, 30140, Hannover, Germany;3. Department of Biology, Kunsan National University, Gunsan, Republic of Korea;4. Department of Terrestrial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB, Wageningen, the Netherlands;5. Laboratory of Nematology, Wageningen University, PO Box 8123, 6700 ES, Wageningen, the Netherlands;1. AgResearch, Invermay, Private Bag 50034, Mosgiel 9053, New Zealand;2. AgResearch, Ruakura, Private Bag 3123, Hamilton 3240, New Zealand;1. College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;2. Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China;3. School of Medical and Applied Sciences, Central Queensland University, Bundaberg, QLD 4670, Australia;4. Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA;1. College of Resource and Environmental Science, China Agricultural University, 100193 Beijing, China;2. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029 Beijing, China;3. Department of Soil Science of Temperate Ecosystems, University of Göttingen, 37077 Göttingen, Germany;4. Department of Agropedology, University of Göttingen, 37077 Göttingen, Germany |
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| Abstract: | 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) (p<0.01) was found. Total CH4 uptake during the growing seasons (May–September) 2004 and 2005 at WG01 and UG99 was quantified as 1.15 and 2.15 kg C ha−1, respectively. Annual rates of CH4 uptake were approximately 1.91 (WG01) and 3.58 kg C ha−1 (UG99), respectively. These results indicate that winter-grazing of steppe significantly reduced atmospheric CH4 uptake by ca. 47%. The winter-grazing practice may have inhibited CH4 uptake by (a) increasing the likelihood of physiological water stress for CH4-consuming bacteria during dry periods, (b) decreasing gas diffusion into the soil and, (c) reducing the populations of CH4 oxidizing bacteria. These three mechanisms could have collectively or independently facilitated the observed inhibitory effects. Our results suggest that grazing exerts a considerable negative impact on CH4 uptake in semi-arid steppes at regional scales. Notwithstanding, further studies involving year-round, intensive measurements of CH4 uptake are needed. |
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