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

• Published in: Atmospheric environment (1994) Vol. 41; no. 28; pp. 5948 - 5958
• Main Authors: Liu, Chunyan, Holst, Jirko, Brüggemann, Nicolas, Butterbach-Bahl, Klaus, Yao, Zhisheng, Yue, Jin, Han, Shenghui, Han, Xingguo, Krümmelbein, Julia, Horn, Rainer, Zheng, Xunhua
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-09-2007; Elsevier Science
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Chemical composition and interactions. Ionic interactions and processes; Climatology. Bioclimatology. Climate change; Earth, ocean, space; Exact sciences and technology; External geophysics; Fundamental and applied biological sciences. Psychology; Gas diffusion; Grazing; Meteorology; Methane uptake; Moisture; Steppe; Synecology; Terrestrial ecosystems; Far East; China; Inner Mongolia China; China, People's Rep., Inner Mongolia; China, People's Rep; Methane uptake; Grazing; Steppe; Gas diffusion; Moisture; time variations; air-ground interface; Environmental factor; greenhouse gas; Winter; Air biosphere interaction; Gramineae; Semi arid zone; Plantae; Biogeochemical cycle; carbon cycle; Source sink relationship; steppes; Edaphic factor; Atmospheric chemistry; angiosperms; Asia; Monocotyledoneae; methane; Spermatophyta
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2007.03.017

Steppe ecosystems are regarded as an important sink of atmospheric methane (CH
4) and grazing is hypothesized to reduce CH
4 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 CH
4 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 CH
4 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 CH
4 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 CH
4 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 CH
4 uptake by ca. 47%. The winter-grazing practice may have inhibited CH
4 uptake by (a) increasing the likelihood of physiological water stress for CH
4-consuming bacteria during dry periods, (b) decreasing gas diffusion into the soil and, (c) reducing the populations of CH
4 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 CH
4 uptake in semi-arid steppes at regional scales. Notwithstanding, further studies involving year-round, intensive measurements of CH
4 uptake are needed.