Influence of increasing temperature and nitrogen input on greenhouse gas emissions from a desert steppe soil in Inner Mongolia

Abstract

We investigated the effect of increasing soil temperature and nitrogen on greenhouse gas (GHG) emissions [carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O)] from a desert steppe soil in Inner Mongolia, China. Two temperature levels (heating versus no heating) and two nitrogen (N) fertilizer application levels (0 and 100 kg N ha⁻¹year⁻¹) were examined in a complete randomized design with six replications. The GHG surface fluxes and their concentrations in soil (0 to 50 cm) were collected bi-weekly from June 2006 to November 2007. Carbon dioxide and N₂O emissions were not affected by heating or N treatment, but compared with other seasons, CO₂ was higher in summer [average of 29.6 versus 8.6 mg carbon (C) m⁻²h⁻¹ over all other seasons] and N₂O was lower in winter (average of 2.6 versus 4.0 mg N m⁻²h⁻¹ over all other seasons). Desert steppe soil is a CH₄ sink with the highest rate of consumption occurring in summer. Heating decreased CH₄ consumption only in the summer. Increasing surface soil temperature by 1.3°C or applying 100 kg ha⁻¹year⁻¹ N fertilizer had no effect on the overall GHG emissions. Seasonal variability in GHG emission reflected changes in temperature and soil moisture content. At an average CH₄ consumption rate of 31.65 µg C m⁻²h⁻¹, the 30.73 million ha of desert steppe soil in Inner Mongolia can consume (sequestrate) about 85 × 10⁶kg CH₄-C, an offset equivalent to 711 × 10⁶kg CO₂-C emissions annually. Thus, desert steppe soil should be considered an important CH₄ sink and its potential in reducing GHG emission and mitigating climate change warrants further investigation.

Keywords:

• Desert steppe, increasing temperature, methane
• nitrogen fertilizer application, nitrous oxide.

Acknowledgments

The funding for this research was provided by the Agriculture and Agri-Food Canada (AAFC), the National Natural Science Foundation of China (No. 30860060, 30590382), “sustainable utilization for grassland resources” innovation team (NDTD2010-5) and the Science and Technology Supporting Program (No. 2008BAD95B03), P. R. China. The authors gratefully acknowledge the scholarship to the senior authors by China Scholarship Council, Ministry of Education, P. R. China and the technical support from Greg Travis, Pam Caffyn, Brett Hill and Clarence Gilbertson in gas and soil analysis at the AAFC Lethbridge Research Centre. Special thanks to Alata and Baoyin Hexige for their dedication in carrying out the fieldwork and students from Inner Mongolia Agricultural University in collection of field samples and laboratory analyzes, and Dr Jim Moyer, Chi Chang and Mark S. Goettel for helpful suggestions and comments for the revised manuscript.