China's grazed temperate grasslands are a net source of atmospheric methane |
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| Authors: | Zhi-Ping Wang Yang Song Jay Gulledge Qiang Yu Hong-Sheng Liu Xing-Guo Han |
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| Institution: | 1. Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, 1, Sec. 3, Zhongxiao E. Rd., Taipei 106, Taiwan;2. Birck Nanotechnology Center and School of Industrial Engineering, Purdue University, West Lafayette, IN 47906, USA;1. Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan, ROC;2. Department of Electrophysics, National Chiao Tung University, Hsinchu, 30013, Taiwan, ROC;3. Center For Nanotechnology, Material Science, and Microsystem, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan, ROC;1. Department of control technology and instrument, Lanzhou Jiaotong University, Lanzhou 730070, PR China;2. School of Electronic and Information Engineering, Lanzhou Jiaotong University, Lanzhou 730070, PR China;3. Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011, USA |
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| Abstract: | A budget for the methane (CH4) cycle in the Xilin River basin of Inner Mongolia is presented. The annual CH4 budget in this region depends primarily on the sum of atmospheric CH4 uptake by upland soils, emission from small wetlands, and emission from grazing ruminants (sheep, goats, and cattle). Flux rates for these processes were averaged over multiple years with differing summer rainfall. Although uplands constitute the vast majority of land area, they consume much less CH4 per unit area than is emitted by wetlands and ruminants. Atmospheric CH4 uptake by upland soils was ?3.3 and ?4.8 kg CH4 ha?1 y?1 in grazed and ungrazed areas, respectively. Average CH4 emission was 791.0 kg CH4 ha?1 y?1 from wetlands and 8.6 kg CH4 ha?1 y?1 from ruminants. The basin area-weighted average of all three processes was 6.8 kg CH4 ha?1 y?1, indicating that ruminant production has converted this basin to a net source of atmospheric CH4. The total CH4 emission from the Xilin River basin was 7.29 Gg CH4 y?1. The current grazing intensity is about eightfold higher than that which would result in a net zero CH4 flux. Since grazing intensity has increased throughout western China, it is likely that ruminant production has converted China's grazed temperate grasslands to a net source of atmospheric CH4 overall. |
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