Effects of soil warming, rainfall reduction and water table level on CH4 emissions from the Zoige peatland in China

Abstract The Zoige Plateau features approximately 4605 km 2 of peatlands, making it the largest peatland area in China. This area stored 2.9 Pg peat during the Holocene, yet little is known about methane (CH 4 ) emissions from this region. In this study, we designed a mesocosm experiment to measure CH 4 emissions during the growing seasons of 2009–2010 under different scenarios involving soil warming, 20% reduction in rainfall and changes in the water table level. Our results showed that CH 4 emissions were higher in 2009 than in 2010 under all experimental conditions. Average soil temperature was approximately 11.4 °C under control conditions, 13.3 °C under soil warming conditions, 12.7 °C with 20% rainfall reduction, and 13.4 °C under combined conditions of soil warming and 20% reduced rainfall. For the single factor effect, soil warming treatment increased average CH 4 emissions by 28%, while rainfall reduction increased it by 30%; however, neither increase was statistically significant. In contrast, the combined effect of soil warming and rainfall reduction significantly decreased CH 4 emissions by an average of 58%. Extending this result across the entire peatland area in the Zoige Plateau translates into approximately 5.3 Gg of CH 4 uptake per year. These results suggest that a drier and warmer Zoige Plateau will become a CH 4 sink. Our study also found a positive relationship between water table level and CH 4 emissions. Average CH 4 emissions decreased by approximately 82% as water drawdown varied from 0 (0.94 mg CH 4  m −2  h −1 ) to −50 cm (0.17 mg CH 4  m −2  h −1 ). When we simultaneously examined the effect of all three factors of water table level, soil warming and rainfall reduction on CH 4 emissions, we found soil warming and rainfall effect on CH 4 emissions varied with water table levels. However, none of the three factors significantly affected CH 4 emissions at a water table depth of 30 cm below peat depth.