Short-term response of soil CH4 flux to simulated precipitation in a winter wheat field on the Loess Plateau, Northwest China.

To understand the short-term response of soil CH₄ flux to different precipitation events in a winter wheat field on the Loess Plateau, we conducted precipitation simulation experiments during winter wheat jointing stage and summer fallow period to measure the soil CH₄ flux in 0 to 72 h after precipitation simulation of 1 to 32 mm. Results showed that CH₄ flux during 0 to 72 h fluctuated at 1 to 8 mm of precipitation application and peaked at 16 and 32 mm. Cumulative CH₄ flux after 72 h of precipitation (CH₄-C) increased linearly with the precipitation amount (P) (wheat jointing stage: CH₄-C=2.45P-6.09, R²=0.92, P<0.01; summer fallow: CH₄-C=2.43P-4.73, R²=0.91, P<0.01). Statistical analysis showed that CH₄ flux was also correlated with soil water content and microbial biomass carbon but not with soil temperature. In the long run, small precipitation events (1-8 mm) could enhance the intensity of soil CH₄ sink and such promoting effect would be weakened with further increase in precipitation amount. However, large precipitation events (≥16 mm) could change the soil function from CH₄ sink to source by stimulating the activity of soil methanogens during short-term periods. [ABSTRACT FROM AUTHOR]