Effect of soil moisture fluctuations on CO2 and N2O emission in alpine meadow ecosystem

Under the influence of topography and climate, plateau grassland soil experiences frequent soil moisture fluctuations. To explore the influence of soil moisture fluctuations on CO2 and N2O emission from alpine meadows in the Qinghai-Tibet Plateau, we used an undisturbed soil column to simulate soil water content fluctuation from a high (60 cm3·cm-3) to low value (30 cm3·cm-3),and to a high (60 cm3·cm-3) again; this duration of each phase was 38, 57, and 46 days. A soil column with constant HYPERLINK “javascript:;” humidity level (soil humidity 60 cm3·cm-3) was considered the control. The results showed that: 1) soil moisture fluctuations significantly increased CO2 emission. A significant relationship was observed between CO2 emission and soil temperature; additionally, CO2 emission correlated positively with soil dissolved organic carbon (DOC) concentration in the first high soil-water content phase. 2) Moisture fluctuations significantly decreased N2O emission. In the control treatment, there was a strong significant negative correlation between N2O emission and NH4+-N; however, no close relation between N2O emission and NH4+-N level was observed throughout the moisture fluctuation process.