Response of methane emissions to temperature and moisture changes at different soil depths in the submerged plant zones of Poyang Lake

This study analyzes the different response of CH4 emissions from two soil depths to temperature and moisture changes, as well as the interactive effects of temperature, moisture and soil layer. To accomplish this objective, soils in the submerged plant zones of Poyang Lake were sampled at depths of 0-10 cm and 10-30 cm. Subsequently, the soil samples were incubated for two years at two distinct temperatures（18℃ vs 28℃） and at two moisture treatments（the initial soil moisture during initial soil sampling vs the moisture at 2 cm water depth）.The results showed that the soil CH4 emissions varied from 0.01 to 3.63 μgCH4-C kg-1 d-1 for the 0-10 cm depth samples, and 0.02 to 1.99 μgCH4-C kg-1 d-1 for the 10-30 cm depth samples, respectively. Temperature, moisture, soil layer and their interactions all had significant effects on soil CH4 emissions（P < 0.01）, though the soil layer had the maximum impact. It was observed that the temperature sensitivity of soil CH4 emissions from the 0-10 cm depth samples was higher than that of the 10-30 cm depth sample for both of the moisture treatments. Both mean and cumulative soil CH4 emissions from the 0-10 cm depth samples were significantly higher than the 10-30 cm depth samples. In addition, soil CH4 emissions in the early incubation period were higher than the later period, suggesting that the substrate availability can play a substantial role in soil CH4 emissions in wetlands.