Variation in soil respiration and its driving factors in rainfed winter wheat fields with different mulching measures

A field experiment was conducted to study soil respiration and its relations with soil temperature and soil moisture in rainfed winter wheat fields in the Loess Plateau. Four treatments were included as two rates of 9000 kg/ha and 4500 kg/ha with straw mulching (M9000 and M4500), plastic film mulching (PM) and the control without mulching (CK). The results show that the dynamic tendency of soil respiration is in a single peak pattern, and the peak of PM is appeared at the jointing stage, the peaks of the others treatments are observed at the heading stage. The mean soil respiration rates of the CK, M4500, M9000 and PM treatments during the whole growing season are CO2 1.54, 1.44, 1.45 and 1.75 mol/(m2s), respectively, and the difference between the PM and CK is significant（P0.05）. The range of the temperature sensitivities of soil respiration (Q10) is from 1.86 to 2.39 for the four treatments in the whole growing season. The Q10 values are higher when the soil temperature is lower than 5℃. On the contrary, the soil temperature affects soil respiration slightly when it is greater than 5℃. There are weak negative correlations between soil moisture and soil respiration during the whole growing season while there are no correlations for the CK and M4500. These results demonstrate that the soil moisture has a little effect on soil respiration during our studies. The regression models including both soil temperature and soil moisture could better explain 0.827, 0.816, 0.896 and 0.729 of soil respiration for the CK, M4500, M9000 and PM, respectively (P0.01).