Abstract: [Objective] We investigated the characteristic of soil respiration rate and its responses to soil temperature and soil moisture in a shrubland ecosystem in Mu Us Desert to provide a scientifics basis for predicting soil carbon emission in semiarid region.[Method] The trench method has used in a typical Artemisia ordosica community in Yanchi County to separate the components of soil respiration. Using an automated chamber system, soil respiration rate was measured continuously from April to October 2014 in both trenched and control plots. An exponential function was used to fit the relationship between soil respiration rates and soil temperature (T_s), and a linear regression was used to test the relationship between soil water content (SWC) and temperature normalized soil respiration rates (the ratio of observed values to estimated values).[Result] At the diurnal scale, autotrophic respiration ratio (R_A) showed a middy depression, and reached the peak value earlier (11:00) than T_s (15:00), while heterotrophic respiration ratio (R_H)peaked in consistent with T_s. During mid-growing season (Jun-Aug), the temperature sensitivity (Q₁₀) of total soil respiration ratio (R_T), R_A and R_H was 1.51, 1.40, and 1.88, respectively. However, the response of R_A to T_s was modified by SWC. When SWC < 8%, T_sexplained only 36% of the variation in R_A (Q₁₀=1.10) and temperature normalized R_A showed a significant linear relationship with SWC. When SWC > 8%, R_A increased exponentially with increasing T_s (R² =0.75,Q₁₀=1.88), and there was no significant relationship between temperature normalized R_A and SWC. In contrast to R_A, SWC had little effect on the relationship between R_H and temperature, R_Hincreased exponentially with increase of T_s under different water conditions (R² > 0.65). The contribution of R_A to R_T (R_A/R_T) showed a middy depression at diurnal scale. At the seasonal scale, R_A/R_T showed clear seasonal variation. R_A/R_T averaged 54% during May-Aug and was higher (69%) during Sep-Oct.[Conclusion] At the diurnal scale, R_A was decoupled from T_s, while R_H was primarily controlled by T_s. At the seasonal scale, R_Hwas primarily controlled by T_swith a higher Q₁₀ than that of R_A. However, the response of R_A to T_s was regulated by SWC. The variations in R_A/R_T at diurnal and seasonal scales are most likely derived from the different responses of R_A and R_H to environmental factors. Our result could help understand the dynamics in soil respiration and provided a scientific basis for predicting carbon budget in semiarid regions.

Key words: soil temperature, soil water content, Q₁₀, soil autotrophic respiration, soil heterotrophic respiration, Mu Us Desert, Artemisia ordosica