The response of soil respiration (Rs) to soil temperature and moisture have been well documented in forests, but data and information from desert shrub ecosystems are limited. Soil CO2 efflux from a desert shrub ecosystem was measured continuously with automated chambers in Ningxia, northwest China, from June to October 2012. The responses of Rs to Ts was strongly affected diurnally by soil moisture, with the diel variation in Rs being strongly related to 10 cm soil temperature (Ts) at moderate and high soil volumetric water content (VWC), but less related to Ts at low VWC. Ts typically lagged Rs by 3–4 h, however, the lag time varied in relation to VWC, with increased lag times at low VWC. Over the seasonal cycle, daily mean Rs was positively correlated with Ts when VWC exceeded 0.08 m3 m−3, but became decoupled from Ts when VWC dropped below this threshold. The annual temperature sensitivity of Rs (Q10) was 1.5. The short-term sensitivity of Rs to Ts, computed using three-day windows, varied significantly over the seasonal cycle; the short-term Q10 was negatively correlated with Ts and positively correlated with VWC. These results suggest the potential for a negative feedback to climate warming in desert ecosystems, related to the impact of low soil moisture on Rs. The results highlight the biological causes of diel hysteresis between Rs and Ts and the need for carbon cycle models to account for the interacting effects of Ts and VWC as joint determinants of Rs in desert ecosystem
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