Precipitation determines the magnitude and direction of interannual responses of soil respiration to experimental warming

Background and aims: Soil respiration (R_s) is expected to positively feedback to climate warming. The strength of this feedback is uncertain as numerous environmental factors, such as precipitation and soil moisture, can moderate the warming response of R_s. Methods: We combined seven-year R_s measurements in a warming experiment in the Tibetan alpine grassland with a meta-analysis on grassland warming experiments globally to investigate how precipitation and soil moisture influences the warming response of R_s. We further analyzed the warming responses of heterotrophic (R_h) and autotrophic (R_a) components of R_s. Results: Warming enhanced growing-season R_s in the wet years but decreased it in the dry years in the field experiment at the Tibetan grassland. Precipitation modulated the warming responses of growing-season R_s via R_h, but not R_a. Consistent with the field experiment, a positive relationship between precipitation and the warming response of growing-season R_s was also observed in the global-scale meta-analysis on grassland warming experiments. Conclusions: Precipitation influences the warming effects on R_s and could result in variation in warming response of R_s across years and experimental systems. Empirical functions provided by this study could be used to reduce the uncertainty in predicting R_s in a warmer future.