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

Background and aims: Soil respiration (Rs) 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 Rs. Methods: We combined seven-year Rs 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 Rs. We further analyzed the warming responses of heterotrophic (Rh) and autotrophic (Ra) components of Rs. Results: Warming enhanced growing-season Rs 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 Rs via Rh, but not Ra. Consistent with the field experiment, a positive relationship between precipitation and the warming response of growing-season Rs was also observed in the global-scale meta-analysis on grassland warming experiments. Conclusions: Precipitation influences the warming effects on Rs and could result in variation in warming response of Rs across years and experimental systems. Empirical functions provided by this study could be used to reduce the uncertainty in predicting Rs in a warmer future. [ABSTRACT FROM AUTHOR]