1. The amplifying interannual precipitation variability has been observed globally and is projected to intensify under climate change scenarios. However, its impacts on terrestrial vegetation and carbon (C) sink have not been well investigated.

2. As part of a field manipulative experiment with three precipitation variabilities (20%, 40%, and 60%) in a semiarid grassland, this study was conducted to examine the responses of ecosystem C cycling to increased precipitation variability.

3. Across the 3 experimental years from 2010 to 2012, amplified precipitation variability enhances gross primary productivity (GPP) and ecosystem respiration (ER) as both GPP and ER were more sensitive to above- than below-average precipitation. In addition, the larger responses of GPP than ER to precipitation variability resulted in an enhancement of net ecosystem productivity (NEP), and the magnitudes of NEP increased with the increasing precipitation variability. More species with higher sensitivity to increased precipitation under wet condition and the insensitive response of root growth to decreased precipitation could largely be responsible for the above observations, which suggest that the semiarid grassland was more sensitive to wet treatment yet strongly resistant to drought.

4. Our results provide empirical evidence that intensified precipitation variability could stimulate grassland C sink. The findings revealed in this study could facilitate the mechanistic understanding and imply the potential positive feedback of climate variability-terrestrial C sink.