Our simulation results showed that soil WHC determines partitioning of precipitation among runoff, evaporation, and transpiration, and consequently regulates ecosystem responses to global environmental change. Fractions of precipitation that are used for evaporation and transpiration increase with WHC but decrease with WHC for runoff.  Usually, the soil with high WHC can greatly buffer water stress during long drought periods, particularly after a large rainfall event. NPP, R_h, and NEP usually increase with soil WHC in ambient and doubled precipitation scenarios but increase from 10 to 15% of WHC followed by declines under the halved precipitation amount regardless precipitation intensity. Warming and CO₂ effects on soil water content, evapotranspiration, and runoff are magnified by soil WHC.  Regulatory patterns of soil WHC on responses of NPP, R_h, and NEP to warming are complex. In general, CO₂ effect on NPP, R_h, and NEP increases with soil WHC.  Our results indicate that variations in soil water holding capacity may be one of the major causes underlying variable responses of ecosystems to global changes observed from different experiments.