The role of non-rainfall water on physiological activation in desert biological soil crusts

•Non-rainfall water can activate the physiological activity of BSCs.•Non-rainfall water leads to carbon loss and low rates of nitrogen fixation in BSCs.•Thresholds of non-rainfall water for Fv/Fm activation decreased along with BSC succession.•Annual effective non-rainfall water events increased along with BSC succession.•BSCs organisms mainly utilize non-rainfall water to keep alive rather than growth.