Two dry/wet treatments were established to simulate fluctua-tions in soil moisture:moderately wet to dry(soil moisture ranging from 80% to 60% WFPS,MDW)and normally wet–dry(soil moisture ranging from 80%to 40% WFPS ,NDW)(Fig.1).The ranges of the soil water content(40%–80%WFPS)were based on related studies(Yu and Zhao,2015),and 60%WFPS appears to be the threshold between water-limited and aeration-limited microbial processes(Menéndez et al.,2012).The result of an initial experiment agreed with this statement;the cumulative N2O emissions increased by 0.38 mg N kg1 as soil moisture increased from 40% WFPS to 60% WFPS.