<p>Climate change is altering precipitation from small/frequent to large/infrequent rainfall events in the Northern Great Plains. It is unclear how this regime shift in precipitation could influence carbon flux in C3 and C4 grass-dominated plant communities. The objective of this study is to explore the effect of large/infrequent rainfall events on net ecosystem exchange (NEE), ecosystem respiration (RECO), aboveground biomass (AGB) and leaf N and lignin concentration in C3 and C4 plant communities in a mixed-grass prairie. We conducted a rain-manipulation experiment with either small/frequent precipitation events consistent with current conditions or large/infrequent precipitation events that may become more common in future; total precipitation was held constant. The experiment was conducted in two plant communities (C3 and C4 grass-dominated) in western South Dakota during the growing season from 2020 to 2022. We observed large/infrequent rainfall events: (1) decreased NEE (C-uptake) in the C3 plant community during early growing season but had little influence on the C4 community and (2) did not change RECO, AGB, leaf N, C/N and Lig/N in either plant community the entire growing season. We conclude: (1) large/infrequent rainfall events could reduce NEE in C3 plant communities; (2) the decreased NEE caused by large/infrequent rainfall events in the C3 plant community did not translate into decreased AGB; and (3) the C4 plant community in the Northern Great Plains may be resistant to climate change-induced shifts toward large/infrequent rainfall events.</p>