Resilience of arid floodplain ecosystems is measured by the ability of the floodplain to return to a functioning wet phase after a dry phase, and vice versa. We monitored the understorey community of an arid river-floodplain complex that was restored to an ephemeral regime in c. 2005.

Three sites were monitored annually from 2010–2013, from each of three hydrological regime categories: 1) ephemeral, 2) permanent-ephemeral (previously permanently inundated, now ephemeral), 3) permanently inundated. Surveys included wet and dry phases.

Data was analysed using functional groups to detect broad differences among hydrological regime categories and survey years. Species were allocated to functional groups reflecting water requirements, broadly: terrestrial-dry, don’t require water-logged soil to germinate, don’t tolerate flooding; terrestrial-damp, require water-logged soil to germinate, don’t tolerate flooding; amphibious, require water-logged soil to germinate, tolerate or respond to flooding.

Functional group diversity and composition shifted significantly between survey years; terrestrial-dry plants characterised dry phases, terrestrial-damp and amphibious plants characterised the wet phase. The plant community at ephemeral sites showed the greatest response, with a larger proportion of terrestrial-damp and amphibious plants during wet years than permanent-ephemeral or permanent sites; and a larger shift in proportion of functional groups from the wet phase to the dry phase.

Our findings provide evidence that understorey plant communities of arid floodplains are more resilient under ‘natural’ hydrological management (i.e. ephemeral) than when artificially permanently inundated. The levels of resilience identified in the ephemeral sites may be a useful reference for measuring successful rehabilitation of the system.