Return of the lignum dead: Resilience of an arid floodplain shrub to drought

- We confirm lignum regenerates from dormancy.
- We found lignum regeneration is influenced by increasing duration of dormancy.
- As lignum dormancy interval increased, lignum regeneration decreased.
- Lignum regeneration success varied across locations and years.
- Understanding the limits of dormancy supports arid floodplain management.

In semi-arid regions, woody floodplain plants have developed methods of tolerance to both flooding and drought. Understanding the limits of tolerance to drought is critical to the efforts of restoring these communities. In Australia, Tangled Lignum (Duma florulenta (Meisn.) T. M. Schust) is an ecologically significant floodplain shrub that dominates large areas of the Murray-Darling and Lake Eyre Basins. This study investigates the resilience of lignum plants to dry periods by examining the capacity of plants to regenerate from dormancy. In particular, this study sought to test the hypothesis that lignum regeneration is influenced by increasing duration of dormancy. Variability in regeneration response across the study period was also looked at in relation to regional rainfall and flow. Lignum plants were surveyed at 12 sites on the Murray River floodplain in north-western Victoria. Sites were monitored seven times between 2006-07 and 2012-13. This study found that although lignum can regenerate from dormancy, regeneration is not guaranteed and the likelihood of successful regeneration varies among locations and diminishes with increasing length of dormancy. Lignum communities should be managed to maintain condition and resilience to drought in order to give lignum plants the greatest chance of regeneration success.