Seed germination requirements of an Australian semi-arid floodplain

Abstract

Plants that occur on floodplains in dryland regions often use floods to disperse and germinate seeds, which establish during and following flooding events. Acacia stenophylla (river cooba) is a perennial tree, common in the riparian habitats of the Murray-Darling Basin, Australia. The aims of this study were to (1) determine the relationship between seed germination and seedling establishment of A. stenophylla and hydrological conditions, (2) determine the buoyancy of its seeds and, hence, ability to disperse by hydrochory and (3) provide recommendations on the hydrological requirements for A. stenophylla recruitment. Seedling recruitment data collected between 2014 and 2020 on the floodplain of the lower Lachlan River were compared with time since flooding. In a glasshouse experiment, seeds of A. stenophylla within their pods and with their pods removed were exposed to one of five experimental treatments (rainfall, soaked soil, and inundated for 20 and 40 days), over a period of 50 days. A. stenophylla germinated during and following flooding and following high rainfall. Seeds in pods floated for 8 days. A. stenophylla establishes during and following flooding and requires 1 month of flooding followed by flood recession to maximise seed germination. This research contributes to our broader understanding of the reproductive biology of one of the less studied Acacia species.