Riley Hodgson, Flinders University
Craig Liddicoat, Flinders University
Christian Cando-Dumancela, Flinders University
Colette Blyth, University of Adelaide
Carl Watson, Flinders University
Martin Breed, Flinders University 

Habitat loss and poor recruitment rates have crippled the conservation status of Acacia whibleyana, an endangered plant endemic to the Tumby Bay region of South Australia. Disrupted plant-soil feedbacks can undermine community interactions between native plants and associated soil microbiota. Reintroducing soil microbiota during revegetation may therefore help restore ecological links between species and aid A. whibleyana conservation efforts. We explored the role of soil microbiota on A. whibleyana germination and seedling fitness traits through a 17 week greenhouse experiment to inform recovery efforts. A total of 140 seeds were grown across 7 treatment soils. Soil treatments included local soil (sourced from under A. whibleyana canopies), potting-medium, three inoculation ratios (3:1, 1:1, 1:3 local soil:potting-medium), sterilised local soil, and sterilised potting-medium. Physiochemical conditions were measured, and soil bacteria were characterised using 16s rRNA amplicon sequencing, which exhibited strong differentiation with respect to diversity and community composition across soil treatments. Whole soil inoculations of 1:1 local soil to potting medium reduced germination rates, while sterilisation of the soil improved the time for first seed germination. There was no effect of treatment on A. whibleyana biomass, root-mass fraction, specific leaf area, or specific root length. Through a maximum likelihood, multi-model inferencing approach, we identified important implications of soil physiochemical conditions for A. whibleyana growth. The detrimental influences of the 1:1 inoculation suggests that poor inoculation strategies can adversely impact A. whibleyana germination. As such, land managers should cautiously consider soil mediums for revegetation, and the microbial communities active in plantings. Further research into the mechanisms of these biotic and abiotic interactions will aid the persistence of A. whibleyana.