Solving the pearl bluebush seed deficit for post-mining revegetation

Pearl bluebush’s infrequent seeding

At JA, pearl bluebush (Maireana sedifolia) is a native species that has shown very low flowering and seed production. The blueish-grey shrub is indigenous to the arid zones of Australia. Finding viable seeds have been challenging, only 64kg has been collected since 2020. Out of the 289 hectare rehabilitated at JA so far, 200 hectares remain without any pearl bluebush. Reintroducing this species in these areas would require over 32,800kg of seed, an amount that is currently unobtainable.

Not just an ordinary shrub, but a dominant species

Since pearl bluebush is the most common native plant at JA, its absence is a major setback for the success of the restored ecosystem. Among other consequences, fauna that rely on pearl bluebush for shelter may not return, and potentially not perform their vital pollination, nutrient cycling, and seed distribution services, preventing the success of the entire ecosystem.

To seed or not to seed: what could be preventing flowering?

While shorter-lived plant species reproduce even when resources are tight,  pearl bluebush, which can live for up to 300 years is a little more selective. When conditions aren’t right, it prioritisies survival over reproduction. In the arid zone where it usually grows, water is the main limiting factor. To see if adding water could improve seeding production, an irrigation system was set up around pearl bluebush at JA. But after 6 years of constant watering, not a single harvestable seed appeared. This frustrating outcome was a clear sign that water isn’t the only scarce resource preventing reproduction.

The vital role of nitrogen in flowering

Another resource that’s often in short supply for plants in the arid zone is nitrogen. Plants absorb nitrogen from the soil and is essential for reproduction. Nitrogen is a major component of chlorophyll molecules, amino acids, and proteins all of what are plant needs to both survive and reproduce. It is possible that a lack of nitrogen may be one of the reasons that pearl bluebush isn’t producing many seeds.

Can we fix the seed shortage?

With the help of Iluka Resources, Jaclyn’s team at the University of Adelaide is working to find solutions to the pearl bluebush seed shortage.

The first step in this research is identifying if nitrogen is actually stopping pearl bluebush from flowering. From there, the team are testing to determine whether adding synthetic nitrogen fertilizer could boost flowering and seed production rates

Could facilitation be a natural solution?

Further research is underway to see if western myall trees (Acacia papyrocarpa) and biological soil crusts (a living layer of mosses, lichens, and cyanobacteria) could help improve flowering in pearl bluebush. These organisms support nitrogen-fixing bacteria, which can boost nitrogen content of the surrounding soil. If they do support the reproduction of pearl bluebush, they could provide a more natural solution to increase soil nitrogen levels and consequently, help pearl bluebush’s flowering capacity.

Solving the flowering mystery could be essential for conservation

Discovering the true cause behind the limited flowering of pearl bluebush is key to solving the seed shortage. If nitrogen proves to be the missing piece, a dedicated seed orchard could be established using nitrogen fertilizer or planting alongside incorporated symbiotic nitrogen-fixing species to produce the necessary seed supply. This inisight could support Iluka in meeting the seed requirements , while benefitting post- mining revegetation and conservation efforts across Australia. Solving this flowering mystery has the potential to transform these restoration practices as well as safeguard the future of this valuable native species.