Life on the edge

Dr Wolfgang Lewandrowski (Research Scientist), Dr Carole Elliott (Research Scientist)

Translocation of rare cliff-dwellers

Location, location, location! Stunning views over an ancient, eroded landscape!

Tetrathecas from the Goldfields of Western Australia are a unique group of plants living life on the top of craggy, ironstone ridges.

These small iron-loving shrubs are often locally abundant, but endemic to a single or few ridges. Several Tetratheca species are rare or endangered and require restoration post mining.

Tetratheca erubescens in full bloom, wedged into a banded ironstone cliff, Koolyanobbing Range. Photo: Wolfgang Lewandrowski

Translocation is critical to the restoration of Tetratheca establishing new populations into new sites away from continuing threats or degrading processes.

Threatened and rare plant species often have highly-specialised traits that enable them to live in extreme environments. However, these pose significant challenges to their successful restoration.

Building on 15 years of threatened species research on Banded Ironstone Formations (BIF) in Western Australia, we embarked on an integrated approach to inform the translocation of the rare Tetratheca erubescens J.P.Bull. This prior history into species distribution models, fine-scale habitat assessment, genetic diversity and structure, plant-water relations, and pollination of Tetrathecas were critical for planning translocations.

Tetratheca erubescens is a shrub with only 6,300 individuals covering 3.5 ha over a 1.6 km range exclusively on BIF on the Koolyanobbing Range. It grows out of rock cracks, fissures or holes on rocky outcrops or cliff faces. Recent mining removed around 900 plants, with a Ministerial Condition mandating to ‘establish a new selfsustaining population … on a suitable landform that is suitable for the species’. Four experimental translocations were established between 2017 and 2020.

Habitat modelling showed T. erubescens was able to grow best where it accessed water-catchments and climatic refuges within the rock. Banded ironstone stores moisture which plants can access in holes that are a part of a complex network of cracks and fissures. This knowledge was critical to finding locations for new plants and led to higher survival in translocation sites.

Tetratheca erubescens seedling emerges from a drill hole. Seeds were treated to alleviate dormancy. Germination, emergence and survival were monitored for the lifetime of the seedlings. Photo: Wolfgang Lewandrowski

Translocated Tetratheca erubescens cutting flowering and surviving in a drill-hole on banded ironstone formations. Photo: Wolfgang Lewandrowski

Assessment of genetic diversity and relationships between geographically separated T. erubescens populations were critical to inform seed collection zones and sampling of cuttings for propagation. Tube stock and seeds have been planted across five experimental translocation sites in pre-drilled rock holes for four years.

A range of horticultural treatments and field designs were trialled to determine optimal growth and performance. Seeds are generally considered the most cost-effective means to restore at scale, so understanding the conditions that trigger seed germination and seedling emergence is important.

The translocation sites are being monitored regularly to follow plant survival, health and reproduction, compared to natural populations. This includes ecophysiological measurements that provide a useful tool to quantify stressresponses and key for understanding plant physiological function relative to their environment.

Our greatest challenge is understanding below ground processes: how plant roots grow and access water through cracks and crevices within the rock.

Ecophysiological assessments of Tetratheca erubescens using a gas exchange analyser to determine photosynthetic rates and fluorescence. Photo: Wolfgang Lewandrowski

The success of the T. erubescens research project is attributed to inter-disciplinary collaborations and links between science and practice. More than 100 scientists, practitioners and volunteers have made contributions.

The project has also provided opportunity to train the next generation of restoration scientists and practitioners through engagement with universities, volunteer groups and the community. Our outreach includes volunteer opportunities, research projects and on-ground engagement with industry. We look forward to what the future of this project holds and continue to engage with passion and persistence to improve our ability to translocate rare species that inhabit these extreme environments.

The stats

4 experimental translocations installed

3057 tube stock planted

6000 seeds sown

100+ people involved