Trial translocations into edaphically modified habitats enhanced the regeneration of prickly raspwort on Eyre Peninsula, South Australia

Summary

Prickly raspwort (Haloragis eyreana), a Critically Endangered perennial herb endemic to South Australia's Eyre Peninsula with roughly 16,000 individuals confined to a tiny 0.8 km2 area of occupancy, has been declining at monitored sites due to agricultural clearing, weed encroachment and soil compaction from roadworks. The Department of Environment and Natural Resources, working with the local council near Cummins, tested whether artificially lowering soil to mimic the species' natural low-lying, moisture-retentive habitat could improve translocation success, excavating trenches 400-500mm deep alongside undisturbed and artificially lowered soil crests, then transplanting micropropagated plants from eight local provenances onto each surface level in August 2003. While all original transplants across every treatment died within four years, natural recruitment of new seedlings and root suckers began in year three at all sites; by year eight, trenches supported the strongest regeneration at 18 plants per square meter, aided by consistently higher soil moisture and reduced weed competition, compared to just 2 plants per square meter in undisturbed controls. A parallel direct-seeding trial found low but measurable germination, with low crests outperforming high crests and controls. Consecutive drought years in 2006-2007 caused losses across all treatments. The project rates itself Successful, crediting deliberate soil excavation for creating microhabitats that added over 1,000 new naturally regenerating plants across four new sites within the species' range.