Seed biology implications for the maintenance and establishment of Tetratheca juncea (Tremandraceae), a vulnerable Australian species

Abstract

Tetratheca juncea Smith is an endemic and vulnerable shrub species with apparently poor recruitment from New South Wales, Australia. Lack of understanding of seed biology limits management options for promoting survival of existing populations and recruitment of new populations. This study investigated the soil seed bank, seed viability, germination and seed dormancy. The plants release seeds in January but no seeds germinated from soil collected near the plants in September 1999, irrespective of the soil being treated by smoke, heat or fire. When sampled again in February 2001, seeds were present in the soil seed bank but were not viable. Viability testing of seeds collected from the plants determined that at least a third of the seeds being produced were viable, even after storage for 6 months. Seed germination and dormancy investigations found that the seeds germinated following exposure to smoke or scarification of the seed coat. Untreated seeds did not germinate during the preliminary study, although a proportion of untreated seeds germinated from a later seed lot. Fire management is important for promoting the survival of this species and the soil seed bank cannot be relied on for re-establishment of populations as the longevity of the soil seed bank seems to be short. Many other species of Tetratheca are also rare or threatened and this study suggests that hand-collected seeds treated with fire-related stimuli may be important for re-establishing those species and that the soil seed bank requires assessment before being relied on as a source of propagules or for maintaining a population.