Factors influencing the germination, establishment and distribution of Micromyrtus minutiflora (Myrtaceae), in western Sydney, New South Wales

Context. Little is known of the ecology of Micromyrtus minutiflora, a threatened plant species endemic to the Cumberland subregion, New South Wales, Australia. Aims. To fill ecological knowledge gaps of M. minutiflora, including habitat preferences, population size and structure, survivorship; and responses to fire and disturbance to inform appropriate management practices. Methods. Surveys of distribution and abundance, regeneration mode and response to fire, survivorship, size-class analysis, greenhouse germination experiments using soil blocks; and plant tissue and soil analyses. Key results. Micromyrtus minutiflora was estimated to have a population of ~4.3 × 10⁶, an extent of occurrence of ~13 000 ha and ~1.5% area of occupancy within study areas. It is strongly associated with low tree canopy cover (few trees), dispersive clay soils and Castlereagh Scribbly Gum Woodland. In the one area studied, survivorship decreased by ~15% per annum across 14 years. However, total population numbers were stable across 3 years, indicating continuous recruitment. Size distributions were unimodal and continuous from small to large plants, consistent with recruitment matching mortality. Plants lack a lignotuber and have a high shoot:root ratio. Seedling emergence was unaffected by mechanical disturbance, but heat and smoke significantly increased germination. Conclusions. This species is abundant on dispersive clays but restricted to the northern Cumberland Plain in open woodland areas. It is an obligate seeder; plants are killed by fire and can flower within 2 years of germination. Implications. Understanding its soil seedbank dynamics is pertinent in determining an appropriate fire regime to maintain habitat while not directly threatening populations. Populations require regular monitoring.