Recruitment dynamics of the long-lived obligate seeders Callitris intratropica (Cupressaceae) and Petraeomyrtus punicea (Myrtaceae)

The fire-prone sandstone Arnhem Plateau is recognised as an international centre of plant species diversity. Key regional long-lived obligate seeders include the coniferous tree Callitris intratropica R.T.Baker & H.G.Smith, and the endemic myrtaceous, serotinous shrub Petraeomyrtus punicea (Byrnes) Craven. The paper reports a 6year study of seedling-recruitment dynamics in natural stands of both species. For C. intratropica, it was found that (1) contrary to other published observations, initial growth was slow, with juveniles taking ~10 years to attain 2-m height, (2) maturation substantially exceeds 10 years and (3) previously unreported, even juveniles may occasionally resprout following very low-intensity fires after 100% scorch. For P. punicea, (1) maturation in some individuals commences as early as 4 years but generally takes at least 1–2 years longer and (2) juveniles (as well as adults) are killed following 100% scorch. The results emphasise the need for management-imposed fire regimes dominated by patchy, low-intensity fires for conservation of regional long-lived obligate seeders.