Monitoring of plant phenology and seed production identifies two distinct seed collection seasons in the Australian arid zone

Abstract

Phenological patterns including peak flowering and seed production of 19 grass, herb, shrub and tree species were studied in the Pilbara biogeographic region of Western Australia. Each plant population was monitored monthly over an 18-month period. Qualitative data was collected capturing plant phenophases. Plant fecundity was estimated using X-ray analyses to determine the proportion of seeds produced. Two main phenological patterns were established across plant life-forms. Precipitation during the summer wet season provided sufficient soil moisture for grasses to emerge from a dormant vegetative state and rapidly transition into flowering and seed production. In contrast, the deeper-rooted shrubs and herbs commenced flowering before the onset of the summer rains, completing their reproductive cycle before the period of higher moisture availability. The patterns observed indicated that the different plant life-forms co-existing within the Pilbara differentially exploit the available resources of this arid region. The contrasting phenological patterns between plant life-forms across seasons likely represent adaptations to a competitive, arid environment where water is the limiting resource. To meet the increasing demand for native seeds of diverse plant species for ecosystem restoration, plant phenological data will become increasingly important for deriving seed supply strategies from wild or managed plant populations.