Mast seeding and the El Nino-Southern Oscillation: a long-term relationship?

Recognition of the effects of inter-annual climate change on earth systems has led to a greater understanding of the various forces that influence natural systems. The El Nio-Southern Oscillation (ENSO) is, arguably, the most well-known and widely researched inter-annual climate mode. The effects of ENSO on natural systems include changes in fire-regimes, rainfall and temperature patterns, oceanic upwelling and plant reproduction. Here, I posit a long-term relationship between ENSO and temporal changes in the abundance of a long-lived rainforest conifer, Lagarostrobos franklinii, in western Tasmania, Australia. An increase in pollen from L. franklinii occurs at a number of sites across the landscape of western Tasmania in concert with a marked increase in the frequency and amplitude of El Nio events in the tropical Pacific Ocean, a trend that resulted in an increase in the occurrence of moisture stress in the Tasmanian region. Based on limited, and albeit speculative, data, I propose mast seeding as the mechanism through which ENSO influences L. franklinii population dynamics over long time-scales. This hypothesis draws on the established link between ENSO and mast seeding in plant species that inhabit a range of biomes under the influence of ENSO. I draw upon ecological, palaeoecological and palaeoclimatological data to highlight a potential link between L. franklinii and ENSO for at least 130,000 years.