Emma Sumner has recently completed her honours under John Morgan with the RCAAE at La Trobe University. Emma studied the biotic and abotic factors that affect local distributions of a model alpine plant, Alpine Podolepis (Podolepis robusta). This was investigated using various field and laboratory experiments designed to understand what controls the local distribution of this plant.

Emma found that Alpine Podolepis has a far greater fundamental niche than is currently realised at Mt Hotham, with facilitative interactions playing a strong role across range edges. A transplant experiment along a temperature and moisture gradient found that close interspecific neighbours significantly increased survival and growth of planted seedlings, compared with seedlings planted in canopy gaps. This pattern was found to be consistent, even below the current distribution of Alpine Podolepis where it was expected that close interspecific neighbours would result in stronger competitive interactions.

Emma’s thesis highlight the importance of facilitative interactions at the seedling stage in the alpine zone, demonstrating that biotic factors act to constrain or widen the theoretical niche. Emma argues that biotic interactions, dispersal limitation, and recruitment processes may enforce stronger limits to geographic distribution than climatic tolerances per se and that predictions on how plant species may respond to climate change would benefit from incorporating these factors.