Changes in the ecology and control of introduced non-native plants following pest herbivore eradication in the sub-Antarctic: Stellaria media

Research Objectives

  • Monitor changes in populations of palatable invasive non-native plants that most threaten the recovery of ecosystem structure and function on Macquarie Island following the eradication of rabbits, rats and mice; and
  • Determine whether the ecology of the weed species with most limited distribution, Stellaria media, is conducive to its management or eradication in this early post-herbivore period.

Data on this dicotyledonous weed will complement that collected by our team on the widespread sub-Antarctic grass, Poa annua.

By understanding these issues, we will assist in the development of effective, low-impact control options for island management and sub-Antarctic and international plant eradication programs.

Methods

Three data collection periods on Macquarie Island, and experimental activities at UNE.

  • Literature review.
  • Distribution, cover and plant size mapping, and detailed vegetation surveys at several infested sites.
  • Random seedbank sampling to characterise soil seedbank ecology.
  • Seed burial to monitor longevity and viability.
  • Seedlining emergence and growth: in-situ monitoring and ex-situ experiments.
  • Physical control: in-situ experiments involving hand weeding, digging, cutting plants and scalping.
  • Herbicide control: ex-situ experimental trials under sub-Antarctic conditions using screened herbicides.
  • Herbicide soil dynamics: investigate the interactive effects of soil type, herbicide type and incubation period on herbicide fate.

Stellaria media

  • A cosmopolitan species which has spread to tropical regions of Africa, South America and Asia and to the islands of the Arctic and sub-Antarctic.
  • An annual, over-wintering, or sometimes perennial herb, able to survive temperatures of -10°C.
  • Prefers cool, shady, moist habitats, and well adapted to the Macquarie Island environment.
  • Spreads by rooting at the nodes and forms thick, succulent mats 30-40 cm tall.
  • Known to quickly enter areas disturbed by humans and animals.
  • Spread has been associated with colonies of burrowing seabirds, surface nesting birds, and marine mammals in sub-Antarctic and sub-Arctic conditions.

Student monitoring stellar media plots on Macquarie Island

About Macquarie Island

Map of Sub Antarctica

Map: Macquarie Island in the sub-Antarctic

The sub-Antarctic

  • 45-60 °S
  • Wet, windy and cold
  • Depauperate flora and faunas > isolation and harsh climate
  • High conservation value > wildlife, endemics, unique environments.

Macquarie Island location

  • 54°30'S, 158°57'E
  • Southern Ocean
  • Between Tasmania and Antarctica.

Macquarie Island — natural history

  • Climate: wet, windy, cold
  • Biogeography: elongated, undulating plateau, oceanic origin
  • Soils: peats, dry tundra
  • Flora: 42 vascular plants, many bryophytes, 3 aliens
  • Fauna: seals, albatross, penguins, seabirds.

Macquarie Island

Macquarie Island

Invasive species in the sub-Antartic

  • Biological invasions substantially affect the structure and function of ecosystems
  • Most serious threat to the conservation of the sub-Antarctic
  • Over 108 alien vascular plants
  • Majority are transient/persistent and restricted, some aggressively spreading and invading
  • Risk of invasion increasing.