Azorella macquariensis (Macquarie Cushion)is one of only four plants endemic to Macquarie Island. It is the dominant species of the feldmark, a plant community on the plateau uplands comprising of dwarf flowering plants, mosses, lichens, liverworts, interspersed with patches of bare ground. The feldmark covers 45% of the Island and A. macquariensis is considered to be a keystone species of this community.
King Penguin tour the Station on Macquarie Island while sleepy friends look on.
Macquarie Island is a subantarctic Australian Territory managed by the Tasmanian Government Parks and Wildlife Service. It lies approximately 1545km South Southeast of the Botanic Gardens and was inscribed on the World Heritage List in 1997 on the basis of its “outstanding natural universal values”. The entire island is approx 34 km long and 5 km wide and has been managed as a nature reserve since 1970.
Macquarie Island is unique in its origin in that it is a very rare example of recently uplifted oceanic crust formed around 11 million years ago. It is the only place on earth where rocks from the earth’s mantle are being actively exposed above sea level. Unlike other Subantarctic Islands, there are no active volcanoes or glaciers creating geological deposits on the island making its origin entirely oceanic.
Five plant communities have been identified on the island consisting of grassland, herbfield, fen, bog and feldmark. The vascular flora is small, consisting of 46 species and of these four are endemic – Azorella macquariensis, Puccinellia macquariensis(a grass) and two orchid species, Nematoceras dienemus and Nematoceras sulcatum.
In late 2008, Dr Dana Bergstrom from the Australian Antarctic Divison (AAD) noticed large areas of cushions dying back or dying across the Island. Initial thoughts were that there was a disease spreading through the population, however subsequent extensive surveys and research work is indicating that the cause of the dieback appears to be multifactorial. A contributing factor may be a slight shift in climatic conditions occurring on Macquarie Island. The Primary Industries, Parks, Water & Environment’s (DPIPWE) Resource Management and Conservation Division plant scientists have been conducting a range of research projects on the island and a recently published example can be found at – http://dx.doi.org/10.1071/BT13207
The Royal Tasmanian Botanical Gardens has been involved in the conservation of this species since 2009 when a collection of plants and seed were brought back from the Island to hold as insurance and for research into the cause of the dieback.
The seed collection was received by the Tasmanian Seed Conservation Centre. The collection however was very small and a second collection was made in March 2010. The dense nature of the cushion means that the small,single-seeded fruits are held very close to the plant making collection very slow and difficult in Macquarie’s cold, windy climate. The 2010 collection was large enough to allow germination studies to be performed and testing is currently underway. Initial results suggest that this species exhibits physiological dormancy .
The plant material also presented problems for research work. The RTBG facilities could not provide the strict quarantine conditions required to maintain the plants and they were housed in a coolroom facility at the Newtown Laboratories of DPIPWE. Creating the environmental conditions required to maintain this species long-term is difficult and expensive. With this in mind the decision was made to develop a potted conservation collection on Macquarie Island itself.
Horticulture on Macquarie
In March 2010 Michelle Lang, RTBG Nursery Supervisor, travelled down to Macquarie Island to set up a trial potted conservation collection. Twelve months later all nine plants settled well into their high rise lifestyle (see image). The plants were potted into 800mm long plastic pipes to provide perfect drainage, as well as protection from rabbits and potential soil pathogens. All plants were provided with an automated watering system operated by a rain sensor.
Plans were developed a viable on-Island ex-situ conservation collection, consisting of approximately 50 individual plants collected from wide –ranging populations of A.macquariensis from across the Island. This collection will also serve as a seed orchard, where individual plants may be cross-pollinated to hopefully enhance seed-set and broaden the genetic make-up of the seed collected.
PWS Ranger Chris Howard demonstrating camera frame Feb 2017
Images of each plant are taken by the Parks and Wildlife Rangers on Macquarie Island each month and emailed to staff at the RTBG, to closely monitor their health. From the comparative images below taken in 2010 and 2012 good growth rates can been clearly seen with a number of individuals, proving this as a successful method of ensuring the conservation of this species.