Included here is a series of subantarctic islands comprising the Kerguelen Islands, Marion Island, Prince Edward Islands, Crozet Islands, Heard Islands, McDonald Island, Saint Paul Island and Amsterdam Island. Uplands are mainly characterised by forms of fjaeldmark.

Kerguelenian Azorella Fjaeldmark

Fjaeldmark is an open vegetation of sporadic, stunted, often cushion forming flowering plants and bryophytes usually accompanied by lichens. They develop wherever the climate is sufficiently harsh to prevent the formation of closed vegetation, and typically occur in cold, windy upland areas sometimes described as ‘wind-deserts’ On Marion and Prince Edward Islands they cover large areas between 100-500m above sea level. However, despite the severe conditions, these are some of the most species-rich parts of this zone. The most conspicuous plants are the cushion forming flowering plant Azorella selago and the mosses Andreaea acutifolia and Racomitrium crispulum. The cushion forming moss Ditrichum strictum is also distinctive. Among the other characteristic taxa are several endemic or near endemic bryophytes including Grimmia kerguelensis, Psilopilum cf. tristaniense and Verrucidens microcarpus. An interesting feature of the vegetation is the occurrence of completely spherical colonies of moss, which are free to blow around in the wind. Species such as Andreaea regularis, Ditrichum strictum and Holodontium pumilum have all been recorded as ‘moss balls’. It is not completely clear how these form but because they seem to be confined to cold climates it has been suggested that the instability of the substratum as a result of cryoturbatic processes is one of the causative factors. Azorella selago fjaeldmark occur on a number of sub Antarctic islands. Kerguelen also has a form fjaeldmark dominated by the endemic species Lyallia kerguelensis (Caryophyllaceae) and Poa kerguelensis (Poaceae).

References

Bergstrom, D. M. & Chown, S. L. 1999. Life at the front: history, ecology and change on southern ocean islands. Tree, 14: 472-477.

Chapuis, J. L., Frenot, Y. & Lebouvier, M. 2004. Recovery of native plant communities after eradication of rabbits from the sub Antarctic Kerguelen Islands, and the influence of climate change. Biological Conservation, 117: 167-179.

Frenot, Y., Gloaguen, J. C., Cannavacciuolo, M. & Bellido, A. 1998. Primary succession on the glacier forelands in the sub Antarctic Kerguelen Islands. Journal of Vegetation Science, 9: 75-84.

Gremmen, N. J. M. 1982. The vegetation of the sub Antarctic islands Marion and Prince Edward. Dr W. Junk Publishers.

Grolle, R. 2002. The Hepaticae and Anthocerotae of the sub Antarctic and temperate islands in the eastern Southern Hemisphere - an annotated list. Journal of Bryology, 24: 57-80.

Kidder, J. H. 1876. Contributions to the natural history of Kerguelen Island made in connection with the United States transit-of-Venus Expedition, 1874-75. Bulletin of United States National Museum, No. 3.

Scott, J. J. 1990. Changes in the vegetation on Heard Island 1947-1987. In: Antarctic Ecosystems. Ecological Change and Conservation. Eds. K. R. Kerry and G. Hempel. Springer-Verlag.

Smith, H. G. et al. 1974. A biological survey of St Paul’s Rocks in the equatorial Atlantic Ocean. Biological Journal of the Linnaean Society, 6: 89-96.

Wace, N. M. 1960. The botany of southern oceanic islands. The Royal Society Expedition to Southern Chile. Proceedings of the Royal Society, 152: 475-490.

Wace, N. M. 1965. Vascular Plants. In: Biogeography and Ecology in Antarctica. Eds. Mieghem, J. Van, Oye, P. Van and Schell, J. Dr Junk Publishers. The Hague.