Diapensia
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| Diapensia lapponica L. |
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Diapensia lapponica is a plant in the family Diapensiaceae, and the only species in the genus Diapensia. It is a circumboreal arctic-alpine species which grows on exposed rocky ridges that are kept free from snow by high winds [1].
It is a small cushion-forming evergreen perennial shrub, up to 15 cm in height. It has oval blunt leathery toothless leaves, up to 1 cm long, which are arranged in dense rosettes. It bears solitary white flowers, on stems up to 3 cm tall.
It could be aged by counting growth-rings, and on this basis, many Canadian plants have been shown to live to over a century old [2].
Two subspecies are recognised:
- Diapensia lapponica subsp. lapponica in eastern North America, Greenland, Scotland, Scandinavia, and western Arctic Russia
- Diapensia lapponica subsp. obovata in eastern Arctic Russia, Korea, Japan, Alaska and the Yukon
[edit] Status in Britain
In Britain, Diapensia is found only at a single site, Sgurr an Utha (grid reference NM889838), near Glenfinnan in Lochaber, the species' most southerly site in Europe. Here, the species occurs on acidic soil among stones on the ridge between the summit of Sgurr an Utha and the adjoining hill called Fraoch-bheinn, at 760 to 780 metres above sea-level. Its total extent at this site is less than 5,000 m². A total of 1,200 clumps or mats have been counted, and monitoring since 1980 has not detected any change in this population.
The discovery of Diapensia took place in July 1951; C. F. Tebbutt, a birdwatcher, found the plant, recognising it as "something different" [3]. Diapensia was one of a trio of Arctic plants discovered in Scotland in the early 1950s. Although no new species to Britain had been discovered in Scotland since Victorian times, in 1950, the Arctic plant Koenigia islandica had been found on the Isle of Skye, and in 1952, Artemisia norvegica was found on Cul Mor [4]. A photograph of the plant by Robert Moyes Adam taken on 14 June 1952 (soon after the initial discovery) is held by the St Andrews University Library [5].
It flowers at this site in May or June, the exact time varying from year to year. Some sources state that the species is found at a second site [6][7] but recent sources state that this is not the case [8][9].
The plant is listed in the 3rd edition of the British vascular plant Red Data Book [8] as vulnerable. It is also protected under Schedule 8 of the Wildlife and Countryside Act 1981.
[edit] References
- ^ Tiffany, W. N. (1972). Snow cover and the Diapensia lapponica habitat in the White Mountains, New Hampshire. Rhodora 74: 358–377.
- ^ Day, R. T. & P. J. Scott (1985). The biology of Diapensia lapponica in Newfoundland. The Canadian Field Naturalist 98: 425–439.
- ^ Grant Roger, J. (1952). Diapensia lapponica in Scotland. Transactions of the Botanical Society of Scotland 36: 34–37.
- ^ Marren, Peter (1999). Britain's Rare Flowers. Academic Press, London. ISBN 0-85661-114-X.
- ^ Diapensia lapponica, single cushion between rocks, summit ridge between Sgurr an Utha and Fraoch-bheinn, Glenfinnan Hills. University of St Andrews.
- ^ Garrard, Ian & David Streeter. The Wild flowers of the British Isles. Midsummer Books, London.
- ^ Wildlife in Glenfinnan. Glenfinnan Estate.
- ^ a b Wigginton, M. J. (1999). British Red Data Books 1. Vascular Plants (3rd edition). Joint Nature Conservation Committee, Peterborough.
- ^ Preston, C. D., D. A. Pearman & T. D. Dines (2002). The New Atlas of the British and Irish Flora. Oxford University Press, Oxford. ISBN 0-19-851067-5.
