Deschampsia setacea

Taxonomy 

Accepted name: Deschampsia setacea (Huds.) Hack.

Common name: Bog Hair-grass.

Synonyms:

  • Aira setacea Huds.
  • Aira uliginosa Weihe & Boenn.
  • Deschampsia discolor R. & S.

Chromosome No.: 2n = 14 (Stace 2010).

 Deschampsia setacea

Distribution 

Widely but thinly distributed throughout the British Isles, mainly in northernmost Scotland, in the New Forest and on the west coast of Ireland around Connemara.

It is considered to be a European endemic, extending from southern Scandinavia to northern Spain, and eastwards to Poland. However, it also occurs in Chile, where it is considered to be a non-invasive alien (Jorge Chiapella, pers. comm.).

BSBI Hectad Map 

Click on the map to view full-size on the BSBI Maps Scheme website.

Ecology 

This is a perennial grass that usually grows on bare peat on the margins of lakes and pools in heathland and bogs. It seems unable to tolerate competition or to persist in a closed sward. Typical associates include Juncus bulbosus and Molinia caerulea.

Altitudinal limit: 320 m at Loch Morlich, v.c. 97, in 1969, A. & M. Mullins (Pearman 2004).

Rodwell (1991) gives only one vegetation community for it: M30, which is an unquantified assemblage of plants that occur in inundation habitats. It is often found in the absence of any close associates (see photo), so standard vegetation surveying techniques are not much use in determining its ecological preferences.

Status 

  • Origin: native. It was first collected at Stratton Heath, Norfolk, by Benjamin Stillingfleet in 1755 (Hudson 1762).
  • Rarity: Nationally Scarce in Britain, but only because there are large populations in NW Scotland. It is rare in England, Wales and Ireland and absent from Northern Ireland.
  • Threat: with a Change Index of -0.04 in the New Atlas, it is continuing a slow decline throughout its range.
  • Conservation: considered an axiophyte wherever it occurs.
Further Work 

Although there has been an undoubted loss of this species from many sites in England, it is interesting to note a steady increase in the number of dots in Scotland, North Wales, western Ireland and even southern England since the first Atlas (Perring & Walters 1962). This is generally ascribed to better recording, but there is no real evidence that this is really true - it could conceivably be increasing in some areas. How could such a possibility be tested?

The apparent lack of any ecological studies seems odd for such a nationally important species. Given its restricted world distribution and its rarity, it would be a natural candidate for a future Biodiversity Action Plan, and it is almost certainly a universal axiophyte.

References 
  • Hudson, W. 1762. Flora Anglica. C. Moran, London.
  • Hughes, M.G.B. 1984. Deschampsia setacea (Hudson) Hackel new to south-western England. Watsonia 15, 34-36.
Citation 
Lockton, A.J. (date accessed). Species account: Deschampsia setacea. Botanical Society of the British Isles, www.bsbi.org.uk.

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