BSBI Species Accounts ArchiveCarex elongata
Thu, 08/12/2010 - 17:57 | 
markd
The name Carex elongata L., Elongated Sedge, is accepted by all authorities.
Chromosome No.: 2n = 56 (Stace 2010).
Photograph: A.J. Lockton
C. elongata is widely but sparsely distributed throughout the British Isles. In Scarce Plants (Stewart, Pearman & Preston 1994) Dick David described how it had disappeared from canals and ponds in the Manchester area and showed a fairly dramatic decline. In the New Atlas (Preston, Pearman & Dines 2002) it is shown as slightly increasing. However, the maps do seem to show a long-term decline that may well be continuing.
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- Origin: native.
- Rarity: Nationally Scarce in Britain (Stewart, Pearman & Preston 1994); similarly scarce in Ireland.
- Threat: listed as ‘Least Concern’ (Cheffings & Farrell 2005).
- Conservation: it is universally regarded as an axiophyte, usually as an indicator of ancient woodland. In Hampshire and Surrey, populations have been boosted by apparently successful reintroductions (data from the TPDB).
The ecology of C. elongata is perhaps its most interesting attribute. It is most typically a plant of W5 Alnus glutinosa woodland on scrubbed-over mires that are inundated by surface water. Jermy et al. (2007) say it also occurs in W2 Salix-Betula woodland and C.R. Hall (pers. comm.) considers that it grows in W6 Alnus glutinosa woodland in Hampshire. David (1994) describes how it often occurs on floating wood, and Mallabar (1998) takes this one step further, suggesting that seeds tend to germinate on rotting wood, due to some association that has not yet been defined. This might explain why David (op. cit.) considered seeds to have low viability. In the past, C. elongata was found on the rotting wooden piles of canals, but it appears to have completely gone from canals now as wood is no longer used in their construction. C. elongata populations fluctuate enormously in size, being most successful in late-successional sites as they start to dry out. Hencott Pool in Shropshire was considered one of the best sites for it in the 1980s, with hundreds of plants, but it had almost gone from there twenty years later (Lockton & Whild 2003) as the pool dried out and the canopy closed. Hill et al. (1999) give it an Ellenberg L value of 5, which is for half shade, and it presumably cannot thrive under a very dense woodland canopy.
More research into its highly specialised ecological niche would be worthwhile, including a more detailed examination of its vegetation communities. A close watch should be kept on its distribution to find out whether it is in fact declining.
- David, R.W. 1994. Carex elongata. In: Scarce Plants (Stewart, Pearman & Preston).
- Jermy, C., Simpson, D., Foley, M. & Porter, M. 2007. Sedges of the British Isles, 3rd ed. Botanical Society of the British Isles, London.
- Lockton, A.J. & Whild, S.J. 2003. A botanical survey of Hencott Pool. Whild Associates report to English Nature, Shrewsbury.
- Mallabar, J. 1998. Habitat status and niche requirements of Carex elongata L. in Britain. MSc dissertation, School of Biological Sciences, University of Birmingham.
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