BSBI Species Accounts ArchiveFestuca altissima
Fri, 08/27/2010 - 14:28 | 
markd
Festuca altissima All. Wood Fescue
Chromosome No.: 2n = 14 (several authors). A single report of 2n = 42 by Stahlin (1929) probably arose as a result of confusion with Schedonorus arundinaceus or S. giganteus.
Photography: A.J. Richards
A rather isolated species, placed by itself in section Drymanthele, and not known to hybridise. The other broad-leaved fescues form clasping auricles at the top of the sheath, and have 5-nerved lemmas (often appearing 3-nerved) which are often awned. In F. altissima the lemmas are 3-nerved, although only the central nerve is conspicuous so that they appear 1-nerved.
As this scarce and vanishing species typically grows on inaccessible cliffs in ravines, these technical distinctions are not often available for examination, and this is a plant which is usually identified by its ‘jizz’. Usually it is helpful to examine suitable sites with a good pair of binoculars. Typically, a site is examined at a distance from the other side of the ravine, a bridge or from the opposite side of the river. Plants are gregarious and form regular many-leaved tussocks, bearing uniform flat rather dark somewhat shiny evergreen leaves up to 50 cm long which arch upwards at an angle of about 45 degrees and only droop slightly at the apex. The persistent sheaths are rather dark brown and lend a purplish hue to the base of the tussock. The leaves are about 10 mm wide, and so are narrower than Luzula sylvatica, but broader than Deschampsia cespitosa which are almost invariably associates. At a distance, other confusion species can include Schedonorus (Festuca) giganteus and Bromus ramosus, but they do not form many-leaved regular tussocks to the same extent, are a paler green with grooved leaves and the leaves droop more; and Brachypodium sylvaticum which is also paler and more drooping, and is a smaller plant. If flowering panicles are present on F. altissima, they are characteristically narrow and tall, with erect branches (spreading or drooping branches in all confusion species), and it is usually possible to note that awns are absent, thus ruling out S. giganteus. With practise, this species can be accurately identified with binoculars at a range of up to 100 m at any time of year.
Photography: A.J. Richards
Although F. altissima occurs southwards to northern Spain and northern Greece, it is restricted to montane areas with humid climates and reliable summer rainfall. It occurs eastwards to the Urals, but in Scandinavia the distribution is distinctly Atlantic (Hulten 1950).
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Nearly all sites are in old, often largely undisturbed primary woodland. Restricted to difficult terrain, which has resulted in restricted forest clearance. Consequently, most habitats are not threatened. However, F. altissima almost invariably coexists with Luzula sylvatica which tends to be much more successful, aggressive and catholic in its requirements and appears to outcompete it. I suspect that warmer summers have allowed the latter to disperse into and survive in niches previously occupied by the grass. Typically inhabits horizontal joints in near vertical cliffs above rivers, under deciduous trees in partial or complete, often deep, shade. Mostly commonly found on rather calcareous sandstones. Associated species suggest that absence from large areas of apparently suitable habitat can be explained by the low carbonate content of the sandstone, giving rise to soils of too acidic a reaction. Also grows in hard limestone and dolerite. Invariably occurs within 50 m of water, and is often found only just above flood level and not higher up the cliff. Undoubtedly needs continuous levels of high humidity at all times, and the observation in Cope & Gray (2009) that it is shallow-rooted may explain its very stringent habitat requirements, and vulnerability to competition, as well as dislodging. Subsidiary habitats include vegetated talus below cliffs if above flood level, and wooded limestone pavement. To associated species listed in Cope & Gray (Galium odoratum, Luzula sylvatica, Melica spp., Polystichum spp., Sanicula europaea) can be added Dryopteris dilatata, D. filix-mas, Deschampsia cespitosa, Bromus ramosus, Schedonorus giganteus and Brachypodium sylvaticum. Typically the woodland (NVC W8) is dominated by Quercus spp., but may include Fraxinus excelsior and the cliff scrubby Ulmus glabra and Corylus avellana. In many sites it flowers rarely, or few inflorescences are produced. It suffers from the usual problems experienced by chasmophytes, so that establishment may depend upon seeds being caught in spiders webs, and seedlings are unusual. Most populations consist of mature tussocks which may be a considerable age. Consequently, attrition from competition and erosion may exceed the regenerative power of the population.
- Origin: native.
- Rarity: not rare in Britain or Ireland.
- Threat: both Perring (in Preston et al. 2002) and Cope & Gray (2009) are optimistic about the present status, pointing out that it was seriously under-recorded for Perring & Walters (1962). To say that the regions in which it occurs were ‘not well recorded’ is disingenuous. Rather, some botanists have since learnt which habitats it grows in and how to recognise it from a distance, information which has yet to appear in an identification guide. My experience is largely restricted to Northumberland and Durham, where this is a rare and threatened species which is represented by very few populations. Most of these are represented by a very few individuals, some populations have disappeared completely, and all probably contain fewer individuals than when first recorded. Although now known from more than 100 hectads in Britain, twice as many as in Perring & Walters (1962), I believe this is a species threatened by climate change, and populations should be monitored in areas where it is more widespread such as the Lake District and the Trossachs, to see if populations remain stable.
- Conservation: listed as an axiophyte in all counties that have it.
Future work should include base-line population surveys with regular follows-ups to determine whether populations are stable.
- Hulten E. 1950. Atlas of the distribution of vascular plants in NW Europe. Kartografiska Institut, Stockholm.
- Stahlin A. 1929. Morphologische und cytologische untersuchungen an Gramineen. Pflanzenbau 1: 330-397
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