Asplenium septentrionale

Tracheophyta PteropsidaAspleniaceaeAspleniumAsplenium septentrionale

Ecology

An often long-lived, evergreen fern of well-drained, exposed, sunny, usually acidic rock faces, metalliferous mine spoil and the sides of unmortared stone walls. In Ireland, it grows on ultrabasic rocks. 0-535 m (Moel yr Ogof, Caerns.), formerly to 715 m at Llyn y Cwn (Caerns.).

Status

Native

World Distribution

European Temperate element; also in C. Asia and western N. America.

Broad Habitats

Inland rock (quarries, cliffs, screes)

Light (Ellenberg): 8

Moisture (Ellenberg): 3

Reaction (Ellenberg): 2

Nitrogen (Ellenberg): 2

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 2.5

July Mean Temperature (Celsius): 13.2

Annual Precipitation (mm): 1825

Height (cm): 15

Perennation - primary

Perennial

Life Form - primary

Hemicryptophyte

Woodiness

Herbaceous

Clonality - primary

Little or no vegetative spread

Count of 10km squares in Great Britain: 55

Count of 10km squares in Ireland: 2

Count of 10km squares in the Channel Isles: 0

Atlas Change Index: -0.08

JNCC Designations

NBNSYS0000002051

Scarce Atlas Account

Scarce Atlas Account: 

Asplenium septentrionale (L.) Hoffm.

Forked spleenwort

Status: scarce

 

This fern is characteristic of rock crevices and earthy, unmortared wails on dry, south-facing, unshaded slopes. It usually grows on hard, base-poor, dark-coloured rocks, in crevices on vertical surfaces and on the sides more often than on the tops of walls, and is also occasionally found on spoil heaps of metalliferous mines and on old, mortared walls. Commonly associated species include Agrostis capillaris, Asplenium ruta-muraria, A. trichomanes subsp. trichomanes, Athyrium filix-femina, Festuca ovina, Teucrium scorodonia, Thymus polytrichus, Ulex europaeus, U. gallii and, on mine waste, Racomitrium lanuginosum. The reasons for its association with metalliferous mines are uncertain. It has been found at low to moderate elevations, mostly in mountainous districts, from sea level in northwest Scotland to 460 metres at Blake Rigg and Cwmorthin, but is perhaps gone from the latter.

A. septentrionale is a winter-green, clump-forming, usually gregarious perennial. The clumps are slow-growing and long-lived. Establishment and spread can be rapid on old earthy walls, some populations in mid Wales having increased tenfold in the last three or four decades, but on natural rock, establishment of new plants must be a rare event, as also is spread to new sites. A particular stage in the decay of earthy walls seems to favour colonisation. Dark-coloured rock may provide valuable thermal qualities, while shade and waterlogging seem to be deleterious.

It is decreasing in natural sites but increasing in some synanthropic ones. This species has probably disappeared from at least half its former sites in Scotland, England and North Wales. Most populations consist of very few plants. However, populations in Cardigan, where there are now some 1200 plants chiefly associated with lead-mine remains, are expanding rapidly and several new sites seem to have been colonised, but there is no spread to natural rock sites. Past extinctions were at least partly caused by collecting, while more recent losses have probably been caused mostly by shading resulting from scrub encroachment and afforestation.

Widespread throughout the northern hemisphere, especially in the mountains, and generally continental or northern-montane. It is thus probably under unusual stress in the cool, wet, oceanic zone where the suitable sites for it in Britain are found. In Europe it is rare around the Mediterranean (Jalas & Suominen 1972).

For stimulating accounts of its ecology, from which much of the above was drawn, see Page (1982, 1988).

 

A. O. Chater

Atlas text references

Atlas (9a)
Curtis TGF, McGough HN
1988.  The Irish Red Data Book. 1. Vascular Plants.
Hultén E, Fries M
1986.  Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1972)
Bangerter EB, Cannon JFM, Jermy AC
1978.  Ferns and their allies. The Island of Mull: a survey of its flora and environment. :12.1-12.7.
Meusel H, Jäger E, Weinert E
1965.  Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
Page CN
1997.  The ferns of Britain and Ireland, edn 2.
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.