Synonymy

Armeria maritima-Grimmia maritima rock crevice community Ostenfeld 1908; Armeria maritima-Ligusticum scoticum low cliff vegetation Petch 1933; Armeria maritima-Grimmia maritima and Asplenium marinum-Grimmia maritima Associations Birks 1973; Habitat Groups II & III Goldsmith 1975; Armeria maritima-Grimmia maritima association Malloch & Okusanya 1979.

Constant species

Armeria maritima, Festuca rubra, Ligusticum scoticum, Schistidium maritimum.

Physiognomy

As in the Crithmo-Spergularietum, the vegetation comprises a low-growing, very open cover, mainly of vascular perennials whose precise arrangement is strongly influenced by the availability and pattern of rockcrevices. There is no single dominant but Armeria maritima, Festuca rubra and Ligusticum scoticum may each be abundant in particular stands. Plantago maritima, Rhodiola rosea and Silene vulgaris ssp. maritima are frequent. Although Schistidium maritimum is occasionally present in the Crithmo-Spergularietum, it is here constant, though always in small amounts. Other bryophytes are rare. Birks (1973) recorded Anaptychia fusca and Ramalina siliquosa as frequently occurring lichens exclusive to this vegetation on Skye.

Asplenium marinum is an occasional in the community but it may become locally abundant in sheltered rockcrevices with Trichostomum brachydontium (Birks 1973).

Habitat

The Armeria-Ligusticum community replaces Crithmo-Spergularietum as the most maritime vascular plant community north of Galloway. It occurs on all rock types, being limited mainly by the physical structure of the deposits. On softer sandstones, such as parts of the Old Red Sandstone which comprises much of the Caithness cliffs, the vegetation cover tends to be greater than usual.