Synonymy

Mountain Callunetum Metcalfe 1950 p.p.; Lichen heaths Poore & McVean 1957p.p.; Cladineto-Callunetum McVean & Ratcliffe 1962, Prentice & Prentice 1975 p.p.; Calluna heath, dwarf lichen-rich facies Edgell 1969; Dwarf mountain heaths Gimingham 1972 p.p.; Empetrum hermaphroditum-Racomitrium lanuginosum community Birse & Robertson 1976; Empetrum hermaphroditum-Cetraria nivalis nodum Birks & Huntley 1979; Alectorio-Callunetum vulgaris (Birse & Robertson 1976) Birse 1980.

Constant species

Calluna vulgaris, Empetrum nigrum hermaphroditum, Racomitrium lanuginosum, Alectoria nigricans, Cetraria islandica, Cladonia arbuscula, C. rangiferina, C. uncialis, Cornicularia aculeata.

Rare species

Arctostaphylos uva-ursi, Loiseleuria procumbens.

Physiognomy

The Calluna vulgaris-Cladonia arbuscula heath has a dwarfed mat of sub-shrubs with few vascular associates but with a prominent contribution from lichens, which form an often co-dominant patchwork and which can be so abundant in total as to give stands a grey or yellowish hue even from a distance. The sub-shrub mat is commonly less than 5 cm thick, only rarely more than 8 cm, and it can form a fairly extensive and uniform cover, but it is usually discontinuous, sometimes very fragmentary and occasionally disposed in rather particular patterns related to exposure to wind and frost, characteristically severe in the places where this community occurs. Calluna vulgaris is the most frequent component and generally the most abundant, growing in prostrate fashion and often with its flattened branches orientated downwind. These may thus come to overlie older branches of other heather plants, all having their young leafy shoots knotted together into a tight carpet (Metcalfe 1950), or be arranged in wave-like bands with intervening strips of bare or lichen-covered ground, active shoot growth confined to the sheltered lee faces of the bushes (Crampton 1911, Watt 1947). Over gently-sloping ground, similar vegetated zones may develop on small solifluction terraces, where frost-heave and the filtering downhill of rain water and snow-melt push mineral particles among the distal branches of the heather, building up a riser in which shoots can renew their growth, while behind there forms a bare tread (Metcalfe 1950). Wind can contribute to the formation of this kind of microtopography, blowing often this time against the direction of sub-shrub growth as it whips up and over brows, stunting and trimming the advancing front of the bushes but scouring out the back of each terrace and accentuating the steps (Metcalfe 1950, Prentice & Prentice 1975).