Synonymy

Arctostaphylos mat Crampton 1911; Loiseleuria-Arctous sociation Poore & McVean 1957; Arctoeto-Callunetum McVean & Ratcliffe 1962, Prentice & Prentice 1975; Alectorio-Callunetum vulgaris (Birse & Robertson 1976) Birse 1980p.p.; Vaccinio-Ericetum cinereae (Birse & Robertson 1976) Birse 1980 p.p.

Constant species

Arctostaphylos alpinus, Calluna vulgaris, Deschampsia flexuosa, Huperzia selago, Racomitrium lanuginosum, Cladonia arbuscula, C. uncialis.

Rare species

Arctostaphylos alpinus, A. uva-ursi, Loiseleuriaprocumbens, Cetraria norvegica.

Physiognomy

Arctostaphylos alpinus occurs with some frequency and occasionally with local abundance in various kinds of dwarfed sub-shrub vegetation, but, through the heart of its range, it is most typical of this Calluna vulgaris-A. alpinus heath where it is a constant, though generally a subordinate one, in the woody mat. Characteristically here, this is very low, almost always less than a decimetre thick, sometimes just a couple of centimetres and often discontinuous with stretches of bare stones between. It is usually dominated by Calluna, the bushes stunted or flattened in the direction of the wind, with the muchcontorted branches finely interlocked. A. alpinus almost always contributes less than 25% of the cover of the mat, but its prostrate stems can grow beneath the heather and they put up little branched sprigs with rather striking bright green reticulate leaves. A. uva-ursi, of generally similar growth habit though with evergreen foliage, also occurs very occasionally in small amounts.

One or other of the crowberries is also very frequent, though of only low to moderate cover, with the creeping stems ramifying among the mat: Empetrum nigrum ssp. hermaphroditum is strongly preferential to the higher altitudes from which this kind of vegetation was first described, and ssp. nigrum largely confined to lower situations. Loiseleuria procumbens, another creeping evergreen Arctic-Alpine, is also characteristically found with ssp. hermaphroditum here, the Calluna-A. alpinus heath providing its major locus in the western part of its range. Erica cinerea, on the other hand, is a frequent companion of ssp. nigrum in lower-altitude stands of the community.

Vaccinium myrtillus occurs commonly throughout, but typically as sparse shoots, and V. uliginosum and V. vitis-idaea are only very occasionally found. Salix herbacea is sometimes seen as small scattered sprigs. Juniperus communis ssp. nana occurs in some stands, but the generally small contribution of this plant here helps distinguish this vegetation from the Calluna-Juniperus heath.