H8 - Calluna Vulgaris-Ulex Gallii Heath

Summary

Synonymy

Limestone heath Hope-Simpson & Willis 1955 p.p.; Agrosto-Ulicetum gallii Shimwell 1968 p.p.; Ulici-Ericetum cinereae Bridgewater 1970; Calluno-S cille turn vernae, Ulex gallii subassociation Malloch 1971 ; Calluna-Ulex gallii heaths Gimingham 1972; Grass-heath Ward et al. 1912a p.p.

Constant species

Calluna vulgaris, Erica cinerea, Ulex gallii.

Rare species

Agrostis curtisii, Viola lactea.

Physiognomy

The Calluna vulgaris-Ulex gallii heath is a floristically rather diverse community with only three constants overall, but its characteristic mixture of Calluna vulgaris, Ulex gallii and Erica cinerea, typically lacking E. tetralix, Molinia caerulea or Agrostis curtisii, is quite diagnostic. Often, the three sub-shrubs are co-dominant, though their proportions are quite variable and locally each can be poorly represented, E. cinerea in particular tending to become patchy where the community extends on to cooler aspects and to higher altitudes. In the latter situations, too, this kind of heath can have small amounts of Vaccinium myrtillus. On disturbed ground, as along pathways or over abandoned fields and settlements, U. europaeus may occur with some abundance.

Typically, the sub-shrub canopy is of high cover, sometimes excluding all but a very sparse herbaceous component but, quite often, the bushes are separated by systems of grassy runnels and, where the vegetation has been open to grazing, the structural contrast between these two components can be sharply accentuated. Where the bushes themselves are nibbled, a common occurrence, the canopy can be reduced in height: it is generally less than 30 cm, and a frequent picture is of dense ‘hedgehogs’ of gorse with short, but rather more untidy, bushes of heather scattered amongst them. In coastal stands, too, exposure to wind helps limit subshrub growth and, in exceptional cases, cliff-top heaths which are also heavily grazed can have a very tight cover of woody growth no more than a few centimetres high. Burning can also affect the structure and composition of the vegetation: controlled fires are rare but accidental burns can open up the ground, providing an opportunity for local dominance of U. gallii which can sprout vigorously from surviving buried stools, or E. cinerea, which can seed prolifically and out-perform Calluna in the early years of recovery, particularly on warmer aspects. Such temporary perturbations of dominance may also allow Pteridium aquilinum to increase its representation in this kind of heath.