HE4B Molinia caerulea – Nardus stricta heath
Vegetation
This is a rather variable community in which the main field layer species are Molinia caerulea, Nardus stricta and Carex panicea. Dwarf shrub cover is provided by Erica tetralix and Calluna vulgaris but is typically low. Other constant vascular plants are Potentilla erecta, Narthecium ossifragum and Trichophorum cespitosum/germanicum. In addition to Carex panicea, there are several frequent species which are indicators of disturbance or flushing: Juncus squarrosus, Juncus bulbosus, Eleocharis multicaulis and Carex viridula. In the bryophyte layer, the main species are Racomitrium lanuginosum, Hypnum jutlandicum and Campylopus atrovirens. Sphagnum compactum, an indicator of disturbance, is occasional.
Ecology
This vegetation occurs mainly on the middle slopes of hills and mountains, on peaty, acidic, infertile soils (mean altitude = 241 m, n = 14; mean slope = 13.2°, n = 13). It may develop from other wet heath types due to grazing pressure (mean extent of bare peat = 17.3%, n = 39). There is also a distinct element of flushing.
Sub-communities
Two sub-communities have been described. The Juncus bulbosus – Carex echinata sub-community (HE4Bi) represents the more flushed examples of this assemblage. Eriophorum angustifolium, Carex echinata, Juncus bulbosus, Eleocharis multicaulis and Drosera rotundifolia are all much more frequent there than in the grassier Nardus stricta – Agrostis canina/vinealis sub-community (HE4Bii) in which Juncus squarrosus is often found.
Similar communities
From other HE4 Molinia heath communities, HE4B is differentiated by the high cover of Carex panicea and the presence of other flush-preferring species. It is noteworthy that ‘brown mosses’ associated with alkaline flushes and fens are not typically found in this community. From the grassland communities of the GL4 Nardus stricta – Galium saxatile group, HE4B differs in the abundance of heath species including Molinia caerulea, Narthecium ossifragum and Erica tetralix.
Conservation value
This is on average a species-rich community (species/4 m2 = 20.8, n =133). Most instances can be referred to the EU HD Annex I habitat 4010 Wet heath but there are also some cases from habitat 7130 Blanket bog (active)*.
Management
This community, which often forms parts of commonages, is usually used as rough grazing land (typically for sheep) and there are signs of overgrazing. Burning may be periodically used across large areas to suppress the dwarf shrubs and encourage grass growth. Another threat is agricultural improvement.