|Scientific name||Molinia caerulea – Potentilla erecta – Erica tetralix heath|
|Common name||Purple Moor-grass – Tormentil – Cross-leaved Heath heath|
Download full pdf synopsis: HE4D
Dense Molinia caerulea dominates this community, often forming dense tussocks and a thick litter layer. The only other constant species is Potentilla erecta. Frequently there is some spindly growth of Erica tetralix and occasionally some Calluna vulgaris or Myrica gale, but dwarf shrub cover is typically very low. Other occasional plants are Succisa pratensis, Agrostis canina/vinealis and Anthoxanthum odoratum. The bryophyte layer is very sparse or absent; some hunting amongst the leaf litter may reveal some patches of Sphagnum capillifolium, Hypnum jutlandicum or Kindbergia praelonga.
This is mostly a community of lowland peatlands, usually occurring as a part of wet heaths or disturbed blanket bog. Soils are wet, acidic and infertile. There may be some degree of groundwater flushing but it is not pronounced.
No sub-communities have been described for this community.
The very high cover of Molinia caerulea separates this assemblage from the other bog and heath communities, even the others within the HE4 Molinia caerulea – Polygala serpyllifolia group. Dense Molinia tussocks are also found in the similar GL1D Molinia caerulea – Potentilla erecta grassland, but that is a community of more mesotrophic wetland systems and the tussocks are accompanied by species such as Agrostis stolonifera, Filipendula ulmaria, Holcus lanatus and Galium palustre.
This is on average a very species-poor community. Most examples represent either non-priority versions of EU HD Annex I habitat 7130 Blanket bog (active)* or rather marginal types of habitat 4010 Wet heath, depending upon context and peat depth.
Whilst this vegetation may occur naturally as a type of weak flush, it has probably developed in many instances due to negative impacts on the habitat, such as overgrazing, typically by sheep, or burning. On deeper peats, turf-cutting and associated drainage works may be contributing factors. Threats include agricultural improvement and afforestation.