SD17: Potentilla anserina-Carex nigra dune-slack community

Summary

Constant species

Agrostis stolonifera, Carex nigra, Potentilla anserina, Calliergon cuspidatum.

Physiognomy

The Potentilla anserina-Carex nigra dune-slack community comprises generally closed swards up to a decimetre or so high dominated by mixtures of grasses, sedges and rosette or mat-forming herbs. Especially distinctive is the combination of Agrostis stolonifera and Carex nigra with Potentilla anserina, each of these sometimes present in abundance and the last particularly striking when dominating in a ground carpet. Festuca rubra and Holcus lanatus are also very frequent in certain of the sub-communities and there is occasionally some Juncus articulatus. Salix repens is typically of limited occurrence here, though it is frequent and locally abundant in one type of Potentilla-Carex slack.

The other most frequent vascular associates overall are Ranunculus repens, Trifolium repens, Cardamine pratensis, Equisetum palustre and Euphrasia officinalis agg. Tall herbs like Iris pseudacorus, Angelica sylvestris and Filipendula ulmaria can give a locally distinctive stamp to the vegetation while species such as Elymus repens, Triglochin maritima and Carex disticha may lend a hint of the upper salt-marsh.

The only bryophyte which is at all frequent in the community is Calliergon cuspidatum and it can be locally abundant. Other species like Plagiomnium rostratum, Brachythecium rutabulum and Eurhynchium praelongum occur very sparsely.

Sub-communities

Festuca-rubra-Ranunculus repens sub-community. In this grassy kind of Potentilla-Carex vegetation, Festuca rubra is very frequent and of quite high cover with common records too for Ranunculus repens, Bellis perennis and Trifolium repens.