SD13: Sagina nodosa-Bryum pseudotriquetrum dune-slack community

Summary

Synonymy

Calliergon cuspidatum-Salix repens nodum Jones 1992 p.p.; Young dry slack nodum Jones 1992

Constant species

Carex arenaria, Juncus articulatus, Leontodon hispidus, Sagina nodosa, Salix repens, Aneura pinguis, Bryum pseudotriquetrum.

Rare species

Equisetum variegatum, Pyrola rotundifolia, Moerckia hibernica, Petalophyllum ralfsii.

Physiognomy

The Sagina nodosa-Bryum pseudotriquetrum dune-slack community comprises short and often rather open swards dominated by a low and patchy cover of Salix repens, a patchy turf of grasses and diminutive herbs and a sometimes extensive contingent of mosses and thalloid liverworts. The vegetation is typically submerged briefly and to shallow depths in the winter and it is on the bare damp patches of sand and shell debris exposed as the water level falls that the various ephemerals and less competitive bryophytes of the community can gain a hold.

Apart from S. repens, the commonest vascular perennials are Carex arenaria, Juncus articulatus and Agrostis stolonifera, all typically represented by sparse shoots, with small scattered rosettes of Leontodon hispidus. Among these, by late spring, there are often numerous tiny plants of Sagina nodosa with the more prominent Centaurium eythraea. Seedlings of Rubus caesius occasionally figure and there are sparse plants of Samolus valerandi, Mentha aquatica, Carex serotina, Equisetum palustre and Taraxacum officinale agg. Ammophila arenaria is typically very scarce in this vegetation and of insignificant cover.