Constant species

Ranunculus baudotii.

Rare species

Ranunculus baudotii.

Physiognomy

The Ranunculetum baudotii comprises stands of vegetation dominated by open or closed covers of Ranunculus baudotii. It can grow as an annual or perennial plant and is morphologically very variable, being found sometimes with laminar leaves, sometimes without, and able to thrive submerged, when it forms spreading to erect clumps, or terrestrially, when it assumes a prostrate form.

No other species is constant throughout, but there are occasional plants of Zannichellia palustris, Ceratophyllum submersum, Potamogeton pectinatus, Ruppia maritima, Callitriche stagnalis, C. obtusangula and C. platycarpa among submerged stands, with floating Lemna minor and L. gibba. Hippuris vulgaris is also locally common among this kind of vegetation. Where the community occurs on moist ground, Callitriche and Lemna spp. are the usual associates.

Habitat

The community is of local occurrence around the coast of Britain, mainly in the south, where it is characteristic of the shallows and margins of standing and slowmoving, usually brackish, waters in streams, dykes and pools, often now among reclaimed grazing marshes, sometimes in dune-slacks. Disturbance of moist ground in such situations may favour the local spread of this vegetation and it can become prominent in ephemeral habitats, but overall the range of the plant seems to be declining.

R. baudotii has an Oceanic Southern distribution through Europe as a whole (Matthews 1955) and, although it has scattered stations along those parts of the Scottish coast where the winters tend to be equable, it is much more common around the seaboard of southern Britain (Perring & Walters 1962). It has been reported from some inland salt marshes (Rich & Rich 1988) and saline stretches of the Chesterfield canal (M. Palmer, personal communication), but almost all records occur on and around coastal and estuarine sites and, though the plant is tolerant of both fresh and salt water in cultivation (Cook 1966), it strongly favours brackish conditions in the wild.

It also prefers standing or at most sluggishly moving waters, so it is concentrated in that zone where fresh water draining across flat or gently sloping land meets the influence of tidal or estuarine flow.