A20 - Ranunculus Peltatus Community Ranunculetum Peltati Sauer 1947

Summary

Synonymy

Vegetation of nearly stagnant waters Tansley 1911 p.p.

Constant species Ranunculus peltatus.

Physiognomy

The Ranunculetum peltati is dominated by clumps or patches of Ranunculus peltatus, the most variable of the British crowfoots. It can grow as an annual or perennial, submerged in a spreading or erect form, as a frail, floating plant or occur terrestrially, when it is loosely tufted (Haslam 1978, Rich & Rich 1988). Many stands are small and cover can be very sparse, but luxuriant plants develop in congenial situations with maximum growth in early summer.

The Ranunculetum peltati is frequently found in close association with other kinds of aquatic and marginal vegetation, including patches of the Ranunculetum aquatilis, and it can be very difficult to distinguish the two dominants from one another (Holmes 1979, Rich & Rich 1988). In denser stands, however, associates are few and usually not very abundant and such plants as do occur are often amphibious or water-margin herbs. Lemna minor and L. gibba are often found on the surface of the water or moist mud, with L. trisulca occasionally caught among the submerged shoots, and there can be patches of Callitriche spp., C. platycarpa in the stands sampled. Potamogeton natans and Polygonum amphibium are occasionally seen and sometimes there are plants of other Ranunculus spp., such as R. sceleratus, R. trichophyllus and R. circinatus. Later in the season, Glycerio-Sparganion plants often become prominent with patches of Nasturtium officinale, Glyceria fluitans, G. plicata, Apium nodiflorum and Berula erecta.

Habitat

The Ranunculetum peltati is characteristic of the shallows and margins of mesotrophic to quite nutrient-rich waters, occasionally fairly fast-flowing, though usually sluggish or still. It appears to occur through most of southern Britain outside the highland areas, but is especially frequent in the English lowlands. It withstands seasonal or periodic drying out of the habitat and this enables it to persist in fluctuating or ephemeral water bodies.

R. peltatus can be hard to distinguish from R. aquatilis (Holmes 1979, Rich & Rich 1988) and the two taxa are clearly similar in their geographical distribution and ecological preferences, though it has sometimes rather puzzlingly been reported that they do not in fact occur together (Cook 1966). Like the Ranunculetum aquatilis, this vegetation is commonly found growing submerged, and it may penetrate a little deeper (Holmes 1979), although most stands seem to occur in less than 1 m of water.