WE2A Persicaria maculosa – Limosella aquatica inundation community
Vegetation
This is an open community of muddy ground in which the constant species are Persicaria maculosa, Limosella aquatica, Agrostis stolonifera, Gnaphilium uliginousm and Juncus bufonius. Other knotweeds, Persicaria hydropiper and Polygonum aviculare are also fairly frequent here, as are water-cresses in the form of Rorippa palustris, Rorippa islandica or Rorippa nasturtium-aquaticum agg. Water-starworts are a feature of this community with both Callitriche palustris and Callitriche stagnalis having been recorded. Bryophyte cover is very low or absent, although the notable ephemeral liverwort Riccia cavernosa may be spotted.
Ecology
The Persicaria maculosa – Limosella aquatica inundation community occurs on banks of turloughs, reservoirs and rivers, where there is seasonal flooding. The community’s many annual species establish on the fertile mud or stony substrate as it becomes exposed by dropping water levels.
Sub-communities
No sub-communities are described.
Similar communities
Persicaria maculosa is also a key species in the WE1F Persicaria maculosa – Polygonum aviculare weed community, but that is found in drier situations and lacks Rorippa spp., Callitriche spp. and Limosella aquatica.
Conservation value
Examples of this community may correspond to EU HD Annex I habitat 3270 Chenopodion rubri. Limosella aquatica has a restricted distribution in Ireland and is listed on the Flora (Protection) Order, 2015. Species/4 m2 = 9.8, n = 16.
Management
This habitat is dependent upon relatively short periods of exposure that allow the annual species to flourish but prevent perennials from outcompeting them; thus any alterations to hydrological regimes would be problematic. Poaching by livestock is also a threat.