Survey, characterisation and condition assessment of Palustriella dominated springs 'H7220 Petrifying springs with tufa formation (Cratoneurion)' in Gloucestershire, England

摘要

Twenty-two Gloucestershire sites were surveyed between 18th and 29th January 2017.ud Gloucestershire, due to its geology, often steep topography, very high levels of saturated calcium carbonate associated with springs of the Stroud Valley area in particular and large areas of woodland, has a large potential for the H7220 petrifying spring habitat.ud Fifteen sites (68%) are identified as having the European Annex 1 habitat H7220, Petrifying springs with tufa formation (Cratoneuron) while 7 sites had tufa formation without H7220.ud The total estimated area for H7220 habitat surveyed within Gloucestershire is 2 ha ranging in size from just 0.0001 ha (Sedbury Cliff) to 0.76 ha (Alder Carr) with the greatest length being some 600 m (Dowdeswell).ud The H7720 feature has been assessed as being in favourable condition for all of the 15 sites where it has been shown to occur although shading (planted conifers) and water quality (Nitrogen) have been highlighted as having potential for negative impact.ud No plants of conservation concern were recorded as directly associated with H7220 vegetation although the following were recorded more generally from sites: the aquatic moss Fissidens rivularis (Slade Brook), 6 Red data Book England (Near Threatened) flowering plants; 8 flowering plants generally considered to be ancient woodland indicators.ud Spring and seepages (particularly when calcareous and/or wooded) are of great importance for invertebrates (crane flies, soldier flies and some specialized snails and water beetles). These habitats are widespread in the UK (and include the H7720 habitat) but their associated invertebrate fauna is poorly known.ud Observations suggest that Palustriella commutata starts growth on firm substrates, mainly stones or living roots, as opposed to deadwood or rotting organic matter and is associated with slower flows and often more gently sloping sites.ud Restoration of H7720 is considered for two sites and restoration techniques discussed.