OR/17/020 Conclusions

Farr, G, and Graham, J. 2017. Survey, characterisation and condition assessment of Palustriella dominated springs 'H7220 Petrifying springs with tufa formation (Cratoneurion)' in Gloucestershire, England. British Geological Survey Internal Report, OR/17/020.

• Gloucestershire, due to its geology and often steep topography, has a large potential for the H7220 petrifying spring habitat.
• The total estimated area for ‘new’ H7220 habitat in Gloucestershire is 2 ha.
• During this study we identified 15 sites that fit the European Annex 1 habitat H7220, Petrifying springs with tufa formation (Cratoneurion)
• Seven sites had tufa formation but did not have Palustriella commutata.
• H7220 sites can vary greatly in area, the smallest was just 0.0001 ha (Sedbury Cliff) and the largest was 0.76 ha (Alder Carr).
• H7220 sites can also vary greatly in length, with the longest tufa stream section identified as H7220 being some 600 m in length (Dowdeswell).
• The following bryophytes are recorded as directly associated with tufa (Palustriella commutata, Cratoneuron filicinum, Pellia endiviifolia, Fissidens pusillus, Fissidens crassipes, Fissidens rivularis, Fissidens adianthoides, Conocephalum conicum, Chiloscyphus polyanthos, Eucladium verticillatum, Didymodon tophaceus and Platyhypnidium ripariodes).
• Nitrate and phosphate values were applied and although several sites exceeded the nitrate threshold value, we could not see any evidence for unfavourable condition at these sites.
• 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.
• Observations include the preference of Palustriella commutata to grow in areas of slowly flowing water, this may be one reason for the relatively small H7220 habitat at Slade Brook when compared to slower flowing sites.
• Observations include the preference of Palustriella commutata to grow on firm substrates, mainly stones or living roots, as opposed to deadwood or rotting organic matter. We think that stones rather than organic matter (e.g. logs) may provide a better foundation for the restoration of Palustriella commutata dams and pools.
• 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.
• 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.