OR/14/043 Selection of H7220 Petrifying springs with tufa formation (Cratoneurion) by other EU member states

Farr, G, Graham, J, and Stratford, C. 2014. Survey, characterisation and condition assessment of Palustriella dominated springs 'H7220 Petrifying springs with tufa formation (Cratoneurion)' in Wales. British Geological Survey Internal Report, OR/14/043.

Since the recent publication of the Interpretation Manuel of European Union Habitats (European Commission, 2013), a number of recent and relevant ecological studies provide for the selection of H7220 Petrifying springs in a small number of EU member states. These studies are either existing (i.e. relevant to the selection of H7220 springs) or were undertaken very near to publication of the interpretation manual (i.e. pre-emptive to the duty to select H7220 springs).

These studies have all followed the European Commission’s Interpretation Manuel in selection of H7220 springs in that all sites selected (or surveyed or characterised) were ‘springs with active formation of tufa’.

The following two studies (in particular) highlight the difficulties in selecting H7220 springs within different EU member states when there are local differences in geology, types of site (such as Boreal mountain, wooded and stream side), occurrence and types of tufa deposition, natural occurrence of key plant species that characterise the vegetation type:

Ireland — All sites described had actively forming tufa accumulations associated with bryophytes (usually Palustriella commutata) with many sites in woodland and/or associated with streams. Most of the tufa formations (relating with certainty to Carboniferous Limestone glacial drift but perhaps also calcareous strata within the Old Red Sandstone) are described as ‘cascades’ (formed by water flowing or trickling down a slope) and associated formations (Heery, 2007).

Netherlands — Tufa formation associated with hard-water springs is very rare in the Netherlands. The potential area of H7220 is naturally limited by specific geological and hydrological conditions and thus restricted to areas underlain by limestone or other calcareous rocks. Only in Limburg does groundwater rich in calcium carbonate come to the surface, allowing deposits of tufa to be formed.

The overall quality of the habitat varied considerably from one place to another, as well as within sites. Ninety-six of the investigated springs (34 percent) failed to qualify as H7220, and the quality of over 50% of the 187 springs that did qualify was poor, mostly as a result of desiccation or due to a tufa coverage far below the minimum of 10 m². Springs with extensive tufa banks and tufa cascades are restricted to the Bunder-en Elsloërbos wood and the Noorbeemden/Hoogbos wood, both Natura 2000 sites. The quality of habitat type H7220 in the Geuldal valley and several smaller sites is far lower, though some good examples of petrifying springs with tufa were observed near Vliek and Waterval.

Among the qualifying species, Brachythecium rivulare and Cratoneuron filicinum appeared to be very common. The very rare Palustriella commutata was only found in springs in the Bunder-en Elsloërbos and Noorbeemden/Hoogbos woods, where extensive stands of Palustriella commutata were identified as Cratoneurion, an underestimated and so far under described bryophyte syntaxon in the Netherlands. (K van Dort et al., 2012).