The class Montio-Cardaminetea includes vegetation of springs with constant water flow. These habitats, which function as islands for highly specialized and sensitive biota, are endangered by ongoing landscape and climatic changes. Although a harmonized classification into vegetation units is necessary for effective habitat conservation, there is currently no synthetic classification of the class Montio-Cardaminetea. Here a large set of vegetation-plot records was obtained from national and private databases. The aim was to validate the EuroVegChecklist classification scheme, search for additional ecologically meaningful vegetation types and develop an automatic system for classifying new plots from Europe. We formally defined the cores of eight of the ten EuroVegChecklist alliances: Caricion remotae, Cratoneurion commutati, Lycopodo europaei-Cratoneurion commutati, Epilobio nutantis-Montion, KoenigioMicrojuncion, Mniobryo-Epilobion hornemanii, Philonotidion seriatae (Cardamino-Montion) and Swertio perennis-Anisothecion squarrosi, which were also reproduced by unsupervised classifications. Both unsupervised and semi-supervised classifications further suggested two alliances not previously recognized in the EuroVegChecklist: Anthelion julaceae (liverwort dominated subalpine to alpine springs in highly oceanic regions in Britain) and Cratoneuro filicini-Calthion laetae (mesotrophic herb-rich subalpine and alpine springs). The unsupervised classifications mainly reflected the base saturation gradient, distinguishing between calcareous and non-calcareous springs. Therefore, it is suggested the order Montio-Cardaminetalia, which is broadly delimited in the EuroVegChecklist, be divided into two separate orders and the following three orders should be distinguished within the class Montio-Cardaminetea: CardaminoChrysosplenietalia (non-calcareous forest springs; Caricion remotae), Cardamino-Cratoneuretalia (calcareous springs; Cratoneurion commutati, Lycopodo europaei-Cratoneurion commutati) and Montio-Cardaminetalia (non-calcareous non-forest springs; all other alliances).

Introduction. Rates of deposition of tufa in petrifying springs are complex and highly variable, and the growth rates of associated bryophytes are poorly known. Methods. Tufa deposition and bryophyte growth rates were measured using novel methods at six petrifying spring sites in Ireland, north-western Europe. Tufa height was measured at 293 point locations, from 2011 to 2013, using fixed bars mounted above actively growing deposits. Most samples were bryophyte-dominated and the height increments of individual species were measured. Environmental factors were recorded and the chemical composition of spring water was analysed. Results and Conclusions. Tufa deposits increased in height by 20.5 +/- 1.1 mm.yr(-1) on average. The pleurocarpous moss Palustriella commutata, in particular, was associated with rapid deposition. Mixed effects modelling revealed a significant interaction between P. commutata and the presence of surface water: together, they increased annual deposition of tufa by 5.7 +/- 1.9 mm. The mean height increment for bare, unvegetated tufa was only 16.5 +/- 3.0 mm.yr(-1). Palustriella commutata can outgrow the mean rate of tufa deposition, with a mean annual increment of 27.6 +/- 1.9 mm in depth of sward. The smaller acrocarpous mosses Didymodon tophaceus and Eucladium verticillatum grew in height by only 9.1 +/- 1.6 mm.yr(-1) and 9.5 +/- 1.3 mm.yr(-1) respectively; these two species cannot, therefore, contend with the most rapid rates of tufa deposition. A colonisation cycle was observed, involving competitive displacement of the smaller species by P. commutata. Non-intrusive methods enabled rapid deposition rates to be detected.

Aims: To investigate the floristic and abiotic characteristics of the Habitats Directive priority habitat 'Petrifying springs with tufa formation (Cratoneurion)'. Location: The island of Ireland, north-western Europe. Methods: Vascular plants, bryophytes and abiotic variables were recorded in a field survey of 186 releves (4 m(2)). Releves were assigned to groups based on species composition, using fuzzy clustering and Indicator Species Analysis. Eight plant communities were described. Results: Group 1 Eucladium verticillatum-Pellia endiviifolia Tufa Cascades, of steep slopes, are related to Continental Eucladietum verticillati and Adiantion communities. Group 2 Palustriella commutata-Geranium robertianum Springheads and Group 3 Brachythecium rivularePlatyhy-pnidium riparioides Tufaceous Streams and Flushes are woodland communities related to the Equiseto telmatejae-Fraxinetum and the Pellio endiviifoliae-Cratoneuretum commutati. Groups 1 to 3 fall broadly within the Brachythecio rivularis-Cratoneuretum forest spring vegetation type. Group 4 Palustriella commutataAgrostis stolonifera Springheads are intermediate between Groups 1 to 3 and Groups 5 to 8. Group 5 Schoenus nigricans Springs, Group 6 Carex lepidocarpa Small Sedge Springs and Group 7 Palustriella falcata-Carex panicea Springs are transitional to Caricion davallianae small-sedge fen communities. Group 8 Saxifraga aizoides-Seligeria oelandica Springs are ecologically distinctive, species-rich assemblages confined to montane cliffs, with a restricted distribution in upland limestone regions, containing a number of nationally and internationally rare taxa. Of our eight groups, Groups 7 and 8 have the closest affinities with Cratoneureturn falcati spring communities. Abiotic variables differ significantly among the eight groups. Slope, macronutrient levels and shading by tree canopies are highly significantly related to the main axes of variation in the floristic data. Species diversity is inversely related to phosphate levels. Group 8 communities are irrigated by water of the highest pH and lowest solute concentrations. Conclusions: Our eight groups characterise variation within the habitat, elucidate ecological gradients with related habitats and facilitate conservation of this ecologically distinctive habitat.