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Mountain mires 255Spring vegetationSpring vegetation is developed around concentratedoutflows of subsoil water. Some authors (e.g.SJORS 1946, 1948a) have placed the spring vegetationwithin the fen series. Others (e.g. G. SAMUELS­SON 1917, KALELA 1939 and NORDHAGEN 1943)have laid stress upon the rich occurrence of meadowplants. In fact, there is a gradient from springvegetation rich in fen plants to spring vegetationrich in meadow plants (spring fen to spring meadow,SJORS 1950b, p. 190).Especially in the bottom layer there are specieswhich more or less obviously prefer spring vegeta tion, e.g., Cratoneurum spp., Philonotis fontana, Ph.seriata, Bryum W eigelii, Dicranella squarrosa andScapania uliginosa. Among vascular plants characterizingspring vegetation are Saxifraga aizoides,Epilobium Hornemanni, E. alsinifolium and Montiafontana ssp. lamprosperma.Along the rich-to-poor gradient three main typesof spring vegetation can be distinguished. TheCratoneurum spring vegetation (Cratoneureto-Saxifragionaizoidis, NoRDHAGEN 1936a, 1943), occurringin calcareous areas, is characterized by Cratoneurumcommutatum (incl. var. falcatum), C. decipiens andLeiocolea bantriensis. Saxifraga aizoides, a mountainplant, seems to be the only field layer speciesactually preferring Cratoneurum vegetation, butthere are numerous other field layer species. Manyof them occur also in either rich fen or meadowvegetation, or both, and distinguish the Cratoneurumvegetation from poorer types of spring vegetation,e.g., Crepis paludosa, Cystopteris montana,Thalictrum alpinum and Carex capillaris. C. vaginatais common but hardly exclusive to "rich"vegetation. From mountain or upland areas Cratoneurumspring vegetation has been described byNORDHAGEN (1936a, 1943), KALELA (1939), SJORS(1946, pp. 82-83; 1950a, pp. 27-29), DAHL (1956,pp. 210-212) and A. PERSSON (1961, pp. 134---141).In non-calcareous mountain districts the springvegetation is dominated above all by Philonotisfontana, Ph. tomentella and Pohlia (Mniobryum)albicans (Mniobryo-Epilobion Hornemanni, NoRD­HAGEN 1943; Philonotis-Pohlia albicans vegetation,A. PERSSON 1961). Other important bottom layerspecies are, e.g., Bryum W eigelii and Dicranellasquarrosa, but Cratoneurum species are of littleimportance. Field layer species are less numerous,most of them also occurring in the Cratoneurumvegetation. Among them can be mentioned Epilobiumspp., mainly E. Hornemanni, Angelica archangelica,Polygonum viviparum, Saxifraga stellaris,Stellaria nemorum, Equisetum arvense and Phleumcommutatum. This type of spring vegetation isdescribed by G. SAMUELSSON (1917), KALELA (1939,pp. 367-374), NORDHAGEN (op. C., pp. 420-441),DAHL (1956, pp. 200-210), A. PERSSON (op. c., pp.142-144), and FRANSSON (1963, p. 291).The third type of spring vegetation is found onthe poorest rocks only and is characterized aboveall by Scapania uliginosa together with, e.g., Drepanocladusexannulatus, Philonotis fontana, SphagnumGirgensohnii, S. Lindbergii, S. parvifolium andS. teres (G. SAMUELSSON 1917, DAHL 1956, KALELA1939, SJORS 1946 and A. PERSSON 1961). Cratoneurumspecies are absent, and even Pohlia albicansin the poorest types. In the vry sparse field layergrow various unpretentious plants, even non-hygrophytes,e.g., Andromeda polifolia, Betula nana,Salix spp. (small individuals), Vaccinium uliginosum,Pinguicula vulgaris, Saxifraga stellaris, Epilobiumspp., Deschampsia caespitosa, D. flexuosa,Eriophorum angustifolium, Equisetum silvaticumand Trichophorum caespitosum.When the described spring vegetation series iscompared with the rich fen-poor fen series, Cratoneurumspring vegetation corresponds to extremelyrich fen vegetation, Philonotis-Pohlia albicansvegetation to moderately rich fen vegetation andScapania uliginosa spring vegetation to intermediatefen vegetation (SJORS 1950b, p. 190; A. PERSSON1961, p. 147).Notes on acidityThe differentiation of the mountain mire andspring vegetation along the rich-to-poor gradientruns parallel to differences in the acid-base statusof the peat and the water. Early measurements ofpH in water from mountain mire sites were carriedout by 0HRISTOPHERSEN (1925, see also. NORDHAGEN1928). KALLIOLA (1939) and NORDHAGEN (1943)have published values of pH obtained from peat.Acta Phytogeogr. Suec. 50