fulltext - DiVA

The southern mires 155In addition, as a result of the greater flow of water,the poor fen vegetation is also better supplied withK than the bog vegetation, for the amount of Ksupplied per unit area in a fen increases in proportionto the flow of water. There is a much greaterquotient of this element dissolved in the waterthan of N and P. Some additions of all kinds ofnutrients to the mire margin may be derived fromlitter produced by near-by forest trees.Rich fen vegetationThe poor fen vegetation already mentioned isespecially characteristic of the Archaean areas in·the uplands. Only locally is here found a type of fenvegetation that can be referred to the moderately(or transitional) rich fen vegetation or Warnstorfio­Scorpidion. It is easily separated from similartypes of poor fen vegetation through the bottomlayer. In the mud-bottoms Scorpidium scorpioidesis found, either alone or together with any of thespecies of the Sphagnum subsecundum group. Thealgal vegetation is rich in species (THUNMARK 1942,Du RIETZ 1950a and c, FLENSBURG in this book).Normally above water-level in summer there aretwo alternating communities, both with a closedbottom layer, one characterized by Campyliumstellatum and Drepanocladus revolvens and theother by Sphagnum plumulosum and S. teres. Hummockswith S. fuscum and (more rarely) S. rubellumare common.The rather sparse field layer is similar to that inthe treeless poor fen vegetation of mire expansetype. Differential species occurring in this type ofvegetation are in its wetter parts, e.g., Carexpanicea, C. tumidicarpa, Eleocharis pauciflora andTriglochin palustre, and in its drier parts, e.g.Trichophorum alpinum. In the hummock vegetationCarex dioeca is one of the few differential species,when compared with the corresponding poor fenhummock vegetation. The rare northern speciesCarex livida and Juncus stygius may occur in themud-bottoms and become less rare further north.Erica tetralix, N arthecium ossifragum and M oliniacoerulea are species often met with in those Oarnpylium-Drepanocladuscommunities which occur insouth-western Sweden.This and similar types of mire vegetation do not11 - 652151 APhS 50only occur where the surrounding mineral soil isricher than usual in basic minerals. Adjacent tosprings or other outflows of subsoil water they arealso met with in areas of poor soils. In the fen vegetationfed by such springs or seepages the followingspecies often occur: M enyanthes trifoliata, Trientaliseuropaea, Viola palustris, Carex rostrata, Juncusarticulatus, Calliergonella cuspidata, Drepanocladusexannulatus, Mnium punctatum, Philonotis fontana,Sphagnum plumulosum and S. teres.The pH of the open water in sites with these typesof fen vegetation is about 5.5-6.0 and the contentof Ca generally somewhat higher than in watersfrom sites with poor fen vegetation (WITTING 1947,1948; MALMER 1962b). Of fundamental importancefor the development of this type of vegetation isprobably a constant supply of subsoil water fromdeeper, unleached layers of mineral soil. On siteswith poor fen vegetation, in contrast, a supply ofsuch water seems to be of small importance ascompared to the supply of water of more superficialorigin (MALMER 1962 a).In calcareous areas (mainly in the lowland) richerfen types prevail. The treeless vegetation on mainlyhorizontal fen sites shows a very characteristic differentiationin the bottom layer. Together withalgae in the wettest parts grow scattered individualsof Scorpidium scorpioides, sometimes with Calliergontrifarium intermingled. On slightly less wetsites Campylium stellatum and Drepanocladus revolvens(including D. intermedius) form a closed bottomlayer mixed in with Campylium elodes and Preissiaquadrata. At a higher level these species are replacedby Ctenidium molluscum and Fissidens adianthoides,often together with Bryum pseudotriquetrum.In the field layer a corresponding differentiationis hardly distinct. Scattered individuals of Carexlepidocarpa, C. panicea, Eriophorum latifolium, Juncusalpinus ssp. arthrophyllus and Triglochinpalustrecharacterize the wettest parts. Above this level thetussock-forming Schoenus ferrugineus is the mostcommon dominant, sometimes overgrown by M oliniacoerulea or Sesleria coerulea. There are manyother typical species, e.g. Dactylorchis spp., Epipactispalustris, Liparis Loeselii, Parnassia palus-.Acta Phytogeogr. Suec. 50