fulltext - DiVA

Mountain MiresBy AKE PERSSON1 ntroductionMires are often common in the subalpine regionof the Scandinavian mountain range and maysometimes cover large areas. As this region is largelyvery humid, they are even found on markedlysloping ground. They deposit peat in significantlayers even though these are generally shallowerthan in the mires situated in the coniferous forestregions. In the low-alpine region mires (usuallyfens) may be common but they are mainly rathersmall and have usually very shallow peat layers.They occupy plane or only slightly sloping ground.The uppermost impoverished fen vegetation isfound in the middle-alpine region on a very thinpeat layer or directly on the mineral soil.Concerning descriptive classification of mirevegetation in the Scandes the most importantworks have been written in Norway (NoRDHAGEN1928, 1936a, 1943, E. DAHL 1956) and Finland(KALELA 1939, KALLIOLA 1939). In Sweden themountain mire vegetation is unsatisfactorily known.Investigations have been carried out in Dalarna byG. SAMUELSSON (1917), inSarek by TENGWALL (1920)and in north-western Harjedalen and south-westernJamtland by H. SMITH (1920). SJ6Rs (1946) andFRANSSON (1963) have published descriptions ofmire communities in western Jamtland. Bog vegetationin northern Lule Lappmark has been treatedby BJ6RKMAN & Du RIETz (1923).The Tornetrask area in Lappland, northernmostSweden, is the most extensively investigated areain Sweden regarding mountain mires. Mire vegetationhas been investigated by SYLVEN (1904),TH. C. E. FRIES (1913), Du RIETZ (l921a, b), M.WITTING (1949), A. PERSSON & RUNEMARK (1950),A. PERSSON (1961, 1962) and SoNESSON (in progress).The mountain mires are mainly developed asfens, i.e., they are supplied with mineral soil water.True bog vegetation is rare (cf. below).Rich fen vegetationIn calcareous areas the mountain fens are intheir wettest parts occupied by Scorpidium scorpioidescommunities. The sparse field layer ischaracterized mainly by true mire plants such asTriglochin palustre, Eleocharis pauciflora, Eriophorumangustifolium, Oarex limosa, 0. magellanica,0. chordorrhiza, 0. saxatilis and 0. rostrata. Scorpidiumscorpioides is the main dominant in the bottomlayer which is not always closed. Oalliergon trifarium,Drepanocladus exannulatus, D. procerus andD. revolvens (incl. var. intermedius) can be prominent,the latter in somewhat drier places. Drepanocladusexannulatus and D. procerus are commonabove all in "less rich" types (moderately ortransitional rich fen vegetation, see below).Most of the field layer plants capable of growingin these very moist habitats occupied by Scorpidiumvegetation are more or less indifferent with regardto other ecological gradients. Therefore the classificationof the mentioned communities is difficult.Scorpidium communities are distributed almostthroughout Scandinavia but the regional variationis small (for further information, see DAHL 1956,pp. 232-234). NoRDHAGEN (1943, pp. 519-530) andDAHL (I.e.) place these communities in Stygio ­Caricion limosae together with similar communitieswhere Scorpidium is replaced by Drepanocladusexannulatus.In not too wet localities in calcareous districtsa fen vegetation very rich in species is developed.It is easily characterized by its bottom layer.Acta Phytogeog1·. Suec. 50