fulltext - DiVA

230 LENNART GRANMARKsome of the great lakes intended as reservoirs forthe hydroelectric development and therefore investigatedsince the middle fifties under the guidanceof G. EINAR Du RIETZ.The transparency in these lakes differs duringvarious seasons and from one lake to another. Somehave a transparency between 600 and 800 cm inAugust and a few 800 to 1100 cm. (In lakes receivinggreat quantities of glacial ooze during the summerthe Secchi disc may sometimes disappear at only15 cm.) The colour of water against the white discis often green or yellow-green. In general the lakeshave a - pH range of 6.6-7.0 and their specificconductivity x20 ·106 is usually 15 to 30. Thus theconcentration of dissolved electrolytes is very low,for instance the calcium value lies in some lakes at1.8 mg Cafl, in other lakes at 2.8 mg.Fig. 2. Zonation on exposed steep rock, Lake Satisjaure,W part. Note the conspicuous lower limit of foliaceouslichens, and the lack of soil up to the lowest birches. Topleft: Betula nana. Aug. 15, 1961. Photo L. Granmark.lakes we find a usually sparse vegetation of Isoetesechinospora, I. lacustris, Ranunculus reptans,Subularia aquatica, M yriophyllum alterniflorum,Utricularia spp., Hippuris vulgaris, and a stonewart(Nitella sp.). The floating-leaf plants sometimesgrow more densely, often represented bySparganium Friesii, S. angustifolium, Ranunculuspeltatus, the white-flowering Nymphaea candidaand the yellow Nuphar luteum and N. pumilum(with hybrid swarms). Also various species ofpondweed occur, e.g. Potamogeton natans, P. perfoliatus,P. alpinus, in Muddusjaure even P. pusillus.On or near the shores grow Phragmites communis,Hippuris vulgaris and the marsh plants Equisetumfluviatile, Scirpus lacustris, Menyanthes trifoliata,Oarex aquatilis and 0. rostrata.HIGH-TRANSPARENT LAKES.-Our knowledgeabout the water vegetation of clear oligotrophiclakes in the woodland of Lule Lappmark is incompleteand nearly all small lakes situated betweenthe river valleys remain uninvestigated.More information has been gathered concerningLAKE SATISJAURE .-As our knowledge of vegetationand chemical conditions in the waters of thiswoodland region is so scanty, a single example witha short description might be of interest. Among themany tributaries of the Stora Lule river, one of thegreatest is the Vietasjokk with a drainage area of2371 km2• Lake Satisjaure, located at an altitude of440 m, is the only large woodland lake in the catchmentarea of the Vietasjokk. Although Satisjaurelies partly in the National Park of Stora Sjofallet,it is intended to become a reservoir for the largeVietas power plant still under construction, andit is already spoilt as a natural habitat for littoraland aquatic life. The lake has a surface area of48 km2, it is 28 km long but its greatest width isonly 3 km. The mean depth is about 30 m, thegreatest known depth 60 m. Near the north-westernpart of the lake lie Mts. Joubmotjakko (1192 m)and Nieras (1463 m) but the other surroundingheights do not exceed 900 m. The slopes next tothe lake are partly covered with primeval forestschiefly of pine and spruce.The shores of Satisjaure consist for the main partof boulders, shingle or deposits of coarse gravel.Shores oi fine gravel, sand or mud occur less frequently.As sheltered beaches are rare, the shoresare much affected by the action of the prevailingstrong winds and rough waves, and in consequenceActa Phytogeog1-. Suec. 50