5 m 



Chart 1. Chart of snow-bed vegetation at altitude of 1090 m in the Rondane 

 Region, Norway, occurring as zones because of the response of species to 

 depth and duration of snow cover. Community boundaries are shown in 

 heavy lines, relief in light form-lines. (See Chart 2 for frequency distribution 

 of species along transect shown in broken line.) (A) Cetrarietum nivalis; 

 (B) Cladonietum alpestris-Betuletosum; (C) Myrtilletum dicranetosum; 

 (D) Deschampsieto-Dicranetum fuscae; (E) Phyllodoco-Juncetum trifidi. 

 (After Dahl, E. (62), "Rondane, Mountain Vegetation in South Norway and 

 Its Relation to the Environment," Figure 9, Aschehoug & Co., Oslo, 1956.) 



nants and the moss Dicranum fuscescens and the hepatic Orthocaulis 

 Jloerkei making up most of the ground cover. A dark-colored, low 

 shrub zone occupies the lower parts of the slopes, with Vaccinium 

 myrtillus as the chief dominant and having the same ground cover 

 as in the preceding area (see Charts 1 and 2). The next higher 

 zone is light-colored, consisting mostly of the lichen Cladonia 

 alpestris. On top of the ridge where the snow cover is lacking or 

 thin and melts early, the lichens are chiefly Cetraria nivalis and 

 Alectoria ochroleuca.^"^ Some species grow where the snow lasts long 

 and hence it appears that their amplitude range is narrow, while 

 other species such as Vaccinium myrtillus, growing where the snow 

 cover is medium in depth, have a fairly wide range. The lichen 



18 



Species and Populatioims 



