Above the tree line , there is often a band of dwarf pine trees ( Pinus mugo ) , which is taking place of dwarf shrubs . These shrubs are Rhododendron ferrugineum ( on acid soils ) or Rhododendron hirsutum ( on non-acid soils ) . Above the forestry , there is often a band of short pine trees ( Pinus mugo ) , which is in turn superseded by dwarf shrubs , typically Rhododendron ferrugineum ( on acid soils ) or Rhododendron hirsutum ( on alkaline soils ) .