cold-resistant green cushions (clumps

coldresistant plant green cushions clumps ecological forms combining plants rockfoil desert cold cryophyte novaya zemlya saxifrage saxifraga deertongue ecology arctic circle landscape sod soil arid biocenosis chickweed climate crushed rock ecotourism environmental education frigid grasses habitat harsh conditions hummock lichen life condition liverworts microbiota northern nature pioneer association complex polar debris survival guide strategy tundra tussock vegetation community xerophytes cold-resistant ecology types based cryophyte arc