I first encountered reindeer lichen in the high elevations of the Smokies in Tennessee and North Carolina. It grows on heath balds with sand myrtle, azalea, mountain ash and other plants that survive in places that have little soil nutrients and lots of wind.
This lichen grows on bare soil. It has a bushy structure. It is white when it is dry and pale green when it is wet. It is a survivor and lives not only at the top of mountains, but in the northern most latitudes in the boreal forest and on the tundra in the arctic circle.
These are tough organisms - made up of a fungal and algal partner. They are a main food source for Caribou (Reindeer), Moose, and Musk Ox that live in arctic ecosystems. They have special bacteria in their guts to digest the lichen.
Reindeer lichens and other lichens and mosses growing close together form mats that sequester carbon, help regulate water tables, maintain cool soils, and prevent soil erosion. They are very important organisms in northern ecosystems.
Check out this article on Food of Santa's Reindeer from The Outside Story published by Northern Woodlands.