Grand Canyon National Park
There is a great deal of exposed rock in and around the Grand Canyon. Much of of that rock is covered by lichens.
A lichen is what one could call a simple biological “community” because it is made up of at least two mutually-dependent organisms. In a lichen, some type of fungi is found along with green algae and /or cyanobacteria.
A lichen community is therefore stronger than either fungus or algae alone. Here's how they help each other out; the green algae uses the photosynthesis process to produce food for the fungus, while the fungus protects the algae from the elements and extracts nutrients from the rocks and soil.
Lichens usually colonize north-facing surfaces since exposure to the sun's heat and radiation is less on north-facing rocks and slopes. Lichens may also grow on healthy, mature cryptobiotic soil crust, and occasionally on live or dead plant material. Many species of lichen are found within Grand Canyon National Park.
Lichens are well adapted to arid climates since they can produce food at any temperature above freezing. Another thing that makes lichens good desert survivors is that they can soak up more than their weight in water. Fungi and green algae are non-vasular plants (without roots and stems) so they can directly soak up dew and rain into their cells.
Colorado River Plant List (280kb Excel Worksheet)
Canyon Sketches Vol 16 - January 2010
Canyon Sketches Vol 06 - October 2008