Lichens and nitrogen cycling

Some types of lichen are able to fix nitrogen from the atmosphere. This process relies on the presence of cyanobacteria as a partner species within the lichen. The ability to fix nitrogen enables lichen to live in nutrient-poor environments. Lichen can also extract nitrogen from the rocks on which they grow.

Nitrogen fixation, and hence the abundance of lichen and their host plants, may be decreased by application of nitrogen-based agricultural fertilizer and by atmospheric pollution.