What is symbiosis between trees and mushrooms?

Mycorrhiza is a symbiotic relationship of trees with certain types of root fungi. Specific mycorrhiza, especially ectomycorrhiza, produce large reproductive bodies such as fungi along the base of the tree. The fungus gets its nutrients from the tree, and the tree contains carbohydrates and a breeding ground for the fungus. Ectomycorrhiza is limited to a few tree families, many of which do not grow without fungi. Some examples of these trees include beeches, alders, oaks, eucalyptus, pines, and spruces.