These specialized fungi invade the root tissue and form a structure referred to as mycorrhizae. Ectomycorrhizae live on and in the roots of pine, spruce, fir, beech, eucalyptus, alder, oak, and hickory trees. Ectomycorrhizal feeder roots are swollen and normally are forked, in the case of pine. Endomycorrhizae live in the roots of maple, sycamore, ash, sweetgum, walnut, cypress, cedar, and some poplar trees. These fungi grow into the root cells and lack a mantle.
Trees benefit from mycorrhizae in several ways.
The availability of nutrients to the trees. Resistance to certain root diseases. The tolerance of the tree to stress. Mycorrhizal formation is usually adequate under natural conditions. The mycorrhizal fungi live in the forest soils and duff, and invade the new tree seedling from the start.