Mycorrhizal partnerships are symbiotic, or, mutually beneficial, relationships between plants and fungi, that take place around plant roots.

Mycorrhrizae  in the soil have been shown to be essential to plant growth by facilitating the uptake of minerals and nutrients by breaking them down into available forms for the trees to use  as well as stimulating fine root development that lengthen the life of the roots.

They can also protect plants from drought, predators (such as nematode worms), and pathogens (micro-organisms that cause disease). Furthermore, in areas polluted by toxic heavy metals, fungi can buffer their plant partners against harm.

A diversity of fungi is desirable, as different fungi specialize in different functions, as mentioned above. One fungal species may be good at taking up particular nutrients, while another will be better at producing enzymes.

Threats to Mycorrhizae
Mycorrhizae can be damaged by soil compaction and disturbance, as well as by the use of certain chemicals, all of which occur in intensive agriculture and landscape maintenance.

Applying large amounts of inorganic fertilizers to young trees, can suppress the development of mycorrhizae. Excess nitrogen, whether from fertilizer use or atmospheric pollution, affects the reproductive parts of the fungus, and so could have long term effects on fungal populations.

Development practices have greatly affected the life in the soil.  Adding a handful of decaying leaves into a hole that a new tree is planted in can inoculate the soil and help bring back the organisms that the trees need so much!