Mycorrhizal fungi are a critical linkage between the soil, containing water and inorganic and organic nutrients, and the plant itself, the photosynthetic unit that converts solar energy to complex C compounds upon which the terrestrial world depends. Sir Arthur G. Tansley (696) first defined the term ecosystem, noting that organisms cannot be separated from their environment, thereby forming a biological–chemical–physical system, or an ecosystem within a relatively stable but dynamic equilibrium. This, the origin of the term ecosystem, breaks down Clements’ concept of biome, where climate is the overriding regulator of the community, into a view of the multiplicity of interacting biotic, chemical, and physical components that allow for the existence of life.