A great many terrestrial plants live in close association with fungi. The features of this association known as mycorrhiza, are those of a mutualistic symbiosis. Almost all plants form mycorrhizae whereby the fungus provides soil resources to the plant in exchange for energy manufactured by the plant. The symbiosis means greater productivity under stress for the plant and a steady energy supply for the fungus. This book addresses the diverse and complex ways in which mycorrhizae affect the mechanisms for plant survival as individuals and populations, for community structure, and for ecosystem functioning. It integrates information on organisms interacting with mycorrhizae from bacteria to mammals. The author takes a unique evolutionary/ecological approach to describe how and under what conditions mycorrhizae influence basic ecological processes. The applications of mycorrhizal symbioses range from managing natural and agricultural lands to biotechnological processes that enhance agricultural productivity and sustainability.