Arbuscular mycorrhizal fungi: Essential belowground organisms for earth life but sensitive to a changing environment

Changes in the soil and environment rarely occur in isolation and new insights into their impacts on arbuscular mycorrhizal fungi (AMF) in moderating ecosystems processes are needed. Any climate, soil and/or plant type change affects activity and biomass of extra radical mycelia of AMF and can consequently impact on the physiology of the host plant as well as on soil structure and rhizospheric microorganisms. Mycorrhizae have immediate access to plant root exudates and can alter the chemical composition and relative abundance of these exudates, which are a source of nutrients for many soil organisms. Thus, mycorrhizal symbiosis can directly and indirectly influence soil microbes, nutrient cycling and plant growth. Studies have revealed that AMF arecosmopolitan organisms which are present around the world and in particular in tropical dry forests, in temperate grasslands and in riparian forests. However, mycorrhizae formation is susceptible to environmental changes in both soils as well as in host plant populations. Due to the large number of factors affecting mycorrhizas the symbiosis is stilllittle understood and it is not yet been efficiently used despite their enormous potentiality. This work explores the current research on the effects of environmental changes produced by human activities on the mycorrhizal symbioses, drawing on results mainly in agroecosystems and succession on disturbed ecosystems from Argentina and Brazil.Additionally, factors affecting indigenous mycorrhiza from different successional stages in the semiarid region of Brazil ecosystems and their possible role in the composition and stability of plant communities are discussed.     Key words: Arbuscular mycorrhiza, environmental changes, human activities.