The Impact of Mycorrhizosphere Bacterial Communities on Soil Biofunctioning in Tropical and Mediterranean Forest Ecosystems

Mycorrhizal fungi constitute a key functional group of soil biota that greatly contribute to productivity and sustainability of terrestrial ecosystems. These are ubiquitous components of most of the ecosystems throughout the world and are considered key ecological factors in governing the cycles of major plant nutrients and in sustaining the vegetation cover (van der Hejden eta!. 1998; Requena et al. 2001; Schreiner et al. 2003). Two major forms of mycorrhizae are usually recognized: the arbuscular mycorrhiza (AM) and the ectomycorrhizas (ECMs). AM symbiosis is the most widespread mycorrhizal association type with plants that have true roots, i.e. pteridophytes, gymnosperms and angiosperms (Read eta!. 2000).