Although the main roles of the plant roots are: to strongly maintain the plant in the soil, to adsorb water and nutrients from the soil, and to interact with the soil microorganisms, they are also able to influence the soil structure through these five mechanisms: (1) soil penetration by roots, (2) soil water fluctuations, (3) rhizodeposition, (4) root degradation, and (5) root trapping of soil particles (Rillig and Mummey, 2006). By affecting plant growth (root/shoot ratio) AM may influence these activities (Miransariet al., 2007, 2008).