Soil structure depends on the association between mineral soil particles (sand, silt, and clay) and organic matter, in which
aggregates of different size and stability are formed (54). Mechanically resistant microaggregates (,250 mm) evolve
through interactions of primary particles with microorganisms,plant roots, fungal hyphae, polysaccharides, and humic materials.They build distinctly less stable macroaggregates (.250 mm), which can be destroyed by changing the soil management (54). This kind of aggregation is held together by a network of roots and hyphae (46). The structural organization of soil particles provides a spatially heterogeneous habitat for microorganisms characterized by different substrate, nutrient, and oxygen concentrations and water contents as well as variable pH values (37).