Soil structure and its functions in ecosystems: Phase matter & scale matter

Soil structure is the spatial arrangement of a vast array of pore sizes and shapes, driven by the aggregation of soil particles through a range of processes (Letey, 1991). As soil structure
provides pathways for the transport of water, nutrients and gases, and habitats for microorganisms and fauna, it is a fundamental property of soil fertility and quality. Soil structure is composed of two contrast phases, the solid phase of particles and aggregates and the pore phase with a wide range from nanometer to centimeter or even larger in size (Fig. 1). Interacting with these phases is water, which is held in pores by capillarity forces and affects bonding between soil particles.