ABSTRACT
The vesicular horizon is a surface, or near surface, soil horizon composed of tiny non-connected circular, ovoid, or prolate pores commonly called vesicles. The horizon has been found to form in soils of a variety of parent materials deposited via eolian processes as dust and is often composed of fine textures. Vesicle pore formation is hypothesized to occur by several different processes with the most widely accepted being entrapped air and soil particle movement following soil wetting (air entrapment due to a wetting front from rain or snowmelt). Field vesicular porosity has been noted to occur within platy and columnar structure. While fragile and easily disturbed by most fauna and humans, vesicular horizons have been noted to persist in environments where surface stability is greatest; increasing surface stability can be due to crusts, pavements or landscape age. The vesicular horizon has been hypothesized to restrict plant growth with one possible mechanism being that non-interconnected pores found in the horizon may restrict water movement through the horizon, especially in thicker horizons. Field research on hydraulic properties of vesicular horizons has noted significantly lower hydraulic conductivities in vesicular horizons on surfaces of increasing geomorphic age because of greater accumulations of clay. Owing to its effect on water movement into arid soils, the vesicular horizon may be the most influential soil horizon in arid landscape geomorphology and pedogenesis.
