Pore Morphology of Vesicular Horizons Following Disturbance and Reformation in the Field

Increasing desertification and anthropogenic soil disturbance is of growing concern to restoration ecologists in the Southwestern United States. This study examines how a common soil horizon of arid lands, the vesicular horizon, which is characterized by its discontinuous pores, responds to disturbance. The vesicular horizon is a near surface soil horizon typically composed of fine grained windblown material found beneath a desert pavement. Disturbance to the vesicular horizon may result in a change in pore morphology that will alter water movement through the horizon, affecting the ecology of the region. This research examines differences in pore morphology (area, perimeter, length and width), particle size, pH, calcium carbonate content (CCE) and conductivity (EC) between disturbed and undisturbed soils. Results indicate no significant difference in vesicle pore size with disturbance. Analyses of pore shape do indicate differences in types of pores formed; the percentage of pores with vesicular shape decrease while interstitial (irregular, between grains) shaped pores increase with disturbance. An increase in interstitial pores may result in more facilitated water movement to lower horizons than there would be in a soil with discontinuous vesicular pores, which could affect the vegetation growing in these areas. The re-formation of vesicular horizon porosity in a disturbed soil may be related to its prior (undisturbed) physical and chemical characteristics. This study is the first to document the morphology of pores that have been re-formed following disturbance in the field.