MICROPHYTIC CRUST INFLUENCE ON WIND EROSION

Wind is a persistent force in arid and semiarid lands. Microphytic crusts have been attributed with the ability to reduce wind erosion because of soil binding qualities. The purpose of this research was to determine if microphytic crusts contribute to soil stability in an arid land setting. Threshold friction velocity is the wind speed necessary for the initiation of soil erosion and, thus, is a measure of soil surface stability. A portable wind tunnel was used to determine threshold friction velocity on soil surfaces consisting of microphytic crusts living and undisturbed (control), chemically killed microphytic crusts but otherwise undisturbed (chemically killed), and microphytic crusts mechanically removed from the soil surface (scalped) to approximate conditions of absence. Significantly lower threshold friction velocities were measured within the scalped treatment than in the control or chemically killed treatments. Threshold friction velocities were not significantly different among control and chemically killed treatments. Significantly more wind-eroded material, entrained in the airstream and trapped by an inline filter, was obtained from the scalped treatment than from chemically killed or control treatments. Additionally, wind erosion occurred at significantly lower wind speeds in the scalped treatment. Microphytic crusts helped contribute to soil stability by binding soil particles, mainly by linked strands of cyanobacteria. Additional designed experiments are warranted to determine how the stabilizing influence of microphytic crusts are affected by type, degree, frequency, and season of disturbance and to answer pragmatic questions of concern to managers, such as determining acceptable levels of crust disruption and the wind speeds associated with erosion.