MICROPHYTIC CRUST INFLUENCE ON WIND EROSION

Wind is a persistent force in arid and semiarid lands. Microphytic cru sts have been attributed with the ability to reduce wind erosion becau se of soil binding qualities. The purpose of this research was to dete rmine if microphytic crusts contribute to soil stability in an arid la nd setting. Threshold friction velocity is the wind speed necessary fo r the initiation of soil erosion and, thus, is a measure of soil surfa ce stability. A portable wind tunnel was used to determine threshold f riction velocity on soil surfaces consisting of microphytic crusts liv ing and undisturbed (control), chemically killed microphytic crusts bu t otherwise undisturbed (chemically killed), and microphytic crusts me chanically removed from the soil surface (scalped) to approximate cond itions of absence. Significantly lower threshold friction velocities w ere measured within the scalped treatment than in the control or chemi cally killed treatments. Threshold friction velocities were not signif icantly different among control and chemically killed treatments. Sign ificantly more wind-eroded material, entrained in the airstream and tr apped by an inline filter, was obtained from the scalped treatment tha n from chemically killed or control treatments. Additionally, wind ero sion occurred at significantly lower wind speeds in the scalped treatm ent. 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 i nfluence of microphytic crusts are affected by type, degree, frequency , and season of disturbance and to answer pragmatic questions of conce rn to managers, such as determining acceptable levels of crust disrupt ion and the wind speeds associated with erosion.