Effect of vegetation removal on airflow patterns and dune dynamics in the southwest Kalahari desert

Authors

  • G. F. S. Wiggs,

    Corresponding author
    1. School of Natural and Environmental Sciences, Division of Geography, Coventry University, Priory Street, Coventry CV1 5FB, UK
    • Department of Geography, The University, Western Bank, Sheffield S10 2TN, UK
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  • I. Livingstone,

    1. School of Natural and Environmental Sciences, Division of Geography, Coventry University, Priory Street, Coventry CV1 5FB, UK
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  • D. S. G. Thomas,

    1. School of Natural and Environmental Sciences, Division of Geography, Coventry University, Priory Street, Coventry CV1 5FB, UK
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  • J. E. Bullard

    1. Department of Geography, The University, Western Bank, Sheffield S10 2TN, UK
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Abstract

Vegetation is a major control of dune surface activity. To assess the effect of removing vegetation from otherwise largely inactive sand-dune surfaces, two field experiments were undertaken in the southwest Kalahari Desert of southern Africa. In the first, wind velocity profiles were measured on two flat surfaces, one vegetated and one where vegetation had been removed by fire. In the second, levels of dune surface activity were measured on burnt and vegetated sites over a ten week period. The data indicate a striking increase in the near-surface wind velocity allied to a decrease in shear stress after the destruction of the vegetation canopy as a result of burning, grazing or drought. Measurements on the consequences of such changes in the airflow patterns on dune dynamics suggest a three-fold increase in dune surface activity after vegetation clearance. The dunes therefore have a staggered response to the contemporary environment, being largely inactive relicts for much of the time, but becoming more active as vegetation is episodically removed.

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