WIND EROSION IN AGRICULTURAL SOILS - AN EXAMPLE OF LIMITED SUPPLY OF PARTICLES AVAILABLE FOR EROSION

Soil erosion by wind is a complex process since many interacting facto rs are involved. In addition, wind erosion can show a considerable spa tial and temporal variability associated with changes in soil surface conditions. During a wind erosion experiment conducted in August 1995 within an agricultural field of Central Aragon (NE Spain) [Lopez, M.V. , Sabre, M., Gracia, R., Arrue, J.L., Comes, L., 1998. Tillage effects on soil surface conditions and dust emission by wind erosion in semia rid Aragon (NE Spain). Soil Tillage Res. (in press)], a decay in dust emission (vertical dust flux) with an increase in wind speed was obser ved at the end of the experimental period. A further analysis of the e volution of the vertical flux with time in response to changes in soil erodibility is shown in the present study. The analysis is based on t he comparison of the measured flux with the potential flux predicted f or identical wind conditions assuming that the supply of erodible mate rial at the soil surface was unlimited. The potential flux was estimat ed by using the dust emission model developed by Marticorena and Berga metti [Maticorena, B., Bergametti, G., 1995. Modeling the atmospheric dust cycle: 1. Design of a soil-derived dust emission scheme. J. Geoph ys. Res. 100, pp. 16415-16430]. The model is based on the parameteriza tion of the threshold wind shear velocity as a function of the aggrega te size distribution and the roughness length of soil surface. The res ults indicate that the observed reduction in soil erodibility with tim e was probably due to variations in the aggregate size distribution an d, more precisely, to a limited supply of erodible particles at the so il surface. This study underlines the need to consider the temporal va riability of the surface conditions in wind erosion research and deriv ed models. (C) 1998 Elsevier Science B.V. All rights reserved.