The sensitivity of erosion and erodibility of forest soils to structure and strength

Long- and short-term variation in erosion and erodibility of soils occurs d ue to changes in the physical properties of soil with time. Any change in e rodibility and related soil properties may be dependent on the structural s ensitivity of the soil. We exposed three forest soils to four erosion treat ments under simulated rain, to test the hypothesis that changes in erodibil ity are related to structural changes in soil arising from wetting and dryi ng. We measured sediment concentration and soil physical conditions (includ ing soil strength) before and after erosion. Erodibility of soil was estima ted with a steady-state erosion model GUEST. For the well-aggregated soil w ith stable structure, there was little erosion irrespective of the treatmen ts and soil strength changed little after a drying cycle. For the other two soils with less stable structure, variation in erosion agreed reasonably w ith variation in soil strength. However. erodibility did not vary consisten tly with strength, in particular, when the soils were rewetted after drying . Our analysis shows that interpretation of temporal variation of erodibili ty is uncertain, as strength of soil can change due to the development of c ohesive bonds between structural units of soil with or without a change in packing density, (C) 2001 Elsevier Science B.V. All rights reserved.