Effect of soil surface sealing on the hydrological response and the vegetation cover of semi-arid areas (Invited)

Bare soil surfaces in semi-arid areas are prone to sealing, which involves the formation of a compacted and thus less permeable layer at the vicinity of the soil surface. This particular interface of the soil-atmosphere system affects the two main hydrologic fluxes in such areas: infiltration and evaporation. It follows that local rainfall-runoff relations are directly impacted by the formation of this layer with logical consequences to water availability for vegetation development. The role of soil surface sealing in shaping such hydrological responses of a semi-arid hillslope in Southern Israel is described on a quantitative basis using a modeling approach that links the seal hydraulic properties to the physical characteristics of the hillslope. A two-dimensional surface runoff model is applied to represent the joint impact of the seal layer, the microtopography and the vegetation patches on spatial and temporal features of the rainfall-runoff relationship. The seal layer and the vegetation patches affect runoff generation, while microtopography affects mainly overland flow patterns. More water is supplied to the vegetation patches via runoff re-infiltration under soil surface sealing conditions, thus enabling establishment and development of vegetation cover.