CONICET | Buscador de Institutos y Recursos Humanos

It has been assumed that bare soil (BS) inter-patches in semi arid spotted vegetation behave as sources ofwater to near vegetated soil (VS) patches. However, little evidence has been gained from direct measurementsof overland and infiltration water fluxes between bare soil inter-patches and shrub mounds at ascale compatible with available high resolution imagery and hydrological modeling techniques. Theobjective of this study is to address the thin scale internal redistribution of water between BS interpatchesand vegetated mounds at relatively flat spotted semiarid landscapes. The relation between plantcover, topography and runoff was inspected with non-parametric association coefficients based on highresolution remotely sensed imagery, ground truth topographic elevation and spatial-explicit field data onpotential runoff. Measurements of advective flows at the same spatial scale were carried out at microplotsof BS and shrub mounds. Water fluxes between BS inter-patch and a shrub mound were simulatedunder varying typical Patagonian rainfall scenarios with an hydrological model. Results obtained revealedthat the soil properties, infiltration and overland flow metrics at the mounds and inter-patches exhibitspatially and dynamic variable hydraulic properties. High micro-topographic roughness and depressionstorage thickened overland flow depth at VS patches. At BS inter-patches prevailing low slopes anddepression storage were found to be important variables attenuating the surface runoff. At both rainfallscenarios simulated, the soil under the shrub mound accumulated more moisture (from direct rain) andreached saturation long before this occurred in BS nearby inter-patch area. Overland flow at the interpatchwas attenuated as it reached the border of the patch, diverging from the latter as it followed the(small) topographic gradient. The overland flow generated inside the vegetated mound was effectivelyretained at the typical Summer rainfall scenario; while several threads of runoff were routed outsidethe mound at the typical Winter rainfall scenario. The results here shown fail to detect: (a) enough runoffmomentum that could route runon onto the vegetated mounds and (b) a contrast in infiltration ratesbetween BS and the vegetated mound enough to lead to a free-surface gradient in ponded water thatcould inundate the mound