Livestock stations as foci of groundwater recharge and nitrate leaching in a sandy desert of the Central Monte

MEGLIOLI, P.; ARANÍBAR, J.; VILLAGRA, P.E.; ALVAREZ, J.A.; JOBBAGY, E.

ECOHYDROLOGY

JOHN WILEY & SONS INC

Lugar: New York; Año: 2012

1936-0584

This study evaluates how extensive traditional grazing systems can disrupt the ecological andhydrological linkages in an arid groundwater-coupled ecosystem. In arid lands it is often assumedthat all precipitation inputs are evapotranspired, preventing local recharge of groundwater. Whilethis is the case for undisturbed Prosopis flexuosa woodlands in sandy areas of the Monte desert(Argentina), we propose that intense vegetation disturbances associated with the establishment ofpastoralist settlements (i.e. livestock stations) could alter this condition, initiating groundwaterrecharge and favoring nitrate leaching. We first characterized vegetation and land use indicatorsand then nitrate and water dynamics in three pairs of neighboring livestock and undisturbedcontrol woodlands. In livestock stations we found lower cover of live plants, biological soil crusts,and dead wood, but higher dung cover. Soils sampled down to the water table depth showed higher moisture and nitrate content and lower chloride and total salt stocks in livestock stations,suggesting higher water percolation and N input/transport rates. Higher groundwater nitrateconcentrations in livestock stations supported the notion that these areas behave as foci of N andwater export from ecosystems to the phreatic aquifer. Our study reinforces the idea that vegetationin arid areas prevents downward surface-groundwater interactions, but it also indicates that humanmodifications of vegetation disrupt this control, reducing surface water consumption, and allowingvertical movement of water and solutes to the aquifer, which can modifying groundwater quality.Disruptions of ecological processes by livestock activities clearly affect the hydrological linksbetween surface and groundwater