Disturbance effects on arid groundwater coupled ecosystems (Mendoza)

MEGLIOLI, PABLO ANDRÉS; ARANIBAR, JULIETA NELIDA; VILLAGRA PABLO EUGENIO; ALVAREZ, JUAN AGUSTÍN

San Juan

Congreso; II Reunión Conjunta de las Sociedades de Biología de la Republica Argentina; 2011

Shallow groundwater is an important resource for plants and local people in drylands. The modification of the disturbance regime by different land uses can alter several aspects of ecosystems functioning. We evaluated the effects of traditional livestock posts, generally consisting of a housing unit, corrals, a water well, and domestic animals, on vegetation, water and nitrate dynamics in the Monte desert (Mendoza). We postulated that the removal of the vegetation in livestock posts and the accumulation of urine and dung allow water percolation, facilitating nitrate leaching and local groundwater recharge. We analyzed nitrate and water dynamics mediated by animals and vegetation in three livestock areas and their nearby relatively undisturbed woodlands. We found higher water and nitrate, and lower chloride contents in soil profiles obtained in livestock concentration areas, where bare soil and dung densities were higher. Low soil chlorides indicate that water is percolated to the subsoil and into the groundwater, transporting nitrate to the aquifer. We also found other indicators of human impacts that may be useful to evaluate degradation, such as lower soil crust cover, standing dead wood, grass cover, and seeds. Our results show that human activity, even as traditional and extensive livestock production, affects the interactions among water, vegetation, and nitrate, facilitating the movement of water and solutes to the aquifer.