Land-use and topography shape soil and groundwater salinity incentral Argentina

NOSETTO MD; ACOSTA AM; JAYAWICKREME DH; BALLESTEROS SI

AGRICULTURAL WATER MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 p. 120 - 129

0378-3774

Being one of the oldest and most serious environmental problems, soil and groundwater salinization posescritical challenges for the managing of agricultural and natural areas. Together with climate, topographyand land-use are main controls dictating salt accumulation patterns at different spatial scales. In thispaper, we quantified the response of salt accumulation to the interactive effects of topography (lowland-upland gradients) and vegetation (annual crops, tree plantations, native grasslands) across a sub-humidsedimentary landscape with shallow groundwater in the Inland Pampas of Argentina. We measured saltstocks from the surface down to the water-table through soil coring and their horizontal distributionthrough electrical-resistivity imaging in eleven fields occupied by annual crops, eucalyptus plantationsand grasslands, encompassing water-table depth gradients of 1?6 m below the surface. Land-use andtopography exerted strong influences on salinity and explained together 82% and 66% of the spatialvariability of groundwater salinity and soil salt accumulation (0?2 m of depth), respectively. As a singleexplanatory variable, land-use overwhelmed topography dictating salinity patterns. Tree plantationsstored 7?8 times more salts than croplands and grasslands throughout the unsaturated soil profile inareas with shallow water-tables (<3.5-m depth). As groundwater became shallower, its salinity and thatof the unsaturated soil above it increased, although the slope of this relationship was significantly higherin tree plantations. Soil salinity profiles and electrical-resistivity imaging showed maximum salinizationaround the water-table in tree plantations, indicating that groundwater absorption and solute exclusionby tree roots may be the dominant salinization mechanism. Our study highlights the strong influence ofland-use on salinization patterns, which can be even stronger than the more widely recognized controls ofclimate and topography, and proposes some guidelines for a better use of vegetation to manage hydrologyin salt-affected areas. A poor comprehension of this influence, as well as its underlying mechanisms, maylead to incorrect diagnosis of salinization and the implementation of ineffective management actions.