Hydraulic lift in and between vegetation patches in arid Argentina

Abstract

This study was conducted in the Monte Austral Neuquino (MAN), Provincia de Neuquén, Argentina (39°20’ S; 69°19’ W). Vegetation is distributed at the site as vegetation patches. There are two contrasting sites on the soil of these patches: location 1, under the canopy of major perennial grasses and shrubs, and location 2, which includes the vegetation uncovered interspaces between the patches. The hypothesis of this work was that hydraulic lift is greater under than between the vegetation patches. Thermocouple psychrometers were placed under the shrubs and in the interspaces in each of two vegetation patches, and water potential measurements were taken. Soil water content was also determined by the gravimetric method. Obtained results lead to reject the posted hypothesis. Evidences of the occurrence of hydraulic lift were found neither under the shrubs nor in the interspaces between vegetation patches. This was because soil water content and soil water potential did not increase after transpiration was inhibited when plastic, black tents completely covered all plants in each vegetation patch. It is likely that hydraulic lift does not play an ecologically important role in the phenomenon of facilitation produced by the shrub presence, fact which has been demonstrated by parallel research to the one reported here. Several alternatives which could contribute to explain the obtained results are discussed.