Water status, drought responses, and growth of Prosopis flexuosa trees with different access to the water table in a warm South American desert

GIORDANO CARLA V; GUEVARA, ARANZAZÚ; BOCCALANDRO HERNÁN E; SARTOR CARMEN; VILLAGRA P. E.

PLANT ECOLOGY

SPRINGER

Año: 2011 vol. 212 p. 1123 - 1134

1385-0237

Prosopis flexuosa trees dominate woodlandsin the Central Monte Desert (Mendoza, Argentina),with € mm rainfall, exploiting the watertable recharged by Andean rivers, and also growing indunes with no access to the water table. Prosopiswoodlands were extensively logged during developmentof the agricultural oasis, and surface andgroundwater irrigation could lower the depth of thewater table in the future.Weevaluated tree populationswith decreasing access to the water table: valley adulttrees, valley saplings, and dune adult trees, in order toassess their ecophysiological response to water tableaccessibility. High and seasonally stable pre-dawn leafwater potentials (-2.2 ± 0.2 to -1.2 ± 0.07 MPa)indicated that valley adults utilize larger and morestable water reservoirs than valley saplings and duneadults (-3.8 ± 0.3 to -1.3 ± 0.07 MPa), with highermidday leaf conductance to water vapor (valley adults*250; dune adults0 mmol m-2 s-1), potentiallyhigher CO2 uptake, and increased radial growth rate(valley adults 4.1 ± 0.07; dune adults 2.9 ± 0.02mm year-1). Trees with poor access to the water tableexhibited drought tolerance responses such as middaystomata closure, leaflet closure, and osmotic adjustment.Stomata density decreased in response to droughtwhen leaf expansion was restricted. The combinationof phreatophytism and drought tolerance would enlargeP. flexuosa habitats and buffer populations againstchanges in rainfall dynamics and water table depth.