The adjustment of Prosopis tamarugo hydraulic architecture traits has a homeostatic effect over its performance under descent of phreatic level in the Atacama Desert

Abstract

Prosopis tamarugo undergoes several modifications of its hydraulic architecture, which has a homeostatic effect on its performance under descent of phreatic level. Groundwater extraction for mining has generated a large area of descent of phreatic level in the Llamara Salt Flat, Atacama Desert, where Prosopis tamarugo lives as a strict phreatophyte. We study different hydraulic architecture traits of P. tamarugo after 12 years of exposure to a descent of phreatic level of ~ 11 m to assess its acclimation capacity. Under this condition, tree size was reduced making the structure of trees shrubbier. At branch level, leaf shedding increased Huber Value and theoretical leaf-specific hydraulic conductivity. At vascular tissue level, vessel composition decreased significantly due to an increase in vessel density and a slight decrease in mean vessel area. This meant that there were no differences of theoretical sapwood-specific hydraulic conductivity and wood density between conditions of descent of phreatic level. Although the theoretical hydraulic efficiency is high under descent of phreatic level, a lower midday water potential indicates other possible factors that may affect its performance (e.g., microclimate, daily loss of conductivity and a high root resistances). The above is consistent with a higher leaf mass per area of the remaining leaves, but no differences were observed in stomatal conductance, leaf 13C isotopic composition and predawn water potential between descent condition. While the adjustment of hydraulic architecture traits has a homeostatic effect on P. tamarugo performance, it is necessary to evaluate the limits of its resistance to contribute to its conservation in a context of intervention of its habit, mainly due to demographic growth and non-metallic mining.