Further observations on the water relations ofProsopis tamarugo of the northern Atacama desert.

Prosopis tamarugo, a tree native to the Atacama desert of Chile apparently has unique water relations. It is proposed that in its native habitat, where there is essentially no precipitation, establishment occurs during the rare flooding periods, with water coming as runoff from the Andes. These plants subsequently exist as phreatophytes tapping the relatively shallow ground water. Although phreatophytic, the plants appears to come under increasing drought stress as the growing season progresses. Because of the very low water potentials of the salty surface soils, water evidently moves from the plant into the soil under certain conditions. This water may be reabsorbed subsequently and used by the plant as the water table capillary fringe is depleted toward the end of the leafy period.