Squandering water in drylands: the water?use strategy of the phreatophyte <i>Ziziphus lotus</i> in a groundwater?dependent ecosystem

Premise Water is the most limiting factor in dryland ecosystems, and plants are adapted to cope with this constraint. Particularly vulnerable phreatophytic from groundwater-dependent ecosystems (GDEs) regions that have face water regime alterations due impacts of climate land-use changes. Methods We investigated two aspects related water-use strategy a keystone species dominates one few terrestrial GDEs European drylands (Ziziphus lotus): where it obtains how regulates its use. (1) evaluated plants’ sources use patterns using multiple-isotope approach (?2H, ?18O, ?13C); (2) assessed regulation plant potential by characterizing on an isohydric–anisohydric continuum; (3) response increasing stress along depth-to-groundwater (DTGW) gradient measuring foliar gas exchange nutrient concentrations. Results Ziziphus lotus behaves as facultative or partial phreatophyte extreme anisohydric stomatal regulation. However, DTGW increased, Z. reduced groundwater, total uptake, limited transpiration loss while efficiency. also found physiological threshold at 14 m depth which could indicate maximum rooting length beyond optimal function not be sustained. Conclusions Species such survive squandering because substantial groundwater uptake. identification thresholds indicates drawdowns level would jeopardize functioning GDE.