Mechanistic insights into water use strategies and heat tolerance of Australian native trees in saline soils: Implications for phytoremediation under climate change

Abstract Aims This study evaluates the water use strategies and physiological resilience of three Australian native tree species in saline soils to assess their potential for phytoremediation under climate change. We hypothesise that species with high water demand and delayed stomatal closure under aridity can enhance soil salinity mitigation through sustained transpiration and groundwater regulation. Methods Continuous sap flow measurements were recorded over 12 months on nine trees (three per species) from three species across three moderately saline sites in Melbourne, Australia. Detailed analyses of morphological traits, sapwood properties, and soil profiles (including texture and water content) were conducted. Diurnal sap flow patterns, peak flow timing, and physiological responses to temperature and vapour pressure deficit (VPD) were evaluated to determine species-specific thresholds for heat and drought tolerance. Results Melaleuca styphelioides exhibited the highest water use, consuming 128% and 97% more water monthly than Lophostemon confertus and Corymbia maculata , respectively. Its peak sap flow occurred later in the day (15:00–17:00), coinciding with sustained stomatal conductance under high VPD (1.9–2.0 kPa) and extreme temperatures (41 °C). Optimal physiological performance for this species occurred at higher temperatures (32.2–33.4 °C) and VPD (1.9–2.0 kPa). Conclusions Melaleuca styphelioides may warrant further investigation as a potential candidate for water management in saline environments, given its higher water consumption and ability to maintain sap flow under elevated temperature and VPD conditions. These findings suggest that additional research, incorporating larger sample sizes and direct measurements of soil salinity changes, would be valuable to evaluate the suitability of this species for phytoremediation applications in aridifying regions.