Abstract
In many arid and semi-arid regions, increasing water scarcity pushes woody species to their physiological limits, making strong drought resistance essential for adaptive forest management. Here, we examined morpho-physiological and biochemical drought responses of the forestry-relevant Persian oak (Quercus brantii Lindl.) and black poplar (Populus nigra L.). In a 120-day greenhouse pot experiment, seedlings were subjected to three watering regimes (FC100, FC60, and FC30, indicating percentages of field capacity). Under FC100 conditions, all biomass measures and the total and specific leaf area of oak were significantly greater compared to those of poplar. FC60-exposed poplar seedlings exhibited strong declines in relative water content (RWC; −33%) and carotenoids (−46%) and a surge in electrolyte leakage (EL; +51%), while these parameters did not change significantly in oak. Although both species showed 80% EL under FC30 conditions, poplar suffered more severe drought damage than oak as evidenced by a 65% lower survival, stronger reductions in RWC and total chlorophyll, as well as stronger increases in oxidative stress markers. Accordingly, poplar seedlings displayed a drought-related 56% decline in quality index while only statistically insignificant reductions occurred in oak seedlings. The superior drought resistance of oak seedlings implies economically more viable nursery production and better seedling establishment, suggesting a shift towards Persian oak-dominated forestry in its natural range under future climate projections.