Contrasting Water-Use Strategies of Ailanthus altissima and Crataegus orientalis Under Drought Stress Reveal Restoration Potential in Mediterranean Drylands

Water availability is the primary environmental factor limiting plant settlement in arid and semi-arid ecosystems, and increasing drought stress due to climate change is making forest restoration efforts in the Mediterranean basin increasingly critical. The Eastern Mediterranean region of Turkey, particularly Kahramanmaraş Province, is characterized by increasingly severe drought stress resulting from low natural precipitation and rising temperatures under global warming. This study comparatively evaluates the ecophysiological responses of Ailanthus altissima (Mill.) Swingle and Crataegus orientalis Pall. ex M. Bieb. under adequate irrigation and drought-stress conditions. To determine plant water status, pre-dawn and midday leaf water potentials were measured; water use efficiency (WUE) was calculated using net photosynthesis rate, stomatal conductance, and transpiration parameters. Both species were able to maintain photosynthetic activity under drought conditions and showed higher WUE values compared to control conditions. However, significant differences in physiological adaptation strategies emerged between the species. Ailanthus altissima exhibited a water-spending strategy with rapid physiological adjustment, while Crataegus orientalis adopted a conservative water-saving strategy through pronounced stomatal regulation. Modeling results, supported by spatial drought stress indices, have shown that both species have high adaptation potential in arid and semi-arid rehabilitation areas. The findings reveal that ecophysiological characteristics play a critical role in the selection of drought-tolerant woody species and provide a scientific basis for sustainable forest restoration under climate change.