Arid and semiarid ecosystems face significant water scarcity due to high evaporation rates exceeding precipitation. This study examines temporal variations in water relations of two woody species, Vachellia schaffneri (S. Watson) Seigler & Ebinger, and Prosopis laevigata (Humb. & Bonpl. ex Willd.) M.C. Johnst, and one epiphyte, Tillandsia recurvata (L.) L. (Bromeliaceae), to assess their drought tolerance and water storage capacity. We hypothesized that species with greater water storage capacity would exhibit lower drought tolerance due to reduced osmotic adjustments, whereas species with lower storage capacity would maintain turgor through osmotic regulation and cell wall rigidity. Predawn and midday water potentials (Ψ_pd, Ψ_md) were measured, and pressure–volume (P–V) curves were used to derive parameters such as saturated water content (SWC), osmotic potential (π_o), turgor loss point (Ψ_TLP), relative water content at Ψ_TLP (RWC_TLP), bulk modulus of elasticity (ε), and full turgor capacitance (C_FT). Significant correlations were found between C_FT and Ψ_TLP (positive), π_o (positive), and ε (negative). P. laevigata and T. recurvata exhibited higher water storage capacities (41.46 and 26.45 MPa⁻¹, respectively) but had a lower ability to maintain cell turgor under drought conditions. In contrast, V. schaffneri exhibited the lowest water storage capacity (11.88 MPa⁻¹) but demonstrated the highest ability to maintain cell turgor (Ψ_TLP = −1.31 MPa) and superior osmotic adjustments (π_o = −0.59 MPa). Both V. schaffneri and P. laevigata exhibited rigid cell walls, whereas T. recurvata displayed greater elasticity in its cell structures. The lowest moisture content in V. schaffneri suggests increased flammability and fire spread potential. Future studies should focus on live fuel moisture content across more species, explore seasonal variations in hydraulic traits, and integrate these physiological parameters into fire risk models to enhance wildfire prediction and management.

Arid and semiarid ecosystems are characterized by substantial water loss through evaporation, exceeding precipitation, which makes water scarcity a critical challenge for plant survival. This study examined temporal variations in water relations parameters in two woody species, Acacia schaffneri and Prosopis laevigata, and one epiphytic species, Tillandsia recurvata. The aim was to explore the relationships between hydraulic traits conferring drought tolerance and water storage capacity, as well as to derive the live fuel moisture content at the turgor loss point. Predawn and midday water potentials (Ψpd, Ψmd) were measured in the field, while pressure-volume (P-V) curves were used to derive parameters such as saturated water content (SWC), osmotic potential (Πo), turgor loss point (ΨTLP), relative water content at ΨTLP (RWCTLP), bulk modulus of elasticity (ε), and full turgor capacitance (CFT). Significant correlations were found between CFT and ΨTLP (positive), Πo (positive), and ε (negative). P. laevigata and T. recurvata exhibited higher water storage capacities (41.46 and 26.45 MPa⁻¹, respectively) but had a lower ability to maintain cell turgor under drought conditions. In contrast, A. schaffneri exhibited the lowest water storage capacity (11.88 MPa⁻¹) but demonstrated the highest ability to maintain cell turgor (ΨTLP = -1.31 MPa) and superior osmotic adjustments (Πo = -0.59 MPa). Both A. schaffneri and P. laevigata exhibited rigid cell walls, whereas T. recurvata displayed greater elasticity in its cell structures. The lowest moisture content was observed in A. schaffneri, suggesting higher fire ignition risk. These findings enhance understanding of drought tolerance mechanisms and fire susceptibility in arid regions, offering insights into species-specific adaptations to water stress.