Hydraulic Parameters of Pressure-Volume Curves and Their Relationship with the Moisture Content of Live Fuels in Two Woody Species and an Epiphyte

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.