Predawn disequilibrium between soil and plant water potentials in seedlings of two Mediterranean Oak Species (Quercus ilex and Quercus suber)
Increasing aridity and climate extremes are challenging the resilience of key Mediterranean species. Proxies that indicate plant water status, physiological condition and soil water availability are valuable tools for management planning. However, their reliability requires species-specific validati...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2026 |
| País: | España |
| Institución: | Universitat de Lleida (UdL) |
| Repositorio: | Repositori Obert UdL |
| OAI Identifier: | oai:dnet:.___________::72a477f53e09bb23450cebd740618295 |
| Acceso en línea: | https://doi.org/10.3390/f17010049 https://hdl.handle.net/10459.1/469914 |
| Access Level: | acceso abierto |
| Palabra clave: | Predawn disequilibrium (PDD) Soil water potential (ΨS) Leaf water potential (ΨL) Predawn water potential (ΨPD) |
| Sumario: | Increasing aridity and climate extremes are challenging the resilience of key Mediterranean species. Proxies that indicate plant water status, physiological condition and soil water availability are valuable tools for management planning. However, their reliability requires species-specific validation under dynamic environmental conditions. This study examined the relationship between predawn leaf water potential (ΨPD) and soil water potential (ΨS) in potted seedlings of two co-occurring Mediterranean evergreen oaks, Q. ilex and Q. suber, subjected to imposed soil drying under greenhouse conditions. We further quantified the occurrence and magnitude of predawn disequilibrium (PDD)—the mismatch between ΨPD and ΨS—and evaluated its association with soil water availability, plant water-status indicators, environmental factors, and physiological variables. In parallel, we assessed stomatal closure dynamics during the desiccation phase and characterised species-specific mortality patterns under progressive drought. Linear Mixed-Effects Models (LMMs), with pot identity included as a random factor, were fitted to assess the relationship between ΨPD and ΨS, as well as the occurrence of PDD and its potential drivers for each species. Stomatal conductance (gs) responses to ΨS were evaluated using a paired t-test and an additional LMM. Finally, Generalised Linear Mixed-Effects Models (GLMMs) were used to analyse interspecific differences in mortality. We confirmed a tight relationship between ΨPD and ΨS, followed by a consistent PDD in both species, with magnitudes of 0.53 MPa for Q. ilex and 0.98 MPa for Q. suber, which increased significantly with drought severity. Our findings suggest that PDD under the studied conditions is primarily driven by soil water depletion and plant desiccation, as indicated by its negative correlation with water status parameters, as well as by its increase with progressive drought. Both oaks exhibited a water-saving strategy, with stomatal closure initiated around ΨS = −0.31 MPa (Q. ilex) and −0.42 MPa (Q. suber). Despite their physiological similarities, Q. suber showed higher mortality under imposed drought. These results encourage modelling the relationship between ΨPD and ΨS to accurately interpret plant and soil water needs in Mediterranean oaks, especially under soil water scarcity, and highlight species-specific responses critical for forest management and restoration under climate change. |
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