Predictions of the energy and carbon balance of Mediterranean shrub species under future climate scenarios

Chronically rising air temperatures and increasing soil drought threaten terrestrial ecosystems by pushing plants closer to their physiological limits, thereby altering carbon uptake, growth, and survival. However, how vegetation responds to current and future warm and dry conditions remains poorly understood, especially in high-risk Mediterranean shrublands characterized by hot, dry summers.

In this study, we combine extensive field measurements and process-based modeling to assess shrubland responses to current and future climate conditions. During summer 2024, we collected leaf and wood traits related to plant economic spectra, thermal and drought tolerances, and photosynthesis. Data were obtained for six dominant Mediterranean shrub species (Amelanchier ovalis, Arbutus unedo, Pistacia lentiscus, Rhamnus alaternus, Buxus sempervirens, and Salvia rosmarinus) across six sites along a climatic gradient in Catalonia (North-East Spain). Additional climatic data were compiled from national meteorological station networks. These datasets were used to parameterize the trait-enabled ecosystem model MEDFATE 2.9.3 to simulate daily individual-level photosynthesis, net carbon uptake, respiration, transpiration rates, and energy balance. Originally developed for forest ecosystems, MEDFATE was adapted here to represent shrubland structure and function. Simulations were conducted under current climate conditions and future scenarios of increased temperature and reduced soil water availability based on IPCC projections. To maintain model tractability, simulations focused on the summer period, when climatic stress is highest.

By comparing interspecific differences in physiological responses across current and projected climate scenarios, this research aims to advance understanding of future vegetation dynamics in Mediterranean shrublands exposed to increasing heat and drought stress. Overall, this work helps bridge key knowledge gaps in plant ecophysiological responses to climate extremes and provides valuable insights for predicting shrubland vulnerability and informing future management strategies.