Mass and Energy Flows Modelling: Part I - Assessment of Forest Primary Productivity and Transpiration Trends

This study quantifies the impact of climate change on several species (Quercus cerris, Fraxinus angustifolia subsp. oxycarpa, Phillyrea latifolia, and Pistacia lentiscus) in a mixed Mediterranean forest. Key physiological parameters as net assimilation, stomatal conductance, and transpiration rates were measured using an infrared gas exchange analyzer (Ciras-2). These measurements were used to develop and calibrate a modified version of the biochemical model of photosynthesis by Farquhar and von Caemmerer. The improved model simulates instantaneous, species-specific net assimilation, stomatal conductance, and transpiration rates. The model results can be integrated over time to obtain gross/net primary productivity and transpiration values for each species within a selected timeframe. Current and future climate data, based on different Shared Socioeconomic Pathways (SSPs), were used to assess changes in physiological parameters under various climatic conditions. The results show that ecophysiological parameters (gas exchange) decrease on average during intensified water stress in the summer. Different water resource utilization strategies were observed among the species. This predictive model of primary productivity, based on climate scenarios, confirms the different response capabilities of the species. P. latifolia and F. oxycarpa show reduced primary productivity under the SSP8.5 scenario, while P , lentiscus and Q. cerris show increased productivity. This highlights the model's significance in understanding and predicting species responses to climate change.