Modelling the ecohydrological responses of two eucalyptus–dominated catchments in Central and Southern Portugal with contrasting edaphoclimatic characteristics to future climate scenarios

Study region: Central and Southern Portugal. Study focus: Despite the global importance of eucalyptus, the impacts of climate change on eucalyptus–dominated forest catchments have been seldom explored. The present study assessed the ecohydrological response of two contrasting eucalyptus–dominated catchments (Braçal: terraced, semi–humid climate; Caniceira: flatten, semi–arid climate) to climate change, using two SWAT models calibrated with field data for streamflow, leaf area index, evapotranspiration and stem biomass. The hydrological models were driven by three regional EURO–CORDEX climate models (CM5, CM5A, and NorESM1) under two Representative Concentration Pathways (RCPs 4.5 and 8.5), being run over three 12–year periods to represent a complete eucalyptus growth cycle (2024–2036, 2037–2048, and 2049–2060). New hydrologic insights for the region: Under RCP 4.5, water yield is foreseen to decrease from 2024 to 2060, for both catchments, while under RCP 8.5, a positive impact is anticipated, especially for 2049–2060. Stem biomass tended to increase in both catchments from 2024 to 2060, possibly due to increasing CO2 concentrations stimulating eucalyptus growth. Water scarcity was consistently more severe at the semi–arid than semi–humid catchment from 2024 to 2060, particularly during the dry season. SWAT outputs provide scientific evidence for forest managers to define adaptative strategies to mitigate the negative impacts of future climate conditions (particularly droughts) on eucalyptus production forests.