Forest degradation has been accentuated in recent years by climate change and drought. This study consists of producing quality plants and understanding their ecophysiological behavior in the face of water stress. Plants of two broadleaves (Quercus suber, Ceratonia siliqua) and two conifers (Tetraclinis articulata, Cedrus atlantica) aged 6 months subjected to water stress. The basic (Ψb) and minimum (Ψm) leaf water potential ware measured and processed according to climatic factors for the 4 forest species. The results show that the leaf water potential in Quercus suber presents more negative values (-0.42 MPa) for basic leaf water potential and (-1.43 MPa) for minimum leaf water potential than the other forest species studied. While Cedrus atlantica presents the least negative values for minimum leaf water potential (-0.89 MPa). These results allowed us to define the species that is more resistant to water stress and climate change. However, they refer us to more general questions concerning the mechanisms of water use in forest plants.