Logarithmic regression analyses between irradiance (ISF %) and the following parameters: (A) leaf specific construction costs (CC), (B) area related leaf construction costs (CC_a), (C) leaf nitrogen content per unit area (N_a), and (D) leaf total mineral content (TM). In case of significant interrelations regression lines and equations are shown. Beech (open squares and solid lines), ash (crosses and short-dashed broken line), and sycamore maple (solid triangles and long-dashed broken line).