Evolution of the mass and thickness of the convective envelope (in units of stellar mass and radius; 1 means fully convective), the temperature of the envelope at its base (the horizontal dashed line shows the typical Li burning temperature at 2.5 × 10⁶ K), and the resulting A(Li), according to models by Siess et al. (2000). The bottom panel includes the solar model from Piau & Turck-Chièze (2002). The vertical dashed lines mark the ZAMS ages for the different stellar masses and use the same color-code as indicated in the legend.