  Lithium abundances in open clusters provide an effective way of probing
mixing processes in the interior of solar-type stars and convection is not the
only mixing mechanism at work. To understand which mixing mechanisms are
occurring in low-mass stars, we test non-standard models, which were calibrated
using the Sun, with observations of three open clusters of different ages, the
Hyades, NGC 752, and M67. We collected all available data, and for the open
cluster NGC 752, we redetermine the equivalent widths and the lithium
abundances. Two sets of evolutionary models were computed, one grid of only
standard models with microscopic diffusion and one grid with rotation-induced
mixing, at metallicity [Fe/H] = 0.13, 0.0, and 0.01 dex, respectively, using
the Toulouse-Geneva evolution code. We compare observations with models in a
color-magnitude diagram for each cluster to infer a cluster age and a stellar
mass for each cluster member. Then, for each cluster we analyze the lithium
abundance of each star as a function of mass. The data for the open clusters
Hyades, NGC 752, and M67, are compatible with lithium abundance being a
function of both age and mass for stars in these clusters. Our models with
meridional circulation qualitatively reproduce the general trend of lithium
abundance evolution as a function of stellar mass in all three clusters. This
study points out the importance of mass dependence in the evolution of lithium
abundance as a function of age. Comparison between models with and without
rotation-induced mixing shows that the inclusion of meridional circulation is
essential to account for lithium depletion in low-mass stars. However, our
results suggest that other mechanisms should be included to explain the Li-dip
and the lithium dispersion in low-mass stars.
