  We simulate the fragmentation processes in the \CaCa collisions at the
bombarding energy 1.05 GeV/u using the Lorentz covariant RQMD and the
non-covariant QMD approaches, incorporated with the statistical decay model. By
comparing the results of RQMD with those of QMD, we examine the relativistic
effects and find that the multiplicity of the $\alpha$ particle after the
statistical decay process is sensitive to the relativistic effects. It is shown
that the Lorentz covariant approach is necessary to analyze the fragmentation
process even at the energy around \Elab = 1 GeV/u as long as we are concerned
with the final observables of the mass distribution, particularly, the light
fragments around $A = 3 \sim 4$.
