  The chemical enrichment and stellar abundance ratios of galaxies which form
in a hierarchical clustering scheme are calculated. For this purpose I adopt
the star formation histories (SFH) as they are delivered by semi-analytic
models in Kauffmann (1996}. It turns out that the average SFH of cluster
ellipticals does not yield globally alpha-enhanced stellar populations. The
star burst that occurs when the elliptical forms in the major merger plays
therefore a crucial role in producing alpha-enhancement. Only under the
assumption that the IMF is significantly flattened with respect to the Salpeter
value during the burst, a Mg/Fe overabundant population can be obtained. In
particular for the interpretation of radial gradients in metallicity and
alpha-enhancement, the mixing of global and burst populations are of great
importance. The model predicts bright field galaxies to be less alpha-enhanced
than their counterparts in clusters.
