We analyze the onset of local oscillations in a class of cellular auto
mata introduced by Vieira and Bisch (1993). They consist in one autoca
talytic reaction and a ring of spontaneously decaying processes. We ex
plain, in the context of recent studies on synchronization of generali
zed Forest-Fire models, why a minimum number of chemical species is ne
eded for oscillations to take place. Numerical simulations confirm our
analysis.