  A spatially extended Lotka-Volterra system of two competing species in the
presence of two correlated noise sources is analyzed: (i) an external
multiplicative time correlated noise, which mimics the interaction between the
system and the environment; (ii) a dichotomous stochastic process, whose jump
rate is a periodic function, which represents the interaction parameter between
the species. The moment equations for the species densities are derived in
Gaussian approximation, using a mean field approach. Within this formalism we
study the effect of the external time correlated noise on the ecosystem
dynamics. We find that the time behavior of the $1^{st}$ order moments are
independent on the multiplicative noise source. However the behavior of the
$2^{nd}$ order moments is strongly affected both by the intensity and the
correlation time of the multiplicative noise. Finally we compare our results
with those obtained studying the system dynamics by a coupled map lattice
model.
