  Close to the critical point associated with nascent of bistability and large
wavelength pattern forming regime, {\it the Lifshitz point}, the dynamics of
many ecological spatially extended systems can be reduced to a simple partial
differential equation. This weak gradient approximation is greatly useful for
the investigation of localized vegetation patches and gaps. In this
contribution, we present a general derivation of the most simple vegetation
model without any specification of the shape of Kernel used to describe the
facilitative and the competitive interactions between individual plants. The
coefficients of the obtained model depend on the choice of the form of the
Kernel under consideration. Based on this simple vegetation model, we focus
more on gaps and patches interaction. In the case of gaps, the interaction
alternates between attractive and repulsive depending on the distance
separating the gaps. This allows for the stabilization of bounded states and
clusters of gaps. However, in the case of localized patches, the interaction is
always repulsive. In this former case, bounded states of patches are excluded.
The analytical formula of the interaction potential is derived and reviewed for
both types of interactions and checked by numerical investigation of the model
equation.
