Vegetation ecosystem simulation, at the landscape or crop level, is a challenging topic involving multidisciplinary aspects. Several models of biophysical components must be coupled properly in order to obtain a meaningful simulation. This also raises interesting problems in software architecture. In this paper, we first outline a synchronisation formalism and software architecture adapted to the simulation of systems built from several coupled models. The models are linked by caches that provide inputs and receive outputs, and control the time step of the simulation. Next, we describe specific models for resource management and plant growth, that are essential for landscape simulation. The resource models are designed to solve transparently the problem of competition. The implemented plant model involves three environmental parameters (temperature, light, water) and uptakes water according to plant growth. Finally, these models are coupled in simulations of a plant interacting with water resource, showing various complex behaviours in time.