An introduction on below-ground environment and resource acquisition, withspecial reference on trees. Simulation models should include plant structure and function

Resource acquisition within the soil is a complex process, which consists o f several sub-processes involving both the soil and the plant. A brief anal ysis of the whole system is presented, first by focusing on the components of the system, and then on the successive events. This analysis stresses th e diversity and specificity of the components involved, as well as their in teractive roles, at several organisation levels, both in space and time. Th erefore, a systemic approach using dynamic models is defended in order to g ather available knowledge and gain new insight within the whole system. In comparison to many of the traditional modelling approaches, which tended to over-simplify the plant part of the system, some new and promising attempt s are presented. These new models give a good illustration of what can be e xpected to be gained by associating structural and functional characteristi cs of the plant components.