Prographes sylvestres et groupes profinis presque libres

In this article we want to give an analogous in the profinite case to the following theorem: an abstract group is free if and only if it acts freely on a tree. In a first time we define a combinatory object, the protrees, which are particular inductive systems extracted from projective systems of graphs. Then we define a notion of profinite action. These objects allow us to give the following analogous: a profinite group contains a dense abstract free subgroup if and only if it acts profreely on a protree.