Holomorphic dynamics and trees of spheres

In this thesis we introduce a compactification of families of rational maps dynamically marked of degree d>1 using the Deligne-Mumford compactification in the special case of genus zero. We show that elements of the compactified space can be identified with dynamical covers of trees of spheres and give some of their properties. With this compactification we can reprove results of J. Kiwi on rescaling-limits without using Berkovich spaces and give an interpretation of other works.