The dynamics of the vegetal recolonization in phosphated chalk quarries abandoned in northern France: a phytosociological and systemic analysis.

The winning of the phosphated chalk in northern France has led to the creat ion of vast opencast quarries, for the most part abandoned at the end of th e thirties and now recolonized by the vegetation. We, have undertaken a phy tosociological analysis of the communities involved in this recolonization and attempted in a reconstruction of its main stages thanks to a systemic a pproach. The initial stage consists in a mosaic of therophytic and hemicryptophytic communities, these last being characterized by a competition between severa l phytosociological classes. The orientation of the dynamics is then determ ined by the nature of biotic factors, with different but convergent ways be tween bottoms, slopes and plateau of quarries. This study has allowed 1) to characterize vegetal communities involved in t he recolonization, 2) to clarify their spatio-temporal organization and the factors governing the initial "phytodynamical complex".