Installation et maintien d'espèces forestières feuillues dans les paysages agricoles en déprise : Approche expérimentale de l'importance des facteurs environnementaux

Most of our current landscapes are the result of centuries-old human modelling. Like many areas, the valleys in the northern French Alps have been experiencing significant farmland abandonment for more than fifty years. The fields, hay-making meadows and pasturelands on the Maurienne's southern slopes are being colonized by woodlands. Acer pseudoplatanus and Fraxinus excelsior are dominant in these woodlands, which are considered to be only transitional. However, in their undergrowth, there is hardly any regeneration of later successional species such as Picea abies, Abies alba or Fagus sylvatica. What is the origin of this apparent deficiency in recruitment of such tree species? One hypothesis emphasizes the soil enrichment brought about by agro-pastoral management and the exploitative behaviour of maple and ash. To test this hypothesis, we designed a three-year experiment that includes several biotic treatments (adult trees canopy, herbaceous neighbours, species considered). The experiment will help to understand the internal processes of this ecosystem. By combining the results with those obtained in other fields, such as descriptive and functional ecology, we can learn how these systems and their dominant species respond to changes in anthropic activity.