Analysis and experimentation on ecosystems

The domain of the Haute-Provence Observatory (OHP) : hermas and downy oak forest, from the XVIII century to now The 95 hectares area of the Observatoire de Haute-Provence (OHP, Observatory of Haute-Provence, an astronomical observatory) has been the property of the National Centre for Scientific Research (CNRS) since 1939. This domain is located in the rural community of Saint-Michel-l’Observatoire, in the département of Alpes-de- Haute-Provence. The climate is subhumid supramediterranean with a mean annual rainfall of 830 mm. The OHP hosts a variety of plant formations typical of the Haute-Provence landscape : most of it is a coppice of Downy Oak (Quercus pubescens) on a soil of compact limestone. In this work we trace the evolution of the land use and property, of the agricultural practices and of the vegetation since the XVIIIth century. We show that the current landscape is the complex product of the agricultural practices that did not change notably until the first half of the XXth century, and remained within the property of a single owner until now. The poorness of the soils, the evolution of the land from “hermas” (agricultural soils that are not cultivated) to the downy oak coppices, and the specific tax system in Provence until the XIXth century can explain the present landscape. This study has been made within the framework of the Oak Observatory at OHP (O3HP), a recent and innovative facility for the study of the dynamics of the Downy Oak forest under the stress of climate change.