Título del Cahier: La mycorhization des plantes forestières en milieu aride et semi-aride et la lutte contre la désertification dans le bassin méditerranéen = Mycorrhization of forest plants under arid and semi-arid conditions and desertification control in the MediterraneaWe have assessed the effect of controlled mycorrhizal infection in the nursery and the application of urban compost on the survival and on the aboveground and belowground biomass of Quercus ilex ssp. ballota seedlings planted in the field. They were planted on limestone and marls, under dry thermo Mediterranean climate. After two years Quercus ilex ssp. ballota seedlings mortality was relatively high (42-70%) and was not affected by bedrock. Compost had a negative effect on the survival and growth of seedlings, probably due to the interspecific competition. Controlled mycorrhizal infection showed no effect on the aboveground biomass of the seedlings. Mortality of the seedlings treated with mycorhizal fungi was lower, although the difference was not statistically significant.Generalitat Valenciana (Programa de Investigación de las Zonas Afectadas por Incendios Forestales en la Comunidad Valenciana, proyecto "Ensayos de Especies Autóctonas y Técnicas de Restauración Forestal") y la C.E.C. DG XII (EV5V-CT94-0475; "Reclamation of Mediterranean Ecosystems Affected by Wildfires"