Increasing productivity of multipurpose lands; (proceedings)

agroforesteria agroforesterie agroforestry arid zones bois de chauffage fitomejoramiento forest land forest plantations fuelwood indigenous organisms land productivity multiple land use natural regeneration pepiniere plant breeding plant nurseries plante ligneuse productividad de la tierra projet de recherche recherche research research projects sahel terrain forestier tierras forestales uso multiple de la tierra viveros woody plants zone aride