Potentialities of ecological engineering strategy based on native arbuscular mycorrhizal community for improving afforestation programs with carob trees in degraded environments

• Rhizophagus is the main mycorrhizal fungi associated to carob trees.
• Carob inoculation with a native AM community has a sustainable plant promoting effect in natural degraded soils.
• AM inoculation has a strong positive impact on soil microbial functioning.
• Ecological engineering strategy based on native mycorrhizal community is a promising tool for efficient revegetation of degraded soils.

Efficient afforestation programs are crucial to limit soil degradation in various arid and semi-arid ecosystems. However, the success of these programs is dependant to the plant type selected for revegetation and the methods used for seedling production. Exotic fast-growing trees have been largely planted but their use is currently controversial because of their potential negative ecological impacts. Whereas the positive impact of arbuscular mycorrhizal (AM) fungal inoculation in nursery was demonstrated, few studies focused on the monitoring of mycorrhizal inoculation in arid and semi-arid ecosystems. In addition, the majority of studies are based on single-species inocula with non native AM fungal strains. The current study aims at evaluating the efficiency of mycorrhizal inoculation of the emblematic Mediterranean carob tree (Ceratonia siliqua) in a Moroccan degraded site, through an ecological engineering strategy based on the use of a complex native AM community (naturally associated to carob trees). Results demonstrate the high potential of this approach by improving sustainably the growth and nutrient status of carob trees in a 3-year-old plantation and also by inducing a positive soil microbial environment for nutrient cycling and environmental stress resistance.