Nurse shrubs increased the early growth of Cupressus seedlings by enhancing belowground mutualism and soil microbial activity

The influence of shrubs used as nurse plants was tested on the growth of Cupressus atlantica, on microbial activity and on arbuscular mycorrhizal (AM) soil potential in a Mediterranean environment. An experimental plantation was conducted combining uninoculated, arbuscular mycorrhized Cypress seedlings and an association between Lavandula stoechas planted close to newly planted C. atlantica seedlings. After three years plantation, this association between C. atlantica and L. stoechas lead to a higher growth of C. atlantica and better soil microbial characteristics compared to the control treatment. AM mycelium network, total microbial activity, dehydrogenase activity, phosphate-solubilizing fluorescent pseudomonads and N, P nutrient uptake by C. atlantica, were significantly higher in the presence of L. stoechas than those recorded in the other treatments. This pioneer shrubs facilitates the early establishment of Cypress seedlings by improving soil microbial characteristics and AM fungus community development. Given that the facilitative effect of one plant species to another increases with abiotic stress, the benefits of this technique would be useful in reforestation programs undertaken to rehabilitate degraded areas in Mediterranean region.