Differences in nutrient availability and mycorrhizal infectivity in soils invaded by an exotic plant negatively influence the development of indigenous Acacia species

Plant species (exotic invasive vs native non-invasive) colonization pattern and the relation with the soil nutrient availability and AM fungi abundance, was investigated. Soil samples were collected from two sites: one invaded by the exotic plant, Amaranthus viridis, and one uninvaded site for chemical and AM propagules density analyses. Additionally, we grew five Sahelian Acacia species in soil from the two sites, sterilized or not, to test the involvement of soil biota in the invasion process. While nutrient availability was significantly higher in soil samples from the invaded sites, a drastic reduction in AM fungal community density, was observed. Moreover, Acacia seedlings’ growth was severely reduced in soils invaded by Amaranthus and this effect was similar to that of sterilized soil of both origins. The observed growth inhibition was accompanied by reduction of AM colonization and nodulation of the roots. Finally, the influence of soil chemistry and AM symbiosis on exotic plants’ invasion processes is discussed.