Abstract
Soil salinization has become a major global ecosystem sustainability issue. In Senegal, promising ecosystem restoration of salt-affected lands has been reached by the implementation of ecological engineering strategies based on beneficial associations between Casuarina species and salt-tolerant symbiotic microorganisms. However, the extent of impacts of symbiont inoculants on the native soil microbiota, and consequently soil functioning is fragmentary. The current study aimed at evaluating the changes in the native soil microbiota associated with the use of a symbiont inoculant in mixed Casuarinaceae plantations in salt-affected lands. The symbiont inoculation lead to a decrease of soil fungal diversity, but not bacteria. However, the whole soil microbiota structure was impacted by symbiont inoculation, as by salinity and Casuarina species. Casuarina species also impacted the diversity of dominant taxa constituting soil microbiota, but only salinity affected bacterial diversity. Important modifications of soil microbiota functionalities were revealed, notably a decrease of bacterial pathogens related to symbiont inoculation and increased abundance of fungal pathogens with salinity. Soil nutrient cycling was also impacted by symbiont inoculation, mostly micronutrient cycling and N fixation, but salinity and Casuarina species were the main factors affecting N cycling in soil.