Mycorrhiza-Assisted Phytoremediation and Intercropping Strategies Improved the Health of a Contaminated Soil from a Peri-Urban Area

Soils of abandoned and vacant lands in the periphery of cities are frequently subjected to illegal dumping and can undergo degradation processes, such as depletion of organic matter and nutrients, reduced biodiversity and the presence of contaminants, which may exert an intense abiotic stress on biological communities. Mycorrhiza-assisted phytoremediation and intercropping strategies are most suitable options for the remediation of these sites. To this end, a two-year field experiment was conducted at a peri-urban site contaminated with petroleum hydrocarbons and polychlorinated biphenyls, in which the effects of plant growth (spontaneous plant species, Medicago sativa, Populus x canadensis, alone vs. intercropping) and the inoculation of a commercial arbuscular-mycorrhizal and ectomycorrhizal inoculum were assessed. Contaminant degradation, plant performance and biodiversity, as well as a variety of microbial indicators of soil health (microbial biomass, activity and diversity parameters), were determined. Special attention was paid to the rhizosphere bacterial and fungal microbiome by measuring structural diversity and composition via amplicon sequencing. The establishment of spontaneous vegetation led to greater plant and soil microbial diversity. Intercropping enhanced the activity of soil enzymes involved in nutrient cycling. The mycorrhizal treatment was a key contributor to the establishment of intercropping with poplar and alfalfa. Treated soils exhibited higher microbial abundance than untreated soils. Our study evidenced the potential of mycorrhiza-assisted phytoremediation and intercropping strategies to improve soil health in degraded peri-urban areas