Synergistic Roles of Plant–Microbe Interactions and Soil Aggregate Dynamics in the Phytostabilization of Ion-Adsorption Rare Earth Tailings

Abandoned ion-adsorption rare earth (REE) tailings, defined by low pH, low organic matter, and low fertility (“3L”) conditions, drive severe environmental degradation and demand urgent restoration. This study examined the “plants–microorganisms–soil aggregates” (PMA) system’s role in soil structure and ecological recovery, comparing sluggish natural succession with swift phytostabilization. Field trials assessed reclamation treatments, including organic amendments and mixed commercial grass planting (BAG), against naturally succeeding sites. Under “3L” limits, natural succession faltered, whereas phytostabilization increased total carbon (TC) from 0.175% to 0.474%, total nitrogen (TN) from 0.015% to 0.036%, and total phosphorus (TP) from 0.004% to 0.011% within 16 months (T3), boosting the Soil Quality Index (SQI). Root-associated aggregates (Agg_root) and plant growth-promoting bacteria (PGPB) enhanced stability with biocrusts aiding soil cohesion. By T3, the plot with BAG achieved over 80% vegetation coverage and 27.5% biocrust coverage, outperforming the naturally recovering sites. Phytostabilization reduced extractable REE (EREE) concentrations through pH shifts and microbial immobilization, contrasting with persistent REE mobility in untreated sites. The Soil Quality Index (SQI) and Ecological Environmental Quality Index (EEQI) provided a holistic assessment, with BAG scoring an EEQI of 0.92 on a scale from 0 to 1, indicating excellent ecological conditions and substantially outperforming the gradual improvements observed during natural succession. This contrast reveals the PMA system’s strength in rapidly restoring REE tailings, reducing contamination risks, and rebuilding ecosystem functions. These findings position phytostabilization as a cost-effective and scalable solution for restoring mining─degraded landscapes─with potential transferability to other mining types or ecologically stressed regions, thereby offering critical insights for sustainable rehabilitation under harsh environmental conditions.