Growth-tolerance tradeoffs shape the survival outcomes and ecophysiological strategies of Atlantic Forest species in the rehabilitation of mining-impacted sites.

The initial performance of seedlings of tree species from different functional groups, regarding the growth-defense tradeoff, might determine its long-term success during the rehabilitation of mining areas. We monitored the field performance of six native tree species of the Atlantic Forest in the Fundão dam tailing that has been under rehabilitation for 35 months. Additionally, we explored the morphophysiological traits driving the superior performance of three species. The study examined the survival strategies of pioneer species (Anadenanthera colubrina, Bixa orellana, Peltophorum dubium) and secondary species (Cedrela fissilis, Handroanthus impetiginosus, Handroanthus serratifolius), as well as the photosynthetic, nutritional, and antioxidant metabolism of the successful species. Most species accumulated excessive Fe in their leaves, except for the pioneer species A. colubrina and P. dubium. However, the nutritional status of the plants, concerning leaf nutrient concentration, was adequate for their growth in the waste. The species A. colubrina, C. fissilis, and H. serratifolius exhibited poor physiological performance, primarily due to substrate compaction and excessive foliar metal concentrations. The successful performance of P. dubium was attributed to avoidance mechanisms, allowing a cost-effective growth-defense tradeoff, thus maintaining photosynthetic efficiency at the expense of energy investment in antioxidant protection. The excess Fe allocation in the photosynthetic tissues of B. orellana was linked to a greater investment in antioxidant metabolism, which was related to the protection of the photosynthetic machinery. The Fe hyperaccumulation in H. impetiginosus led to increased oxidative damage, which was mitigated by investments in tolerance mechanisms, including photosynthetic adjustments (stomatal limitation, non-photochemical energy dissipation), as well as the activation of the enzymatic antioxidant system. The persistence and success of the Atlantic Forest tree species were not related to their ecological successional classification. Instead, it was the different mechanisms of tolerance and avoidance that allowed both pioneer and secondary species to thrive in the impacted area.