Atlantic forest tree enhances photoprotective and thermotolerance in soils contaminated by mining tailings

Abstract

Large-scale mining disasters in tropical regions impose long-term pressures on ecosystems by degrading soil fertility and exposing native vegetation to chemical and physical disturbances. This study investigates whether Eugenia florida, a native tree species found in both tailings-impacted and reference areas of the Rio Doce Basin in Brazil, exhibits physiological adjustments that confer resilience to combined edaphic and thermal constraints. We assessed soil properties and 16 physiological traits related to nutrient status, photosynthetic efficiency, photoprotection, and thermal tolerance. Soils in the impacted area exhibited markedly lower organic matter, cation exchange capacity, and nutrient concentrations, along with increased iron concentration. Despite a 10% reduction in nitrogen balance index, plants in the impacted area exhibited 10% more chlorophyll and 19% more flavonoids, indicating compensatory pigment production and enhanced antioxidant capacity. Photosynthetic performance remained stable across environments, but individuals in the impacted area displayed elevated regulated energy dissipation and reduced unregulated energy loss, suggesting efficient photoprotective adjustments. Transient fluorescence analyses revealed intensified excitation fluxes and greater heat dissipation per reaction centre. Thermal thresholds, defined as temperatures causing 15% and 50% reductions in photosynthetic efficiency, were significantly higher in impacted individuals. Multivariate analyses identified excitation flux traits as key predictors of thermal resilience. Physiological function in E. florida is sustained through integrated plastic responses under long-term soil degradation and thermal constraints. Its ability to modulate energy fluxes and antioxidant defences highlights its potential as a candidate species for ecological restoration in tropical regions increasingly affected by human disturbance and climate extremes.