Mining and processing of manganese (Mn) minerals are activities that may result in the generation of large amounts of wastes and serious environmental impacts. Several strategies have been employed to remediate areas with high Mn concentrations, but many of them imply high investments and high risk of secondary pollution. This study aimed to evaluate the phytostabilization potential of Mimosa caesalpiniaefolia Benth. in Mn mining soil influenced by inoculation with arbuscular mycorrhizal fungi (AMF). The experimental design was completely randomized, with four treatments [not inoculated (control), inoculated with Rhizophagus clarus; inoculated with Claroideoglomus etunicatum and inoculated with Rhizophagus clarus + Claroideoglomus etunicatum (Mix)], and four replicates. Inoculation with Mix and C. etunicatum had higher efficiency in protecting plants against excess Mn, due to the greater retention of this element in the roots and lower translocation to the shoots. Inoculation with R. clarus did not influence plant development and reduction of Mn contents in the shoots. The association of the AMF Mix and C. etunicatum with the species Mimosa caesalpiniaefolia Benth. enhances Mn phytostabilization in mining soils with high concentration of this element. The use of multivariate analyses proved to be an important tool with respect to the behavior of biometric, chemical and microbiological variables in mining soil with high Mn concentration.

Biological soil crusts (BSC) are commonly found in soils in the drylands regions, which can influence stabilization, water retention, nutrient cycling (particularly carbon (C) and nitrogen (N) dynamics), and several ecological processes. However, the composition of BSC in Brazilian soils undergoing the desertification process remains poorly understood. This study aimed to characterize the bacterial community in BSC formed in a Brazilian semiarid region under the desertification process. Thus, a highly desertified region was selected from which 34 BSC samples were collected. The total DNA of the BSC was extracted from 0.5 g samples, and the bacterial community was sequenced by a Next Generation Sequencing (NGS) platform (Miseq – Illumina®) using universal primers (515F and 806R). Bioinformatic analysis was carried out in QIIME (v.1.9), and the Operational Taxonomic Units (OTU) table was constructed following the Sumaclust methodology. The pH of BSC, C, N, and phosphorus contents was analyzed. Our study identified a diverse bacterial community in the BSCs. Cyanobacteria, Chloroflexi, and Proteobacteria phyla presented the greatest relative abundance (%) across the samples. Cyanobacteria were dominated by the orders Nostocales and Leptolyngbyales. The prediction of the putative functions found that mostf OTU were related to phototrophy, photosynthetic cyanobacteria, and photoautotrophy. The study found correlations between bacterial phyla and BSC properties, with Cyanobacteria positively related to C. Chloroflexi, Armatimonadetes, and WPS-2 were negatively correlated with C and N contents. These results suggest the critical roles bacteria communities play in BSCs from the Caatinga biome and highlight the potential impact of environmental factors on their diversity and functions.

Mining activity severely degrades soil, increases heavy metal contamination, and hinders ecological recovery. Arbuscular mycorrhizal fungi (AMF) offer a promising strategy for restoration, but their use in Fabaceae plants, especially in mine-degraded soils, remains underexplored. This study evaluated AMF inoculation effects on soil enzymes and Mimosa caesalpiniaefolia growth in Scheelite-mining-degraded soil. In a 10-weeks greenhouse experiment, plants were grown with different AMF species (Gigaspora margarita, Acaulospora foveata, Rhizoglomus clarum, and Mix—a combination of the three species) and without inoculation. Growth parameters, seedling quality, mycorrhizal attributes, enzymatic activity, and stoichiometry were assessed. Inoculated plants showed a greater growth compared with the control. The highest spore abundances occurred in Mix (2820), R. clarum (2261), and A. foveata (2318), with the mycorrhizal colonization highest in Mix (25.78%) and R. clarum (25.70%). The Dickson quality index was higher in R. clarum and A. foveata. The enzymatic activity varied compared with the control: β-glucosidase was higher in Mix (+62%) and A. foveata (+46%); arylsulfatase and urease increased in all AMF treatments; and acid phosphatase was highest in R. clarum (+121%). A stoichiometry and vector analysis indicated a lower P limitation in Mix and A. foveata, reflecting the trade-off between P availability and symbiotic costs. These findings highlight the biotechnological potential of AMF, particularly Mix and R. clarum, in enhancing the M. caesalpiniaefolia growth and soil enzymatic activity in mining-degraded areas.