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In 2015, the failure of the Fundão dam in Mariana, Brazil released ~43 million m3 of iron mining tailings into the environment. Despite restoration initiatives in the following years, few studies-and most focused on revegetation-have evaluated the effectiveness of the restoration process in areas impacted by the disaster. We aimed to evaluate the responses of the arthropod community in areas impacted by iron mining tailings deposition from the Fundão dam that is in the restoration process. We defined sampling units in the riparian zone of the Gualaxo do Norte River, which is under restoration, and in a native not impacted riparian zone. We collected soil arthropods using pitfall traps and sampled environmental variables in the same sites. We used generalize least squares models (GLS) to test if the restored areas already presented values of arthropod diversity and functional group abundance similar to the reference area and to test which environmental variables are influencing arthropod diversity. We also tested how large the differences of arthropod community composition between the study areas and used the index of indicator species (IndVal) to verify which species could be used as an indicator of reference or restoration areas. The diversity of arthropods and the functional groups of detritivores and omnivores were higher in the native riparian zone. Understory density, soil density, organic matter content, and microbial biomass carbon were the environmental variables that significantly explained the diversity and species composition of arthropods. We show that restoration areas still have different soil arthropod diversity values and community composition when compared to reference areas. Evaluating the response of the arthropod community to the restoration process and long-term monitoring are essential to achieve a satisfactory result in this process and achieve a self-sustaining ecosystem.

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Tailings from iron mining are characterized by high concentrations of iron and manganese oxides, as well as high pH values. With these characteristics, most of the potentially toxic elements (PTE) contained in the tailings are somewhat unavailable. The aim of the present study was to evaluate how a reduction in the pH of iron mine tailings may affect PTE availabilities. The tailings were collected on the banks of the Gualaxo do Norte River (Mariana, MG, Brazil), one of the main areas impacted by the rupture of the Fundão Dam (Barragem de Fundão). A completely randomized experimental design was used, including five pH values (6.4, 5.4, 4.3, 3.7, and 3.4) and five replications. The concentrations of the PTE (Ba, Cr, Cd, Co, Cu, Fe, Mn, Pb, Ni, and Zn) were determined after extraction following different methodologies: USEPA 3051A, DTPA, Mehlich-1, Mehlich-3, and distilled water. A comparison of the available concentrations of the elements in the tailings with those in a soil not impacted by tailings shows that Cr, Cd, Cu, Fe, Mn, Ni, Ba, and Co were higher in the soil impacted by the tailings. The different methods used for evaluating the availability of PTE in the tailings at various pH exhibited the following decreasing order in relation to the quantity extracted: Mehlich-3 > Mehlich-1 > DTPA > distilled water. However, regarding sensitivity to change in pH, the order was DTPA > water > Mehlich-1 > Mehlich-3. The increases in the concentrations of PTE due to the reduction in the pH of the tailings did not lead to concentrations that exceed the limits of Brazilian regulations. The DTPA extractant exhibited higher coefficients of correlation between the PTE concentrations and the pH of the tailings, proving to be suitable for use in areas affected by the deposition of iron mine tailings.

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Monitoring degraded areas is essential for evaluation of the quality of the rehabilitation process. In this study, we evaluate how the physical and chemical characteristics of the mixture of iron ore tailings with the soil have affected the soil microbial biomass and activity in areas along the Gualaxo do Norte River after the Fundão Dam disaster. Composite soil samples were collected from areas that were impacted (I) and not impacted (NI) by the tailings. The following attributes were evaluated: chemical element content; soil density, porosity, and texture; microbial biomass carbon; basal respiration; and enzyme activity and density of microbial groups (bacteria, actinobacteria, fungi, arbuscular mycorrhizae, phosphate solubilizers, cellulolytic microorganisms, nitrifiers, ammonifiers, and diazotrophs). According to result, the deposition of tailings increased the pH and the soil available P, Cr, Fe, and Mn content and reduced organic matter. The physical and biological attributes were negatively affected, with increases in the silt content and density of the soil, and reduction in macroporosity and in the microbial biomass and activity of the soil (respiration and enzymes) in the impacted area. However, the impacted areas exhibited greater densities of some microbial groups (cellulolytic microorganisms, nitrifiers, and diazotrophic bacteria). Modifications in the organic matter and silt content are the main attributes associated with deposition of the tailings that affected soil microbial biomass and microbial activity. This may affect erosive conditions and the functionality of the ecosystem, indicating an imbalance in this environment. In contrast, the higher density of some microbial groups in the impacted areas show the high rehabilitation potential of these areas.

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The heavy metal mercury (Hg) is one of the most complex and toxic pollutants. When present in soils, it may impair plant growth, but the intensity of damage depends on the physical-chemical properties of the soil such as pH, clay, and organic matter content, which in turn affects Hg sorption and bioavailability. Understanding Hg potential damage to staple food crops is of paramount relevance. Here, we evaluated the physiological effects of Hg in Phaseolus vulgaris (common bean) and Avena sativa (oat) cultivated in two Oxisols with contrasting properties: Rhodic Acrudox (RA) and Typic Hapludox (TH). We performed four independent experiments (one per species/soil combination) that lasted 30 days each. Treatments were composed by HgCl2 concentrations in soils (0 to 80 mg kg-1 Hg). At the end of the experiment, we determined the impact of Hg on photosynthesis, nutritional status, and oxidative stress. Cultivation in TH contaminated with Hg resulted in oxidative stress in common bean and decreased photosynthesis/P accumulation in oat. No deleterious effects on physiological variables were detected in both species when cultivated in the RA soil. In general, we conclude that the lower Hg sorption in the TH soil resulted in toxicity-like responses, while acclimation-like responses were observed in plants cultivated in RA, reinforcing soil physical-chemical properties as key features driving Hg toxicity in Oxisols. Graphical abstract.

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Copper is a micronutrient for living organisms, but at high concentrations it may cause several deleterious effects. The objective of this study was to evaluate the behavior of agricultural crops to different concentrations of Cu in the soil. The species Triticum aestivum (wheat), Zea mays (maize), Oryza sativa (rice), Phaseolus vulgaris (dry bean), Glycine max (soybean), and Raphanus sativus (radish) were cultivated in the soils Typic Hapludox (TyHpx) and Rhodic Acrudox (RhAcx). The experiment was carried out in a greenhouse and the soils were set in pots in a completely randomized design, with four replicates per treatment adding the following Cu concentrations (as Cu-nitrate): 0, 75, 150, 300, 600, 800, 1000, 1200 mg kg-¹ dry soil. Measurements of biological variables, such as shoot dry weight (SDW), plant height, stem diameter, and number of leaves were carried out, in addition to determining Cu content in the SDW. At the TyHpx, a decreasing order of tolerance to Cu phytotoxicity was: dry bean, maize, soybean, wheat, radish, and rice. However, at the RhAcx, the decreasing order was: maize, soybean, radish, wheat, dry bean, and rice. The species that revealed the highest sensitivity to high Cu concentrations in soil was rice and that with the lowest sensitivity was maize.

O cobre é um micronutriente para organismos vivos, mas em altas concentrações pode causar vários efeitos deletérios. O objetivo deste estudo foi avaliar o comportamento de culturas agrícolas em diferentes concentrações de Cu no solo. As espécies Triticum aestivum (trigo), Zea mays (milho), Oryza sativa (arroz), Phaseolus vulgaris (feijão), Glycine max (soja) e Raphanus sativus (rabanete) foram cultivadas nos solos Latossolo Vermelho Amarelo distrófico típico (LVAd) e Latossolo Vermelho distroférrico típico (LVdf). O experimento foi realizado em casa de vegetação e os solos foram colocados em vasos, em delineamento inteiramente casualizado, com quatro repetições por tratamento, adicionando às seguintes concentrações de Cu (como nitrato de Cu): 0, 75, 150, 300, 600, 800, 1000, 1200 mg kg-¹ de solo seco. Foram realizadas medidas das variáveis biológicas matéria seca da parte aérea (MSPA), altura da planta, diâmetro do caule e número de folhas, além disso foi determinado o teor de Cu na MSPA. No LVAd, a ordem decrescente de tolerância à fitotoxicidade do Cu foi: feijão, milho, soja, trigo, rabanete e arroz. No entanto, no LVdf, a ordem decrescente foi: milho, soja, rabanete, trigo, feijão e arroz. A espécie que revelou maior sensibilidade às altas concentrações de Cu no solo foi o arroz e a que apresentou menor sensibilidade foi o milho.

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Copper is a micronutrient for living organisms, but at high concentrations it may cause several deleterious effects. The objective of this study was to evaluate the behavior of agricultural crops to different concentrations of Cu in the soil. The species Triticum aestivum (wheat), Zea mays (maize), Oryza sativa (rice), Phaseolus vulgaris (dry bean), Glycine max (soybean), and Raphanus sativus (radish) were cultivated in the soils Typic Hapludox (TyHpx) and Rhodic Acrudox (RhAcx). The experiment was carried out in a greenhouse and the soils were set in pots in a completely randomized design, with four replicates per treatment adding the following Cu concentrations (as Cu-nitrate): 0, 75, 150, 300, 600, 800, 1000, 1200 mg kg-¹ dry soil. Measurements of biological variables, such as shoot dry weight (SDW), plant height, stem diameter, and number of leaves were carried out, in addition to determining Cu content in the SDW. At the TyHpx, a decreasing order of tolerance to Cu phytotoxicity was: dry bean, maize, soybean, wheat, radish, and rice. However, at the RhAcx, the decreasing order was: maize, soybean, radish, wheat, dry bean, and rice. The species that revealed the highest sensitivity to high Cu concentrations in soil was rice and that with the lowest sensitivity was maize.(AU)

O cobre é um micronutriente para organismos vivos, mas em altas concentrações pode causar vários efeitos deletérios. O objetivo deste estudo foi avaliar o comportamento de culturas agrícolas em diferentes concentrações de Cu no solo. As espécies Triticum aestivum (trigo), Zea mays (milho), Oryza sativa (arroz), Phaseolus vulgaris (feijão), Glycine max (soja) e Raphanus sativus (rabanete) foram cultivadas nos solos Latossolo Vermelho Amarelo distrófico típico (LVAd) e Latossolo Vermelho distroférrico típico (LVdf). O experimento foi realizado em casa de vegetação e os solos foram colocados em vasos, em delineamento inteiramente casualizado, com quatro repetições por tratamento, adicionando às seguintes concentrações de Cu (como nitrato de Cu): 0, 75, 150, 300, 600, 800, 1000, 1200 mg kg-¹ de solo seco. Foram realizadas medidas das variáveis biológicas matéria seca da parte aérea (MSPA), altura da planta, diâmetro do caule e número de folhas, além disso foi determinado o teor de Cu na MSPA. No LVAd, a ordem decrescente de tolerância à fitotoxicidade do Cu foi: feijão, milho, soja, trigo, rabanete e arroz. No entanto, no LVdf, a ordem decrescente foi: milho, soja, rabanete, trigo, feijão e arroz. A espécie que revelou maior sensibilidade às altas concentrações de Cu no solo foi o arroz e a que apresentou menor sensibilidade foi o milho.(AU)

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Agroforestry systems are an alternative option for sustainable production management. These systems contain trees that absorb nutrients from deeper layers of the soil and leaf litter that help improve the soil quality of the rough terrain in high altitude areas, which are areas extremely susceptible to environmental degradation. The aim of this study was to characterize the stock and nutrients in litter, soil activity and the population of microorganisms in coffee (Coffea arabica L.) plantations under high altitude agroforestry systems in the semi-arid region of the state of Pernambuco, Brazil. Samples were collected from the surface litter together with soil samples taken at two depths (0-10 and 10-20 cm) from areas each subject to one of the following four treatments: agroforestry system (AS), native forest (NF), biodynamic system (BS) and coffee control (CT).The coffee plantation had been abandoned for nearly 15 years and, although there had been no management or harvesting, still contained productive coffee plants. The accumulation of litter and mean nutrient content of the litter, the soil nutrient content, microbial biomass carbon, total carbon, total nitrogen, C/N ratio, basal respiration, microbial quotient, metabolic quotient and microbial populations (total bacteria, fluorescent bacteria group, total fungi and Trichoderma spp.) were all analyzed. The systems thatwere exposed to human intervention (A and BS) differed in their chemical attributes and contained higher levels of nutrients when compared to NF and CT. BS for coffee production at high altitude can be used as a sustainable alternative in the high altitude zones of the semi-arid region in Brazil, which is an area that is highly susceptible to environmental degradation.

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Agroforestry systems are an alternative option for sustainable production management. These systems contain trees that absorb nutrients from deeper layers of the soil and leaf litter that help improve the soil quality of the rough terrain in high altitude areas, which are areas extremely susceptible to environmental degradation. The aim of this study was to characterize the stock and nutrients in litter, soil activity and the population of microorganisms in coffee (Coffea arabica L.) plantations under high altitude agroforestry systems in the semi-arid region of the state of Pernambuco, Brazil. Samples were collected from the surface litter together with soil samples taken at two depths (0-10 and 10-20 cm) from areas each subject to one of the following four treatments: agroforestry system (AS), native forest (NF), biodynamic system (BS) and coffee control (CT).The coffee plantation had been abandoned for nearly 15 years and, although there had been no management or harvesting, still contained productive coffee plants. The accumulation of litter and mean nutrient content of the litter, the soil nutrient content, microbial biomass carbon, total carbon, total nitrogen, C/N ratio, basal respiration, microbial quotient, metabolic quotient and microbial populations (total bacteria, fluorescent bacteria group, total fungi and Trichoderma spp.) were all analyzed. The systems thatwere exposed to human intervention (A and BS) differed in their chemical attributes and contained higher levels of nutrients when compared to NF and CT. BS for coffee production at high altitude can be used as a sustainable alternative in the high altitude zones of the semi-arid region in Brazil, which is an area that is highly susceptible to environmental degradation.(AU)

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The extracellular matrix (ECM) contains important cues for tissue homeostasis and morphogenesis. The matricellular protein tenascin-C (TN-C) is overexpressed in remodeling tissues and cancer. In the present work, we studied the effect of different ECM-which exhibited a significant diversity in their TN-C content-in endothelial survival, proliferation and tubulogenic differentiation: autologous (endothelial) ECM devoid of TN-C, but bearing large amounts of FN; fibroblast ECM, bearing both high TN-C and FN contents; and finally, glioma-derived matrices, usually poor in FN, but very rich in TN-C. HUVECs initially adhered to the immobilized matrix produced by U373 MG glioma cells, but significantly detached and died by anoikis (50 to 80%) after 24h, as compared with cells incubated with endothelial and fibroblast matrices. Surviving endothelial cells (20 to 50%) became up to 6-fold more proliferative and formed 74-97% less tube-like structures in vitro than cells grown on non-tumoral matrices. An antibody against the EGF-like repeats of tenascin-C (TN-C) partially rescued cells from the tubulogenic defect, indicating that this molecule is responsible for the selection of highly proliferative and tubulogenic defective endothelial cells. Interestingly, by using defined substrata, in conditions that mimic glioma and normal cell ECM composition, we observed that fibronectin (FN) modulates the TN-C-induced selection of endothelial cells. Our data show that TN-C is able to modulate endothelial branching morphogenesis in vitro and, since it is prevalent in matrices of injured and tumor tissues, also suggest a role for this protein in vascular morphogenesis, in these physiological contexts.

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