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Highlights: [•] A total of 36 AMF species were recovered in pasture and forest. [•] Conversion of pasture to forest influence AMF taxonomic composition. [•] AMF species richness and abundance distribution were similar between forest and pasture. [Copyright &y& Elsevier]

Graphical abstract Highlights • The trophic relationships between earthworms and three species of AMF were evaluated. • P. corethrurus produces more casts eating on roots with R. clarus and C. etunicatum. • P. corethrurus concentrate propagules of R. clarus and C. etunicatum in their casts. • R. clarus and C. etunicatum spores extracted from casts germinate better. • P. corethrurus shows feed preference for roots with R. clarus and C. etunicatum. Abstract Earthworms and arbuscular mycorrhizal fungi (AMF) are essential for nutrient cycling and organic matter dynamics in terrestrial ecosystems. In soils, they tightly interact especially in the rhizosphere. Therefore, the objective of this study was to evaluate the trophic relationship between the earthworm Pontoscolex corethrurus and three species of AMF (Rhizophagus clarus , Claroideoglomus etunicatum , and Gigaspora margarita). We performed bioassays with different experimental designs and treatments, to evaluate cast production by P. corethrurus in the three different substrates, the number of AMF propagules after ingestion by earthworms, the germination capacity of ingested spores, the earthworm feeding preferences, and the influence of AMF species on earthworm growth. P. corethrurus produced more casts when R. clarus and C. etunicatum was present in the food source. Spore number, percentage of germinated spores and most probable number of infective propagules of R. clarus and C. etunicatum were higher in earthworm casts than in soil inocula, whereas opposite trend of results was found with G. margarita , suggesting that the digestion of AMF propagules by P. corethrurus varies with the AMF species. Earthworm weight increased when they were fed with R. clarus and G. margarita soil-inocula, but individuals showed no clear preference for different AMF species. Roots colonized by R. clarus were more attractive to P. corethrurus. Findings of this study have important implications for the roles of P. corethrurus in mycorrhizal potential of R. clarus e C. etunicatum and in the reduction of the propagules of G. margarita in soil. [ABSTRACT FROM AUTHOR]

Following a survey in herbaria in Brazil and abroad, complemented by a survey of the literature and searches of biodiversity data, 66 taxa of Eriocaulaceae have been identified in the Brazilian Amazon, as defined by the states of Acre, Amapá, Amazonas, Pará, Rondônia and Roraima. Six genera of Eriocaulaceae were found in the Amazon with the following taxon numbers: Comanthera (3 taxa), Eriocaulon (10), Paepalanthus (15), Rondonanthus (2), Syngonanthus (35) and Tonina (1). Of this total, 25 taxa present distributions in the states of the Amazon and other Brazilian states (considered as widely distributed) and the remaining 41 taxa are restricted to the Amazon Rainforest biome. The distribution data for 31 species were used for Species Distribution Modelling, due to the low number of occurrence points reported for the other taxa, 17 of those are known from a single location. The overlap of these models indicates areas from Amapá, Amazonas, Pará and Roraima where modelled species are most likely to occur. These data can further contribute to the location of new populations of species of Eriocaulaceae. New detection of Eriocaulaceae species can assist in filling the gaps on their geographic distribution and ecology, contributing to the protection or restoration of priority areas set aside for their conservation. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of lime, fertilizers, mycorrhizal fungi, and selected rhizobia strains on the growth of four woody legume species, Albizia lebbeck (L.) Benth., Enterolobium contortisiliquum (Vell.) Morong. , Leucaena leucocephala (Lam.) de Wit, and Sesbania virgata (Cav.) Pers. in a low-fertility soil. The experiment was conducted under greenhouse condition in plastic pots (4 kg). Eight treatments and eight replicates per treatment were performed in a completely randomized design. The treatments were: (1) complete treatment (C) (NPK fertilization + micronutrients + liming + MR that is inoculation with mycorrhizal fungi and rhizobia); (2) C minus N (C − N that is as C without the addition of N); (3) C − N − M (as C − N without inoculation with arbuscular mycorrhizal fungi (AMF)); (4) C − N −R (as C − N without inoculation of rhizobia); (5) C − N − liming (as C − N without liming); (6) C − N − micro (as C − N without addition of micronutrients); (7) C − N − P (as C − N without addition of P); (8) control without fertilization, liming, and without inoculation with AMF and rhizobia. After 4 months of growth, we determined the yield of individual plants, nodulation, mycorrhizal colonization, and nutrient contents. Phosphorus was the most limiting nutrient for plant growth, followed by nitrogen. L. leucocephala and S. virgata had the most robust response to the addition of micronutrients and liming, showing an increase in nutrient content, plant height, and root and shoot dry matter. When compared to the single inoculation, the dual inoculation increased growth of all plants, except that of A. lebbeck, which did not respond to either rhizobia or mycorrhizal fungi inoculation. [ABSTRACT FROM AUTHOR]

Rare earths elements (REEs) can affect plant growth positively. Besides their intentional agricultural use, REEs have also been involuntarily applied to soils through phosphate (P) fertilizers. This study aimed to evaluate the effects of REEs contained in P fertilizers on increasing legume crops yield in Brazilian agroecosystems. Field experiments were conducted with Phaseolus vulgaris L. and Glycine max (L.) Merrill with four sources of P (a pure ammonium phosphate with no REEs and three single superphosphates—SSP—with varying REEs contents) applied to the soil at four P rates (0, 17.5, 35, 70 kg ha−1). Irrespectively of the rate, the SSP—Catalão (richest in total and soluble REEs among the sources tested) consistently increased the yield of common bean (~ 30%) in relation to the control (ammonium phosphate). Single superphosphate Araxá (intermediate REEs content) also increased common bean yield. For soybean, the SSP-Catalão, at the 70 kg P ha−1 rate, was superior to the control (at the same level of P) and to the treatment without P addition. Our results showed that the REEs, present as impurities in phosphate fertilizers, increase their effectiveness on legume crops yield. These findings are relevant, as producers could enhance yield with REEs-rich P-fertilizers, especially in tropical agroecosystems, where high application rates are required. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) play a key role in plant nutrition and in the maintenance of soil fertility in agroecosystems, but their survival can be affected by different agricultural practices, including the use of pesticides. In this work, we assessed the impact of chemicals with herbicidal and fungicidal activity on mycelial growth and structure of the worldwide distributed AMF Funneliformis mosseae. Results showed that mycelial growth and interconnectedness of three different F. mosseae lineages were affected by the chemicals tested at concentrations lower than those indicated for agricultural use. Indeed, benomyl reduced mycelial growth in one lineage and fenhexamid negatively affected germlings growth in the three lineages, while both fungicides significantly affected mycelial viability and induced abnormal hyphal branching. The three F. mosseae lineages showed sensitivity to herbicides, with significant growth and viability decreases in the presence of the active ingredient glufosinate ammonium and a low viability at increasing concentrations of dicamba. Anastomosis rates were reduced by the two fungicides and by very low levels of the herbicide glufosinate, whose impact on AMF networks should be further investigated, given its wide use in agriculture. Our results suggest that the use of some pesticides in agroecosystems may lead to growth reduction and disruption of AMF mycelial structural traits, even in AMF species able to tolerate soil disturbance, posing serious threats to AMF symbiotic performance and to the maintenance of soil mycorrhizal potential. • Fungicides affect mycelial growth and viability of arbuscular mycorrhizal fungi. • Mycelial interconnectedness of arbuscular mycorrhizal fungi is reduced by fungicides. • The herbicide glufosinate decreases mycelial growth and interconnectedness. [ABSTRACT FROM AUTHOR]

Abstract To protect indigenous land and avoid the spread of deforestation in the Amazon, state and federal Brazilian agencies recognized several protected areas since the 1990s. However, the importance of these protected areas in the water cycle and the hydrologic connection with surrounding landscapes is little analyzed. In this study, we evaluated the role of preserved and deforested areas in the water balance in the Itacaiúnas River Basin using the MGB hydrological model. We estimated the impacts of land cover changes on evapotranspiration and discharge for four scenarios: Preserved (1984 land cover), Recent (2013 land cover, with 50% deforestation), Hypothetical deforestation of protected areas (70% deforestation) and complete deforestation of protected areas (79% deforestation). We showed that deforestation of the remaining preserved area could be responsible for a decrease of 23% (3.5 km³/year) in water transfer to the atmosphere by evapotranspiration. Furthermore, we showed that each 15% of deforestation occurring between the Preserved and Recent scenarios increased the average discharges by 5.4% (40 m³/s). Additionally, past land cover changes in the headwaters of the Itacaiúnas River Basin caused statistically significant changes in discharges inside the protected areas. This insight is considered important due to the association between increases in discharges and water quality issues. The results suggest that headwater areas of secondary drainages that run into the forested domains should be prioritized for reforestation programs. Likewise, the reforestation of nonprotected areas could be responsible for restoring ecosystem services, including hydrological functions, biodiversity and water quality. Highlights • Hydrologic modeling of an important ungauged river basin of Amazon Biome affected by deforestation. • MGB hydrologic model was used to estimate discharges and evapotranspiration in Itacaiúnas River Basin. • Important feedbacks involving evapotranspiration and discharge processes are affected by land use/land cover changes. • Insights of the streamflow inside the protected areas covered by forests are affected by land cover changes. • Insights on the role of protected areas in the hydrological processes and connection with surrounding landscapes. [ABSTRACT FROM AUTHOR]

Abstract Several studies have been carried out to compare and/or improve instrumental analytical techniques capable of quantifying trace elements, rare earths included. Sample dissolution is a key step in this process and the choice of the most appropriate technique depends on many factors, e.g., digestion power, laboratory workability, available instrumentation, and timing. Alkaline fusion and acid digestion are often the preferred techniques for decomposition of geological samples due to their precision and accuracy. The aim of this study was to evaluate dissolution techniques for determination of REE in phosphate products by ICP-MS. For this, twenty samples of phosphate products were selected from the fertilizer quality control program of the Brazilian Ministry of Agriculture, Livestock, and Food Supply. Samples of these products were digested by either microwave digestion or alkaline fusion. Both methods yielded accurate results, with alkaline fusion being slightly more efficient than microwave digestion in the extraction of light REE. However, this difference between methods was not observed for heavy REE and it did not affect the REE signatures. The information provided in this paper can assist in the choice of dissolution techniques for REE quantification, especially in phosphate fertilizers. In addition, the equations provided in this paper may also be used to interconvert the results from both methods. Graphical abstract Unlabelled Image Highlights • Sample dissolution methods for quantitative analysis of REE using ICP-MS have been compared. • Hierarchical clustering has been performed to compare the similarity of dissolution methods. • REE signatures have been used to compare dissolution methods for phosphate fertilizers. [ABSTRACT FROM AUTHOR]

Environmental legislation in many countries demands the rehabilitation of degraded areas to minimize environmental impacts. Brazilian laws require the restitution of self-sustaining ecosystems to historical conditions but ignore the emergence of novel ecosystems due to large-scale changes, such as species invasions, extinctions, and land-use or climate changes, although these novel ecosystems might fulfill ecosystem services in similar ways as historic ecosystems. Thorough discussions of rehabilitation goals, target ecosystems, applied methods, and approaches to achieving mine land rehabilitation, as well as dialogues about the advantages and risks of chemical inputs or non-native, non-invasive species that include all political, economic, social, and academic stakeholders are necessary to achieve biological feasibility, sociocultural acceptance, economic viability, and institutional tractability during environmental rehabilitation. Scientific knowledge of natural and rehabilitating ecosystems is indispensable for advancing these discussions and achieving more sustainable mining. Both mining companies and public institutions are responsible for obtaining this knowledge. [ABSTRACT FROM AUTHOR]

Highlights • Endangered Isoetes cangae produces large quantities of viable spores per sporangia. • Large number of sporelings emerge from male and female spores in vitro culture. • The megaspore nutrient reserve ensures longstanding sporeling growth. • Sporelings are able to grow in a range of substrates and temperature regimes. • Successful growth and low mortality suggest that I. cangae is a resilient species. Abstract Isoëtes L. is a nearly cosmopolitan rhizomorphic lycopsid genus fundamental to disentangling plant evolution because of its singular position in the Plantae kingdom. A threatened Amazonian species recently described is I. cangae, inhabiting an oligotrophic upland lake over an iron-rich region facing substantial environmental alterations. In this study, we aim to optimize a reproduction protocol that can assist in the conservation efforts of Isoëtes species in tropical areas. We observed an average of 126 megaspores or 318,000 microspores per sporangia in field-collected plants. We obtained an elevated percentage of sporelings (63%) from an in vitro mixed culture of mega- and microspores. In addition, we recovered a large number of sporelings around adult plants after cultivating them over quartzite sand and distilled water. The megaspore nutrient reserve ensured longstanding sporeling growth and development in these environmental conditions. However, the sporeling growth rate increased when they were planted over their original lake sediments or over an organic substrate, with nonsignificant differences between the substrates. An increase in temperature also increased the sporeling growth rate. Together with the very low sporeling mortality, these results suggest that I. cangae is a resilient species able to grow and colonize environments with low trophic characteristics with a range of substrates and temperature regimes. The protocols established in this study could be useful for the ex situ propagation and growth of a large number of sporelings, representing critical steps towards the population rescue and conservation of tropical Isoëtes species. [ABSTRACT FROM AUTHOR]

Abstract Rehabilitation of tailing dams poses important challenges because sterile materials and poor or even toxic soils hinder plant development and the regeneration of the pre-mining-activity biota. In this study, we analyzed the effectiveness of rehabilitating a 14-year-old manganese tailing dam by comparing three different regeneration treatments (topsoil application, seedling plantation and spontaneous regeneration) with undisturbed reference sites. We used soil chemical composition, taxonomic, functional and phylogenetic diversity and the above-ground tree biomass as indicators of rehabilitation success. In terms of soil chemical composition, we showed that the seedling and natural regeneration treatments were similar to one another but different from the reference sites. Topsoil application presented an intermediate chemical composition between the reference site and the other two treatments. Moreover, the species richness, Shannon diversity index and phylogenetic diversity indicated faster rehabilitation of ecosystem biodiversity with the topsoil treatment, although levels from reference are not yet achieved. We also observed higher basal area and biomass production in the topsoil treatment. However, these patterns were not observed for functional diversity, for which no differences among treatments were observed. We concluded that topsoil application provided the best results; however, we must emphasize that even this approach was not sufficient to rehabilitate the system to the similar level of biodiversity found in the surrounding ecosystem up to the present. Highlights • Topsoil application showed good results for manganese tailings dam rehabilitation. • Functional and phylogenetic diversity can be used for rehabilitation monitoring. • Reference sites showed different biodiversity attributes than rehabilitated areas. [ABSTRACT FROM AUTHOR]

Despite the urgent demand for sustainable mining, the revegetation and rehabilitation of areas degraded by mining activities remain challenging. Uncertainties about species selection, the management and control of alien invasive species and monitoring procedures require ongoing multidisciplinary research. Modern functional and phylogenetic approaches in community ecology represent powerful tools to enhance the entire rehabilitation process and to overcome these challenges, but methodologies that incorporate up-to-date phylogenetic information or knowledge about intraspecific variation along rehabilitation trajectories must be developed. Functional and phylogenetic criteria may play an especially important role in guiding the definition of faster-growing, more resistant species mixtures that can be applied in mine land revegetation and rehabilitation. Limiting similarity approaches may help to reduce biological invasions, enabling native vegetation to outcompete alien invasive species and aiding in the development of enduring mechanisms for controlling such species in rehabilitated mine land. Finally, incorporating phylogenetic and functional aspects into monitoring of the success of mine land rehabilitation with additional tools, such as remote sensing or metabarcoding, can enrich scientific knowledge about ecosystem functions such as nutrient cycling, community assembly and resource availability while providing sound information about the success of revegetation activities. In the middle to long term, research activities on these topics can provide valuable technical recommendations for all aspects of the management of rehabilitated ecosystems, thus contributing to more sustainable mining. [ABSTRACT FROM AUTHOR]

In 2015, the Fundão Dam collapse released over 40 million m3 of iron mine tailings, causing several environmental damages. Certain affected areas were revegetated with a mix of fast-growing species that can allowed the return of some organisms of soil fauna. Nematodes are the most abundant multicellular organisms in soil and are commonly used as bioindicators. Therefore, this study aimed to use the nematode community as bioindicators of the restoration process of an area affected by iron tailings at the margins of the Gualaxo do Norte River. Soil samples were collected from affected and native forest areas to perform physical, chemical, biochemical, and biological analyses. Nematodes were identified and classified according to feeding habits and on a colonizer-persisters (cp) scale. A non-metrical multidimensional scaling and PERMANOVA were conducted to assess differences between communities. Shannon's diversity index and the maturity index were significantly higher in the restoration area. There was a difference in the composition and the structure of nematode communities of the restoration and reference area, nematode genus occurrence and abundance were different between the areas resulting in differences in feeding habits and life strategies according to the cp scale. The cp-5 nematodes are more abundant in the restoration area and cp-1 in the forest reference area. Bacterivore nematodes were more abundant in the reference forest area. In addition, the soil attributes in the restoration area were altered following the tailings deposition. Such alterations include high pH, low organic matter content, and low microbial biomass, which consequently influenced the structure and the composition of the nematode community. This is likely the first report of soil nematode community diversity in the areas of the Rio Doce Basin impacted by the Fundão tailings, and nematodes proved to be good bioindicators to show the differences between the restoration and forest reference area. • This is the first study with nematodes in the impacted areas by Fundão tailings. • There is a great diversity of nematodes in the area under restoration process. • The nematode community between the restoration area and the reference is distinct. [ABSTRACT FROM AUTHOR]

Long-term human-induced impacts have significantly changed the Amazonian landscape. The most dramatic land cover and land use (LCLU) changes began in the early 1970s with the establishment of the Trans-Amazon Highway and large government projects associated with the expansion of agricultural settlement and cattle ranching, which cleared significant tropical forest cover in the areas of new and accelerated human development. Taking the changes in the LCLU over the past four decades as a basis, this study aims to determine the consequences of land cover (forest and savanna) and land use (pasturelands, mining and urban) changes on the hydroclimatology of the Itacaiúnas River watershed area of the located in the southeastern Amazon region. We analyzed a multi-decadal Landsat dataset from 1973, 1984, 1994, 2004 and 2013 and a 40-yr time series of water discharge from the Itacaiúnas River, as well as air temperature and relative humidity data over this drainage area for the same period. We employed standard Landsat image processing techniques in conjunction with a geographic object-based image analysis and multi-resolution classification approach. With the goal of detecting possible long-term trends, non-parametric Mann–Kendall test was applied, based on a Sen slope estimator on a 40-yr annual PREC, TMED and RH time series, considering the spatial average of the entire watershed. In the 1970s, the region was entirely covered by forest (99%) and savanna (∼0.3%). Four decades later, only ∼48% of the tropical forest remains, while pasturelands occupy approximately 50% of the watershed area. Moreover, in protected areas, nearly 97% of the tropical forest remains conserved, while the forest cover of non-protected areas is quite fragmented and, consequently, unevenly distributed, covering an area of only 30%. Based on observational data analysis, there is evidence that the conversion of forest cover to extensive and homogeneous pasturelands was accompanied by systematic modifications to the hydroclimatology cycle of the Itacaiúnas watershed, thus highlighting drier environmental conditions due to a rise in the region's air temperature, a decrease in the relative humidity, and an increase in river discharge. [ABSTRACT FROM AUTHOR]

Phosphate fertilizers are critical for crop production in tropical soils, which are known for having high phosphate-fixing capacity and aluminum saturation, as well as low pH and calcium contents. Fluorine is a component of many phosphate rocks used to make phosphate fertilizers, via a process that generates hexafluorosilicic acid (H 2 SiF 6 ). While many treatment technologies have been proposed for removal of fluorine in industrial facilities, little attention has been given to a process of neutralizing H 2 SiF 6 with calcium oxide aiming to find out an alternative and sustainable use of a by-product with a great potential for beneficial use in tropical agriculture. This study evaluated the effect of a by-product of phosphoric acid production (fluorite with silicon oxide, hereafter called AgroSiCa) on soil properties as well as on growth of soybean and corn. Two experiments (2 crops) were conducted under greenhouse conditions in a completely randomized 3 × 5 × 2 × 3 factorial design as follows: three soils (Red Latosol, Red-Yellow Latosol, and Cambisol), five doses of AgroSiCa (0; 0.5; 1.0; 2.0; 4.0 t ha −1 ), two doses of phosphorus (2 × %clay and 4 × %clay), with three replicates, totaling 90 plots for each experiment. The application of AgroSiCa resulted in a slight increase of soil pH. Significant increases in calcium, phosphate, and silicon levels in soil solution and in shoots of maize and soybean were observed at all doses of AgroSiCa. We also found very low levels of fluoride in all soil leachates. Significant reduction of labile aluminum was found in all soils after the cultivation of maize and soybean. In sum, AgroSiCa improved soil properties and contributed to a better growth of both crops. Our results show that reacting H 2 SiF 6 derived from the wet-process phosphoric acid production with calcium oxide leads to a by-product with potential for agricultural use, especially when applied in highly-weathered soils. Besides providing calcium and silicon to plants, the use of such by-product in soils with high phosphate-fixing capacity and high aluminum saturation delivers additional benefits, since fluoride and silicon can play an important role in improving soil conditions due to the formation of less plant-toxic forms of aluminum, as well as upon decreasing phosphate fixation, thus improving root development and making fertilizer-derived phosphate more available for plant growth. [ABSTRACT FROM AUTHOR]

Highlights: [•] All isolates abundantly colonized the corn roots, but only 23 promoted higher growth and P content. [•] The ability to promote growth and P nutrition was independent of the origin of the isolates. [•] Physiological responses were related to the ability of the fungi to provide P to the host in 93% of the fungus-plant combinations. [•] Functional variability can be greater between isolates of the same species than between isolates of distinct species. [•] The morphological characterization agreed with the genotypic characterization by 18S rDNA PCR-RFLP and sequencing. [•] R. clarus and S. heterogama isolates were consistently efficient in promoting corn growth. [Copyright &y& Elsevier]

• Geochemical background values in soils of Itacaiúnas River Basin are presented. • The validity of log-ratio transformation in compositional data analysis was discussed. • mMAD is the most preferred method for determining geochemical background values. • CONAMA Resolution 420/2009 limits are unrealistic to determine anthropogenic impact in Itacaiúnas soils. • High anomalies of Cr, Cu, and Ni are linked to catchment lithology and mineralization. This study aims at providing high quality soil geochemical data at a regional scale (1 sample per 25 km2) to understand the source and distribution of potentially toxic elements (PTEs: Al, As, Ba, Cd, Cu, Co, Cr, Fe, Hg, Mo, Mn, Ni, Pb, Se, U, V, and Zn) and to define their geochemical background threshold values (GBTVs) in the Itacaiúnas River Basin (IRB), Brazilian Amazon. A total of 2958 soil samples were collected at two depths (surface: 0–10 cm; bottom: 30–50 cm) and the fine fractions (<0.117 mm) were analyzed by ICP-MS and ICP-AES after aqua-regia digestion. The compositional nature of geochemical data was evaluated using the log-ratio approach and compared with traditional methods. Results show that compared to raw/log-transformation, centred log-ratio (clr) transformation improves spatial mapping and also better separated variables in Principal Component Analysis (PCA). Correlation analysis based on the isometric log-ratio (ilr) transformation in heat-maps provides reliable and better structure of the results. The spatial maps (clr) indicate that most of the elements in surface and bottom soils are mainly governed by underlying bedrock geology (parent lithologies and mineralization), while anthropogenic factors are insignificant. The resulting clr-based PCA and cluster analyses associated with geological information indicate that geochemical patterns of Fe-Ti-V-Cr-Sc can be linked to mafic to intermediate metavolcanic rocks and banded-iron formations, which are dominant in the Carajás basin, while Ni and Cr distribution pattern is attributed to mafic and ultramafic lithologies, and Cu anomalous values are mainly related to hydrothermal mineralized copper belts. Among the statistical methods applied for estimation of GBTVs, TIF produced the highest BTVs, followed by 98th and mMAD, with few exceptions, while mMAD was considered the more suitable for defining GBTVs. The number of potential anomalies of PTEs identified by these methods follow the order of MAD > 98th > TIF or MAD > TIF > 98th, and overall the anomalies are mostly related to the local lithology/mineralization with no indication of anthropogenic contamination. Compared with Brazilian guidelines (CONAMA Resolution No. 420/2009), the GBTVs determined for Cr, Co, Ni, and Cu by TIF, MAD, and 98th percentile mostly exceeded both IV and PV limits. However, these high values are due to the influence of local lithology. This reveals that the Brazilian CONAMA guidelines of these elements for the IRB are unrealistic because that suggests a large number of sites requiring investigation, which is not consistent with the geochemical evidence. Therefore, site-specific GBTVs must be considered for the accurate evaluation of anthropogenic contamination, as well as the ecological and human health risks of PTEs in this region. [ABSTRACT FROM AUTHOR]

Multi-elemental analysis of high-density (regional-scale) geochemical surveys is an important strategy for multi-purpose applications, particularly in addressing geochemical background concentrations in different sampling media. This approach was applied to the Itacaiúnas River Watershed (IRW), which is situated in the most prominent mining area of Brazil, the Carajás Mineral Province. Microcatchment-based mapping (~50 km2 each) covering the whole extent of IRW was delimited using remote sensing techniques and targeted for sampling. A total of 788 samples, including 27 duplicates, were collected in 2017. The <0.177 mm fraction of all samples was digested by aqua regia and 51 elements were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Geochemical maps for Fe and potentially toxic elements (PTE; As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sn, V, and Zn) and microcatchment-based distribution maps based on threshold values were constructed for the whole IRW. The stream sediment geochemistry is mainly controlled by the local geologic setting and underlying lithology. Geochemical background (GB) values for 43 elements in stream sediments of the IRW were determined by a variety of methods (Tukey's inner fences -TIF, median ± 2*median absolute deviation - MAD, and percentile-based techniques). The results provided from the different methods show a wide range of values, with the MAD method being considered the most appropriate for deriving GB concentrations. A comparison of reference levels for PTE contemplated in the Brazilian regulation in stream sediments, the threshold concentrations obtained for the IRW area, and different study cases around the world is presented in detail. Our findings provide not only valuable information for selecting potential areas for mineral exploration surveys, but also for evaluating geochemical contaminant effects with time-varying treatments. Studies conducted to determine background values at regional scale are needed for environmental decision making, as well as to attest actions in cases of potential contamination. In the absence of these studies, misleading interpretations of the magnitude of contamination levels in a certain area may cause under- or overestimation of ecological and/or human-health risks of PTE. Image 1 • Stream sediments background values of the Itacaiúnas River basin were determined. • Median+2*MAD method gives better results for deriving geochemical background. • There is no clear contamination associated to anthropogenic activities. • Geological setting controls the distribution of Fe and potentially toxic elements. • Regional background studies are needed to define sediment quality guidelines. [ABSTRACT FROM AUTHOR]

Functional ecology provides useful tools for selecting native species for rehabilitation purposes. Here, we evaluated a list of native tree and shrub species as candidates for use in waste pile rehabilitation in the Carajás National Forest, eastern Amazon, Brazil, to increase the diversity and stability of the reinstated communities. Native species lists were compiled from vegetation inventories performed in two different ecosystems in the region, i.e., dense evergreen Amazonian forests and ferriferous savannah formations, locally known as cangas. For prospection, we evaluated the functional differences among the forest, canga and waste pile communities and computed the functional space defined by wood density and 14 leaf traits of species that had already established during former rehabilitation efforts targeting the waste piles. Native species falling within this trait space were selected for further initial rehabilitation activities, while species outside this space were considered unsuitable for this purpose. As a proof of concept, we compared the survival of seedlings of selected and nonselected tree species to evaluate their potential for initial rehabilitation activities. We found functional differences in the communities between the rehabilitating waste piles and natural environments but higher functional congruence with forest than with canga ecosystems, making the conversion of waste piles into forests more likely. The assessment of functional differences enabled the identification of additional species for initial waste pile rehabilitation; we present a list of 76 candidates for future waste pile rehabilitation activities in Carajás National Forest. Our approach was validated by the seedling survival experiment, where selected species showed higher survival than nonselected species, highlighting the suitability of the selected species for initial waste pile rehabilitation in the region to increase the species richness and functional redundancy of the reinstated communities. The validation via the seedling survival experiment furthermore encourages the replication of the proposed functional prospection procedure for other environments to be rehabilitated, with different species sets being sought for different regions. • Functional selection of species for rehabilitation is validated by a proof of concept. • Seventy-six candidates for future waste pile rehabilitation activities are presented. • Suitability is confirmed by higher survival of selected species on waste piles. • Functional congruence indicates the convergence of waste piles to forest ecosystems. [ABSTRACT FROM AUTHOR]

Despite the wide variety of variables commonly employed to measure the success of rehabilitation, the assessment and subsequent definition of indicators of environmental rehabilitation status are not simple tasks. The main challenges are comparing rehabilitated sites with target ecosystems as well as integrating individual environmental and eventually collinear variables into a single tractable measure for the state of a system before effective indicators that track rehabilitation may be modeled. Furthermore, a consensus is lacking regarding which and how many variables need to be surveyed for a reliable estimation of rehabilitation status. Here, we propose a multivariate ordination to integrate variables related to ecological processes, vegetation structure, and community diversity into a single estimation of rehabilitation status. As a case, we employed a curated set of 32 environmental variables retrieved from nonrevegetated, rehabilitating and reference sites associated with iron ore mines from the Urucum Massif, Mato Grosso do Sul, Brazil. By integrating this set of environmental variables into a single estimation of rehabilitation status, the proposed multivariate approach is straightforward and able to adequately address collinearity among variables. The proposed methodology allows for the identification of biases towards single variables, surveys or analyses, which is necessary to rank environmental variables regarding their importance to the assessment. Furthermore, we show that bootstrapping permitted the detection of the minimum number of environmental variables necessary to achieve reliable estimations of the rehabilitation status. Finally, we show that the proposed variable integration enables the definition of case-specific environmental indicators for more rapid assessments of mineland rehabilitation. Thus, the proposed multivariate ordination represents a powerful tool to facilitate the diagnosis of rehabilitating sites worldwide provided that sufficient environmental variables related to ecological processes, diversity and vegetation structure are gathered from nonrehabilitated, rehabilitating and reference study sites. By identifying deviations from predicted rehabilitation trajectories and providing assessments for environmental agencies, this proposed multivariate ordination increases the effectiveness of (mineland) rehabilitation. • A multivariate approach integrating patterns and processes to access mineland rehabilitation. • The approach evaluates importance and biases regarding single or group of variables. • Defining indicators optimizes the selection of variables for further assessments. [ABSTRACT FROM AUTHOR]

The variety, relative importance and eco-evolutionary stability of reproductive barriers are critical to understanding the processes of speciation and species persistence. Here we evaluated the strength of the biotic prezygotic and postzygotic isolation barriers between closely related morning glory species from Amazon canga savannahs. The flower geometry and flower visitor assemblage analyses supported pollination by the bees in lavender-flowered Ipomoea marabaensis and recruitment of hummingbirds as pollinators in red-flowered Ipomoea cavalcantei. Nevertheless, native bee species and alien honeybees foraged on flowers of both species. Real-time interspecific hybridization underscored functionality of the overlap in flower visitor assemblages, questioning the strength of prezygotic isolation underpinned by diversification in flower colour and geometry. Interspecific hybrids were fertile and produced offspring in nature. No significant asymmetry in interspecific hybridization and hybrid incompatibilities among offspring were found, indicating weak postmating and postzygotic isolation. The results suggested that despite floral diversification, the insular-type geographic isolation remains a major barrier to gene flow. Findings set a framework for the future analysis of contemporary evolution of plant-pollinator networks at the population, community, and ecosystem levels in tropical ecosystems that are known to be distinct from the more familiar temperate climate models. [ABSTRACT FROM AUTHOR]

A high resolution systematic geochemical mapping at regional-scale is considered to be the best available method to estimate geochemical baseline levels of trace elements in stream water, and is an essential part of environmental risk assessment. This methodology was applied in a project in the Itacaiúnas River Basin, southeastern Amazon, Brazil, which includes several mines of the Carajás Mineral Province (as part of the Itacaiúnas Geochemical Mapping and Background Project, ItacGMBP). A total of 1429 samples (including 55 duplicates) were collected in 2017 at 900 sites at one sample per microbasin, during both dry and rainy periods. The analyses of 34 elements were carried out using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In general, the waters are slightly alkaline and are classified as mixed Ca-Na-HCO 3 type, indicating that they are mainly influenced by silicate rock weathering. Most metal concentrations in the water are low, except Fe and Mn. Seasonality explains differences in metal concentrations, with higher values being obtained in the rainy season. Baseline threshold values (B TVs) were calculated separately for both seasons by employing different statistical methods: iterative 2σ and DF preferentially delivered a more restrictive or conservative levels, which can be represenative of the natural B TVs (NB TVs), considering as the least degraded with low or no significant level of anthropogenic influence; and 98th percentile provides the ambient B TVs (AB TVs), which consists of natural plus diffuse anthropogenic input in the defined area. The AB TVs of Fe and Mn significantly exceed the WHO (1998) and CONAMA 357/05 limits. Spatial distribution indicates that Fe and Mn are not strictly related to geologic setting, rather they are highly influenced by specific local land use as well as deep weathering of the catchment and intense leaching and run-off during the rainy season. However, higher Mn occurrence in the dry period results from redox cycling of Fe and Mn via biogeochemical processes. The AB TVs of Ni, Cr, and V are controlled by bedrock lithology (geologic setting), mainly associated with mafic-ultramafic rocks; Cu is associated with two large hydrothermally mineralized copper belts. The estimation of baseline levels of As, Se, and Pb were highly limited due to of the large number of samples with results less than detection limits, in this case the 95th percentile was used for their B TVs. Geochemical data as well as anomalous values for most of the metals indicate that anthropogenic influence from point sources is highly negligible in the basin, except at a few points, where high NO 3- has been observed, probably due to more intense human and livestock activity. This study demonstrates that site-specific geochemical baseline assessment is a crucial factor when evaluating surficial water conditions in a large basin. • First detailed high resolution hydrogeochemical survey was carried out in Itacaiúnas basin. • We estimated the natural (NB TV) and ambient (AB TV) baseline threshold values. • High AB TVs of Fe and Mn in waters are related to local land use change activities. • The AB TVs of Cu is highly influenced by the hydrothermal mineralized copper belts. [ABSTRACT FROM AUTHOR]