An alternative risk assessment framework for tropical soil multi-metal contamination using arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are a key group of soil organisms involved in several ecosystem services, but they had not been explored in retrospective ecological risk assessment (ERA) schemes, partially due to a lack of experimental protocols. We aimed to perform a site-specific test to assess the effects of multiple metal contaminated soil (Zn, Cu, Cd, and Pb) on several ecotypes of AMF and evaluate the conceptual fitness of the performed AMF test to include in the TRIAD approach of ERA schemes. The results demonstrated that increasing metal contaminated soil proportions that inhibited 50 % (IC₅₀) of spore germination varied from 28 to >80. Ecotypes such as Claroideoglomus etunicatum (IC₅₀ > 80) and Racocetra gregaria (IC₅₀ > 80) experienced 50 % reduction in spore germination at metals concentrations of 10,776.3 for Zn, 1015.2 Cu, 65.5 Cd, 140.2 mg dm^-3 Pb, that are 3 times higher than those for Acaulospora mellea CMM101 (IC₅₀ 28 [16.2-39.8]) (3441.7 Zn, 333.9 Cu, 17.8 Cd, 56.5 mg dm^-3 Pb). In the evaluation of the suitability of the AMF ecotoxicological test to ERA, both spore germination and germinative tube growth were best evaluated and thus suitable in the following descending order: Tier III, Tier II, and Tier I. Variable effects of multiple-metal contamination on the ecotypes indicates how AMF community is affected in its pre-symbiotic structures. The ecotoxicological test allowed the selection of two species with the greatest sensitivity (Ambispora appendicula and Rhizophagus clarus CMM103) to the metal matrix, with the potential to best fit ERA objectives. The site-specific ecotoxicological test with AMF ex-situ proved adequate as an alternative test for Tiers II and III of TRIAD ERA schemes for metal contaminated areas. Data generated through test results, such as the inhibition concentrations (ICs), could be incorporated into ERAs risk indexes, increasing its ecological relevance, and reducing overall uncertainties.

Rhizobia and endophytic bacteria isolated from rainforest fragments within an iron ore mining site of the Eastern Brazilian Amazon

The aim of the present study was to isolate and evaluate the diversity of rhizobial and endophytic bacterial strains from undisturbed native rainforests within an iron ore mining site of the Serra Norte de Carajás in the Eastern Brazilian Amazon region to assess their biotechnological utility in reclamation of areas. Experiments were conducted to capture strains from samples of the soil of these forests at the sites Arenito II, Noroeste II, and Sul IV using Macroptilium atropurpureum and Mimosa acutistipula var. ferrea as trap host plants. Only M. atropurpureum nodulated, and the different bacterial strains were isolated from its nodules. There was no difference in the number of nodules among the areas, but the Arenito II bacterial community was the most efficient, indicated by the aboveground biomass production and suitable shoot mass/root mass ratio. Fifty-two (52) bacterial isolates were obtained, distributed in five groups, including nodulating and endophytic bacteria: 32 from Arenito II, 12 from Noroeste II, and 8 from Sul IV. The nodulating Bradyrhizobium genus was common to the three areas, whereas Paraburkholderia was found only in Arenito II. The nodD1 gene was amplified in all the strains of both nodulating genera. Strains of the nodulating genus Methylobacterium were also isolated from the three areas; however, they did not nodulate the host of origin, and their nodD1 gene was not amplified. Endophytic strains were also isolated from the genera Paenibacillus, Pantoea, and Leifsonia in Arenito II, Leifsonia in Noroeste I, and Paenibacillus in Sul IV. The greater nodulation and rhizobial and endophytic bacterial diversity observed in Arenito II were probably due to the more suitable edaphic properties of the area. The isolated strains were incorporated in the collection of the Department of Soil Science of UFLA and will be investigated in relation to their symbiotic characteristics with native host plants, as well as their ability to perform other biological processes.

Chemical, physical, and biological attributes in soils affected by deposition of iron ore tailings from the Fundão Dam failure

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.

Phosphorus lability increases with the rehabilitation advance of iron mine land in the eastern Amazon

Impacted areas by iron mining may face challenges in the management of phosphate fertilization and reduced efficiency of rehabilitation practices, thus extending the time required for the rehabilitation of these areas. The objective of this study was to evaluate phosphorus (P) lability in soils of native forest and ferriferous canga areas (savanna vegetation above ironstone outcrops covering iron ore deposits) and in iron mine waste piles undergoing rehabilitation. Benches of the analysed waste pile differ in age of rehabilitation: as the initial rehabilitation stage (INI), we consider benches with fewer than 3 years of rehabilitation; the intermediate stage (INT) were benches with up to 5 years of rehabilitation; and the advanced rehabilitation stage (ADV) corresponds to benches with more than 8 years of rehabilitation activities. Organic and inorganic P fractions were analysed in these areas by chemical fractionation and were classified according to the degree of soil lability. The results show that in the canga environment, there was a predominance of inorganic fractions of moderate lability and moderate stability, with a strong dependency of the soil organic matter (SOM) on the P fractions, whereas there was a greater participation of the moderately labile organic fractions in the forest than in the canga. On the other hand, in the rehabilitation areas, there was an increase in the labile organic and inorganic fractions as the rehabilitation process advanced. The distribution of P in areas undergoing rehabilitation indicates that there is a tendency for P levels to resemble those of native environments, such as the forests.

Mycorrhizal networks facilitate the colonization of legume roots by a symbiotic nitrogen-fixing bacterium

Arbuscular mycorrhizal fungi (AMF) absorb and translocate nutrients from soil to their host plants by means of a wide network of extraradical mycelium (ERM). Here, we assessed whether nitrogen-fixing rhizobia can be transferred to the host legume Glycine max by ERM produced by Glomus formosanum isolate CNPAB020 colonizing the grass Urochloa decumbens. An H-bridge experimental system was developed to evaluate the migration of ERM and of the GFP-tagged Bradyrhizobium diazoefficiens USDA 110 strain across an air gap compartment. Mycorrhizal colonization, nodule formation in legumes, and occurrence of the GFP-tagged strain in root nodules were assessed by optical and confocal laser scanning microscopy. In the presence of non-mycorrhizal U. decumbens, legume roots were neither AMF-colonized nor nodulated. In contrast, G. formosanum ERM crossing the discontinuous compartment connected mycorrhizal U. decumbens and G. max roots, which showed 30-42% mycorrhizal colonization and 7-11 nodules per plant. Fluorescent B. diazoefficiens cells were detected in 94% of G. max root nodules. Our findings reveal that, besides its main activity in nutrient transfer, ERM produced by AMF may facilitate bacterial translocation and the simultaneous associations of plants with beneficial fungi and bacteria, representing an important structure, functional to the establishment of symbiotic relationships.

Source and background threshold values of potentially toxic elements in soils by multivariate statistics and GIS-based mapping: a high density sampling survey in the Parauapebas basin, Brazilian Amazon

A high-density regional-scale soil geochemical survey comprising 727 samples (one sample per each 5 × 5 km grid) was carried out in the Parauapebas sub-basin of the Brazilian Amazonia, under the Itacaiúnas Basin Geochemical Mapping and Background Project. Samples were taken from two depths at each site: surface soil, 0-20 cm and deep soil, 30-50 cm. The ground and sieved (< 75 µm) fraction was digested using aqua regia and analyzed for 51 elements by inductively coupled plasma mass spectrometry (ICPMS). All data were used here, but the principal focus was on the potential toxic elements (PTEs) and Fe and Mn to evaluate the spatial distribution patterns and to establish their geochemical background concentrations in soils. Geochemical maps as well as principal component analysis (PCA) show that the distribution patterns of the elements are very similar between surface and deep soils. The PCA, applied on clr-transformed data, identified four major associations: Fe-Ti-V-Sc-Cu-Cr-Ni (Gp-1); Zr-Hf-U-Nb-Th-Al-P-Mo-Ga (Gp-2); K-Na-Ca-Mg-Ba-Rb-Sr (Gp-3); and La-Ce-Co-Mn-Y-Zn-Cd (Gp-4). Moreover, the distribution patterns of elements varied significantly among the three major geological domains. The whole data indicate a strong imprint of local geological setting in the geochemical associations and point to a dominant geogenic origin for the analyzed elements. Copper and Fe in Gp-1 were enriched in the Carajás basin and are associated with metavolcanic rocks and banded-iron formations, respectively. However, the spatial distribution of Cu is also highly influenced by two hydrothermal mineralized copper belts. Ni-Cr in Gp-1 are highly correlated and spatially associated with mafic and ultramafic units. The Gp-2 is partially composed of high field strength elements (Zr, Hf, Nb, U, Th) that could be linked to occurrences of A-type Neoarchean granites. The Gp-3 elements are mobile elements which are commonly found in feldspars and other rock-forming minerals being liberated by chemical weathering. The background threshold values (BTV) were estimated separately for surface and deep soils using different methods. The '75th percentile', which commonly used for the estimation of the quality reference values (QRVs) following the Brazilian regulation, gave more restrictive or conservative (low) BTVs, while the 'M_MAD' was more realistic to define high BTVs that can better represent the so-called mineralized/normal background. Compared with CONAMA Resolution (No. 420/2009), the conservative BTVs of most of the toxic elements were below the prevention limits (PV), except Cu, but when the high BTVs are considered, Cu, Co, Cr and Ni exceeded the PV limits. The degree of contamination (C_deg), based on the conservative BTVs, indicates low contamination, except in the Carajás basin, which shows many anomalies and had high contamination mainly from Cu, Cr and Ni, but this is similar between surface and deep soils indicating that the observed high anomalies are strictly related to geogenic control. This is supported when the C_deg is calculated using the high BTVs, which indicates low contamination. This suggests that the use of only conservative BTVs for the entire region might overestimate the significance of anthropogenic contamination; thus, we suggest the use of high BTVs for effective assessment of soil contamination in this region. The methodology and results of this study may help developing strategies for geochemical mapping in other Carajás soils or in other Amazonian soils with similar characteristics.

Geography is essential for reproductive isolation between florally diversified morning glory species from Amazon canga savannahs

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.

Ionic speciation and risks associated with agricultural use of industrial biosolid applied in Inceptisol

The evaluation of the chemical leaching potential from soils amended with biosolid is of extreme importance for environmental safety of agricultural use of these residues. The objective of this study was to evaluate the polluting potential and possible risks associated with the agricultural use of biosolids generated by the polyethylene terephthalate (PET) fiber and resin industry through ionic speciation and analysis of the activity of chemical species present in the leached solution from Inceptisol treated with rates 0, 6, 12, 18, 24, 48, 96, and 144 Mg ha^-1 on dry basis. The experiment was conducted in a lysimeter and the treatments with three replications were distributed at random. Chemical leaching was made by application of CaC1₂ 0.01 mol L^-1 solutions in a volume fourfold higher than the water retention capacity of the soil, divided into five leaching events: 210, 245, 280, 315, and 350 days of incubation. Chemical species concentrations in collected leachates were used for ionic speciation by geochemical software Visual MINTEQA2 version 4.0. Impact factor of chemical species was calculated as the ratio between maximum concentration in the leach solution in the treated soil and control. Dissolved organic carbon had strong influence on Pb⁺² and Cu⁺² leaching, but these elements in free or complexed forms presented low activities in solution. Leaching of NO₃^-, Zn⁺², and Na⁺ represents the main environmental risk of agricultural use of this residue. However, these risks can be minimized if technical criteria and critical limits for the agronomic use of biosolids were observed.

The role of protected and deforested areas in the hydrological processes of Itacaiúnas River Basin, eastern Amazonia

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.

Mine land rehabilitation in Brazil: Goals and techniques in the context of legal requirements

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.

Topsoil application during the rehabilitation of a manganese tailing dam increases plant taxonomic, phylogenetic and functional diversity

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.

Arbuscular Mycorrhizal Fungi Favor the Initial Growth of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in Soil Contaminated with Zn, Cu, Pb, and Cd

This study evaluated the effect of inoculation with a mixture of spores of arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, Paraglomus occultum, and Glomus sp.) on the initial establishment of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in soil contaminated with heavy metals. The experiment was conducted in a greenhouse, in plastic pots containing 1.8 kg of soil, which presented 7200, 1140, 480, and 72 mg of Zn, Cu, Pb, and Cd, respectively. The chlorophyll content (SPAD index) of inoculated plants of A. mangium and U. brizantha was higher than those of non-inoculated plants (p < 0.05). No differences were detected for the concentration of heavy metals in plant shoots, whether the plant was inoculated or not. However, inoculated plants had greater root length (S. bicolor and U. brizantha) (p < 0.05) and greater plant height (A. mangium) (p < 0.05). The present results demonstrate that the beneficial effects of AMF on plant growth and the alleviation of contaminants are imperative factors for the rehabilitation of soils contaminated with heavy metals.

Quillworts from the Amazon: A multidisciplinary populational study on Isoetes serracarajensis and Isoetes cangae

Isoetes are ancient quillworts members of the only genus of the order Isoetales. The genus is slow evolving but is resilient, and widespread worldwide. Two recently described species occur in the Eastern Brazilian Amazon, Isoetes serracarajensis and Isoetes cangae. They are found in the ironstone grasslands known as Canga. While I. serracarajensis is present mostly in seasonal water bodies, I. cangae is known to occur in a single permanent lake at the South mountain range. In this work, we undertake an extensive morphological, physiological and genetic characterization of both species to establish species boundaries and better understand the morphological and genetic features of these two species. Our results indicate that the morphological differentiation of the species is subtle and requires a quantitative assessment of morphological elements of the megaspore for diagnosis. We did not detect differences in microspore output, but morphological peculiarities may establish a reproductive barrier. Additionally, genetic analysis using DNA barcodes and whole chloroplast genomes indicate that although the plants are genetically very similar both approaches provide diagnostic characters. There was no indication of population structuring I. serracarajensis. These results set the basis for a deeper understanding of the evolution of the Isoetes genus.

Assessment of the occurrence and richness of arbuscular mycorrhizal fungal spores by direct analysis of field samples and trap culture - a comparative study

In this work, we hypothesized that two spore-based methods, direct analysis of field samples and trap cultures, simultaneously used for assessment of occurrence and species richness of arbuscular mycorrhizal fungi (AMF) may vary in their efficiency according to the environmental conditions and the total AMF species richness of the evaluated ecosystem. The performance of both methods was analyzed based on two datasets: 1) a complete site x species matrix compiled from two studies in different land uses in the Amazon using direct analysis of field samples and trap cultures. 2) Total number of AMF morphotypes detected by both methods in published manuscripts across several ecosystems. From dataset 1, direct analysis of field samples revealed 57 morphotypes, whereas only 21 of these were detected by trap culture. Community variation (beta diversity) analysis revealed that field samples are far more sensitive in detecting shifts in AMF community composition among land uses than trap cultures in the Amazon region, with the combined results of both methods being not better than that obtained only by direct analysis of field samples. Analysis of dataset 2 showed that the relative performance of trap cultures, using direct analysis of field sample as reference, was inversely related to the total observed AMF species richness.

Eriocaulaceae in the Brazilian Amazon and the use of Species Distribution Modelling in its conservation

Abstract 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.

Biological attributes of rehabilitated soils contaminated with heavy metals

This study aimed to evaluate the effects of two rehabilitation systems in sites contaminated by Zn, Cu, Pb, and Cd on biological soil attributes [microbial biomass carbon (Cmic), basal and induced respiration, enzymatic activities, microorganism plate count, and bacterial and fungal community diversity and structure by denaturing gradient gel electrophoresis (DGGE)]. These systems (S1 and S2) consisted of excavation (trenching) and replacement of contaminated soil by uncontaminated soil in rows with Eucalyptus camaldulensis planting (S1-R and S2-R), free of understory vegetation (S1-BR), or completely covered by Brachiaria decumbens (S2-BR) in between rows. A contaminated, non-rehabilitated (NR) site and two contamination-free sites [Cerrado (C) and pasture (P)] were used as controls. Cmic, densities of bacteria and actinobacteria, and enzymatic activities (β-glucosidase, acid phosphatase, and urease) were significantly higher in the rehabilitated sites of system 2 (S2-R and S2-BR). However, even under high heavy metal contents (S1-R), the rehabilitation with eucalyptus was also effective. DGGE analysis revealed similarity in the diversity and structure of bacteria and fungi communities between rehabilitated sites and C site (uncontaminated). Principal component analysis showed clustering of rehabilitated sites (S2-R and S2-BR) with contamination-free sites, and S1-R was intermediate between the most and least contaminated sites, demonstrating that the soil replacement and revegetation improved the biological condition of the soil. The attributes that most explained these clustering were bacterial density, acid phosphatase, β-glucosidase, fungal and actinobacterial densities, Cmic, and induced respiration.

Four decades of land-cover, land-use and hydroclimatology changes in the Itacaiúnas River watershed, southeastern Amazon

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.

Arbuscular mycorrhizal fungi in phytoremediation of contaminated areas by trace elements: mechanisms and major benefits of their applications

In recent decades, the concentration of trace elements has increased in soil and water, mainly by industrialization and urbanization. Recovery of contaminated areas is generally complex. In that respect, microorganisms can be of vital importance by making significant contributions towards the establishment of plants and the stabilization of impacted areas. Among the available strategies for environmental recovery, bioremediation and phytoremediation outstand. Arbuscular mycorrhizal fungi (AMF) are considered the most important type of mycorrhizae for phytoremediation. AMF have broad occurrence in contaminated soils, and evidences suggest they improve plant tolerance to excess of certain trace elements. In this review, the use of AMF in phytoremediation and mechanisms involved in their trace element tolerance are discussed. Additionally, we present some techniques used to study the retention of trace elements by AMF, as well as a summary of studies showing major benefits of AMF for phytoremediation.

Social learning strategies for nut-cracking by tufted capuchin monkeys (Sapajus spp.)

The spontaneous use of stone tools for cracking nuts by tufted capuchin monkeys, now known to be habitual among wild populations in savanna environments, was first described in a semifree group living in the Tietê Ecological Park (SP, Brazil). Nut-cracking at TEP was first observed by our team in 1995 (Ottoni and Mannu in Int J Primatol 22(3):347-358, 2001), and its ontogeny and associated social dynamics, with inexperienced observers highly interested in the activities of proficient individuals, greatly tolerant to scrounging, support hypotheses about social biases on tool-use learning. Here we further analyze the social learning biases, better characterizing: the social context of nut-cracking in which observation by conspecifics occurs, the quality of the nut-cracking behavior itself and whether scrounging may be the motivation behind this behavior. We confirm that the choice of observational targets is an active one; monkeys do not simply observe those who they are socially close to. We investigate social learning strategies, describing how young capuchins choose to observe older, more proficient and dominant individuals during nut-cracking bouts. Monkeys with higher productivity rates were also more frequently targeted by observers, who were tolerated scroungers, further supporting the scrounging hypothesis. Finally, based on changes of the demographic patterns of tool use and observation, we set to retrace data from 14 years of continuous studies. We argue that we have followed the dissemination of the behavior (Transmission Phase) almost from its beginning, when juveniles were the most frequent nutcrackers, to a more common pattern where adults are the most active tool users (Tradition Phase).

Vegetative compatibility and anastomosis formation within and among individual germlings of tropical isolates of arbuscular mycorrhizal fungi (Glomeromycota)

Hyphal anastomoses which play a key role in the formation of interconnected mycorrhizal networks and in genetic exchange among compatible individuals have been studied in a limited number of species and isolates of arbuscular mycorrhizal fungi (AMF), mainly in symbiotic mycelium. In this work, the occurrence and frequency of anastomosis between hyphae of the same and different germlings were assessed in tropical isolates belonging to Acaulospora, Claroideoglomus, Gigaspora, Glomus, Rhizophagus and Scutellospora. Germlings belonging to Acaulospora, Claroideoglomus, Glomus and Rhizophagus formed perfect hyphal fusions, with frequencies ranging from 9.29 ± 3.01 to 79.84 ± 4.39 % within the same germling and from 14.02 ± 7.36 to 91.41 ± 3.92 % between different germlings. Rare fusions, occurring within the same hypha, were detected in Gigaspora species, and no anastomoses were observed in Scutellospora species. The consistent detection of nuclei in perfect fusions suggests that nuclear migration is active both within and between germlings. Present data on anastomosis formation, nuclear migration and germling viability in tropical isolates of AMF widen our knowledge on the extensive and consistent occurrence of successful hyphal fusions in this group of beneficial symbionts. The ability to anastomose and establish protoplasm flow, fundamental for the maintenance of physiological and genetic continuity, may produce important fitness consequences for the obligately biotrophic AMF.

Species richness and spore abundance of arbuscular mycorrhizal fungi across distinct land uses in western Brazilian Amazon

Arbuscular mycorrhizal fungi (AMF) were surveyed for species richness and abundance in sporulation in six distinct land uses in the western Amazon region of Brazil. Areas included mature pristine forest and sites converted to pasture, crops, agroforestry, young and old secondary forest. A total of 61 AMF morphotypes were recovered and 30% of them could not be identified to known species. Fungal communities were dominated by Glomus species but Acaulospora species produced the most abundant sporulation. Acaulospora gedanensis cf., Acaulospora foveata, Acaulospora spinosa, Acaulospora tuberculata, Glomus corymbiforme, Glomus sp15, Scutellospora pellucida, and Archaeospora trappei sporulated in all land use areas. Total spore numbers were highly variable among land uses. Mean species richness in crop, agroforestry, young and old secondary forest sites was twice that in pristine forest and pasture. fungal communities were dominated in all land use areas except young secondary forest by two or three species which accounted for 48% to 63% of all sporulation. Land uses influenced AMF community in (1) frequency of occurrence of sporulating AMF species, (2) mean species diversity, and (3) relative spore abundance. Conversion of pristine forest into distinct land uses does not appear to reduce AMF diversity. Cultural practices adopted in this region maintain a high diversity of arbuscular mycorrhizal fungi.

Inorganic materials as ameliorants for soil remediation of metal toxicity to wild mustard (Sinapis arvensis L.)

The ameliorating effects of different inorganic materials were investigated on a soil originating from a zinc smelter dumping site contaminated by toxic metals. Wild mustard (Sinapis arvensis L.) was used as a test plant. The soil was amended with different doses of mining sludge, Perferric Red Latosol (LVj), steel shots, cyclonic ash, silifertil, and superphosphate. The most effective amendments improved plant growth with 45% and reduced metal uptake by over 70% in comparison to untreated soil. Reductions in availability as estimated by BaCl2-extractable metals reached up to 90% for Zn and 65% for Cd as compared to unamended soil. These reductions were associated with lower shoot and root metal contents. Shoot Zn content was reduced from 1,369 microg g(-1) in plants grown on untreated soil to 377 microg g(-1) when grown on cyclonic ash amended soil while Cd decreased from 267 to 44 microg g(-1) in steel shots amended soil. Superphosphate addition had no ameliorating effect. On the contrary, it increased BaCl2-extractable amounts of Zn. Considering all parameters we determined, steel shots, cyclonic ash and silifertil are the most promising for remediating metal contaminated soil in the tropics. Further studies evaluating impacts, cost-effectiveness and durability of effects will be conducted.

Occurrence and diversity of arbuscular mycorrhizal fungi in trap cultures from soils under different land use systems in the Amazon, Brazil

The aim of this work was to evaluate the occurrence of arbuscular mycorrhizal fungi (AMF) species diversity in soil samples from the Amazon region under distinct land use systems (Forest, Old Secondary Forest, Young Secondary Forest, Agroforestry systems, Crops and Pasture) using two distinct trap cultures. Traps established using Sorghum sudanense and Vigna unguiculata (at Universidade Regional de Blumenau -FURB) and Brachiaria decumbens and Neonotonia wightii (at Universidade Federal de Lavras - UFLA) were grown for 150 days in greenhouse conditions, when spore density and species identification were evaluated. A great variation on species richness was detected in several samples, regardless of the land use systems from where samples were obtained. A total number of 24 AMF species were recovered using both methods of trap cultures, with FURB's traps yielding higher number of species. Acaulospora delicata, A. foveata, Entrophospora colombiana and two undescribed Glomus species were the most abundant and frequent species recovered from the traps. Number of species decreased in each genus according to this order: Acaulospora, Glomus, Entrophospora, Gigaspora, Archaeospora, Scutellospora and Paraglomus. Spore numbers were higher in Young Secondary Forest and Pastures. Our study demonstrated that AMF have a widespread occurrence in all land use systems in Amazon and they sporulate more abundantly in trap cultures from land uses under interference than in the pristine Forest ecosystem.

Isolation and Identification of Vesicular-Arbuscular Mycorrhiza-Stimulatory Compounds from Clover ( Trifolium repens ) Roots

Two isoflavonoids isolated from clover roots grown under phosphate stress were characterized as formononetin (7-hydroxy,4′-methoxy isoflavone) and biochanin A (5,7-dihydroxy,4′-methoxy isoflavone). At 5 ppm, these compounds stimulated hyphal growth in vitro and root colonization of an undescribed vesicular-arbuscular mycorrhiza, a Glomus sp. (INVAM-112). The permethylated products of the two compounds were inactive. These findings suggest that the isoflavonoids studied may act as signal molecules in vesicular-arbuscular mycorrhiza symbiosis.