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• Recurrent fire leads to degraded rainforest (DRf) and herbaceous-shrubby (HS). • Ksat and 6 years of rainfall-soil suction interactions are analyzed. • HS provide shallow soil saturation even during long dry periods. • Fire decreases Ksat in topsoil and it increases soil suction in depth at HS. • Post-fire soil changes tend to favor rapid suction loss in the unsatured zone. The role of fire in vegetation-soil–water interactions and its implications for soil stability and slope failures is poorly documented in humid tropical regions. This paper focuses on the relationships between vegetation change through recurrent fire and its effects on hydraulic conductivity and soil suction. Two monitoring sites were chosen on steep slopes in the mountainous domain of the Atlantic rainforest: the first is representative of degraded secondary rainforest (DRf) 25–30 years after slash and burn agriculture; the other represents herbaceous-shrubby vegetation (HS) resulting from wildfires in short-time intervals (<5 years). Two fires had previously occurred on the HS slope, one in December 2014 and the other in September 2019. Continuous records of rainfall and soil suction at depths of 10, 20, 50, 100, 150, and 220 cm provided a 6-year data collection from January 2015 to December 2020. Hydraulic conductivity (Ksat) field tests were conducted around the two monitoring sites before and after the September 2019 fire. The main results include: a) soil suction in the topsoil of both vegetation covers follow the rainfall inputs with high values of Ksat (DRf = 195 mm/h; HS = 203 mm/h); b) while quick rainfall-suction responses prevail within the DRf soil profile, soil suction at HS maintains a mean suction value around -27 kPa below 100 cm deep; c) field observations attest to the occurrence of hydrophobicity after the 2019 fire; d) Ksat tests just after this fire indicated a decreasing mean value from 203 mm/h to 46 mm/h; and e) by the end of the dry season after fire, there is a delayed increase in soil suction reaching -143 kPa at a depth of 100 cm and in smaller proportions at 220 cm deep. These results indicate that post-fire soil changes tend to favor the sudden loss of soil stability and slope failure during extreme rainfall events. [ABSTRACT FROM AUTHOR]

[Display omitted] • Geochemical data of the Passauna reservoir sediments record the historical anthropogenic activities. • The enrichment factor during the period 1930–1960, attributed to the deforestation occurring in the watershed for agriculture. • the Mn/Fe index shows signs of reduced oxygenation in the bottom waters. Urban water supply reservoirs, their quality and quantity of water are affected by anthropogenic activities and environmental changes. They are aquatic ecosystems that respond to the dynamics of organic loads and nutrients, and episodes of eutrophication. Past disturbances in the watersheds and the water column can be noticed by the vertical distribution of heavy metals and trace metals in the sedimentary core. In this study, two sediment cores from the Passauna reservoir in Curitiba, Brazil were examined to assess the accumulation of heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), and nickel (Ni), and other major elements such as aluminum (Al), iron (Fe), manganese (Mn), potassium (K) and barium (Ba), and their association to pollution. Enrichment factor (EF) and geoaccumulation index (I geo) were applied to the identified accumulation of metals as well as to the level of pollution. The decay of radionuclides, including 210Pb and 137Cs, were used to find the rate of sedimentation over 136 years. The results showed a spatial variation, with the highest concentration of metals found in the upstream part of the reservoir. The EF values of the following metals decreased: in core I, EF(Fe) > EF(Mn) > EF(Cd) > EF(Sb) > EF(Zn) > EF(Cu) > EF(Cr) > EF(Pb); and in core II, EF(Sb) > EF(Pb) > EF(Cd) > EF(Cr) > EF(Fe) > EF(V) > EF(Zn) > EF(Cu) > EF(Ni) > EF(Mn). The I geo values of the metals decreased in core I I geo (Fe) > I geo (Sb) > I geo (Al) > I geo (Zn) > I geo (Cd) > I geo (Cd) > I geo (Ni) > I geo (Cr) > Igeo(Mn) > I geo (Pb) > I geo (V); and in core II, I geo (Sb) > I geo (Cd) > I geo (Pb) > I geo (Al) > I geo (Cr) > I geo (V) > I geo (Fe) > I geo (Cu) > I geo (Ni) > I geo (Zn) > I geo (Mn). We used the Mn/Fe, Cu/Ni, and V(V + Ni) ratio to evidence changes in productivity and redox conditions in the water column over time.We observed that during the period 1930–1970 anthropogenic activities controlled the impacts on reservoir and water quality. The changes in the distribution of metals coincided with the expansion of agriculture and urban area. In addition, redox and productivity showed periods with different rates of productivity as well as alternate periods of trophic levels. In sum, this paper provides information on how the depositional environment affects the geochemical characteristics of sediment, explaining past environmental changes. [ABSTRACT FROM AUTHOR]

The Mogi Guaçu River rises in Bom Repouso (Minas Gerais State — Brazil) in the Mantiqueira Ridge, and flows into the Rio Pardo river at an elevation of 483m in Pontal (São Paulo State — Brazil), after running a 530km long course. Especially along the Lower Mogi Guaçu Basin, the river morphology is extremely sinuous, characterized by intense processes of channel migration, avulsion, abandonment and reactivation of the channel, producing an extensive alluvial plain composed of a series of associated relief forms and sedimentary facies. Among these forms, point bar deposits by lateral accretion, abandoned meanders, paleo-channels and fluvial terraces are notable features. In this sense, the objective of this work was to investigate whether these features could be linked to environmental changes. To reach this goal, soil properties of a catena of the Jataí Ecological Station (Luiz Antonio — São Paulo State) were analyzed in four sectors: Slope, Terrace I, Terrace II and Alluvial Plain. The results from grain-size determination, geochemical and isotopic studies, dating, paleopalynology, coal fragments and micromorphology are presented in this paper. From these analyses, a paleo-environmental evolution divided in three stages is proposed for the area: 130,000YBP (Upper Pleistocene), when the Mogi Guaçu River base level was approximately 6m above the present one; a drier second phase 10,250years BP (Lower Holocene), when an organic horizon was formed inside of an abandoned meander (oxbow lake), and a third phase, 2096 YBP (Upper Holocene), of reactivation of a warm and humid climate that promoted the development of a two meters thick Typic Udifluvent in a sector where the Mogi Guaçu River no more floods due to the incision of its thalweg, reaching more than six-meters depth in the last 130,000years BP. Thus, this paper used a fluvial geomorphologic approach and its interplay with climate to understand how the landscape was shaped from Upper Pleistocene to Holocene, however, Neotectonics might have played a relevant role as well, not only in the Mogi Guaçu River Basin, but also in the Paraná Sedimentary Basin. [ABSTRACT FROM AUTHOR]

• An approach is proposed to assess extreme rainfall-triggered landslides. • 3D unsaturated flow is coupled with the infinite slope method. • Extreme precipitation events are investigated using soil depth models. • 1-year spin up for moisture conditions has little impact on the safety factor. • Simple soil depth models are viable options for landslide susceptibility studies. The susceptibility to shallow landslides is affected by several factors. Rainfall intensity, soil thickness distribution, and antecedent moisture conditions are components that influence the spatio-temporal prediction of landslides at the watershed scale. Yet, the combined impact of these factors on the susceptibility to landslides has been overlooked. The purpose of this paper is to investigate landslides triggered by extreme precipitation in the Tijuca Massif, Rio de Janeiro, southeastern Brazil. Our approach couples a 3D variably saturated flow solver with the infinite slope stability method to calculate the statistical distributions of the safety factor and the pore pressure at the soil–bedrock interface. Numerical simulations were performed for 6 scenarios considering 1-year spin-up time for soil moisture and different spatially distributed soil depths. The results show that during extreme precipitation events, soil depth and initial moisture conditions may not have much influence on the safety factor, as the intensity and duration of rainfall will be the triggering agents. Comparison of simulated unstable zones and field data from mapped landslide scars further supported this conclusion. We conclude that simple soil depth models are feasible options for regional studies of landslide susceptibility. Our findings are relevant to understanding shallow landslides induced by extreme rainfall in Rio de Janeiro and other regions with similar geological and climate settings. [ABSTRACT FROM AUTHOR]

[Display omitted] • Over the last three decades, 123 articles regarding the assessment of rainfall erosivity in Brazil were published. • EI 30 has been the most employed erosivity index in the country. • Pluviographic rainfall data and regression equations are the main methods for obtaining erosivity values. • Kriging is the most widespread technique for obtaining rainfall erosivity maps. • The complete database with all information retrieved from literature was made available. In this paper, we report the results of an in-depth review of scientific literature on the assessment of rainfall erosivity in Brazil and published in peer-reviewed journals over the last three decades. In total, 123 articles regarding this topic in Brazil were published. These studies were analyzed and filtered into categories regarding the bibliographic information, methodology scope, and main results. It was found that the EI 30 has been the most employed erosivity index in the country, while the use of pluviographic rainfall data and regression equations are the main methods for obtaining erosivity values. The magnitudes of annual rainfall erosivity reported for the Brazilian territory range from 59 to 26,891 MJ mm ha-1h−1 year−1. The lowest values are found in the Northeast region and the highest in the North. Kriging is the most widespread technique for obtaining rainfall erosivity maps in Brazil. Furthermore, the Southeast region accounts for the largest number of erosivity studies, while the North has a major lack of erosivity information. The advancements over the last decade are characterized by the use of synthetic series of rainfall and remote sensing products to estimate erosivity, as well as the use of machine learning techniques for its interpolation. For the next years, an increase in the use of these methodologies is expected, as well as an intensification of the assessment of the future patterns of rainfall erosivity over the country. The present review updates the findings regarding the assessment of rainfall erosivity in Brazil and brings a wider overview of the erosivity studies in the country. The information here summarized contributes to the establishment of a conservationist planning of soil and water management on a national scale. Finally, the complete database with all information retrieved from the literature was made available. [ABSTRACT FROM AUTHOR]

• This paper was to characterize the dynamics and spatial aspects of erodibility. • Texture governs higher or lower loss rates according to grain size. • Cultivated IBEs exhibit moderate to high soil loss rates, mainly by runoff. • Texture and organic matter control susceptibility to water erosion in IBEs. • Erodibility factors showed spatial dynamics moderately influenced by relief. Soil erosion generally causes environmental and economic damage to agricultural systems, representing one of the biggest management problems for agriculture. Therefore, understanding the behavior of the erosive process is indispensable for the diagnosis of best conservationist practices of use and management of agricultural resources. The aim of this paper was to characterize the dynamics and spatial aspects of erodibility, its indicators and to evaluate the applicability of the prediction equations of soil loss proposed by Denardin (1990) and Flanagan and Livingston (1995) for cultivated and natural Indian Black Earths (IBEs). Grids with 88 georeferenced sampling points were established for soil sampling at a depth of 0.0–0.20 m. Laboratory analyzes were performed to determine soil particle size and soil organic matter (SOM) analysis. The erodibility factors were calculated and applied univariate analysis, geostatistics and multivariate techniques. Cultivated IBEs exhibit moderate to high soil loss rates even in low slope relief, mainly by runoff. The dynamics of the erodibility factors behave under moderate spatial dependence between the attributes, with high range values and moderate relief influence, indicating high spatial variability, showing the tendency of values of soil losses similar to distances between 15 and 69 m. However, texture and organic matter were the main indicators of erodibility, since medium texture IBEs tend to increase the global and interril erodibility values, and under sandy texture tend to increase erodibility in gully. The increase in SOM elevates erodibility and interril due to the high amount of pyrogenic coal with high capacity to retain water. Therefore, we recommend the adoption of management practices that reduce erosion processes, and mainly avoid the loss of mineralized SOM to maintain crop sustainability. [ABSTRACT FROM AUTHOR]

The current paper presents the evaluation of the ability of the SWAT hydrological model (Soil and Water Assessment Tool) to reproduce continuous daily streamflows of the upper Itapemirim River basin (Brazil). The model parameters were calibrated and validated with data collected from 1993 to 2000. The model was found to be highly sensitive to baseflow, its primary calibration variable. Validation analyses resulted in values of statistical indexes (NS = 0.67; NSlog = 0.68; PBIAS = 22% and RSR = 0.57) that show that SWAT performance was satisfactory in this application. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we review the erosivity studies conducted in Brazil to verify the quality and representativeness of the results generated and to provide a greater understanding of the rainfall erosivity (R factor) in Brazil. We searched the ISI Web of Science, Scopus, SciELO, and Google Scholar databases and in recent theses and dissertations to obtain the following information: latitude, longitude, city, states, length of record (years), altitude, precipitation, R factor, equations calculated and respective determination coefficient (R2). We found 35 studies in Brazil that used pluviographic rainfall data to calculate the rainfall erosivity. These studies were concentrated in the cities of the south and southeast regions (~60% of all the cities studied in Brazil) with a few studies in other regions, mainly in the north. The annual rainfall erosivity in Brazil ranged from 1672 to 22,452MJmm ha−1 h−1 yr−1. The lowest values were found in the northeast region, and the highest values were found in the north region. The rainfall erosivity tends to increase from east to west, particularly in the northern part of the country. In Brazil, there are 73 regression equations to calculate erosivity. These equations can be useful to map rainfall erosivity for the entire country. To this end, techniques already established in Brazil may be used for the interpolation of rainfall erosivity, such as geostatistics and artificial neural networks. [Copyright &y& Elsevier]

• A novel strategy using only sample points to delineate polygons of soil classes. • GEOBIA is a promising approach for digital soil mapping. • The GEOBIA approach improves soil class prediction. The use of techniques to calibrate soil prediction models based on legacy maps is restricted to areas where conventional survey and soil mapping were performed. It is necessary to seek alternatives to calibrate soil predictive models without a legacy soil map. The problem is the difficulty to delineate polygons of soil classes based on soil sampling points. This paper presents a novel digital soil mapping strategy using only georeferenced points of soil profiles to delineate detailed polygons of soil classes by the Geographic Object-Based Image Analysis (GEOBIA) approach and Artificial Neural Networks (ANN) models. The main objective was to evaluate the integration of the GEOBIA approach at different segmentation levels with ANN's models and sampling points to produce a digital soil map of the Vale dos Vinhedos region, in Rio Grande do Sul, Brazil. From a Digital Terrain Model, 10 predictive variables were extracted. From the RapidEye remote sensing image the following spectral variables were extracted: Normalized Difference Vegetation Index and Normalized Difference Water Index. A new set of variables was produced using principal component analysis after standardization of the original variables. The multiresolution segmentation algorithm was used to create image objects at different segmentation levels. Four segmentation levels were tested with scale parameter (SP) 1, 2, 5 and 10; and the Cheesboard segmentation (CS) was used to transform the original pixels into polygons. Information on types of soil was obtained from 163 georeferenced soil profiles. Five ANN's structures were implemented: four for the segmented data (SP01, SP02, SP05 and SP10) and one for the per-pixel approach (CS); 16 repetitions of each ANN were performed. With the best models for each segmentation level, extrapolations of soil classes were performed for the entire study area and validated with a detailed legacy soil map. The per-pixel approach model obtained the worst result. The best result in the extrapolation of soil types found was with the object-based approach (SP1). In our understanding, the scientific community can profit from the proposed methodology particularly when it only has georeferenced points of soil classes and not a legacy map, i.e., immediately after a field survey without the need for photointerpretation for delineation of the soil mapping units. The use of GEOBIA for digital mapping of soil classes seems to be a promising approach for future research. [ABSTRACT FROM AUTHOR]

[Display omitted] • Future impacts of LULC and climate on the streamflow and erosion by new approaches. • SWAT model was applied to estimate future runoff-erosion. • Future climate data generated using GCM coupled to regional circulation model. • The methodology contextualizes potentially significant hydrological changes. • The changes may impact the sustainability of water resources management. Water management in the Caatinga/Atlantic forest ecotone in Brazil is critically dependent on better understanding of potential future changes in streamflow and sediment dynamics. This paper evaluates both the future impacts of land use and land cover (LULC) changes and the impacts of climate change on the streamflow and sediment yield in the Tapacurá River basin in northeastern Brazil, using a novel combination of approaches. Projected climate data derived using global circulation model HadGEM2-ES were coupled to regional circulation model ETA-CPTEC/HadCM3 for two representative concentration pathways (RCP 4.5 and 8.5), with bias correction. Two future LULC scenarios were generated: (a) optimistic (current LULC), and (b) pessimistic (land use change trends continue), using the multilayer perceptron algorithm (MP). The Soil and Water Assessment Tool (SWAT) model was used to estimate future streamflow and erosion for different periods (2011–2040, 2041–2070 and 2071–2099). The SWAT model was calibrated for period of 1995–2003 and validated for 2004–2013. The results showed good accuracy in relation to R2, NSE and PBIAS for the calibration and validation of the runoff, as well as for the verification of the sediment yield. Simulations indicated significant increases in erosion for the pessimistic scenario under RCP 8.5, followed by the pessimistic scenario and RCP 4.5. Lower sediment yields occurred for the optimistic and RCP 8.5, with lower still for the optimistic and RCP 4.5. However, the latter estimates are still considerably higher than baseline conditions. Although higher flows are found for some scenarios, the increases in sediment yield have serious implications for reservoir siltation and storage reduction. Despite modeling uncertainty, the results demonstrate that the proposed methodology has promising scope to contextualize potentially significant regional hydrological changes which have implications for land and biodiversity management and the sustainability of water resources in the Caatinga/Atlantic forest ecotone. [ABSTRACT FROM AUTHOR]

• This study reports the influence of granite types and climate on soil geochemistry. • Chemical composition of I- and S-type granites affects the soil geochemistry. • SEM and EDS are used to relate granite signatures and soil geochemistry. • The granite mineralogy printed different signatures on the soil profiles. • Highest enrichment factor values were observed for I-type granite soil. Soils formed from granites are distributed worldwide, therefore, studies regarding their geochemical signature on tropical soils are important to understand key processes of soil weathering and soil chemistry. This paper reports the effect of S- and I-type granitic rocks on the content and distribution of trace and major elements in soil profiles developed across a climosequence in Northeastern Brazil. In general, soils developed from I-types show greater trace and major element concentrations than those originated from S-types, due to their higher proportion of accessory and mafic minerals. Geochemical mass balance and enrichment factor data suggest that climatic effects showed a less evident effect on the distribution pattern of trace and major elements from soil profiles underlain by S-type granitic rocks. The highest enrichment factor results evidenced in soils formed on I-types are explained by the rock mineralogy, which imparts higher CEC values and proportion of clay to soils. Trace elements were less leached than major elements during chemical weathering, except for Al, Fe, and P. Geochemical mass balance showed that, regardless of the granite type, the highest depletion of trace and major elements in the pedosphere took place in the humid zones as a consequence of weathering intensity. In this zone, except for quartz, the primary minerals were altered to form secondary minerals, giving rise to kaolinitic soils. These results can be used as reference contents of trace and major elements developed from different granitic rocks in environments with tropical climate. Besides, this research sheds some light on the effect of contrasting granites and a climosequence on soil geochemistry. [ABSTRACT FROM AUTHOR]