Main Soil Classes Research Articles

Improvement of data imbalance for digital soil class mapping in Eastern China

A fine-resolution digital soil class map is needed. However, the problem of imbalanced data leads to an inaccurate spatial distribution of the digital soil class map, and the spatial resolution of digital soil class maps at a large scale is low in existing studies. Based on these points, an algorithm of over-sampling and under-sampling was introduced to solve the problem of imbalanced data, and to improve the performance of soil classification model. 316 topsoil samples with eight main soil classes at the great group level were collected in Eastern China. Eight out of twelve prediction variables were determined after the importance evaluation by “Mean Decrease Accuracy” in the random forest (RF) model, including digital elevation model (DEM), enhanced vegetation index (EVI), land surface wetness index (LSWI), land surface temperature (LST), normalized differenced vegetation index (NDVI), and soil texture components. RF model was also applied to complete digital soil class mapping, and the results of treated (over-sampling and under-sampling by randomly increasing or decreasing the number of samples) and untreated data were compared and discussed. Research results indicated that modeling by imbalanced data resulted in uncertain soil classes mapping, with minority classes were lost and with lower accuracies than those of balanced data (overall accuracy = 83.83 %, kappa coefficient = 0.79). After over-sampling and under-sampling treatments, these problems were well solved with an overall accuracy of 96.72 % and a kappa coefficient of 0.93. The accuracy of soil class prediction for minority classes were improved by 12.5 %–54.5 %. Compared to the existing conventional soil map, the new map with a fine resolution of 30 × 30 m is time-effective and more detailed. Validation (point-validation and map-to-map comparison) of the predicted map showed that the output is reliable and can provide a reference for other soil and environmental studies without major difficulties.

Phosphorus Concentrations and Stocks in Different Soil Classes, Uses and Coverages in Agreste Pernambucano, Brazil

Changes in land use cause a mosaic of areas in the landscape with different uses and coverage. This condition compromises soil nutrient stocks, especially phosphorus (P). In this sense, this study aimed to determine the concentrations of extractable and total phosphorus in 04 soil classes (Yellow Argisol, Litholic Neosol, Entisol and Planosol), 04 uses and covers (Open Native Caatinga, Dense Native Caatinga, Agriculture and Pasture) of the soil, in 04 depths (0-10, 10-20, 20-30 and 30-40 cm). To determine the extractable P, the Mehlich 1 and colorimetric reading were used. Total phosphorus was determined by sulfur digestion and colorimetry. The results of extractable and total P concentrations were higher for the Argisol and Planosol classes. It was observed that there were reductions in extractable P concentrations between the soil layers as the soil profile deepened. Depths between 0-20 cm generally showed higher concentrations of extractable and total phosphorus in agriculture. Among the four soil classes studied, the highest average values of extractable and total P stocks occurred in Litholic Neosols and Planosols, mainly due to agricultural use. P deficiency has been a limiting factor to agricultural productivity and, especially in the Agreste region of Pernambuco, where the main soil classes under natural cover have low levels of available and total P.

Soil and vegetation carbon stocks after land-use changes in a seasonally dry tropical forest

The lack of robust scientific data still hinders estimates of soil and plant carbon (C) losses due to land-use changes in most dry tropical ecosystems. The present study investigated the effects of land-use and cover changes on total ecosystem C stocks in NE Brazil, aiming to quantify C losses after the removal of the native forest, known as Caatinga. The sampling design included the four main land-use/cover types (Dense Caatinga, Open Caatinga, Pastures and Crop fields) and the seven main soil classes (Arenosols, Acrisols, Regosols, Ferrasols, Luvisols, Planosols, and Leptosols), a combination that represents over 90% of the region. This design resulted in 192 sampling points (48 in each land-use), distributed proportionally to the area of occurrence of each soil class. In each sampling point, we determined C stocks in soil organic matter (SOM) and roots (to a depth of 1 m or rock layer), aboveground vegetation biomass (trees and herbs, separately), deadwood, and surface litter. Areas covered by Dense Caatinga store, on average, nearly 125 Mg ha−1 of C. Most of this C is stored in the soil organic matter (72.1%), followed by aboveground biomass (15.9%), belowground biomass (7.3%), deadwood (2.9%), litter (1.3%), and herbaceous biomass (0.5%). The substitution of Dense Caatinga to plant pastures and crop fields caused losses of >50% of ecosystem C stocks, reaching almost 65 Mg ha−1 of C, with nearly equal losses from the SOM and vegetation biomass compartments. Open Caatinga store nearly 30% less C than Dense Caatinga. Contrary to what was expected, the overall differences in C stocks between soil classes were not significant, with a few exceptions. We expect that the findings of this study will contribute to a more robust inventory of GHG emissions/removals due to land-use changes in NE Brazil and other dry tropical regions of the globe.

Mineralogical, chemical and electrochemical attributes of soils

A set of attributes endows the soils with distinctive characteristics and astute understanding is required in order to formulate suitable strategies for soil management. The aim of this study was to physically, chemically and mineralogically characterize samples of the main soil classes in Minas Gerais, Brazil, determine the point of zero salt effect (PZSE) and the point of zero charge (PZC), and ascertain the correlation between these factors and soil attributes. The soils evaluated presented different textural classes ranging from loamy sand (Entisol) to very clayey (some Oxisols and Ultisols). The soils differed substantially in terms of fertility, presenting a range from dystrophic (low fertility, base saturation < 50 %) to eutrophic character (fertility, base saturation ≥ 50 %), even within the same soil class, such as the Oxisols, which suggests the concurrence of the parent material. Highly weathered soils are predominant in Minas Gerais and these soils are composed predominantly of kaolinite, gibbsite, goethite and hematite. Traces of hydroxy-Al interlayered vermiculite and illite were also found in the Oxisols, Ultisols and Inceptisols. A correlation between the PZSE and the PZC in the A horizon was observed. A high degree of correlation was observed between the PZC and the exchangeable aluminum and the ratio of iron obtained by ammonium oxalate and dithionite-citrate (Feo/Fed) in both the A and B horizons of soil classes. The results obtained reinforce the importance of knowledge of soil attributes to the adoption of practices such as the management of phosphate fertilization in clayey soils and liming in soils rich in aluminum.

Rill and sheet soil erosion estimation in an area undergoing desertification in the Brazilian semi-arid region

Soil erosion is a serious world problem, especially in areas undergoing desertification. Rill and sheet erosions were estimated in one municipality of the largest desertification nucleus in the Brazilian semi-arid region. Measurements were made in plots located in combinations of the two main soil classes (Luvisol and Planosol, 58 and 40% of the municipal area) and the two predominant vegetation covers (sparse and open, 84 and 7% of the municipal area). The sparse vegetation has 320 plants ha−1 covering 25% of the soil surface and the open vegetation has 495 plants ha−1, covering 40% of the soil surface. Length, width, and depth of all rills were measured in the plots to calculate the soil losses. Sheet erosion was estimated assuming that the height of the soil close to the bases of trees and shrubs in relation to the soil surface away from these bases corresponded to the depth of the lost soil layer. Rill erosion was higher under the sparse vegetation than under the open vegetation: 400 versus 45 Mg ha−1. Sheet erosion did not differ among soils and covers (547–860 Mg ha−1). Soil loss in the municipality was 34 Tg and 24 Eg when extrapolating to the desertification nucleus. Erosion and low vegetation cover are cumulative reinforcing degradation drivers, leading to low crop and livestock productivity, poverty, and social vulnerability. Land use restriction is the main measure to reduce erosion, but it increases social problems.

Geotechnical and hydrological characterization of hillslope deposits for regional landslide prediction modeling

We attempt a characterization of the geotechnical and hydrological properties of hillslope deposits, with the final aim of providing reliable data to distributed catchment-scale numerical models for shallow landslide initiation. The analysis is based on a dataset built up by means of both field tests and laboratory experiments over 100 sites across Tuscany (Italy). The first specific goal is to determine the ranges of variation of the geotechnical and hydrological parameters that control shallow landslide-triggering mechanisms for the main soil classes. The parameters determined in the deposits are: grain size distribution, Atterberg limits, porosity, unit weight, in situ saturated hydraulic conductivity and shear strength parameters. In addition, mineral phases recognition via X-ray powder diffraction has been performed on the different soil types. The deposits mainly consist of well-sorted silty sands with low plastic behavior and extremely variable gravel and clay contents. Statistical analyses carried on these geotechnical and hydrological parameters highlighted that it is not possible to define a typical range of values only with relation to the main mapped lithologies, because soil characteristics are not simply dependent on the bedrock type from which the deposits originated. A second goal is to explore the relationship between soil type (in terms of grain size distribution) and selected morphometric parameters (slope angle, profile curvature, planar curvature and peak distance). The results show that the highest correlation between soil grain size classes and morphometric attributes is with slope curvature, both profile and planar.

Genesis and properties of wetland soils by VIS-NIR-SWIR as a technique for environmental monitoring

Wetlands are important ecosystems characterized by redoximorphic environments producing typical soil forming processes and organic carbon accumulation. Assessments and management of these areas are dependent on knowledge about soil characteristics and variability. By reflectance spectroscopy, information about soils can be obtained since their spectral behaviors are directly related to their chemical, physical, and mineralogical properties reflecting the pedogenetic processes and environment conditions. Our aims were: (a) to characterize the main soil classes of wetlands regarding their spectral behaviors in VIS-NIR-SWIR (350–2500 nm) and relate them to pedogenesis and environmental conditions, (b) to determine spectral ranges (bands) with greater expression of the main soil properties, (c) to identify spectral variations and similarities between hydromorphic soils from wetlands and other soils under different moisture conditions, and (d) to propose spectral models to quantify some chemical and physical soil properties used as environmental quality indicators. Nine soil profiles from the Pantanal region (Mato Grosso State, Brazil) and one from the Serra do Espinhaço Meridional (Minas Gerais State, Brazil) were investigated. Spectral morphology interpretation allowed identifying horizon differences regarding shape, absorption features and reflectance intensity. Some pedogenetic processes of wetland soils related to organic carbon accumulation and oxide iron variation were identified by spectra. Principal Component Analysis allowed discriminating soils from wetland and outside this area (oxidic environment). Quantification of organic carbon was possible with R2 of 0.90 and low error. Quantification of clay content was masked by soils with organic carbon content over 2% where it was not possible to quantify with high R2 and low error both properties when dataset has soil samples with high organic carbon content. By reflectance spectroscopy, important characteristics of wetland soils can be identified and used to distinguish from soils of different environments at low costs, reduced time, and with environmental quality.

The influence of particles recycling on the geochemistry of sediments in a large tropical dam lake in the Amazonian region, Brazil

As a result of over-erosion of soils, the fine particles, which contain the majority of nutrients, are easily washed away from soils, which become deficient in a host of components, accumulating in lakes. On one hand, the accumulation of nutrients-rich sediments are a problem, as they affect the quality of the overlying water and decrease the water storage capacity of the system; on the other hand, sediments may constitute an important resource, as they are often extremely rich in organic and inorganic nutrients in readily available forms. In the framework of an extensive work on the use of rock related materials to enhance the fertility of impoverish soils, this study aimed to evaluate the role on the nutrients cycle, of particles recycling processes from the watershed to the bottom of a large dam reservoir, at a wet tropical region under high weathering conditions. The study focus on the mineralogical transformations that clay particles undergo from the soils of the drainage basin to their final deposition within the reservoir and their influence in terms of the geochemical characteristics of sediments. We studied the bottom sediments that accumulate in two distinct seasonal periods in Tucuruí reservoir, located in the Amazonian Basin, Brazil, and soils from its drainage basin. The surface layers of sediments in twenty sampling points with variable depths, are representative of the different morphological sections of the reservoir. Nineteen soil samples, representing the main soil classes, were collected near the margins of the reservoir. Sediments and soils were subjected to the same array of physical, mineralogical and geochemical analyses: (1) texture, (2) characterization and semi-quantification of the clay fraction mineralogy and (3) geochemical analysis of the total concentration of major elements, organic compounds (organic C and nitrogen), soluble fractions of nutrients (P and K), exchangeable fractions (cation exchange capacity, exchangeable bases and acidity) and pH(H2O).There is a remarkable homogeneity in the sedimentary distribution along the reservoir in terms of the texture and mineralogy of the clay fraction and of the chemistry of the total, soluble and exchangeable phases. These observations contrast with the physical, morphological and chemical heterogeneity of the soils and the setting lithology. Most of the sediments has a higher contribution of fine-grained material and the mineralogy of the clay fraction is dominated by kaolinite in soils and kaolinite and illite in sediments, followed by lesser amounts of gibbsite, goethite, and metahaloisite and by small/vestigial contents of chlorite and smectite. The sediments are mainly inherited from the watershed but there exist marked differences between the accumulated sediments and their parent materials. These differences mainly come from the selective erosion of fine-grained particles and the extreme climatic conditions which enhance complex transformations of mineralogical and chemical nature. Compared with the parental soils, the reservoir sediments show the following differences: (1) enrichment in fine-grained and less dense inorganic particles, (2) aggradative mineralogical transformations, including enrichment in clay minerals with higher cationic adsorption and exchange capacity, (3) degradation of the crystalline structure of Fe- and Al-oxides (goethite, gibbsite), (4) increase in easily leached elements (Mg, Ca, P, K, Na) and decrease in chemically less mobile elements (Si, Fe) and (5) higher contents of organic carbon, nitrogen, and soluble forms of P and K, mainly concentrated in the clay fraction. These transformations are extremely important in the nutrients cycle, denoting that sediments represent an efficient sink for nutrients from the over-erosion of soils. Mineral and organic compounds can permanently or temporarily sequester these nutrients, recycling them and enhancing their availability through the slow release of components from relatively loose crystal structures. These processes can easily explain the enrichment in soluble and exchangeable forms of elements such as P, K, Ca or Mg. This study conclude that the particles recycling in a large tropical dam reservoir which receives high fluxes of allochthonous nutrients, has an important role in the good quality of sediments for agricultural use and in the profitable use of this technology to recover depleted soils in remediation projects in regions near large hydroelectric plants.

Assessment of Model Consistency for Determination of Soil–Water Characteristic Curves

Characterization of the engineering behavior of unsaturated soil is dependent on the soil–water characteristic curve (SWCC), a graphical representation of the relationship between water content or degree of saturation and soil suction. A reasonable description of the SWCC is thus important for the accurate prediction of unsaturated soil parameters. The measurement procedure for determining the SWCC, however, is difficult, expensive, and time-consuming. During the past few decades, researchers have laid a major focus on developing empirical equations for predicting the SWCC, with a large number of empirical models suggested. One of the most crucial questions is how precisely existing equations can represent the SWCC. As different models have different ranges of capability, it is essential to evaluate the precision of the SWCC models used for each particular soil type for better SWCC estimation. It is expected that better estimation of SWCC would be achieved via a thorough statistical consistency analysis of its applicability within a particular soil class. This paper evaluates the consistency and applicability of using four different SWCC equations for defining the relationship between water content and soil suction. Optimization techniques were used to obtain the best fit of the model parameters for three main soil classes: coarse-textured (i.e., sand), medium-textured (i.e., silt), and fine-textured (i.e., clay) soils. The four SWCC models were evaluated and computed for each sample. The results show that the Brooks and Corey model and modified Gardner model was the most consistent in describing the SWCC for sand soils and clay soils, respectively. Both model predictions also exhibit compatibility with samples ranging from low to high soil water content.

Presentation of analytical solutions for seismically induced tunnel lining forces accounting for soil-structure interaction effects

Recently, as the structural design has shifted to the performance design, seismic design of tunnel structures considering soil-structure interaction becomes more important. The effects of soil-structure interaction should not be overlooked for the reason that the interaction effects between a structure and surrounding ground may cause larger external forces to the structure. It has been highlighted that the relative rigidity between the soil and the structure is the predominant factor influencing the soil-structure interaction effects. With an aim to study the effects of tunnel-ground interaction, a number of analyses were carried out in this work, based on the most frequently used analytical expressions for evaluation of seismically induced stress increment in a tunnel lining accounting for the soil-structure interaction effects. These solutions are functions of the shear strain field which is the cause of the ovaling of the circular tunnel cross-section. A value of the average soil shear strain in the range of depths corresponding to the tunnel section, between the tunnel crown and the invert, has been computed through a free-field one-dimensional seismic site response analysis preformed by the code EERA. Various levels of analysis have been undertaken on different soil conditions, considering representative of two main soil classes - stiff soil of good conditions and soft saturated soil of poor conditions, as well as, two extreme cases of tunnel-ground interface - the full-slip and the no-slip conditions. Finally, the results for all the considered cases have been evaluated and compared, and the significant mutual differences with regard to a tunnel-ground interaction have been underlined.

Solos e geoambientes do Parque Nacional do Viruá e entorno, Roraima: visão integrada da paisagem e serviço ambiental

http://dx.doi.org/10.5902/198050989287O Parque Nacional (PARNA) do Viruá ocupa 227.011 ha, na região do baixo Rio Branco, Roraima. A região compreende um extenso mosaico de ambientes complexos inundáveis, florestais e não florestais. Este trabalho teve como objetivo geral detalhar os aspectos pedológicos e geoambientais do Parque e entorno, em uma visão integrada da paisagem e, além disso, estimar o estoque de carbono nos solos e geoambientes. Foram descritos e coletados 29 perfis de solos nas principais fitofisionomias de Campinaranas e Florestas do Parque e entorno. Destacaram-se os seguintes: Espodossolo Humilúvico, Neossolo Quartzarênico, Neossolo Flúvico, Neossolo Litólicos, Latossolo Vermelho-Amarelo, Latossolo Vermelho, Cambissolo Háplico, Cambissolo Flúvico, Gleissolo Háplico e Plintossolo Háplico. Os solos apresentaram distribuição espacial com limites abruptos e com forte associação entre as fitofisionomias. Foram agrupados em três pedoambientes: (1) solos arenosos das campinaranas, (2) solos associados aos inselbergs e adjacências e (3) solos aluviais. Foram mapeadas e descritas 18 unidades geoambientais no Parque e entorno. Os geoambientes predominantes no Parque foram: Planícies Arenosas e Paleodunas com Campinarana Graminosa e Arbustiva em Neossolos Quartzarênicos hidromórficos e Espodossolos; e Planícies de Inundação e Terraços com Floresta de Igapó sobre solos hidromórficos arenosos, com respectivamente 24,6 % e 20,1 % da área estudada. Em termos de estoque total de carbono nos solos, destacaram-se os geoambientes dos complexos arenosos das Campinaranas e associações, com 9450,9 Gg C. A grande extensão e representatividade dos complexos arenosos das Campinaranas fazem do PARNA Viruá uma Unidade de Conservação de proteção integral com forte vocação para preservação e conservação de sistemas arenícolas amazônicos. As áreas sob o domínio de Espodossolos possuem os maiores estoques de carbono orgânico e os complexos arenosos das Campinaranas e associações representam os geoambientes mais relevantes na prestação de serviços ambientais de conservação do carbono nos solos.

HYPERSPECTRAL REMOTE SENSING: EVALUATION OF R95/HSS SENSOR FOR SPATIALIZATION AND CHARACTERIZATION OF SOIL IN MANAUS, AM – BRAZIL

The HSS (Hyperspectral Scanner System) was evaluated for characterization and spatialization of soils in Manaus, AM, Brazil, with 3 meter resolu- tion images. The images (37 bands between 0,43 and 2,37μm) were converted from radiance values to surface reflectance using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) applicative, based on the MODTRAN +4 (Moderate Resolution Transmittance) a radioactive transfer model. Preceding collec- tion of soil samples, the main soil classes were identified through the SAM (Spectral Angle Mapper) method in order to facilitate analysis of the spectral characteristics of the studied area. Finally, for 13 samples, correlations among soil characteristics and spectral data from the HSS sensor, and spectral curves obtained in laboratory were carried out. Results indicated that: (a) the atmospheric correction accomplished with the FLAASH applicative was appropriate, despite difficulties for total removal of the water vapor feature at 0.94μm and at short-wave infrared band, near to 2.0μm. In general, a spectral coherence of the HSS sensor was confirmed with the information found in literature and the spectrum obtained in the laboratory; (b) a good capacity for spectral identification was observed with the SAM classifier as the results provided an appropriate soil preidentification, helping as well to define sites for field work; (c) the spectral curves representative of the soil classes are comparable both for laboratory and sensor data. Usually, correlations between both data acquisition environments (laboratory and HSS) are high.

Caracterização de neossolos regolíticos da região semiárida do Estado de Pernambuco

Estudos de caracterização de solos em regiões ainda pouco exploradas, além de disponibilizarem e ampliarem a base de informações sobre as mais distintas ordens de solos do território nacional, também permitem sistematizar informações sobre suas propriedades, que poderão servir de subsídio para o desenvolvimento de práticas de manejo e uso sustentável das terras. Entre os principais solos recorrentes na região semiárida pernambucana, destacam-se os Neossolos Regolíticos, os quais perfazem aproximadamente 27 % da superfície do Estado e recobrem importantes áreas voltadas à produção agrícola, especialmente à agricultura familiar. Considerando a possibilidade de ocorrência de Neossolos Regolíticos com distintas propriedades físicas, químicas ou mineralógicas, em razão da existência de distintos contextos geológicos e climáticos ao longo do Estado de Pernambuco, o presente trabalho teve como objetivo caracterizar física, química e mineralogicamente Neossolos Regolíticos ao longo da região semiárida do Estado de Pernambuco, bem como relacionar os solos com sua litologia. Para isso, foram selecionados cinco perfis de Neossolos Regolíticos em diversos municípios do Estado de Pernambuco (P1=São Caetano, P2=Lagoa do Ouro, P3=Caetés, P4=São João e P5=Parnamirim). Os perfis foram descritos morfologicamente, coletando-se amostras de todos os horizontes do solo e da rocha do embasamento. Foram realizadas análises físicas e químicas para fins de classificação de solos, análises mineralógicas das frações grossas (cascalho e areia) por microscopia óptica e das frações silte e argila por difração de raios X, além de análises petrográficas das amostras de rochas. De acordo com os resultados, observou-se a ocorrência de solos semelhantes e com pequeno grau de desenvolvimento pedogenético, variando de medianamente a muito profundos, com sequência de horizontes A-AC-C e Cr e textura arenosa a média. Dois perfis apresentaram caráter solódico em profundidade. Todos os solos apresentaram baixos teores de matéria orgânica e P disponível. Apesar dos baixos teores de cátions trocáveis, todos os perfis são eutróficos. A assembleia mineralógica das frações cascalho, areia e silte é constituída essencialmente por quartzo, seguido de feldspatos e mica, corroborando a constituição petrográfica analisada. A caulinita é o principal argilomineral da fração argila em todos os perfis e horizontes estudados, indicando um importante processo de monossialitização em solos autóctones, em clima caracteristicamente semiárido. No perfil P2, devido à posição mais baixa do solo na paisagem, ocorreram minerais esmectíticos com misturas de fases entre montmorilonita, beidelita ou nontronita, identificados pela análise de DRX, empregando o teste de Greene-Kelly.

ERODIBILIDADE DO SOLO NOS TABULEIROS COSTEIROS

In order to determine soil losses caused by water erosion, in different situations, erosion prediction models, such as the Universal Soil Loss Equation (USLE), are used. Their application on agricultural and environmental planning depends on the determination of the USLE factors, including erodibility (K factor). The objective of this study was to determine erodibility for the main soil classes of the Brazilian Coastal Plains region, in Aracruz, Espirito Santo State. The experiment was established in the following soils: medium/clayey texture Yellow Argisol (PA1), Haplic Plinthosol (FX), and moderately rocky Yellow Argisol (PA2). For the calculation of soil erodibility, data of erosivity and soil losses, from November 1997 to May 2004, were used. Soil losses samplings were performed for each rainfall event regarded as erosive. The erodibility values were 0.007 Mg h MJ -1 mm -1 ; 0.017 Mg h MJ -1 mm -1 ; and 0.0004 Mg h MJ -1 mm -1 , for PA1, FX, and PA2, respectively.

UNIDADES PEDOAMBIENTAIS DA REGIÃO DE SANTA TEREZA, ESTADO DO TOCANTINS

A sustainable environmental management, through a joint vision of natural resources, has been adopted for monitoring land sustainability, particularly those with agricultural use. This work aimed the characterization and definition of pedoenvironmental units, to provide subsidies to the development of sustainable land use plans, through the characterization of the main soil classes found in the Santa Tereza region, Tocantins State, Brazil, and their relations with the relief, geology, agriculture suitability, and land use and occupation, with the use of geoprocessing techniques. In the area of study, a pedological transect, with characterization of seven soil representative profiles, was conducted. The soils were classified as Dystrophic Rhodustox, Distrophic Plintustox, Distrophic Haplustox, Distrophic Haplustept, Typic Troppsamment, and Distrophic Tropsaprent, and over 63.5% of the total area was covered with native vegetation. According to the agricultural suitability evaluation, lands were classified as 2(b)c, 4p, 4(p), 5(n), and 6, and four pedoenvironmental units were individualized: Rhodustox domain, Plintustox domain, Rocks domain + Haplustept, and Quartzipsamment domain + Tropsaprent. KEY-WORDS: Tocantins State soils; agricultural suitability; pedoenvironment; environmental sustainability.

Calibração e aplicação do modelo MUSLE em uma microbacia hidrográfica nos Tabuleiros Costeiros brasileiros

A erosão hídrica é uma das principais preocupações relacionadas ao manejo de solos tropicais e o escoamento superficial o responsável pelo transporte e deposição desses sedimentos, razão por que se objetivou, com este estudo, ajustar um modelo semi-empírico às variáveis hidrológicas do escoamento superficial, aplicando-se a Equação Universal de Perdas de Solo Modificada - MUSLE, em uma microbacia hidrográfica ocupada por plantações de eucalipto e floresta nativa, na região dos Tabuleiros Costeiros, Aracruz, ES. As classes de solo ocorrentes na microbacia são o Argissolo Amarelo textura média/argilosa (PA1), Argissolo Amarelo moderadamente rochoso (PA8) e Plintossolo Háplico (FX). O trabalho foi conduzido no período de 1997 a 2004. Modelos para o deflúvio e vazão de pico foram ajustados, obtendo-se estimativas adequadas, podendo-se utilizá-los para simulação hidrológica. O modelo MUSLE mostrou-se apropriado para predições das perdas de solo na microbacia, recomendando-se os coeficientes "a" e "b" iguais a 14,96 e 0,59, respectivamente, com fator topográfico de 1,28.

Unidades ambientais da bacia hidrográfica do Rio Santana, Sul da Bahia

A bacia hidrográfica do Rio Santana apresenta inúmeros problemas ambientais ocasionados pelas atividades econômicas impactantes e pressão antrópica. Para atenuar esses conflitos, garantir a conservação ambiental e a sustentabilidade dessa área de extrema importância para a região, deve-se identificar e conhecer seu ambiente. Este trabalho realizou uma estratificação ambiental na bacia hidrográfica do Rio Santana, analisando as inter-relações entre os elementos das paisagens. A vegetação, a geologia e o relevo foram os critérios utilizados para a delimitação das unidades ambientais, uma vez que, nessa área, estes fatores atuam com maior intensidade na gênese dos solos. Assim, foram identificadas seis unidades ambientais com características peculiares: Planície Quaternária Marinha, Planície Quaternária Estuarina, Tabuleiro Costeiro Sedimentar, Mar de Morros, Depressão Cristalina e Morro Florestado. Adicionalmente, foram caracterizadas as principais classes de solos por meio de análises físicas, químicas e mineralógicas. A diversidade litológica nesta bacia condiciona a grande variedade pedológica, influenciando fortemente as propriedades dos solos. Os resultados obtidos evidenciam os diferentes processos ocorridos em cada unidade ambiental. As principais classes de solos encontradas na região são: Latossolos, Argissolos, Cambissolos, Luvissolos, Neossolos e Gleissolos.

Estudo da relação pedomorfogeológica na distribuição de solos com horizontes B textural e B nítico na paisagem de Lavras (MG)

O entendimento das relações entre geologia, geomorfologia e pedologia auxilia nas atividades de classificação dos solos e na avaliação da distribuição pedológica de uma área. Este trabalho foi motivado pela escassez de estudos dessa natureza na região de Lavras (MG), onde ocorrem várias classes de solos, relacionados com a grande variedade petrológica do material de origem e com a ocorrência de domínios geomorfológicos distintos. O objetivo deste trabalho foi estudar as relações entre material de origem (relação pedogeológica), classes de relevo (relação pedogeomorfológica) e solos com horizontes B textural e B nítico, visando propor um modelo da distribuição desses solos na paisagem de Lavras. Os solos com horizontes B textural e B nítico de ocorrência regional foram selecionados de acordo com o estádio de evolução, que permite preservar características das rochas parentais. Esses solos são desenvolvidos nessa região em relevos ondulados a forte ondulados, originando diferentes classes de solos com horizontes B textural e B nítico relacionados ao material de origem. Para desenvolvimento deste estudo, foram realizadas a interpretação petrológica do substrato rochoso e a individualização do relevo, por meio de classes de declividade. Mediante campanhas de campo, foram selecionados e caracterizados perfis representativos das principais classes dos solos em estudo e foram avaliadas as relações pedogeológicas associadas às relações pedogeomorfológicas, permitindo a proposição de um modelo preditivo de distribuição de solos com horizontes B textural e B nítico na paisagem de Lavras (MG).

Variabilidade espacial de classes de textura, salinidade e condutividade hidráulica de solos em planície aluvial

Visando-se avaliar a distribuição de classes texturais e sua correlação espacial com a infiltrabilidade e salinidade de uma área aluvial, no Agreste de Pernambuco, utilizou-se a geoestatística indicadora segundo uma distribuição binária baseada na presença/ausência de solos francos. Considerando-se pontos de amostragem e de testes de infiltração dispostos ao longo do eixo principal do aluvião, e aleatoriamente distribuídos, analisou-se a variabilidade espacial das classes de solo predominantes, da velocidade de infiltração básica (condutividade hidráulica saturada) e da condutividade elétrica do extrato de saturação da camada subsuperficial, cujos alcances dos semi-variogramas ajustados foram de 333, 320 e 520 m, respectivamente. Verificou-se que a geoestatística indicadora preservou a correlação espacial entre a textura e a condutividade hidráulica, e entre a textura e a condutividade elétrica. Deste modo, as classes de solo predominantes podem ser usadas para representar distintos padrões no tocante ao potencial de lixiviação e à susceptibilidade de salinização. A metodologia indicadora mostra-se promissora para estudo da variabilidade espacial de propriedades físicas de solos aluviais onde predominam classes contrastantes.

Perdas de solo e água por erosão hídrica em sistemas florestais na região de Aracruz (ES)

Avaliaram-se as perdas de solo e água por erosão hídrica em sistemas florestais, relacionando-as com os limites admissíveis de perdas para as principais classes de solo nos Tabuleiros Costeiros da região de Aracruz (ES), com vistas em obter indicativos da adequação do manejo deste sistema de produção. O experimento foi instalado em parcelas em Argissolo Amarelo textura média/argilosa (PA1), Plintossolo Háplico (FX) e Argissolo Amarelo moderadamente rochoso (PA8), com declividade variando de 1,8 a 8,2 %; 1,3 a 12,4 % e 28,8 a 35,5 %, respectivamente, contemplando três situações: eucalipto, mata nativa e solo descoberto. As perdas de solo por erosão hídrica para o sistema com eucalipto apresentaram a seguinte ordem: PA8 &gt; PA1 &gt; FX. As perdas de água por enxurrada para o sistema com eucalipto apresentaram a seguinte ordem: PA8 &gt; FX &gt; PA1, com uma variação de 9,09 a 70,48 mm, correspondendo a 0,79 e 6,1 % da precipitação total anual, respectivamente. As perdas de solo para o povoamento de eucalipto foram bem abaixo dos limites de tolerância para os solos referentes a cada classe, indicando a adequação do manejo deste sistema de produção em relação à erosão hídrica. O fato de as perdas de solo para o eucalipto ficarem relativamente próximas daquelas da mata nativa indica a sustentabilidade daquele ambiente no contexto de erosão.