Sombric-like horizon and xanthization in polychrome subtropical soils from Southern Brazil: implications for soil classification

The occurrence of dark subsurface horizons rich in organic matter (OM) associated with polychrome in the B horizon (yellowish over reddish hue) is common in soils from Southern Brazil. The formation of these horizons and the combination with such morphological attributes has not been properly documented, and neither has the cause effect relationship. Four soil profiles with such sombric-like horizons with a yellowish color at the upper part of the B horizon over red subsoil were studied in Southern Brazil. Results from micromorphology, extractable sesquioxide minerals, clay mineralogy and isomorphic substitution of Fe by Al in iron minerals showed that melanization, xanthization, bioturbation, moderate shrinking/swelling and moderate ferralitization were the most evident pedogenetic processes in role. Xanthization is closely related to the sombric-like horizon formation. In the studied area the findings demonstrated that no clay and OM illuviation had taken place. Therefore, the classification of these soils was revisited, so as to take into account the processes that underlie their genesis with emphasis on xanthization, clay illuviation and soil aggregation. The results suggest that the sombric horizon may need redefinition, unless profiles can be found in which illuviation of clay and/or OM can be proven.(AU)

Sombric-like horizon and xanthization in polychrome subtropical soils from Southern Brazil: implications for soil classification

The occurrence of dark subsurface horizons rich in organic matter (OM) associated with polychrome in the B horizon (yellowish over reddish hue) is common in soils from Southern Brazil. The formation of these horizons and the combination with such morphological attributes has not been properly documented, and neither has the cause effect relationship. Four soil profiles with such sombric-like horizons with a yellowish color at the upper part of the B horizon over red subsoil were studied in Southern Brazil. Results from micromorphology, extractable sesquioxide minerals, clay mineralogy and isomorphic substitution of Fe by Al in iron minerals showed that melanization, xanthization, bioturbation, moderate shrinking/swelling and moderate ferralitization were the most evident pedogenetic processes in role. Xanthization is closely related to the sombric-like horizon formation. In the studied area the findings demonstrated that no clay and OM illuviation had taken place. Therefore, the classification of these soils was revisited, so as to take into account the processes that underlie their genesis with emphasis on xanthization, clay illuviation and soil aggregation. The results suggest that the sombric horizon may need redefinition, unless profiles can be found in which illuviation of clay and/or OM can be proven.

Hydro-physical characterization of soils under the Restinga Forest

ABSTRACT: Knowledge of the hydraulic properties of the soil is of crucial importance to an understanding of the interactions between vegetation, soil and water. There is little information available about the hydraulic properties of Podzol soils found in tropical regions. The aim of this study was to present the soil morphology and hydraulic properties of a toposequence situated in a permanent plot at the Ilha do Cardoso State Park (Cananéia, SP, Brazil). Ultradetailed soil maps were used to define a toposequence inside the permanent plot. Five profiles, representing the main types of soil, were opened along the toposequence, in which Podzols are dominant. The levels of bulk density, sand content, porosity and permeability in these soils were all high. Consequently, these soils have a high level of hydraulic conductivity with low water retention. This behavior undergoes an alteration in the Bh and Bs horizons due to the accumulation of organic and metallic compounds and a changing structure that modifies the pore distribution. Furthermore, the characterization of the hydro-physical functioning of soils in natural environments is an important source of encouragement to further investigative study of soil water dynamics and its relationship to the native vegetation.

Hydro-physical characterization of soils under the Restinga Forest

ABSTRACT: Knowledge of the hydraulic properties of the soil is of crucial importance to an understanding of the interactions between vegetation, soil and water. There is little information available about the hydraulic properties of Podzol soils found in tropical regions. The aim of this study was to present the soil morphology and hydraulic properties of a toposequence situated in a permanent plot at the Ilha do Cardoso State Park (Cananéia, SP, Brazil). Ultradetailed soil maps were used to define a toposequence inside the permanent plot. Five profiles, representing the main types of soil, were opened along the toposequence, in which Podzols are dominant. The levels of bulk density, sand content, porosity and permeability in these soils were all high. Consequently, these soils have a high level of hydraulic conductivity with low water retention. This behavior undergoes an alteration in the Bh and Bs horizons due to the accumulation of organic and metallic compounds and a changing structure that modifies the pore distribution. Furthermore, the characterization of the hydro-physical functioning of soils in natural environments is an important source of encouragement to further investigative study of soil water dynamics and its relationship to the native vegetation.(AU)

Sombric horizon: five decades without evolution

The sombric horizon is a diagnostic subsurface horizon defined in the soil classification system of the United States (Soil Taxonomy) and FAO (WRB), used to classify the soil at different categorical levels. The sombric horizon has a soil color darker than the overlying surface(s) horizon(s), and must show illuvial humus accumulation features, though they are not associated with aluminum (Al), as in the spodic horizon, nor associated with sodium (Na), as in the natric horizon. There are also criteria to distinguish it from buried A horizons. However, since the first references and proposed concept of the sombric horizon in African soils made by Sys and co-workers in the 1960s, and adopted by the Soil Taxonomy edition of 1975, few modifications have been made to its definition. Moreover, the pedogenic process involved in illuvial humus accumulation in these horizons remains inadequately clarified, making the distinction between the sombric and spodic or buried A horizon difficult and unclear. This review reports the historical evolution of the sombric horizon concept, its definition and inconsistencies under different soil classification systems, and the current hypothesis, together with its fragilities, proposed to explain the soil illuvial humus accumulation. Although it is recognized that further research is necessary, alternative criteria are proposed for the definition of the sombric horizon in the Brazilian System of Soil Classification.

Sombric horizon: five decades without evolution

The sombric horizon is a diagnostic subsurface horizon defined in the soil classification system of the United States (Soil Taxonomy) and FAO (WRB), used to classify the soil at different categorical levels. The sombric horizon has a soil color darker than the overlying surface(s) horizon(s), and must show illuvial humus accumulation features, though they are not associated with aluminum (Al), as in the spodic horizon, nor associated with sodium (Na), as in the natric horizon. There are also criteria to distinguish it from buried A horizons. However, since the first references and proposed concept of the sombric horizon in African soils made by Sys and co-workers in the 1960s, and adopted by the Soil Taxonomy edition of 1975, few modifications have been made to its definition. Moreover, the pedogenic process involved in illuvial humus accumulation in these horizons remains inadequately clarified, making the distinction between the sombric and spodic or buried A horizon difficult and unclear. This review reports the historical evolution of the sombric horizon concept, its definition and inconsistencies under different soil classification systems, and the current hypothesis, together with its fragilities, proposed to explain the soil illuvial humus accumulation. Although it is recognized that further research is necessary, alternative criteria are proposed for the definition of the sombric horizon in the Brazilian System of Soil Classification.(AU)

Soil profile, relief features and their relation to structure and distribution of Brazilian Atlantic rain forest trees

In tropical forests, the environmental heterogeneity can provide niche partitioning at local scales and determine the diversity and plant species distribution. Thus, this study aimed to investigate the variations of tree species structure and distribution in response to relief and soil profile features in a portion of the largest remnant of Brazilian Atlantic rain forest. All trees ³ 5 cm diameter at breast height were recorded in two 0.99 ha plots. Topographic survey and a soil characterization were accomplished in both plots. Topsoil samples (0-20 cm) were taken from 88 quadrats and analyzed for chemical and particle size properties. Differences for both diversity and tree density were identified among three kinds of soils. A canonical correspondence analysis (CCA) indicated that the specific abundance varied among the three kinds of soils mapped: a shallow Udept - Orthent / Aquent gradient, probably due to differences in soil drainage. Nutrient content was less likely to affect tree species composition and distribution than relief, pH, Al3+, and soil texture. Some species were randomly distributed and did not show restriction to relief and soil properties. However, preferences in niche occupation detected in this study, derived from the catenary environments found, rise up as an important explanation for the high tree species diversity in tropical forests.

Atributos de solos hidromórficos no Pantanal Norte Matogrossense

The hydromorphic soils, common in the Amazon and the Pantanal, are subject to alternating periods of natural flooding and drying, leading to formation and differentiated characteristics. These soils are closely related to the nature of the sediments, a consequence of the source material and the processes of deposition and sedimentation. The objective of this study was to evaluate the chemical, mineralogical, and morphological profiles of three soils in the North Brazilian Pantanal North (Solonetz, Plinthosol and Gleysol) in order to interpret the relations between their properties and the environment in which they were formed. The Solonetz and Gleysol have higher fertility, as evidenced by the significant values of CEC (cation exchange rate) and base saturation. The lowest levels of Fe2O3 in the Solonetz are related to the reduction and removal of Fe during its genesis. The mineralogy of sand fraction consists mainly of quartz, nodules and concretions of Fe and Mn and to a lesser extent, biotite, muscovite and traces of tourmaline, magnetite, ilmenite, epidote, zircon and rutile. The soil profile was similar in clay mineralogy, consisting of kaolinite, smectite, illite and interstratified illite-smectite type. The clay mineralogy of soils was consistent with the observed chemical differences between them, as the clay Planossolo showed greater activity on smectite and interstratified illite / smectite, with greater total exchangeable bases and CEC, while the Plinthosol and Gleysol, whose predominant mineral was kaolinite, showed a low content of exchangeable bases and lower CEC.

Os solos hidromórficos, comuns na Amazônia e no Pantanal, estão sujeitos à alternância natural de períodos de alagamento e secamento, que conduzem a uma formação e características diferenciadas. Estes solos guardam estreita relação com a natureza do material de origem e com os processos de deposição e sedimentação. O objetivo neste trabalho foi avaliar as características químicas, morfológicas e mineralógicas de três perfis de solos do Pantanal Norte Matogrossense (Planossolo, Plintossolo e Gleissolo), a fim de interpretar as relações entre suas propriedades e o ambiente em que foram formados. Os Planossolos e Gleissolos possuem maior fertilidade natural, evidenciada pelos valores expressivos de CTC (capacidade de troca de cátions) e saturação por bases. Os menores teores de Fe2O3 do Planossolo estão relacionados com a redução e remoção do Fe durante sua gênese A mineralogia da fração areia dos solos é constituída principalmente de quartzo, nódulos e concreções de Fe e de Mn, e em menor grau, biotita, muscovita e traços de turmalina, magnetita, ilmenita, epídoto, zircão e rutilo. Os solos apresentaram perfil mineralógico semelhante na fração argila, constituído por caulinita, esmectita, ilita e interestratificados do tipo ilita-esmectita. A mineralogia da fração argila dos solos foi compatível com as diferenças químicas constatadas entre eles, pois o Planossolo apresentou argila de maior atividade relativa às esmectitas e interestratificados ilita/esmectita, com maior soma de bases trocáveis e CTC, enquanto o Plintossolo e o Gleissolo, cujo mineral predominante foi a caulinita, apresentaram baixo teor de bases trocáveis e menor CTC.

Soil profile, relief features and their relation to structure and distribution of Brazilian Atlantic rain forest trees

In tropical forests, the environmental heterogeneity can provide niche partitioning at local scales and determine the diversity and plant species distribution. Thus, this study aimed to investigate the variations of tree species structure and distribution in response to relief and soil profile features in a portion of the largest remnant of Brazilian Atlantic rain forest. All trees ³ 5 cm diameter at breast height were recorded in two 0.99 ha plots. Topographic survey and a soil characterization were accomplished in both plots. Topsoil samples (0-20 cm) were taken from 88 quadrats and analyzed for chemical and particle size properties. Differences for both diversity and tree density were identified among three kinds of soils. A canonical correspondence analysis (CCA) indicated that the specific abundance varied among the three kinds of soils mapped: a shallow Udept - Orthent / Aquent gradient, probably due to differences in soil drainage. Nutrient content was less likely to affect tree species composition and distribution than relief, pH, Al3+, and soil texture. Some species were randomly distributed and did not show restriction to relief and soil properties. However, preferences in niche occupation detected in this study, derived from the catenary environments found, rise up as an important explanation for the high tree species diversity in tropical forests.

Smectite in mangrove soils of the State of São Paulo, Brazil

Smectitic clay minerals are frequently identified in mangrove soils, but there is little information about their types and origins. Besides their importance in the agronomical and geotechnical areas, smectites play an important environmental role by adsorbing nutrients, organic pollutants and heavy metals. Smectites found in mangrove soils can be of marine or continental detrital origin, or of neoformation origin. Thus, the objective of this study was to identify the types of smectites present in the State of São Paulo mangrove soils (Brazil), and to relate them to their possible origins. Soil samples were taken in five mangroves along the State of Sao Paulo State coast line. The mineral composition of the clay fraction was identified by X-ray Diffractometry (XRD) applying the Greene-Kelly test and by Fourier transform infrared spectroscopy (FTIR). Highlighting the peaks in the 3,560 cm-1 band and in the region near 798 and 820 cm-1, there was a predominance of nontronite in the soil at the Sítio Grande River, Pai Matos Island, Caranguejo Island and Itapanhaú River mangroves, and possibly a lower concentration of ferric montmorillonite in the Escuro River mangrove. Since the continental sediments in these environments are very poor in smectite, the origin of these minerals in the mangrove soils studied is related to sedimentation left by past marine transgressions, to neoformation processes, or yet to a combination of both origins.

Minerais de argila esmectíticos são freqüentemente identificados em solos de manguezais, mas são escassas as informações sobre os tipos encontrados e suas origens. A despeito da importância para a agronomia e geotecnia, as esmectitas desempenham também importante papel no âmbito ambiental, atuando na adsorção de nutrientes, poluentes orgânicos e metais pesados. Esmectitas em solos de manguezais podem ser de origem detrítica, marinha ou continental, e também de neoformação. Assim, este estudo objetivou identificar os tipos de esmectitas presentes em solos de manguezais do Estado de São Paulo e relacioná-los com suas possíveis origens. Para tanto, foram amostrados solos de cinco manguezais distribuídos ao longo do litoral paulista, cuja identificação dos constituintes mineralógicos da fração argila foi realizada por difratometria de raios X (DRX) com aplicação do teste de Greene-Kelly e por espectroscopia no infravermelho com transformada de Fourier (FTIR). Destacando os picos na banda de 3.560 cm-1 e na região próxima a 798 e 820 cm-1, verificou-se o predomínio de nontronita nos solos dos manguezais do Rio Sítio Grande, Ilha de Pai Matos, Ilha do Caranguejo e Rio Itapanhaú e, possivelmente menor participação de montmorilonita férrica no manguezal do Rio Escuro. Como os sedimentos continentais destes ambientes são muito pobres em esmectitas, a origem destes minerais nos solos dos manguezais estudados está relacionada à sedimentação deixada pelas transgressões marinhas pretéritas ou aos processos de neoformação ou, ainda, com uma combinação de ambas origens.

Smectite in mangrove soils of the State of São Paulo, Brazil

Smectitic clay minerals are frequently identified in mangrove soils, but there is little information about their types and origins. Besides their importance in the agronomical and geotechnical areas, smectites play an important environmental role by adsorbing nutrients, organic pollutants and heavy metals. Smectites found in mangrove soils can be of marine or continental detrital origin, or of neoformation origin. Thus, the objective of this study was to identify the types of smectites present in the State of São Paulo mangrove soils (Brazil), and to relate them to their possible origins. Soil samples were taken in five mangroves along the State of Sao Paulo State coast line. The mineral composition of the clay fraction was identified by X-ray Diffractometry (XRD) applying the Greene-Kelly test and by Fourier transform infrared spectroscopy (FTIR). Highlighting the peaks in the 3,560 cm-1 band and in the region near 798 and 820 cm-1, there was a predominance of nontronite in the soil at the Sítio Grande River, Pai Matos Island, Caranguejo Island and Itapanhaú River mangroves, and possibly a lower concentration of ferric montmorillonite in the Escuro River mangrove. Since the continental sediments in these environments are very poor in smectite, the origin of these minerals in the mangrove soils studied is related to sedimentation left by past marine transgressions, to neoformation processes, or yet to a combination of both origins.

Minerais de argila esmectíticos são freqüentemente identificados em solos de manguezais, mas são escassas as informações sobre os tipos encontrados e suas origens. A despeito da importância para a agronomia e geotecnia, as esmectitas desempenham também importante papel no âmbito ambiental, atuando na adsorção de nutrientes, poluentes orgânicos e metais pesados. Esmectitas em solos de manguezais podem ser de origem detrítica, marinha ou continental, e também de neoformação. Assim, este estudo objetivou identificar os tipos de esmectitas presentes em solos de manguezais do Estado de São Paulo e relacioná-los com suas possíveis origens. Para tanto, foram amostrados solos de cinco manguezais distribuídos ao longo do litoral paulista, cuja identificação dos constituintes mineralógicos da fração argila foi realizada por difratometria de raios X (DRX) com aplicação do teste de Greene-Kelly e por espectroscopia no infravermelho com transformada de Fourier (FTIR). Destacando os picos na banda de 3.560 cm-1 e na região próxima a 798 e 820 cm-1, verificou-se o predomínio de nontronita nos solos dos manguezais do Rio Sítio Grande, Ilha de Pai Matos, Ilha do Caranguejo e Rio Itapanhaú e, possivelmente menor participação de montmorilonita férrica no manguezal do Rio Escuro. Como os sedimentos continentais destes ambientes são muito pobres em esmectitas, a origem destes minerais nos solos dos manguezais estudados está relacionada à sedimentação deixada pelas transgressões marinhas pretéritas ou aos processos de neoformação ou, ainda, com uma combinação de ambas origens.

Modelling air temperature for the state of São Paulo, Brazil

Spatial modelling of air temperature (maximum, mean and minimum) of the State of São Paulo (Brazil) was calculated by multiple regression analysis and ordinary kriging. Climatic data (mean values of five or more years) were obtained from 256 meteorological stations distributed uniformly over the State. The correlation between the climatic dependent variables, with latitude and altitude as independent variables was significant and could explain most of the spatial variability. The coefficients of determination (P 0.05) varied in the range of 0.924 and 0.953, showing that multiple regression analysis is an accurate method for the modelling of air temperature for the State of São Paulo. Finally, these regression equations were used together with the kriged maps of the residual errors to build 15 digital maps of air temperature using a 0.5 km² Digital Elevation Model in a Geographic Information System.

Foram utilizadas técnicas de análise de regressão linear múltipla e krigagem ordinária para a modelagem espacial das temperaturas máximas, mínimas, médias do Estado de São Paulo (Brasil). Os dados climáticos foram obtidos de 256 estações climatológicas distribuídas na totalidade do Estado. O período mínimo das séries climáticas utilizadas foi de cinco anos. Os resultados das análises de regressão apresentaram uma boa correlação entre as variáveis dependentes analisadas (temperaturas médias, máximas e mínimas) com a latitude, e a altitude como variáveis independentes. Os coeficientes de determinação (P 0,05) variam entre 0,924 e 0,953 indicando que a regressão múltipla é um método preciso de estimativa da temperatura do ar no Estado de São Paulo. As equações de regressão obtidas foram utilizadas, em conjunto com mapas dos resíduos interpolados por krigagem, para a elaboração de 15 mapas de temperatura do ar sobre um modelo de elevação digital de 0,5 km² de resolução espacial com a ajuda de geoprocessamento.

Modelling air temperature for the state of São Paulo, Brazil

Spatial modelling of air temperature (maximum, mean and minimum) of the State of São Paulo (Brazil) was calculated by multiple regression analysis and ordinary kriging. Climatic data (mean values of five or more years) were obtained from 256 meteorological stations distributed uniformly over the State. The correlation between the climatic dependent variables, with latitude and altitude as independent variables was significant and could explain most of the spatial variability. The coefficients of determination (P 0.05) varied in the range of 0.924 and 0.953, showing that multiple regression analysis is an accurate method for the modelling of air temperature for the State of São Paulo. Finally, these regression equations were used together with the kriged maps of the residual errors to build 15 digital maps of air temperature using a 0.5 km² Digital Elevation Model in a Geographic Information System.

Foram utilizadas técnicas de análise de regressão linear múltipla e krigagem ordinária para a modelagem espacial das temperaturas máximas, mínimas, médias do Estado de São Paulo (Brasil). Os dados climáticos foram obtidos de 256 estações climatológicas distribuídas na totalidade do Estado. O período mínimo das séries climáticas utilizadas foi de cinco anos. Os resultados das análises de regressão apresentaram uma boa correlação entre as variáveis dependentes analisadas (temperaturas médias, máximas e mínimas) com a latitude, e a altitude como variáveis independentes. Os coeficientes de determinação (P 0,05) variam entre 0,924 e 0,953 indicando que a regressão múltipla é um método preciso de estimativa da temperatura do ar no Estado de São Paulo. As equações de regressão obtidas foram utilizadas, em conjunto com mapas dos resíduos interpolados por krigagem, para a elaboração de 15 mapas de temperatura do ar sobre um modelo de elevação digital de 0,5 km² de resolução espacial com a ajuda de geoprocessamento.

Origin of microaggregates in soils with ferralic horizons

Microaggregates that characterize ferralic soils have been hypothesized to have physical, geochemical and/or biological origins. Despite of many studies, the hierarchy between these processes that form microaggregates has seldom been reported. The objective of this work was to study the genesis of microaggregates in a sequence of Ferralic Nitisols developed on Quaternary red clayey sediments and diabase in Piracicaba (SP), Brazil. This issue was tackled by combining optical microscopy, image analysis, scanning electron microscopy and elemental iron quantifications by X-ray fluorescence. Micromorphological investigations showed three different types of microaggregates: (i) oval microaggregates with well sorted quartz grains in their interior; (ii) oval microaggregates without or with poorly sorted quartz grains in their interior; and (iii) dense polyedric microaggregates. These morphological evidences, together with the elemental iron determinations and scanning electron microscopy, revealed the contribution of more than one process for microaggregate formation: (i) the mechanical action of the mesofauna would form the first type of microaggregates (ii) geochemical and biological processes would form the second type and (iii) the fissuration of the soil matrix by expansion and compression processes would form the third type.

Os microagregados, característicos do horizonte B latossólico, podem ser formados a partir de processos físicos, geoquímicos e biológicos. Apesar da quantidade de trabalhos realizados sobre este tema, poucos tem discutido a hierarquia entre os processos que formam estes microagregados. O objetivo deste trabalho foi estudar a gênese dos microagregados numa seqüência de solos localizada em Piracicaba (SP), Brasil. Os solos foram classificados como Nitossolos Vermelhos Eutroférricos latossólicos e desenvolvem-se a partir de sedimentos argilosos vermelhos do Quaternário e diabásio. Para atingir o objetivo deste trabalho foram utilizadas técnicas de microscopia ótica, análise de imagens, microscopia eletrônica de varredura e quantificações elementares de ferro através de fluorescência de raio-X. As investigações micromorfológicas mostraram a presença de três tipos de microagregados: (i) microagregados ovais com grãos de quartzo bem selecionados no seu interior; (ii) microagregados ovais sem grãos de quartzo ou grãos de quartzo mal selecionados no seu interior; e (iii) microagregados poliédricos densos. Estas evidencias morfológicas junto com os dados elementares de ferro e a microscopia eletrônica de varredura mostraram a contribuição de mais de um processo na formação dos microagregados: (i) a ação mecânica da mesofauna seria responsável pela formação do primeiro tipo de microagregados; (ii) processos geoquímicos e biológicos estariam formando o segundo tipo de microagregados; e (iii) a fissuração da matriz do solo por processos de contração e expansão formariam o terceiro tipo de microagregados.

Origin of microaggregates in soils with ferralic horizons

Microaggregates that characterize ferralic soils have been hypothesized to have physical, geochemical and/or biological origins. Despite of many studies, the hierarchy between these processes that form microaggregates has seldom been reported. The objective of this work was to study the genesis of microaggregates in a sequence of Ferralic Nitisols developed on Quaternary red clayey sediments and diabase in Piracicaba (SP), Brazil. This issue was tackled by combining optical microscopy, image analysis, scanning electron microscopy and elemental iron quantifications by X-ray fluorescence. Micromorphological investigations showed three different types of microaggregates: (i) oval microaggregates with well sorted quartz grains in their interior; (ii) oval microaggregates without or with poorly sorted quartz grains in their interior; and (iii) dense polyedric microaggregates. These morphological evidences, together with the elemental iron determinations and scanning electron microscopy, revealed the contribution of more than one process for microaggregate formation: (i) the mechanical action of the mesofauna would form the first type of microaggregates (ii) geochemical and biological processes would form the second type and (iii) the fissuration of the soil matrix by expansion and compression processes would form the third type.

Os microagregados, característicos do horizonte B latossólico, podem ser formados a partir de processos físicos, geoquímicos e biológicos. Apesar da quantidade de trabalhos realizados sobre este tema, poucos tem discutido a hierarquia entre os processos que formam estes microagregados. O objetivo deste trabalho foi estudar a gênese dos microagregados numa seqüência de solos localizada em Piracicaba (SP), Brasil. Os solos foram classificados como Nitossolos Vermelhos Eutroférricos latossólicos e desenvolvem-se a partir de sedimentos argilosos vermelhos do Quaternário e diabásio. Para atingir o objetivo deste trabalho foram utilizadas técnicas de microscopia ótica, análise de imagens, microscopia eletrônica de varredura e quantificações elementares de ferro através de fluorescência de raio-X. As investigações micromorfológicas mostraram a presença de três tipos de microagregados: (i) microagregados ovais com grãos de quartzo bem selecionados no seu interior; (ii) microagregados ovais sem grãos de quartzo ou grãos de quartzo mal selecionados no seu interior; e (iii) microagregados poliédricos densos. Estas evidencias morfológicas junto com os dados elementares de ferro e a microscopia eletrônica de varredura mostraram a contribuição de mais de um processo na formação dos microagregados: (i) a ação mecânica da mesofauna seria responsável pela formação do primeiro tipo de microagregados; (ii) processos geoquímicos e biológicos estariam formando o segundo tipo de microagregados; e (iii) a fissuração da matriz do solo por processos de contração e expansão formariam o terceiro tipo de microagregados.

Learning soil classification with the Kayapó indians

The Kayapó Xicrin do Cateté (Xicrin) indigenous reserve is located within the Amazon forest in Pará (Brazil). The Xicrins have developed a soil classification system that is incorporated in their language and culture. The etymology of their classification system and its logical structure makes it similar and comparable with modern soil classification. The etymology of the Xicrin's language is based on the junction of radicals to form words for different soil names. The name of the soil is formed by the main noun radical "puka", to which adjectives referring to soil morphological attributes are added. Modern classification systems are also based on similar morphological variables, and analytical support for defining boundaries of chemical or physical soil attributes are important only in lower hierarchical levels. Soil scientists have developed a soil classification system that is sensitive for the restrictions and potentialities the soil will show for modern agriculture. The Xicrins classify soils for what is important for their life style, i.e. a harmonic and friendly life with the resources they gain from the forest.

A reserva indígena Kayapó-Xicrin do Cateté esta localizada na floresta amazônica no estado do Pará (Brasil). Os Xicrins desenvolveram uma classificação de solo que esta incorporada ao seu idioma e cultura. A etimologia da classificação dos solos e a sua estrutura lógica são similares com os sistemas modernos de classificação de solos. A etimologia do idioma Xicrin é baseada na união de radicais para formar as palavras e a mesma é utilizada para formar os diferentes nomes dos solos. O nome do solo é formado pelo radical principal "puka" ao qual são adicionados adjetivos referentes aos atributos morfológicos dos solos. Os sistemas de classificação de solos modernos também são baseados nos mesmos atributos morfológicos, apesar de que apoio analítico é importante para definir os limites entre os atributos químicos e físicos dos solos em níveis hierárquicos mais baixos. Os cientistas de solos têm desenvolvido uma classificação de solos interpretativa para as restrições e potencialidades que o solo tem para a agricultura moderna. Os Xicrins classificam o solo para aquilo que é importante para a vida deles, uma vida harmônica e simbiótica com a natureza.

Learning soil classification with the Kayapó indians

The Kayapó Xicrin do Cateté (Xicrin) indigenous reserve is located within the Amazon forest in Pará (Brazil). The Xicrins have developed a soil classification system that is incorporated in their language and culture. The etymology of their classification system and its logical structure makes it similar and comparable with modern soil classification. The etymology of the Xicrin's language is based on the junction of radicals to form words for different soil names. The name of the soil is formed by the main noun radical "puka", to which adjectives referring to soil morphological attributes are added. Modern classification systems are also based on similar morphological variables, and analytical support for defining boundaries of chemical or physical soil attributes are important only in lower hierarchical levels. Soil scientists have developed a soil classification system that is sensitive for the restrictions and potentialities the soil will show for modern agriculture. The Xicrins classify soils for what is important for their life style, i.e. a harmonic and friendly life with the resources they gain from the forest.

A reserva indígena Kayapó-Xicrin do Cateté esta localizada na floresta amazônica no estado do Pará (Brasil). Os Xicrins desenvolveram uma classificação de solo que esta incorporada ao seu idioma e cultura. A etimologia da classificação dos solos e a sua estrutura lógica são similares com os sistemas modernos de classificação de solos. A etimologia do idioma Xicrin é baseada na união de radicais para formar as palavras e a mesma é utilizada para formar os diferentes nomes dos solos. O nome do solo é formado pelo radical principal "puka" ao qual são adicionados adjetivos referentes aos atributos morfológicos dos solos. Os sistemas de classificação de solos modernos também são baseados nos mesmos atributos morfológicos, apesar de que apoio analítico é importante para definir os limites entre os atributos químicos e físicos dos solos em níveis hierárquicos mais baixos. Os cientistas de solos têm desenvolvido uma classificação de solos interpretativa para as restrições e potencialidades que o solo tem para a agricultura moderna. Os Xicrins classificam o solo para aquilo que é importante para a vida deles, uma vida harmônica e simbiótica com a natureza.

Cério (Ce) em ferricretes nodulares desenvolvidos em solos da formação adamantina

The observation of rare earth element (REE) accumulations, especially Ce, has led to an open discussion about the genesis of lateritic weathering systems. In the landscape of the northern State of São Paulo (Brazil), lateritic covers predominantly nodular exist in different topographic levels and, although not documented, constitute a feature that appears frequently on the slopes of Cretaceous sandstones of the Adamantina Formation (Ka). In order to obtain subsidies for the understanding of the genesis and the spatial distribution of these features, the objective of this research was to verify the presence and the form of occurrence of REE, in nodular ferricretes of an Eutric Plinthosol. Submicroscopic studies and microprobe analyses were performed on undeformed samples of Fe and Fe-Mn nodules. These were previously identified in morphological descriptions (macro and micro) of petroplinthic horizons located at the footslope of a toposequence. Cerium, iron and manganese were determined by X ray fluorescence, and iron and manganese were also determined by selective dissolution. Localized accumulations of Ce were found only into petroplinthic nodules with Mn coatings, probably deposited during the definitive lowering of the water table. Ce and Co accompanied the mobilization and segregation of the Mn oxides and hydroxides due of the ability of these Mn species in concentrating and controlling the distribution of certain metallic ions.

O estudo de concentrações anômalas de elementos traço em ferricretes, como cério (Ce) e outros elementos das terras raras, tem apoiado discussões a respeito da gênese dessas feições em diferentes ambientes do planeta. No município de Pindorama (SP), no sopé de uma vertente com domínio de Argissolos Vermelho-Amarelos abrúpticos derivados do arenito cretácico da Formação Adamantina, Grupo Bauru (Ka), ocorrem horizontes ferricretes, cujas características e gênese são escassamente conhecidas, embora sejam de ocorrência comum na região norte do Estado de São Paulo. Procurou-se verificar a presença de concentrações de elementos terras raras nesses solos e assim poder fornecer subsídios para o conhecimento da gênese desses ferricretes, estudando-se um Argissolo Vermelho-Amarelo Eutrófico abrúptico plíntico dessa vertente. Após descrição morfológica do perfil, determinou-se a granulometria, bem como as concentrações de Fe e Mn totais (fluorescência de raios X), extraídos por ataque sulfúrico, ditionito-citrato e por oxalato dos horizontes e dos nódulos encontrados. Em glébulas selecionadas, realizou-se estudos submicroscópicos e microanálises pontuais. Acumulações localizadas de Ce na forma de cerianita (CeO2) foram encontradas apenas nos nódulos petroplínticos que apresentam revestimentos de óxidos de Mn, situados na base do horizonte petroplíntico, e cuja gênese está associada ao rebaixamento definitivo do lençol freático. Cobalto (Co) também se concentra no interior dos nódulos ferro-manganíferos devido à ação co-precipitadora dos óxidos de manganês aí depositados.

Gênese de ferri-argilãs em horizontes B texturais de uma seqüência de solos sobre diabásio em Piracicaba (SP)

The formation of ferriargillans and densing processes were studied on a soil sequence over diabase situated in Piracicaba (SP) Brazil. Morphological, micromorphological, scanning electron microscopic and microanalytical studies were performed on samples taken from three trenches within the sequence. The presence of illuvial ferriargillans was observed mainly in the argillic B horizons and the saprolite, which filled the mamelonar, polyconcave and planar voids which led to their densing. Evidence of temporary hydromorphy suggested that this process would affect the stability of the iron oxide-clay interactions which would promote the mobilization and redistribution of iron and clay.

Numa sequência de solos sobre diabásio localizada no campus da USP em Piracicaba a formação de ferri-argilãs e os processos de adensamento foram estudados. Foram realizados estudos morfológicos, micromorfológicos, de microscopia eletrônica de varredura e microanálise em amostras retiradas de três trincheiras localizadas nesta sequência. A presença de ferri-argilãs de iluviação foi observada nos horizontes B textural e na alterita principalmente preenchendo a porosidade mamelonar, policôncava e fissural provocando o adensamento dos mesmos. Evidências de hidromorfia temporária sugeriram que este processo estaria provocando a desestabilização das ligações ferro-argila facilitando assim a mobilização e redistribuição do ferro e da argila.

Gênese de ferri-argilãs em horizontes B texturais de uma seqüência de solos sobre diabásio em Piracicaba (SP)

The formation of ferriargillans and densing processes were studied on a soil sequence over diabase situated in Piracicaba (SP) Brazil. Morphological, micromorphological, scanning electron microscopic and microanalytical studies were performed on samples taken from three trenches within the sequence. The presence of illuvial ferriargillans was observed mainly in the argillic B horizons and the saprolite, which filled the mamelonar, polyconcave and planar voids which led to their densing. Evidence of temporary hydromorphy suggested that this process would affect the stability of the iron oxide-clay interactions which would promote the mobilization and redistribution of iron and clay.

Numa sequência de solos sobre diabásio localizada no campus da USP em Piracicaba a formação de ferri-argilãs e os processos de adensamento foram estudados. Foram realizados estudos morfológicos, micromorfológicos, de microscopia eletrônica de varredura e microanálise em amostras retiradas de três trincheiras localizadas nesta sequência. A presença de ferri-argilãs de iluviação foi observada nos horizontes B textural e na alterita principalmente preenchendo a porosidade mamelonar, policôncava e fissural provocando o adensamento dos mesmos. Evidências de hidromorfia temporária sugeriram que este processo estaria provocando a desestabilização das ligações ferro-argila facilitando assim a mobilização e redistribuição do ferro e da argila.