RESUMO -O objetivo deste trabalho foi quantificar o carbono orgânico e as frações húmicas de horizontes superficiais de perfis de solo em três topolitossequências no ambiente de Mar de Morros, no município de Pinheiral, RJ. Foram selecionadas as topolitossequências: T1 (basalto), T2 (muscovita-biotita-gnaisse) e T3 (gabro). Os horizontes superficiais de 14 perfis de solo, sob cobertura de pastagem (T1 e T3) e pastagem mista não manejada e leguminosa (pasto sujo/capoeira) (T2), foram descritos e coletados para análises químicas, físicas e do teor de carbono nas frações húmicas. Os teores de carbono orgânico variaram de acordo com o material de origem e decrescem na seguinte ordem: T3 > T1 > T2. Os teores de carbono orgânico aumentam do topo para a várzea na T1, ocorrendo o inverso na T3 e sem um padrão definido na T2. A fração humina predominou em todos os perfis de solo das topolitossequências e foi seguida pela fração ácidos fúlvicos na T1 e de forma equitativa entre as frações ácidos fúlvicos e ácidos húmicos na T2 e T3. Considerando o ambiente similar em termos da vegetação original e o uso agrícola, as mudanças no carbono do solo e nas frações húmicas podem refletir as interações com os componentes minerais e processos pedogenéticos, influenciados pelo material de origem e o relevo. Palavras-chave:Pedogênese. Frações húmicas. Atributos edáficos.ABSTRACT -The aim of this study was to quantify the organic carbon and humic fractions of the surface horizons of soil profiles in three topolito-sequences from the Mar de Morros environment in the town of Pinheiral, in the state of Rio de Janeiro, Brazil. The topolito-sequences selected were: T1 (basalt), T2 (muscovite-biotite-gneiss), and T3 (gabbro). The surface horizons of 14 soil profiles under pasture (T1 and T3), and unmanaged mixed pasture and leguminous plants (shrub/vegetation) (T2), were marked out and collected for chemical and physical analysis, and evaluation of the carbon content of the humic fractions. The organic-carbon content varied according to the source material, decreasing in the order: T3 > T1 > T2. The organic-carbon content increased from the highest point to the lowlands in T1, with the opposite occurring in T3, and no definite pattern being seen in T2. The humin fraction predominated in all the topolito-sequence soil profiles, being followed by the fulvic acid fraction in T1, and by the fulvic and humic acid fractions equally in T2 and T3. Considering the environments as being similar in terms of original vegetation and agricultural use, changes in the carbon and humic fractions of the soil may reflect interactions with mineral components and pedogenic processes, influenced by the original material and the landscape.
Different parent materials participate in the formation of soils in the hilly landscape of "Mar de Morros" in the Atlantic Forest environment. Those derived from mafic igneous rock (gabbro) frequently show erosion problems because of land use, which is aggravated by the mountainous relief and soil attributes. This study evaluated the main pedogenic processes of soils formed from mafic igneous rock (gabbro) in a toposequence in Pinheiral (RJ) by characterizing physical, chemical, mineralogical and micromorphological attributes. The profiles are located at different sections in the toposequence: summit (P1), shoulder (P2), backslope (P3) and footslope (P4).They were classified according to the Brazilian System of Soil Classification (SiBCS) and correlated to Soil Taxonomy. The soil morphology of profiles P2, P3 and P4 is expressed by a brownish-red color, blocky structure with high to moderate development, clay films and clay loam to clay texture, with a textural B horizon. P1 shows less development, with a shallow profile and the sequence of horizons A-C-Cr. The soils have a slightly low degree of weathering, identified by the presence of pyroxenes and feldspars in the sand fraction and montorillonite in the clay fraction; the sum of bases is from 15 to 24 cmol c kg -1 ; and cation exchange capacity (CEC) is from 12 to 22 cmol c kg -1. A significant presence of clay skins was observed in the field and was confirmed by thin section analysis, which showed features such as argillans, ferriargillans and iron nodules. The soil profile at the summit (P1) was classified as Neossolo Regolítico Órtico (Typic Udorthents), and the other profiles as Chernossolo Argilúvicos Órticos (Typic Argiudolls).
The variety of soils in the State of Acre is wide and their chemical profiles are still not fully understood. The nature of the material of origin of these soils is indicated by the high aluminium (Al) content, commonly associated with high calcium (Ca) and magnesium (Mg) contents. The study objective was to use different methods to quantify Al in soils from toposequences formed from material of a sedimentary nature originating from the Solimões Formation, in Acre, Brazil. Trenches were opened at three distinct points in the landscape: shoulder, backslope and footslope positions. Soil samples were collected for physical, chemical, mineralogical analyses. The Al content was quantified using different methods. High Al contents were found in most of these horizons, associated with high Ca and Mg levels, representing the predominant cations in the sum of exchangeable bases. The mineralogy indicates that the soils are still in a low weathering phase, with the presence of significant quantities of 2:1 minerals. Similar Al contents were determined by the methods of NaOH titration, xylenol orange spectrometry and inductively coupled plasma optical emission spectrometry. However, no consistent data were obtained by the pyrocatechol violet method. Extraction with KCl overestimated the exchangeable Al content due to its ability to extract the non-exchangeable Al present in the smectite interlayers. It was observed that high Al contents are related to the instability of the hydroxyl-Al smectite interlayers.
ResumoEste trabalho teve o objetivo de avaliar os teores do fósforo remanescente e correlacioná-los com os atributos químicos, físicos e mineralógicos em horizontes de solos formados a partir de diferentes materiais de origem em três topossequências no município de Pinheiral, RJ. Foram descritos e coletadas amostras de horizontes superficiais (A) e subsuperficiais (B+C) de 14 perfis de solos sob pastagem em três topossequências (T1, T2 e T3), sendo T1 sob basalto, T2 sob muscovita-biotita-gnaisse e T3 sob gabro. Foram realizadas as análises químicas e físicas de rotina, bem como Al e Fe pelo ataque sulfúrico e fluorescência de raios X, Fed (ditionito-citrato-bicarbonato de sódio) e Feo (oxalato ácido de amônio), superfície específica da argila (SE), mineralogia da argila e óxido, e fósforo remanescente (Prem). Variações dos teores de Prem foram observadas, as quais relacionadas à natureza do material de origem, posição na paisagem e grau de desenvolvimento dos solos, o que pode ser analisado pelas variações dos atributos químicos, físicos e mineralógicos. Os teores de Prem seguiram a ordem T2 > T1 = T3 no horizonte A e da T1 > T3 e T2 ~ T1 e T3 nos horizontes B+C. Foram observadas correlações negativas entre os teores de Prem com Fe 2 O 3 (raios X) > Fed > SE > Feo nos horizontes A e com Fe 2 O 3 (ataque sulfúrico) > Fe 2 O 3 (raios X) > argila > Fed > Feo nos horizontes B+C. As análises de componentes principais e agrupamento hierárquico contribuíram para avaliação conjunta dos dados, evidenciando os atributos relacionados e as similaridades entre os solos. Palavras-chave: Adsorção de fosfato, horizontes superficiais e subsuperficiais, atributos dos solos AbstractThis work aimed to evaluate the remaining phosphorus tenors and correlate with the chemical, physical and mineralogical attributes in soils horizons developed from different parent materials in three topossequences in the municipality of Pinheiral, RJ. Were described and collected samples of surface 1 Parte da Tese de Doutorado do terceiro autor apresentada ao Curso de Pós-Graduação em Agronomia,
RESUMOO objetivo deste trabalho foi quantificar os diferentes compartimentos da matéria orgânica de solos sob floresta no estado do Acre. Perfis de solo foram descritos e coletados nos terços superior, terço médio e terço inferior da paisagem localizados nos municípios de Sena Madureira, Manoel Urbano e Feijó, no estado do Acre. Os solos foram caracterizados quanto à composição química, física, frações húmicas e frações oxidáveis. Os teores de carbono orgânico estão concentrados nos horizontes superficiais dos solos, destacados pelo decréscimo abrupto em relação aos demais horizontes. Os teores da argila e de cátions atuam de forma mais efetiva na dinâmica da matéria orgânica em detrimento à posição na paisagem e classe de solo. As análises multivariadas indicam maior similaridade entre os pontos de Sena Madureira (T1) e de Feijó (T3), exceto o ponto do terço superior de Feijó, que é semelhante ao Manoel Urbano (T2).Palavras-chave: atributos dos solos, frações orgânicas, horizonte superficial. Organic Matter Compartments from under Forest Soils in the Acre State ABSTRACTThis study aimed to quantify the different compartments of organic matter from under forest soils in Acre state. Soil profiles were described and sampled on shoulder, backslope and footslope landscape positions located in the counties of Sena Madureira, Manoel Urbano and Feijó, Acre state. Soils were characterized by chemically and physically attribute, humic and oxidizable fractions. The organic carbon is concentrated in the superficial soil horizons, highlighted by the sharp decrease in relation to other horizons. The clay and cations act more effectively on organic matter dynamics than the landscape position and soil class. Multivariate analyzes indicate high similarity between the sites of Sena Madureira (T1) and Feijó (T3), except the shoulder site from Feijó, which is similar to Manoel Urbano (T2).
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