Abstract: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 … Show more
“…(Song et al, 2011). The absolute predominance of Hu in TOC has been reported in other studies on humic substances (Ebeling et al, 2011;Fontana et al, 2014). This high proportion of Hu in TOC fractions, especially in the 0.00-0.15 m layer, is related to the soluble nature of organic matter (FA and HA), which percolates the soil profile, while the Hu, because of its low solubility, is concentrated in surface layers (Benites et al, 2001).…”
Soil organic matter (SOM) fractions result from a variety of environmental processes, which affect incorporation and production rates, decomposition, alteration, and/or mineralization of organic matter. The aim of this study was to characterize SOM under the environments of rain forest, wooded campinarana (grasslands), arboreal-shrubby campinarana, grassy-woody campinarana, and pioneer plants of the Viruá National Park, in the north of the Brazilian Amazon. After chemical and physical characterization and soil classification, total organic carbon (TOC), total N, microbial activity, organic C from fulvic acid fractions (FA), humic acid (HA), and humin (Hu) were determined at two depths (0.00-0.15 and 0.15-0.30 m). The TOC was lower in the grassy-woody campinarana, arboreal-shrubby campinarana, and pioneer formation areas than in the rain forest. Higher values of microbial activity were related to forest ecosystems in soils without physical or water restrictions and with better fertility compared to the other areas. The Hu predominated in all vegetation types studied, especially in the surface layer, because of the more soluble nature of HA and FA; and the higher values of HA/FA ratios in wooded campinaranas indicate that these environments contribute to higher losses of humic substances through fulvic acid forms, due to better drainage conditions.
“…(Song et al, 2011). The absolute predominance of Hu in TOC has been reported in other studies on humic substances (Ebeling et al, 2011;Fontana et al, 2014). This high proportion of Hu in TOC fractions, especially in the 0.00-0.15 m layer, is related to the soluble nature of organic matter (FA and HA), which percolates the soil profile, while the Hu, because of its low solubility, is concentrated in surface layers (Benites et al, 2001).…”
Soil organic matter (SOM) fractions result from a variety of environmental processes, which affect incorporation and production rates, decomposition, alteration, and/or mineralization of organic matter. The aim of this study was to characterize SOM under the environments of rain forest, wooded campinarana (grasslands), arboreal-shrubby campinarana, grassy-woody campinarana, and pioneer plants of the Viruá National Park, in the north of the Brazilian Amazon. After chemical and physical characterization and soil classification, total organic carbon (TOC), total N, microbial activity, organic C from fulvic acid fractions (FA), humic acid (HA), and humin (Hu) were determined at two depths (0.00-0.15 and 0.15-0.30 m). The TOC was lower in the grassy-woody campinarana, arboreal-shrubby campinarana, and pioneer formation areas than in the rain forest. Higher values of microbial activity were related to forest ecosystems in soils without physical or water restrictions and with better fertility compared to the other areas. The Hu predominated in all vegetation types studied, especially in the surface layer, because of the more soluble nature of HA and FA; and the higher values of HA/FA ratios in wooded campinaranas indicate that these environments contribute to higher losses of humic substances through fulvic acid forms, due to better drainage conditions.
“…SOM deposition also occurs in function of other factors, such as the arrangement and abundance of the species present in the area, of phenology, of the succession stage beside the edaphoclimatic factors (CALDEIRA et al, 2008). Fontana et al (2014) quantified the content of organic carbon and humic fractions of surface horizons of soil profiles in three topolithosequences, in Pinheiral, Rio de Janeiro, and verified that soils located in areas of flat relief, top, and floodplain presented a higher content of organic carbon and humic fractions. These results are in agreement with those of the present study.…”
This study aimed to spatialize fractions of organic matter of soil in an agroforestry system (AFS) located in the Atlantic Forest in Brazil. Thirty-one soil samples were collected at depths of 0-10, 10-20 and 20-40 cm from georeferenced collection points. We determined total organic carbon (TOC), particulate carbon (COp), carbon associated with clay and silt (COam), carbon content in the fulvic acid fraction (C-FAF), humic acid fraction (C-HAF) and humin fraction (C-HUM). Semivariogram analysis and model adjustment were carried out using ArcGIS 10.2 software. Subsequently, spatial interpolation was performed using Ordinary Kriging. We observed spatial dependence for all variables except for TOC and COp at the 0-10 cm depth, which presented a pure nugget effect. It was possible to observe modifications in the distribution of humic substances in the study area. The results from this study are similar to those of other studies conducted in naive areas in the Atlantic Forest, demonstrating the benefits of using the agroforestry system. ESPACIALIZAÇÃO DAS FRAÇÕES DA MATÉRIA ORGÂNICA DO SOLO SOB UM SISTEMA AGROFLORESTAL, NA MATA ATLÂNTICA, BRASIL RESUMO: Este estudo teve como objetivo espacializar as frações da matéria orgânica do solo em um sistema agroflorestal (SAF) localizado na Mata Atlântica. Foram coletadas trinta e uma amostras de terra nas profundidades de 0-10, 10-20 e 20-40 cm, sendo cada ponto georeferenciado. Foram determinados os teores de carbono orgânico total (COT), carbono particulado (COp), carbono associado a argila e silte (COam), teor de carbono na fração de ácido fúlvico (C-FAF), fração de ácido húmico (C-FAH) e fração de humina (C-HUM). A análise dos semivariogramas e o ajuste do modelo foram realizados utilizando o software ArcGIS 10.2. Posteriormente foi realizada a interpolação espacial através de Krigagem Ordinária. Foi observada dependência espacial para todas as variáveis, com exceção do COT e COp na profundidade de 0-10 cm, visto que apresentaram efeito pepita puro. Foram verificadas modificações na distribuição das substâncias húmicas na área de estudo. Os resultados deste estudo são semelhantes aos de outros realizados em áreas de Mata Atlântica, demonstrando os benefícios do uso do sistema agroflorestal.
“…This may be related to the fact that FAF varies widely due to land use and may have a low spatial dependence (Melo et al, 2016), which reduces the adjustment quality of geographically weighted models such as GWR. Moreover, this fraction is more dynamic and can easily change with the change of land use (Fontana et al, 2014; Loss et al, 2014). The FAF is more related to soil management and coverage than to pedogenesis, whereas the humic acid fraction (HAF), a more stable fraction, seems to be influenced by the soil usage and by soil formation processes, thus varying with geology, type of soil, SAVI, and elevation, among other factors.…”
The soil organic matter (SOM) content and dynamic are related to vegetation cover, climate, relief, and geology; these factors have strong variation in space in the southeastern of Brazil. The objective of the study was to compare and evaluate performance of classical multiple linear regressions (MLR) and geographically weighted regression (GWR) models to predict soil organic carbon (SOC) and chemical fractions of organic matter in the Brazilian southeastern mountainous region. The regression models were fitted based on SOC and chemical fractions of SOM. The points ( = 89) were selected by pedologist's experience along transects and toposequences. The covariates were also selected using the empirical knowledge of pedologists when choosing variables that drive soil carbon content and its dynamics. Geology map, legacy soils map, terrain attributes derived from digital elevation model, and remote sensing indices derived from RapidEye sensor bands were used as covariates. In all MLR models (except for fulvic acid fraction [FAF]), the legacy soil map was selected as a covariate by the stepwise approach. The geology map was not selected as important covariate to predict FAF and humin (HUM). At least one variable derived from remote sensing was selected by the adjusted models. For the prediction of the SOC, HUM, and FAF, the GWR models had the highest performance. The MLR models extrapolated the results, especially for SOC. The relationships among SOC, SOM fractions, and environmental covariates were affected by local landscape variability, and the GWR model was better at modeling.
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