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Title: Agregação e distribuição da matéria orgânica em solos de terra preta de índio da Amazônia Central.
Other Titles: Aggregation and Distribution of Soil Organic Matter in Terra Preta de Índio of Central Amazon
Keywords: Solos Arqueológicos;  Carbono;  Substâncias húmicas;  Amazonas.;  Amazonian Archeological Soils;  Carbon Stock;  Humic Substances;  Physical Fractionation of Soils.
Issue Date: 28-Feb-2007
Abstract: There is consensus that the black soils of Amazonian known as Terras Pretas de Índio (TPI) are extremely efficient in retaining great quantities of soil organic material (SOM), for long periods of time. However, various important characteristics of TPIs are little known: the distribution of organic matter between humic fractions, and between physical fractions, as well as any change in state of soil aggregation due to SOM of pyrogenic origin. The object of this work is to evaluate and compare the states of aggregation and the distributions of organic fractions in soils of anthropogenic (TPI) and non anthropogenic origin from the State of Amazonas, Brazil. This study was made using soil samples from five areas of the soil type classified as "argissolo" under Brazilian soil classification, two of them TPIs and three which exhibited no evidence of anthropogenic alteration. One of the TPIs (P02) had greater proportions of aggregates stable in water and the other TPI (P01) was little different, statistically, from this. The P02 soil aggregates had the greatest pondered mean diameter (PMD), geometric mean diameter (GMD), fraction with diameter > 2mm, and aggregate stability index (%ASI), indicating that a greater undisturbed time had led to this greater structuring. The TPIs had much higher total organic carbon contents (TOCs) than the other soils, a result which was corroborated by their determined carbon stocks. Chemical fractionation of organic matter also distinguished the TPIs from the other soils, the humin fraction being higher in the TPIs, especially P02. Physical fractionation also showed differences in the distribution of organic matter. The TPI soils had higher fractions of free light material and intra-aggregate light material, compared with the non anthopogenic soils, demonstrating that protection of organic matter was greater in the TPI soils. The carbon and nitrogen contents of the light fractions from the TPIs were greater than those of the comparison soils. The P02 soil exhibited the best environmental quality, principally because of its high SOM content.
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