Data/hora: 23/05/2024 12:27:09

Biblioteca(s): | Embrapa Agrobiologia.
Data corrente: | 02/08/2007
Data da última atualização: | 18/03/2015
Autoria: | DENEF, K.; ZOTARELLI, L.; BODDEY, R. M.; SIX, J.
Afiliação: | Karolien Denef, Colorado State University; Lincoln Zotarelli; Robert Michael Boddey, Embrapa Agrobiologia; Johan Six, University of California Davis.
Título: | Microaggregate-associated carbon as a diagnostic fraction for management-induced changes in soil organic carbon in two oxisols.
Ano de publicação: | 2007
Fonte/Imprenta: | Soil Biology & Biochemistry, Oxford, v. 39, n. 5, p. 1165-1172, may 2007.
Idioma: | Inglês
Notas: | Parceria: Colorado State University, Ghent University, University of Florida, University of California
Conteúdo: | Carbon stabilization by macroaggregate-occluded microaggregates (Mm) has been proposed as a principal mechanism for long-term soil organic carbon (SOC) sequestration in temperate alternative agricultural and (af)forested systems. The aim of this study was to evaluate the importance of the Mm fraction for long-term C stabilization in Oxisols and to validate its diagnostic properties for total SOC changes upon changes in land use. Soil samples were taken from the 0?5 and 5?20 cm soil layers of native forest vegetation (NV), conventional tillage (CT) and no-tillage (NT) systems at an experimental site near Passo Fundo and one near Londrina in Southern Brazil. After aggregate-size separations by wet-sieving, macroaggregate-occluded water-stable microaggregates (53?250 ?m) (Mm) were isolated from large (>2000 ?m) and small (>250 ?m) macroaggregates. Particulate organic matter located inside the Mm (intra-Mm-POM) and the mineral fraction (< 53 ?m) associated with the Mm (mineral-Mm) were separated from the POM fraction located outside the Mm (inter-Mm-POM) by density flotation followed by mechanical dispersion. Sand-free Mm-C concentrations on a macroaggregate basis were generally greater under NV and NT compared to CT in the 0?5 cm depth at both sites. Our findings support the importance of Mm (especially the mineral-Mm fraction) as long-term C-stabilization sites in highly weathered tropical soils under sustainable agricultural and natural systems. At both sites, significant differences in total SOC stocks (g C m-2) among different land use systems were always accompanied by parallel Mm-C stock differences. Though total SOC did not differ among land use systems in the 0?20 cm depth at both sites, Mm-C stocks were greater under NT compared to the CT treatment in the 0?20 cm depth at the Londrina site. We concluded that in these highly weathered tropical soils the Mm-C fraction is a more responsive fraction to management changes than total SOC and represents a diagnostic fraction for present as well as potential total SOC changes upon land-use change.
Palavras-Chave: | Forest; Soil organic.
Thesagro: | Floresta; Solo Orgânico.
Categoria do assunto: | --
Registro original: | Embrapa Agrobiologia (CNPAB)
Exemplares: | CNPAB - (34258-1) - UPC - AP - -- -  -  - 0023232 - DIS