Carbon distribution in particle size fractions of soil organic matter under primary forest and agroforestry systems on two soil types in western Amazonia
Katell
Uguen, INPA, katell@inpa.gov.br
(Presenting)
Thierry
Desjardin, IRD/UFRA, desjardi@ufra.edu.br
Sonia
Sena
Alfaia, INPA, sonia@inpa.gov.br
Flavio
Jesus
Luizão, INPA, fluizao@inpa.gov.br
The aim of the work was to evaluate the carbon distribution in particle size fractions of soil organic matter under primary forest and 12-years old agroforestry systems (AFS) in order to understand the carbon storage mechanisms as soil organic matter (SOM). The study was carried out in six smallholder properties of the RECA Project (Reflorestamento Econômico Consorciado e Adensado) in western Amazonia. Two soil types were compared: Red Oxisol (Latossolo Vermelho) and Yellow-Red Inceptsol (Cambissolo). Soil samples were taken in 10- cm layers up to 50 cm deep, but the particle size fractionation was only performed in the 0-10 cm layer. After dispersing the soil with resin, SOM was sorted into five particle-size fractions: coarse sand (200-2000 mm), fine sand (50-200 mm), coarse silt (20-50 mm), fine silt (2-20 mm), and, clay (0-2 mm). Red Oxisols are clayer (> 60% of clay) and present higher carbon concentrations in the upper soil layer (23.8 mgC. g-1) than the Inceptsols (36% of clay and 13.8 mgC.g-1). The coarse sand fraction had the highest carbon concentrations for both soil types; however, about 60% of total soil carbon was in the clay fraction. No significant differences have been observed in carbon concentrations of the different fractions between natural forest and agroforestry system. Nevertheless, the study on carbon quality, such as the C/N ratio, could reveal differences in SOM between the two land use systems.
Submetido por Katell Uguen em 17-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)