Variations of dissolved organic carbon and soil physical properties under different land uses in central amazonia

Abstract

The purpose of this study was to assess the relationship between dissolved organic carbon (DOC) and physics properties of soil under different land use systems in central Amazonia. The DOC concentrations of primary forest soil were measured in three topographical positions, and in areas of pasture, secondary forest and an agroforestry system (AFs) down to a depth of 2 m. The soil solution was collected and analyzed for the organic C phase during a hydrological cycle. The average dissolved organic carbon (DOC) concentrations followed the sequence: AFs > secondary forest > forest (plateau) > pasture (dry and rainy-dry period), except in the rainy and dry-rainy period, DOC concentration of the pasture soil was equal to or higher than that of other environments in certain layers. Results indicated the capacity of the AFs and secondary forest to recover organic C and/or make it available in soil solution. These are the recommended land use forms to maintain carbon in the terrestrial environment. The DOC was influenced by time, space and depth and decreased with depth. The soil structure, represented by soil aggregation, total organic carbon (TOC) and porosity, exerted great influence on the DOC concentrations in the soil layers and, together with the more labile soil organic matter, determined carbon maintenance in the soil solution. The DOC concentrations measured under vegetation covers and land uses indicate the importance of adequate soil managements to maintain carbon in the soil ecosystem.