Spatial Variability Of SOIL Organic Carbon Stocks In The Brazilian Amazon Forest.

Spatial estimates of tropical soil carbon stocks (CS) are crucial to understanding the role of tropical soil organic carbon in the global carbon cycle. CS is spatially highly variable. In traditional approaches, CS have been derived from estimates for single or very few profiles and spatially linked to existing units of soil or vegetation maps. However, many existing soil profile data are incomplete. The objective of this study was to evaluate CS in Urucu, State of Amazonas, Brazil. And then, use the digital soil mapping approach to predict the spatial distribution of CS in Urucu. This relies on a soil inference model based on spatially referenced environmental layers of topographic and pedologicals attributes. We sampled 96 soil pedons and analyzed them for soil organic carbon. CS were calculated at depths of 0-30 cm and 0-100 cm. Geoestatistic analysis was a modeling tool to the CS spatial variability map for 0-30 cm and 0-100 cm depth interval. Besides, an interpolation by ordinary Kriging and co-Kriging using topographic wetness index (TWI) approach provided CS spatial variability map of high spatial resolution in the top 1 meter of soils. CS spatial variability was significative correlated with clay content and TWI. In the topsoil (0-30 cm) wasn’t observed CS spatial dependence. CS calculated until 100 cm depth ranged between 3,7 kg C m^-2 and 7,9 kg C m^-2, with highest stocks on high slope position. Mean CS was 6,3 kg C m^-2 and, about 49% of SOC was held in the top 0-30 cm depth, which is the most susceptible to changes upon land use and deforestation.