Pedological characterization and carbon stocks in soils from the Solimões geological formation, South-Western Amazon

Abstract

Abstract: This paper aimed to carry out the characterization of attributes, the taxonomic classification and estimate the carbon stocks of soils in the domain of the Solimões (Brazilian river) formation, in the municipality of Marechal Thaumaturgo, Acre – (Brazilian State). Nine soil profiles were described and samples were collected from superficial and subsurface pedogenetic horizons for physicochemical analyses. The taxonomic classification was developed according to the Brazilian Soil Classification System. Among the classified soils the Haplic Vertisols, Haplic Cambisols and Fluvic Neossolos stand out. Amid the morphological attributes, the dark colors in the superficial horizons stand out, with a predominance of hue 7.5 YR; values ranging between 3 and 5; and chroma from 1 to 2. The exchangeable bases, generally, were high, with emphasis on the contents of Ca+2 (2.0 cmol_c.dm^-3 to 38.0 cmol_c.dm^-3) and Mg²⁺ (0.90 cmol_c.dm^-3 to 10.7 cmol_c.dm^-3), respectively. The determined eutrophic character is related to the nature of the source material and the small role of pedogenesis. Carbon stocks ranged from 27.7 Mg.ha^-1 to 69.7 Mg.ha^-1. The occurrence of soils with high activity clay (Ta soils), the clay fraction in greater proportions, as well as eutrophic soils and soils with drainage restriction contributed to greater carbon storage of the soil in relation to other Amazonian states.