Brazilian Latossolos (Ferralsols, Oxisols) from different biomes: a multiproxy study on the spatial variability of the most weathered tropical soils in South America

The Brazilian Latossolos (Ferralsols-WRB, Oxisols-Soil Taxonomy) are generally well-drained soils, strongly and deeply altered, rich in Al and Fe oxyhydroxides, nutrient-poor and morphologically uniform, due to long-term weathering and continuous leaching. Despite the occurrence in all Brazilian territory, little is known about the variability of basic attributes of Latossolos across the country. We hypothesize that the Brazilian Latossolos present a considerable variability in soil attributes that can be regionally manifested and traced according to the environmental characteristics of different Brazilian biomes. In this way, we compared a suite of soil attributes from Latossolos Amarelos, Latossolos Vermelho-Amarelos and Latossolos Vermelhos from the biomes Amazonia, Atlantic Forest, Cerrado, and Caatinga biomes, using robust legacy data produced by published soil surveys. The Latossolos Vermelhos represent the suborder with the greatest degree of weathering, exhibiting the highest contents of Fe and Al oxyhydroxides, clayey texture, greatest microaggregate development, pH and base saturation, and presenting the lowest contents of available P. Conversely, the Latossolos Amarelos exhibited the highest contents of kaolinite, silt, sand, and the highest soil consistency and Al saturation. The Latossolos Vermelho-Amarelos, in turn, presented intermediate characteristics, confirming that soil color is a key attribute for differentiating the pedogenetic development of Latossolos, regardless of the biome. With reference to the Brazilian biomes, the Latossolos of the Cerrado and Atlantic Forest presented the greatest weathering degree, evidenced by the lowest values of Ki, Kr, and silt/clay ratios, as well as other characteristics that reveal the great intensity of desilication, ferralitization, gibbsitization and pedalization. Despite the hot and wet equatorial climate and the general soil acidity in Amazonia, Amazonian Latossolos presented lower pedogenetic development than the Cerrado and Atlantic Forest soils, which are in close association with the sedimentary parent material, resilication by forest Si cycling, subdued topography and poor soil internal drainage. The Latossolos from the semi-arid Caatinga showed the lowest weathering and pedogenesis degrees, and represent relict soils from past wetter climates, preserved in the only Brazilian semi-arid biome.