Pedogenesis of high-mountain soils from Serra da Mantiqueira, Brazil

Resumo

In the Serra da Mantiqueira region the pedogenetic studies contribute to both the understanding of past events
and supporting the conservation of natural resources. This study aimed to characterize the soils from the Minas Gerais highmountains region to evaluate the influence of paleoenvironmental conditions on pedogenesis. Five profiles were selected and
characterized for morphological, physical and chemical properties. Isotopic analyses of 13C were performed in soil samples
collected at depths of 10, 20, 30, 40, 50, 60, 80 and 100 cm; except in P2, which was collected up to 60 cm deep. Erratic
distribution of the particle-size fractions and C contents highlight the sedimentary nature of the profiles, resulting from the
erosive action favored by the relief. High organic C content in subsurface and its accumulation in the surface were observed
in the profi les, which suggests the occurrence of the melanization process. In the profi les P2, P4 and P5 (Cambissolos/ Cambisols)
the brownish color indicates the xanthization process, while in P1 (Argissolo/ Lixisol), is highlighted the process of eluviation
and illuviation resulting in the increase of clay in subsurface and presence of clay films. In P3 (Latossolo/ Ferralsol), the low
values of sum of bases, silica removal and SiO2
/Al2O3
ratio (ki index) values below 1.0 point to the advanced weathering and
the allitization process. The variation in the isotopic signature of δ
13C indicates a drier past condition, with mixed vegetation, with
gradual change of vegetation with predominant C3
photosynthetic pathway. In P1 and P4, the decrease in the contents of δ
13C in
surface results from anthropic action.