Phytoliths as paleopedological records of an histosol-cambisol-ferralsol sequence in Southeastern Brazil

Abstract

Soils can preserve numerous proxies that provide highly useful data on ancient climates or environments. In this study we hypothesized that analysis of the pedological cover combining soil phytolith assemblages and pedological, geochemical and isotopic analyses (δ13C and 14C) allows the reconstruction of events associated with the soil-landscape relationship at a toposequence scale. Soil profiles were collected from a toposequence in the upper montane environment of Mantiqueira Range, Espírito Santo State, in the Southeastern region of Brazil. Samples were collected by horizon/layer for pedological and geochemical analysis, and by depth, at 10-cm intervals, for phytolith and carbon (C) isotope (14C and δ13C) analysis. The soils are characterized by high organic matter contents, favored by the cold and humid climate, which is typical of the upland mountainous environments of Mantiqueira Range. The multiproxy approach provided important information about the paleoenvironmental conditions during the pedogenesis process, allowing to establish pedochronostratigraphic correlations, that improved the understanding of soil-landscape relationships in these environments. Soil-preserved phytolith assemblages, isotopic composition (δ13C) and organic matter dating (14C) indicated variations in the type of plant communities in the studied soils, suggesting climatic changes that influenced the soil formation and evolution. The soils experienced different pedogenesis conditions during the Late Holocene, and are, therefore, considered polygenetic soils. In summary, 3 environmental moments were identified by multiproxy analysis: Phase I (before −2330 cal. yr BP), hotter and drier than the current period; Phase II (from −2330 to −2063 cal. yr BP), colder and wetter than the current period; Phase III (after −2063 cal. yr BP), during which the current climate conditions were established.