Characterization and classification of two soils derived from basic rocks in Pernambuco State Coast, Northeast Brazil

Abstract

Geomorphic surfaces that present soils derived from basic rocks under warm and humid climate are unique scenarios for studying tropical soils. This paper aimed to characterize and classify two pedons derived from basalt at the Atlantic Forest Zone, Pernambuco State, Northeastern coast of Brazil. Two representative pedons (P1 and P2) were selected on a hillslope at the Cabo de Santo Agostinho municipality. Field macromorphological descriptions were carried out and soil horizon were sampled for physical, chemical, mineralogical and micromorphological characterization. The soils were classified, according to the Brazilian System of Soil Classification (and US Soil Taxonomy) as: "Latossolo Vermelho-Amarelo distroférrico argissólico" (Typic Hapludox) (P1) and "Nitossolo Vermelho distroférrico típico" (Rhodic Paleudult) (P2). Pedon 1 differs from Pedon 2 in some aspects. For instance, P1 presents more yellowish colors, absence of clay illuviation, more friable consistence and the prismatic structure undergoes transformation to angular and subangular blocks. Pedon 2 presents ferri-argilans and leptocutans which indicate that vertical and lateral illuviation of clay is an active process in their formation. These chemically poor and mineralogically uniform soils are a result of the high temperature and rainfall of the studied area.

Associations Between Attributes of Nitisols and the Climate of the Southern Coast of Pernambuco

“…It can be associated with some factor such as sandfraction low content, clay-content prevalence (Table 2), secondary mineralogy, and high the microporosity of these soils (CANER et al, 2014). The soil density values found here are lower than are those reported by Oliveira, Ferreira and Marques (2004) for soils in this region. These smaller values should be associated with a minor contribution of tertiary sandy quartz sediments and eolic sediments in the Nitisols studied here.…”

“…Despite the high iron input from basalt weathering, some of these Nitisols show a yellowish hue, due to, among other factors, a better soil moisture maintenance (OLIVEIRA; FERREIRA; MARQUES, 2004). Soil water regime is also associated with the yellowish coloration of Nitisols with high levels of Fe, as described in Kenya (QURESHI;NJIHIA, 1984) and in Australia (CSIRO, 1989).…”

“…Among the few pedological studies developed in Cabo volcano-sedimentary basin, the one of Oliveira, Ferreira and Marques (2004) should be highlighted. In view of the above, further research on the soil-environment relationship are necessary for this region.…”

Weathering of Rhyolites and Soil Formation in an Atlantic Forest Fragment in Northeastern Brazil

“…In addition, the variation of color, from red to yellow, suggests the destabilization of the hematite structure and its conversion to goethite through the xanthization process (Oliveira et al, 2004).…”

“…However, this hypothesis needs to be confirmed in future studies. The formation of goethite in these soils would be more recent and would be associated with changes in the pedogenetic environment that made it, for example, more favorable to the maintenance of moisture in the soils (Oliveira et al, 2004).…”