Banca de DEFESA: LARISSA GONDIM PASCOAL DE OLIVEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LARISSA GONDIM PASCOAL DE OLIVEIRA
DATE: 27/02/2026
TIME: 09:00
LOCAL: Auditório do Programa de Pós-graduação em Ciência do Solo
TITLE:

Pedogenesis of rubric soils in a “Mar de Morros” environment in Pernambuco, Brazil

KEY WORDS:

Red soils, rubification, iron oxides, micronutrients

PAGES: 104
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Gênese, Morfologia e Classificação dos Solos
SUMMARY:

Tropical soils represent one of the most complex and dynamic ecosystems on the planet, due to their formation under conditions of extreme weathering and pedogenic processes such as rubification and xanthization, which result in physical and chemical characteristics that impact agricultural management practices. Therefore, the overall objective of this study is to investigate the genesis of the rubric character in soils of the 'Sea of Hills' (Mar de Morros) environment in the Zona da Mata of Pernambuco, aiming to understand its relationship with mineralogy, climate change, soil fertility, and its taxonomic significance. The study area comprises Latosols (Oxisols) located in the Zona da Mata region of Pernambuco. Chemical and physical soil parameters were evaluated, along with mineralogical composition via X-ray diffraction (XRD), selective iron extraction, total chemical composition by X-ray fluorescence (XRF), micronutrients, lithological discontinuity, micromorphology, and statistical analyses. The four soil profiles exhibited strong morphological and pedogenic similarity, featuring deep profiles with colors ranging from yellowish to reddish. Chemically, the soils showed strong acidity, low exchangeable base content, and high potential acidity and exchangeable Al3+. The Cation Exchange Capacity (CEC) was low, consistent with highly weathered soils dominated by kaolinite and Fe/Al oxides, with low phosphorus availability and high fixation controlled by the soils' oxidic mineralogy. Organic carbon contents were higher at the surface, gradually decreasing with depth. Selective extraction of iron and aluminum revealed a higher concentration of crystalline oxides in the red horizons and a higher content of low-crystallinity oxides at the surface, influenced by organic matter. Micronutrients were influenced by chemical characteristics primarily related to soil fertility. Mineralogical attributes confirmed the relationship between iron oxides and physical, chemical, and morphological features. Micromorphology revealed pedofeatures indicating that Fe mobility is mainly governed by pore hydrology and preferential flow. Multivariate analysis confirmed the separation of soil attributes related to the red and yellow horizons. The soils studied in the Mar de Morros environment of the Pernambuco Zona da Mata were classified as Latossolos Amarelos Distróficos (Dystric Yellow Latosols) according to the SiBCS, with distinctions at the fourth categorical level related to the presence of the rubric character, and as Ferralsols according to the WRB system. The profiles feature a thick latosolic (oxico) B horizon, low clay activity, a reduced silt/clay ratio, and a predominance of kaolinite and crystalline iron oxides, confirming an advanced weathering stage and intense desilication. It was observed that the rubric character, as defined by the SiBCS, applies to soils showing subsoil reddening, characterized by a moist color with a hue redder than 5YR and a value $\le 4$. However, the current definition of this character presents operational limitations, especially regarding the 'value' criterion, necessitating a revision of the rubric character’s wording to ensure greater coherence between taxonomic classification and the chromatic variability observed in highly weathered soils. Overall, chemical, physical, mineralogical, and micromorphological evidence indicates that the rubric character results from the interaction between parent material, weathering intensity, desilication, and the dynamics of iron forms.

COMMITTEE MEMBERS:
Presidente - VALDOMIRO SEVERINO DE SOUZA JUNIOR
Externo à Instituição - JOSÉ COELHO DE ARAÚJO FILHO
Externo à Instituição - MARCELO METRI CORREA