bachelorThesis
Morfologia de microrrelevos Gilgai na região de Caicó - RN
Fecha
2022-07-21Registro en:
LIRA, Damião Isaac de. Morfologia de microrrelevos Gilgai na região de Caicó - RN. 2022. 50 f. Trabalho de Conclusão de Curso (Bacharelado em Geografia) - Departamento de Geografia, Centro de Ensino Superior do Seridó, Universidade Federal do Rio Grande do Norte, Caicó, 2022.
Autor
Lira, Damião Isaac de
Resumen
The Gilgai microrelief is characterized by an alternation of microhighs and
depressions on the soil surface, generally with a clayey texture with the presence of
smectitic minerals that are subject to expansion and contraction cycles according to the
variation of humidity, which is the driving force of its formation. They occur commonly
associated with lowlands with water seasonal accumulation in Vertisols. Due to the lack
of specific literature about Gilgais in Brazilian territory, studies aimed at understanding
it become necessary. Thus, the purpose of the present study is to present a morphometric
and granulometric characterization of Gilgai microreliefs, looking to understand the
distribution patterns of shapes and their granulometric fractions. Sampling was carried
out in the Caicó (RN) region, at two sampling sites with soils of different textural
compositions. The measurement of height, width, and distance between micromounds
was performed in 60 samples per sampling site, totaling 120 measurements. For
granulometric analysis, 24 samples were collected in each sampling site, which 12
correspond to the microhills and 12 to the depressions of the Gilgais. The data obtained
were submitted to statistical tests (ANOVA and Mann-Whitney) to identify significant
differences between sampling sites and between microrelief features. It was verified the
presence of distinct distributions of height, width and distance measurements between
micromounds for the study areas, as well as granulometric segregation patterns between
the Gilgais features, occurring variations in short distances. The characterization
indicated a silt and clay predominance in the micromounds and coarse fractions (pebble
and gravel) and sand in the depressions. Larger micromounds were found at the sampling
site with silty soils, recording the presence of Gilgai at an environment without the
necessary requirements for identifying vertic horizon (Vertissolos). In the clayey
sampling site, smaller micromounds and a higher density of individuals were observed.
The correlations between the micromounds data to the sand fraction suggest this attribute
as a limiting factor for vertical development, and the fine fraction (silt and clay) as an
influencer in higher micromounds height measurements. The analysis also suggests a
correlation between the distance between micromounds and the clay and silt fractions.
The present study discards the hypothesis of homogeneity between Gilgai microreliefs in
the studied region and identifies patterns of textural segregation on the surface.