STATISTICAL MULTIVARIATE ANALYSIS APPLIED TO ENVIRONMENTAL CHARACTERIZATION OF SOIL IN SEMIARID REGION1

Antônio Italcy De Oliveira Júnior,Luiz Alberto Ribeiro Mendonça,Sávio De Brito Fontenele,Adriana Oliveira Araújo,Maria Gorethe De Sousa Lima Brito

doi:10.1590/1983-21252019v32n120rc

Abstract

ABSTRACT Soil is a dynamic and complex system that requires a considerable number of samples for analysis and research purposes. Using multivariate statistical methods, favorable conditions can be created by analyzing the samples, i.e., structural reduction and simplification of the data. The objective of this study was to use multivariate statistical analysis, including factorial analysis (FA) and hierarchical groupings, for the environmental characterization of soils in semiarid regions, considering anthropic (land use and occupation) and topographic aspects (altitude, moisture, granulometry, PR, and organic-matter content). As a case study, the São José Hydrographic Microbasin, which is located in the Cariri region of Ceará, was considered. An FA was performed using the principal component method, with normalized varimax rotation. In hierarchical grouping analysis, the “farthest neighbor” method was used as the hierarchical criterion for grouping, with the measure of dissimilarity given by the “square Euclidean distance.” The FA indicated that two factors explain 75.76% of the total data variance. In the analysis of hierarchical groupings, the samples were agglomerated in three groups with similar characteristics: one with samples collected in an area of the preserved forest and two with samples collected in areas with more anthropized soils. This indicates that the statistical tool used showed sensitivity to distinguish the most conserved soils and soils with different levels of anthropization.

Highlights

The use and occupation of soil, especially the modification of natural vegetation and increasing urbanization, may leave it unprotected, increasing its impermeability
The objective of this study is to use multivariate statistical analysis methods, including factorial analysis (FA) and hierarchical grouping methods, for the environmental characterization of semiarid soils, considering anthropic and topographic aspects, as well as physical and chemical features, in the São José Hydrographic Microbasin (SJHM), which is located in the Cariri region of Ceará
The points of Group 1 appear in Yellowish Red Latosol, Fluvisol Neosol, Litholic Neosol, and Yellowish Red clayey soils and Urbanization, in the SJHM valley, in an area between the exutory and the slope of the plateau, with altitudes varying between approximately 509 and 389 m. Both the FA and the hierarchical grouping analysis contributed to the environmental understanding of the SJHM soil characteristics

Summary

Introduction

The use and occupation of soil, especially the modification of natural vegetation and increasing urbanization, may leave it unprotected, increasing its impermeability. The soil becomes compacted and more susceptible to surface runoff and sediment loss, leading to environmental degradation. Soil degradation has a direct influence on environmental sustainability. In semiarid regions such as northeastern Brazil, whose main characteristics are shallow soils and marked water scarcity (ARAÚJO, 2011), the quality and quantity of water reserves are very sensitive to changes in the water basin soil characteristics. The characterization of the soils in these regions is critical for the preparation of management plans that contribute to socioeconomic and environmental sustainability

Objectives

Methods

Conclusion