Integrating remote and biogeochemical data: Analyzing the potential of gamma ray spectrometric data for mapping Cerrado vegetation types

Abstract

This study integrates remote and chemical data to investigate the potential use of potassium (K), thorium (Th), and uranium (U) radioisotopes for mapping Cerrado physiognomies. Because soil and vegetation are interdependent, the vegetation over the substrate reflects this relationship. Moreover, the physiognomic extracts that accompany the distribution of elements associated with the movement of this substrate in soil can be identified. Gamma ray spectrometric data have been used primarily for mineral exploration; however, the present study addresses the potential of these data for identifying vegetation. Using a multivariate analysis, it is possible to compare radioisotope data and their relationship to vegetation. The current study area is located in the northwest of Goiás, an area of conserved phytophysiognomic diversity that enables studies of the Cerrado vegetation. An initial cluster analysis defined five vegetation cover types: cerradão, cerrado rupestre, cerrado sensu stricto and campo limpo. Dendrograms demonstrated a positive relationship in the radioisotopes absorbed by certain plants; furthermore, their availability in the soil confirmed that it is possible to identify vegetation groups using the same absorption behavior. This soil-plant relationship divides groups that have the capacity for the absorption of radioisotopes with remote gamma-spectrometry data. Even considering that each species might react differently because of absorption and the bioavailability of elements in the soil, a relationship between absorption and remote data was identified. Furthermore, this relationship is reflected in the physiognomy, as confirmed by a multivariate discriminant analysis. The result of the analysis showed the potential of Th and K radioisotopes with regard to phytophysiognomic mapping.