Gênese do solos com horizontes escurecidos no entorno de lagoas salinas desmatadas, Pantanal da Nhecolândia (MS)
Data
2019
Autores
Bonomo, Bruna Castanho Mambre 
Orientadores
Furquim, Sheila Aparecida Correia
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
A sub-região da Nhecolândia, localizada na porção centro-sul do Pantanal, é
caracterizada pela presença de lagoas salinas circundadas por solos halomórficos (com
elevadas concentrações de sais solúveis, sódio ou ambos). Os solos nos arredores dessas
lagoas apresentam um padrão morfológico que vem se alterando com a retirada da
vegetação de cordilheira que as circundam, com o surgimento de um horizonte
escurecido sobre um horizonte esverdeado e pouco permeável, próximo ao fundo da
depressão que abriga a lagoa salina. Nesse estudo, foram analisadas morfológica, física
e quimicamente os solos de três lagoas salinas parcialmente desmatadas, a fim de
entender os processos relacionados a gênese dos solos associados às estas lagoas
salinas. O trabalho baseou-se na hipótese de que, com o desmatamento do complexo
cordilheira-lagoa salina, há a migração da matéria orgânica (MO) em subsuperfície e
seu acúmulo sobre horizontes menos permeáveis, sendo este o processo responsável
pelo surgimento dos horizontes escurecidos. Para tal, foi realizado o levantamento de
solos em campo, análises granulométricas e químicas de rotina. Para quantificação da
matéria orgânica, foi realizada a análise do carbono orgânico e suas frações (ácidos
húmicos, fúlvicos e humina). A partir dos resultados analíticos, mostrou-se que o
horizonte escurecido apresentava pequenas quantidades de MO, dominada
principalmente por ácidos húmicos, sendo tais quantidades não suficientes para
promover o completo escurecimento do solo. Desta forma, partiu-se para novos
procedimentos de investigação, especialmente Microscopia Eletrônica de Varredura
(MEV) acoplada a microssonda (EDS) e Espectrometria de Emissão Óptica com Plasma
(ICP-OES), procurando-se descobrir as quantidades de manganês (Mn) nos solos, um
outro elemento químico responsável pelas colorações escuras. Com os dados obtidos
confirmou-se que a morfologia das salinas desmatadas é bastante semelhante, onde há a
presença de horizontes arenosos, horizontes escurecidos e horizontes esverdeados,
sendo essa morfologia diferente do padrão encontrado nas salinas preservadas. A
quantidade de MO encontrada foi pequena e há altas quantidades de Mn total nos
horizontes escurecidos, revelando que, juntamente com a MO, a dinâmica do Mn na
área está contribuindo para a gênese do horizonte escurecido. Mesmo em baixas
quantidades, a matéria orgânica é capaz de complexar quase que totalmente o Mn que
estiver disponível e, assim, formar zonas ou horizontes escurecidos.
The Nhecolândia sub-region, located in the central Pantanal region, is characterized by the presence of saline lake surrounded by halomorphic soils (with high concentrations of soluble salts, sodium or both). The soils around these lakes have a morphological pattern that is changing due to the deforestation of mountain vegetation that surrounds the lakes, with the appearance of a darkened horizon above a greenish and poorly permeable horizon, near the bottom of the depression that shelters the saline lake. In this study, the soils of three partially deforested saline lakes were morphological, physical and chemically analyzed, aiming to understand the processes related to the genesis of soils associated to these saline lakes. The study was based on the hypothesis that the deforestation on the saline lake-mountain range complex leads to subsurface organic matter migration and its accumulation above poorly permeable horizons, and that is the reason to the formation of darkened horizons. For this, there were made field survey, particle size and chemical periodic soil analysis. To quantify the organic matter, an analysis of organic carbon and its fractions (humic, fulvic and humic acids) was made. Based on the analytical results, it is shown that the darkened horizon had low OM amount, mostly consisted by humic acids, not enough to cause the complete darkening of the soil. Thus, new research procedures were made, especially Scanning Electron Microscopy (SEM) coupled to microprobe (EDS) and Plasma Emission Optical Spectroscopy (ICP-OES), intending to find out the manganese (Mn) amount in the soils, another chemical element responsible for the dark colors. With the analytical results, it’s been confirmed that the deforested saline lakes’ morphology is very similar, with the presence of sandy horizons, darkened horizons and greenish horizons. This morphology is different from the one founded in the preserved saline lake. There were detected low amounts of OM and high amounts of total Mn in the darkened horizons, revealing that, along with OM, the Mn dynamics in the area is contributing to the genesis of the darkened horizon. Even at low amounts, the organic matter is able to complex almost all the available Mn and thus form darkened areas or horizons.
The Nhecolândia sub-region, located in the central Pantanal region, is characterized by the presence of saline lake surrounded by halomorphic soils (with high concentrations of soluble salts, sodium or both). The soils around these lakes have a morphological pattern that is changing due to the deforestation of mountain vegetation that surrounds the lakes, with the appearance of a darkened horizon above a greenish and poorly permeable horizon, near the bottom of the depression that shelters the saline lake. In this study, the soils of three partially deforested saline lakes were morphological, physical and chemically analyzed, aiming to understand the processes related to the genesis of soils associated to these saline lakes. The study was based on the hypothesis that the deforestation on the saline lake-mountain range complex leads to subsurface organic matter migration and its accumulation above poorly permeable horizons, and that is the reason to the formation of darkened horizons. For this, there were made field survey, particle size and chemical periodic soil analysis. To quantify the organic matter, an analysis of organic carbon and its fractions (humic, fulvic and humic acids) was made. Based on the analytical results, it is shown that the darkened horizon had low OM amount, mostly consisted by humic acids, not enough to cause the complete darkening of the soil. Thus, new research procedures were made, especially Scanning Electron Microscopy (SEM) coupled to microprobe (EDS) and Plasma Emission Optical Spectroscopy (ICP-OES), intending to find out the manganese (Mn) amount in the soils, another chemical element responsible for the dark colors. With the analytical results, it’s been confirmed that the deforested saline lakes’ morphology is very similar, with the presence of sandy horizons, darkened horizons and greenish horizons. This morphology is different from the one founded in the preserved saline lake. There were detected low amounts of OM and high amounts of total Mn in the darkened horizons, revealing that, along with OM, the Mn dynamics in the area is contributing to the genesis of the darkened horizon. Even at low amounts, the organic matter is able to complex almost all the available Mn and thus form darkened areas or horizons.