Estrutura e funcionamento de um campo de murundus da savana brasileira
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Data
2021-09-01
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Universidade Federal de Goiás
Resumo
The occurrence of non-anthropogenic earth-mounds dispersed in the landscape occurs in various parts of the world. The mounds fields of the Brazilian Savanna are examples of this category of intriguing natural phenomenon. They cover extensive areas on planning surfaces in the transition from hydromorphic environments to orthomorphic environments, forming a smoothly flat and continuous surface with earth-mounds organized in a standardized way. Often, these micro-reliefs are in framing humid areas that present themselves in the form of small isolated depressions, either associated with the drainage headwaters, or even along small water courses. The morphological characteristics of these mounds seem to be distributed in an orderly manner within the mounds field and associated with hydrological dynamics, however this theme is little explored in the literature. The genesis of these microreliefs is not yet consensual. The main hypotheses for the formation of earth-mounds are divided into: i) construction of earth-mounds by termite action, from the surface of the land; ii) lowering the surroundings of the earth-mounds, due to differential erosion processes; iii) mechanisms of differential erosion and standardization of vegetation. The present thesis aims to: i) present a bibliographic review with a survey of the main studies carried out in mounds fields in Brazil and around the world, as well as on technical-methodological procedures for wetland analysis, microtopography and survey of soil and water aimed at an integrated analysis of the landscape; ii) to analyze the morphological characteristics of the earth-mounds and the structural characteristics of a mounds field in the context of the evolution of the landscape of the Brazilian Savanna; iii) present the main physic physic-chemical hydrological flows and the processes occurring in the soil and in the water of a mounds field, associated with the distribution pattern of the earth-mounds. Unmanned aerial vehicle data (UAV) and orbital satellites were used. The spectral and morphometric data of the study area were manipulated in a Geographic Information System (GIS) environment and analyzed using descriptive, multivariate, and clustering statistical techniques to obtain the structural compartments of the study area. Field activities were also carried out to collect water and soil, as well as physical-chemical-mineralogical analysis of the soil and analysis of the physical-chemical dynamics of the water, in the structural compartments identified. The results show that: i) the geometric characteristics of the earth-mounds, individual (perimeter, area, volume, circularity index and height), or together (distance from the nearest neighbor and density), occurred in an orderly way of the study area. The distribution of the earth-mounds revealed a gradient of geometric values from the edge to the center of the mounds field; ii) the top altitude of the earth-mounds with greater volume has a relative agreement with the altitude of the plateau areas surrounding the study area, indicating that the earth-mounds are remnants of an old surface that connected the plateau to the top of the current earth-mounds; iii) the reflectance analysis of the targets revealed the existence of concentric ordered compartments in the study area. The compartments express the distribution of the characteristics of the surface of the mounds field, such as: the vegetation, the soil and the geometry of the earth mounds; iv) the processes occurring in the soil indicate that: the loss and precipitation of iron, the physical distribution, the accumulation of aluminum and organic matter occur in an orderly manner in the compartments; and v) the superficial and subsurface flows of water identified in the study area, converge from the edge to the center of the mounds field. These flows act in the distribution of the earth-mounds, in the physical-chemical characteristics of the soil and in the chemistry of the water inside the study area. These findings may contribute to the understanding of differential erosion as a source that forms the murundus fields of the Brazilian Savannah, as well as encourage the discovery of new knowledge about the functioning of these environments.
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Palavras-chave
Montes de terra , Áreas úmidas , Padrão espacial , SIG , VANT , Earth-mounds , Wetlands, , Spatial patterns , GIS , UAV
Citação
SALES, J. C. Estrutura e funcionamento de um campo de murundus da savana brasileira. 2021. 138 f. Tese (Doutorado em Geografia) - Universidade Federal de Goiás, Goiânia, 2021.