Avaliação espectral de solos desenvolvidos em uma toposseqüência de diabásio e folhelho da região de Piracicaba, SP

Abstract

RESUMO -Este trabalho teve como objetivo estudar as alterações de solos desenvolvidos numa toposseqüência composta por diabásio e folhelho (Piracicaba, SP), e sua relação com os dados espectrais. Ocorrem na toposseqüência os solos Latossolo Roxo (LR), Latossolo Vermelho-Escuro (LE), Podzólico Vermelho-Escuro (PE), Litossolo (Li) e Aluvial (Al) dos quais foram coletadas amostras a três profundidades. Foram obtidos dados de reflectância bidirecional dessas amostras em laboratório com espectrorradiômetro na faixa de 350 a 2.500 nm. As alterações da reflectância das amostras de solo das camadas superficiais e subsuperficiais foram relacionadas às diferenças nos teores de matéria orgânica e argila, que foram parâmetros importantes na caracterização espectral dos solos. Ao longo da toposseqüência, ocorreram alterações nas características dos solos, principalmente nos teores de ferro e silte e na mineralogia, que influenciaram nos dados espectrais. Os solos desenvolvidos de diabásio apresentaram altos teores de ferro, o que refletiu em concavidades mais acentuadas nas curvas espectrais em 850 nm, e intensidades de reflectância menores, ao contrário dos solos desenvolvidos de folhelho. A reflectância do PE apresentou-se mais intensa do que o LR e LE. Os solos menos intemperizados Li e Al apresentaram intensidades de reflectância mais elevadas que os mais intemperizados, LR e LE.Termos para indexação: sensoriamento remoto, radiometria, reflectância, intemperismo. SPECTRAL REFLECTANCE OF SOILS DEVELOPED ON A TOPOSEQUENCE OF DIABASE AND SHALE IN PIRACICABA, SP, BRAZILABSTRACT -The objective of the present research was to study the spectral reflectance of soils developed on a toposequence composed by diabase and shale, in Piracicaba region, São Paulo State, Brazil. Soil samples were collected at three depths along a transection, as they were, Typic Haplorthox (TH), Rhodic Paleudult (RP), Lithic Distrochrept (L) and Typic Fluvent (TF). Bidirectional spectral reflectance factors of the soil samples were obtained by using a spectroradiometer from 350 to 2,500 nm in laboratory conditions. Spectral alterations observed between the surface and subsurface layers were related to their organic matter and clay content differences; and these soil parameters were important on the spectral characterization of the soils. Along the toposequence, alterations on the soil characteristics occurred, mainly on iron, silt and mineralogy, that influenced variations of the spectral data. Soils developed by diabase presented higher content of iron, that influenced the spectral curve, with a deeper concavity shape at 850 nm, and lower reflectance intensity, differently of the soils developed by shale. The spectral curves of RP presented higher reflectance intensities from TH. The less weathered soils, L and TF, presented higher reflectance intensity than the more weathered soil, TH.Index terms: remote sensing, meteorological instruments, weathering. INTRODUÇÃOUma nação moderna necessita dispor de informações adequadas a respeito dos complexos aspec...

Soil spectral library and its use in soil classification

“…The sub-surface horizons of low pedogenic development (Horizons B incipiente and C) show a greater intensity of reflectance than the surface horizons. This is explained by the greater amount of silt (Table 1) in these horizons, as was also shown by Demattê et al (2000). Furthermore, Grove et al (1992) reported that the presence of feldspars and 2:1 clay minerals contribute to the greater intensity of reflectance (Figure 4).…”

“…However, it was also the region that had soils with higher clay and lower Fe 2 O 3 concentrations, due to the predominant source materials being claystone and siltstone. The absence of opaque minerals enables the high intensity of reflectance, although the intensity of reflectance is medium-high in all profiles, indicating that higher levels of clay have a lower intensity of reflectance and those with higher levels of the silt have a higher intensity of reflectance, as shown by Demattê et al (2000) and Mathews et al (1973). The region has soil surface horizons with high organic matter content, resulting in a lower intensity of spectral reflectance and smoothing the concave feature of iron oxides (850-900 nm).…”

Uso de imagens de satélite na discriminação de solos desenvolvidos de basalto e arenito na região de Paraguaçu Paulista

“…Existe um número razoável de trabalhos que utilizam sensores terrestres para o estudo do comportamento espectral de solos tropicais (Demattê & Garcia, 1999;Vitorello & Galvão, 1999;Demattê et al, 2000a).…”

Magnetic and spectral signatures of Cerrado soils in the state of Goiás, Brazil

“…In the bands from 2,100 to 2,200 nm (Viscarra Rossel, 2011; Demattê et al, 2016), valleys that are characteristic of kaolinite (Kt) were observed in the spectral curves, and, in the band at 2,265 nm (Demattê et al, 2000;Pizarro et al, 2001), valleys that are typical of gibbsite (Gb). All the studied soils showed valleys in the spectral curves that are characteristic of Kt (Figure 1), but only some had valleys characteristic of Gb.…”