Raul Shiso Toma

Savanna woodland soil micromorphology related to water retention

The limiting factors of the Brazilian savanna physical environment have been largely discussed. Soil morphology is fundamental to understand the behavior of soil water flow, soil physical properties and soil-landscape relationships. The aim of this study is to relate soil micro and macromorphologic attributes to soil water retention on a toposequence under native savanna woodland (cerradao) in a permanent plot of 320 m ´ 320 m installed in Assis, SP, Brazil. Samples collected at five points within the toposequence were used to determine the soil macroporosity by means of image analyses, estimated total porosity, chemical analysis, particle size distribution analysis and soil water retention. From the summit down to the footslope, the soils were classified as Rhodic Haplustox, Typic Haplustox and Epiaquic Haplustult, presenting a gradual color transition and a sandy loam texture. In the surface horizons, the higher organic matter content and the high total macroporosity determined a lower soil bulk density and lower water retention. In the Oxisols, the high soil macroporosity results from the packing of microaggregates in the oxic horizon. In the Ultisol, the lower total porosity in the deeper horizons resulted in a higher water retention and an imperfect water drainage. The water retention conditions on the slope influenced the morphological differences in soil color and structure. The low water retention on the surface and oxic horizons, conditioned by the high total macroporosity, is one of the factors that may define the vegetal pattern of the savanna woodland within the permanent plot.

Hydro-physical characterization of soils under tropical semi-deciduous forest

The study of the hydro-physical behavior in soils using toposequences is of great importance for better understanding the soil, water and vegetation relationships. This study aims to assess the hydro-physical and morphological characterization of soil from a toposequence in Galia, state of Sao Paulo, Brazil). The plot covers an area of 10.24 ha (320 × 320 m), located in a semi-deciduous seasonal forest. Based on ultra-detailed soil and topographic maps of the area, a representative transect from the soil in the plot was chosen. Five profiles were opened for the morphological description of the soil horizons, and hydro-physical and micromorphological analyses were performed to characterize the soil. Arenic Haplustult, Arenic Haplustalf and Aquertic Haplustalf were the soil types observed in the plot. The superficial horizons had lower density and greater hydraulic conductivity, porosity and water retention in lower tensions than the deeper horizons. In the sub-superficial horizons, greater water retention at higher tensions and lower hydraulic conductivity were observed, due to structure type and greater clay content. The differences observed in the water retention curves between the sandy E and the clay B horizons were mainly due to the size distribution, shape and type of soil pores.

SOIL FUNCTIONING IN A TOPOSEQUENCE UNDER RAINFOREST IN SÃO PAULO, BRAZIL

O estudo da dinâmica da agua no solo utilizando topossequencias e de grande importância para melhor compreender as relacoes solo-agua-vegetacao. Objetivou-se, com este trabalho, caracterizar fisico, hidrica e morfologicamente os solos da mata do Parque Estadual de Carlos Botelho. A parcela abrange uma area de 10,24 ha (320 x 320 m), localizada sob Floresta Ombrofila Densa (Mata Atlântica de Encosta). Com base nos mapas de solos ultradetalhados e mapas planialtimetricos dessa area, escolheu-se uma transecao representativa dos solos da parcela; nessa, foram abertas cinco trincheiras, onde foi feita a descricao morfologica dos diferentes horizontes dos solos. No estudo da dinâmica da agua no solo, foram feitas analises granulometricas, de densidade do solo e particulas, de curvas de retencao e de medidas de condutividade hidraulica saturada no campo, utilizando-se o permeâmetro de Guelph. Coletaram-se amostras indeformadas para realizar analises de imagens. Os Cambissolos apresentaram-se como os solos predominantes na parcela, mas tambem foram encontradas manchas de Neossolos e Gleissolos. No estudo da caracterizacao fisico-hidrica dos solos da topossequencia escolhida, observou-se mudanca na condutividade hidraulica entre as camadas superficiais e subsuperficiais, de alta/intermediaria para intermediaria/baixa permeabilidade. Essa variacao do comportamento da agua no solo tambem pode ser observada nas curvas de retencao de agua, que evidenciou maior retencao de agua nos horizontes subsuperficiais. Fatores como porosidade total, dimensao, forma e conexao entre os poros foram analisados por meio da analise de imagens. O comportamento fisico-hidrico dos solos foi influenciado pelas caracteristicas morfogenicas do solo.

Assessment of sugarcane harvesting residue effects on soil spectral behavior

When the harvesting of sugarcane involves a mechanized process, plant residues remain on the soil surface, which makes proximal and remote sensing difficult to monitor. This study aimed to evaluate, under laboratory conditions, differences in the soil spectral behavior of surface layers Quartzipsamment and Hapludox soil classes due to increasing levels of sugarcane’s dry (DL) and green (GL) leaf cover on the soil. Soil cover was quantified by supervised classification of the digital images (photography) taken of the treatments. The spectral reflectance of the samples was obtained using the FieldSpec Pro (350 to 2500 nm). TM-Landsat bands were simulated and the Normalized Difference Vegetation Index (NDVI) and soil line were also determined. Soil cover ranged from 0 to 89 % for DL and 0 to 80 % for GL. Dry leaf covering affected the features of the following soil constituents: iron oxides (480, 530 and 900 nm) and kaolinite (2200 nm). Water absorption (1400 and 1900 nm) and chlorophyll (670 nm) were determinant in differentiating between bare soil and GL covering. Bands 3 and 4 and NDVI showed pronounced variations as regards differences in soil cover percentage for both DL and GL. The soil line allowed for discrimination of the bare soil from the covered soil (DL and GL). High resolution sensors from about 50 % of the DL or GL covering are expected to reveal differences in soil spectral behavior. Above this coverage percentage, soil assessment by remote sensing is impaired.