Soil functioning in a toposequence under rainforest in São Paulo, Brazil Funcionamento do solo em uma topossequência sob Mata Atlântica em São Paulo, Brasil

Studies of soil-water dynamics using toposequences are essential to improve the understanding of soil-water-vegetation relationships. This study assessed the hydro-physical and morphological characteristics of soils of Atlantic Rainforest in the Parque Estadual de Carlos Botelho, state of São Paulo, Brazil. The study area of 10.24 ha (320 x 320 m) was covered by dense tropical rainforest (Atlantic Rainforest). Based on soil maps and topographic maps of the area, a representative transect of the soil in this plot was chosen and five soil trenches were opened to determine morphological properties. To evaluate the soil hydro-physical functioning, soil particle size distribution, bulk density (r), particle density (r s), soil water retention curves (SWRC), field saturated hydraulic conductivity (Ks), macroporosity (macro), and microporosity (micro) and total porosity (TP) were determined. Undisturbed samples were collected for micromorphometric image analysis, to determine pore size, shape, and connectivity. The soils in the study area were predominantly Inceptisols, and secondly Entisols and Epiaquic Haplustult. In the soil hydro-physical characterization of the selected transect, a change was observed in Ks between the surface and subsurface layers, from high/intermediate to intermediate/low permeability. This variation in soil-water dynamics was also observed in the SWRC, with higher water retention in the subsurface horizons. The soil hydro-physical behavior was influenced by the morphogenetic characteristics of the soils.O estudo da dinâmica da água no solo utilizando topossequências é de grande importância para melhor compreender as relações solo-água-vegetação. Objetivou-se, com este trabalho, caracterizar físico, hídrica e morfologicamente os solos da mata do Parque Estadual de Carlos Botelho. A parcela abrange uma área de 10,24 ha (320 x 320 m), localizada sob Floresta Ombrófila Densa (Mata Atlântica de Encosta). Com base nos mapas de solos ultradetalhados e mapas planialtimétricos dessa área, escolheu-se uma transeção representativa dos solos da parcela; nessa, foram abertas cinco trincheiras, onde foi feita a descrição morfológica dos diferentes horizontes dos solos. No estudo da dinâmica da água no solo, foram feitas análises granulométricas, de densidade do solo e partículas, de curvas de retenção e de medidas de condutividade hidráulica saturada no campo, utilizando-se o permeâmetro de Guelph. Coletaram-se amostras indeformadas para realizar anál