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ResumoGeomorfometria é uma ciência interdisciplinar (que combina a ciência da terra, matemática e computação) que descreve a superfície terrestre como uma representação numérica com descritores quantitativos. Assim, a geomorfometria evolui com os métodos computacionais presentes em Sistema de Informação Geográfica (SIG), a fim de estudar inúmeros problemas, tais como: susceptibilidade deslizamento de terra, hidrogramas de bacia, erosão do solo, distribuição da vegetação, entre outros. Um tópico de pesquisa importante na Geomorfometria é extrair e classificar formas de relevo a partir do Modelo Digital de Elevação (MDE), que é um pré-requisito para melhorar a compreensão da dinâmica dos geossistemas naturais. Assim, os métodos Revista Brasileira de Geomorfologia v. 13, nº 2 (2012) www.ugb.org.br

The objective was to identify landscape areas with different patterns of variability using a statistic protocol with data of magnetic susceptibility (MS) and soil color that are covariate attributes of soil formation factors and processes. The studied area, of 380 ha, is located in Northeast of São Paulo State, Brazil. An amount of 86 samples was collected using 30 m intervals on the transect. At the transect sides, 150 samples were collected at 159 m intervals (a point each 2.5 ha). First the accuracy limits have been validated in the transect using the technique of Split Moving Windows-SMW. The limits identified in the transect were extrapolated to the sides using the contours of variability maps. The MS peaks SMW, for both depths, presented a correlation with the peaks of clay content (r = 0.7; P b 0.01), hue (varying from 0:37; P b 0.05 to 0.61; P b 0.01) and Normalized Difference Vegetation Index-NDVI (varying from − 0.25 to − 0.35, P b 0.05). The errors of the MS spatial variability maps (6.22-11.85%) were similar to the clay content ones (6:22 to 14:16%). MS was more efficient in the compartmentalization of the landscape (identification of areas with different patterns of variability) than the hue determined by diffuse reflectance spectroscopy in Oxisols under the transition Basalt and Colluvial-Elluvial-Alluvial Deposits. The results of this study can lead to using an alternative strategy that is a mapping of soil attributes and identification of areas with different patterns of pedogenic iron oxide variability.

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We performed phylogeographic and genetic structure analyses of Neothraupis fasciata joined with species distribution modelling to evaluate whether: (1) the distribution of genetic variability shows a pattern expected by the isolation-by-distance model; (2) the influence of the Pleistocene climate changes on species distribution; and (3) climate/climatic stability (hypothesis of climatic stability) as a predictor of population genetic diversity. Based on two molecular datasets (ND2 and FIB-5), the isolation-by-distance hypothesis was not supported. The mitochondrial haplotype network indicated the existence of historically isolated populations at the southern range of the species distribution, and recent population expansion was identified by both neutrality tests and extended Bayesian skyline plot analysis. Thus, the climatic changes during the Pleistocene might have promoted the reconnection of the partially isolated southern populations, which may have persisted in the plateaus during the cycles of savanna contractions. Subsequently, this species (re)colonized northern areas of the species present distribution, following the continuous vegetation on the São Francisco and Central plateaus about 60 kyr, and also reached the Amazonian savannas likely via the central corridor. Thus, our results indicated that the intrinsic relationship between the relief heterogeneity (plateaus and depressions) and the climatic fluctuations, mainly in the Pleistocene, promoted population reconnection and demographic expansion of N. fasciata.

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This study aimed to use spatial uncertainty of magnetic susceptibility (MS) and clay content to improve soilmapping units. In an experimental area of 870 ha, a regular sampling grid containing 371 points was set, in which MS and clay content were assessed at a depth range of 0-0.25 m. Using a digital elevation model and field observations, a 4440-m transect was established on the study area from hilltop to the foothill, toward the gentlest slope. Standard deviation maps based on 200 realizations of the sequential gaussian simulation measured spatial estimate uncertainties. To limit transition zones along the transect, uncertainty isolines representative of the transition between soil-mapping units were selected. Both attributes presented peaks of uncertainties near the change of mapping units, previously known. Uncertainty zones, previously delineated, ranged from 45 to 210 m and from 60 to 170 m, for MS and clay content, respectively. However, after extrapolating the uncertainties to the side of the transect, amplitude changes of the uncertainty zones were observed, especially in the transition regions between landscape shape and geology. Delineation of mapping units, which incorporated the uncertainties of MS and clay content, was similar. However, due to lower cost and promptness, MS becomes the most feasible alternative. Knowing spatial uncertainties enables readjusting limits in maps of soil-mapping units and may support identification of most favorable regions for determining modal pedon representative of each unit.