Though riparian areas generally have a shallow water table and higher soil moisture compared to upslope areas, climatic seasonality may trigger water repellency in tropical riparian forests, which, if persistent, could negatively affect essential ecosystem functions related to water resources protection such as reduced overland-flow, sediment transport, and nutrient filtration. The objective of this study was to answer the following: can tropical riparian forests develop water repellency? If so, does water repellency affect infiltration on a seasonal basis? For this, water repellency and infiltration were measured in a grid of 72 points during a dry and a wet month of a tropical riparian forest with a shallow water table in a region with highly marked climatic seasonality. Water repellency and infiltration were significantly different between the wet and dry months. Water repellency affected negatively infiltration in the dry month, its effect in the wet month was insignificant. As a result, a higher infiltration capacity was observed over the wet period. Previous research has claimed that the development and persistence of repellency in soils could promote other hydrological processes such as overland flow. The findings shown here demonstrate that such phenomenon does not persist longer than the dry season.

Syntropic agroforestry systems (SYS) are a type of agroforestry in which very large amounts of organic matter (50-100 t ha −1 year −1 ) are added to the soil annually from pruning. However, information on the physical, chemical and biological effects of this management on soil is lacking. We characterized a SYS in terms of topsoil permeability (Mini-Disk infiltrometer), soil organic matter (ignition method) and penetration resistance (Stolf penetrometer); we compared the results with those for a no-till soy-maize rotation and those within a native vegetation area (Brazilian Tropical Savanna), all on the same oxisol. The SYS had an infiltration capacity similar to that in the native vegetation area but which was higher than in the no-till arable rotation. We relate this difference to both a lower penetration resistance and a high organic matter content in the SYS, possibly associated with higher litter input and with a greater above and belowground biomass. Our results indicate that SYS can be an efficient system for maintaining water infiltration at levels similar to those observed within natural ecosystems.

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The Brazilian savanna, regionally known as Cerrado is an important water source due to its spatial position in the highlands known as Planalto Central of Brazil. Yet, the hydrological functioning of such complex ecosystems and its many variations is poorly understood. In this paper, we characterized the soil surface permeability to water under in one of the most common vegetation types: the Cerrado típico which is a type of savanna. In doing so, we measured infiltration capacity using the Mini-Disk infiltrometer (n = 15) and soil resistance to penetration using the Stolf penetrometer (n = 7) in a Latossolo (oxisol) under Cerrado típico located in Brasília (Planaltina), Distrito Federal, Brazil. Our  results indicated a high infiltration capacity under Cerrado típico which is potentially associated with a low penetration resistance. This fact might highlight the importance of the natural undisturbed ecosystems, in this case Cerrado típico, as a land-cover which favors hydrological processes which, in turn, promotes soil-groundwater recharge that are inportant to maintain water bodies and reservoirs in the region.

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