Abstract
The search for better living conditions has led the residents of the Brazilian semi-arid region to plant forage crops, leading to a gradual decrease in the native vegetation (Caatinga) of this region. The effects caused by the replacement of Caatinga with palm, for example, have been little studied, especially with regard to the physical and hydraulic properties of the soil. The objective of this study was to compare the physical-hydraulic characteristics of a litholic neosol in two areas having different vegetation cover: one area cultivated with forage palm (O. ficus-indica) and the other covered by native Caatinga. Differences in soil structure, especially in porosity, between the natural and cultivated soils were observed to control the hydrodynamic processes, resulting in changes in water retention curves and hydraulic conductivity. Natural soil presents low values of hydraulic conductivity when compared to those of cultivated soil. This increase is probably due to soil management required for forage palm cultivation. The natural soil structure, characterized by relatively low saturated hydraulic conductivity values, presents an infiltrability that favors surface runoff. Human activities in the study area have promoted changes in the soil’s physical attributes, decreasing density and increasing porosity. Consequently, there is an increase in water infiltration into the soil and a reduction of runoff in cultivated areas, confirming results obtained in previous studies.
Highlights
Steppe Savanna, or Caatinga, covers about 10% of the total Brazilian territory, an area of 734 thousand km2, and is found mainly in the Northeast Region
The plots consisted of 2.0 ha of natural soil, where the Caatinga vegetation is preexistent, and 4.5 ha of soil cultivated with forage palm (O. ficus-indica)
The adjustment of the Weibull equation proved to be appropriate, robust, and fully adapted to modeling the granulometric curves for the studied soils, allowing the methodology proposed by Arya and Heitman to be used to estimate the water retention curve for the soil
Summary
Steppe Savanna, or Caatinga, covers about 10% of the total Brazilian territory, an area of 734 thousand km, and is found mainly in the Northeast Region. It is often marked by two annual dry periods: one long, followed by intermittent rains, and another short, which can become torrentially rainy. The Caatinga has been strongly affected by anthropic action. In addition to destroying vegetation cover, these actions can drastically reduce wildlife populations, affect water quality and disrupt the climate balance and soil balance. Caatinga soils usually have a superficial crust in areas without vegetation which, together with the textural difference between horizons, directly influence the infiltration of water, accentuating the water deficit and causing the few existing plant species in the area to be those that have adapted most fully to this condition (Souza et al, 2016)
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