Spatial behaviour of soil moisture in the root zone of the Caatinga biome

Abstract

-The purpose of this study was to represent the soil moisture in the profile corresponding to the root zone from TDR sensors in a preserved area of the Caatinga biome and analyze the spatialized moisture adjustment equations under different layers of the soil profile. For that, we analyzed three classes of soil (red yellow Ultisol; Hypochromic Luvisol; Udorthent) in the Aiuaba Experimental Watershed, located in the semiarid zone of northeastern Brazil. The hydro-physical parameters representing the soil water retention (field capacity, wilting point and residual moisture) were collected in four campaigns, in six points and in the profiles corresponding to the effective root depth, totaling 216 samples. For the evaluation of the regression models, we used the coefficient of determination, the Pearson correlation and the performance index. The results indicate that the analyzed parameters are homogeneous for the studied soil profiles. The Pearson correlation coefficient indicates a moderate performance for all regression equations. However, the confidence index was determined as very bad for the Red-Yellow Ultisol, passable for the Hypochromic Luvisol and bad for the Udorthent, for the rainy season, and very bad for all classes, for the dry season. Therefore, the use of the regression models is more indicated for periods of higher soil moisture.

Importance of soil‐water to the Caatinga biome, Brazil

“…Although a third layer should have been sampled in SVA 2 , the presence of a very stony layer at the sample spot from about 0.4 m downwards made undisturbed sampling not possible. However, earlier studies (Pinheiro et al ., ; Costa et al ., ) testify the presence of a third rooted layer (0.4–0.6 m) in other spots of the SVA 2 . Therefore, we considered the third layer in our simulations using the hydraulic properties of the second layer.…”

“…Based on previous studies (Güntner et al ., ; Costa et al ., ; Pinheiro et al ., ), the AEB was subdivided into three systems, denominated soil and vegetation associations or soil and vegetation association (SVA) (Figure ). The first association (SVA 1 ), covered with an Acrisol, occupies 20% of the AEB area, and the average rooting depth of the vegetation is 0.8 m. In the second system (SVA 2 , 34% of the experimental area) the soils are classified as Luvisols and the average rooting depth is 0.6 m. SVA 3 has a shallow soil (Regosol) with average rooting depth of 0.4 m, occupying 46% of the AEB.…”

“…A finer‐scale spatial and temporal analysis of the soil water content and meteorological components would allow investigations of the necessary details and also provide a better performance of simulations in current climate models and as well as land–atmosphere interactions. Such an analysis is of utmost importance for semi‐arid regions in general, given the scarcity of hydrological data characterized by high spatial variability (Costa et al ., ; ).…”

Hydrology of a Water‐Limited Forest under Climate Change Scenarios: The Case of the Caatinga Biome, Brazil

“…Leaf shedding is the main characteristic and survival strategy to cope with up to nine months of the rainless season. Figure 1 displays the Aiuaba Experimental Basin together with its three soil and vegetation associations (SVA) [10,18,19] and the sampling site for soil hydraulic properties and root length distribution [10]. …”

Use of proximal sensor for soil classes separation applying Principal Component Analysis (PCA)

“…Based on the assessment of the environmental dynamics in this basin, the area was divided into three associations between soil and vegetation (ASVs) that were defined as homogeneous units for studies of the environmental variables. Pinheiro et al (2016) and Costa et al (2013) classified the ASVs based on their predominance of soil and vegetation, which are presented in Table 1. Four soil samples were collected in characteristic profiles at each ASV.…”