Mineral Soil Texture–Land Cover Dependency on Microwave Dielectric Models in an Arid Environment

Saeid Gharechelou,Brian A Johnson,Ryutaro Tateishi

doi:10.3390/land9020039

Saeid Gharechelou, Brian A Johnson + Show 1 more

Open Access

https://doi.org/10.3390/land9020039

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Abstract

In this study, we measured and characterized the relative dielectric constant of mineral soils over the 0.3–3.0 frequency range, and compared our measurements with values of three dielectric constant simulation models (the Wang, Dobson, and Mironov models). The interrelationship between land cover and soil texture with respect to the dielectric constant was also investigated. Topsoil samples (0–10 cm) were collected from homogenous areas based on a land unit map of the study site, located in the Gamsar Plain in northern Iran. The field soil samples were then analyzed in the laboratory using a dielectric probe toolkit to measure the soil dielectric constant. In addition, we analyzed the behaviors of the dielectric constant of the soil samples under a variety of moisture content and soil fraction conditions (after oven-drying the field samples), with the goal of better understanding how these factors affect microwave remote sensing backscattering characteristics. Our laboratory dielectric constant measurements of the real part (ε′) of the frequency dependence between the factors showed the best agreement with the results obtained by the Mironov, Dobson, and Wang models, respectively, but our laboratory measurements of the imaginary part (ε″) did not respond well and showed a higher value in low frequency because of salinity impacts. All data were analyzed by integrating them with other geophysical data in GIS, such as land cover and soil textures. The result of the dielectric constant properties analysis showed that land cover influences the moisture condition, even within the same soil texture type.

Highlights

In microwave remote sensing backscattering models, the value of the soil dielectric constant is important for retrieving soil water contents
The laboratory measurements were conducted for each soil sample under different soil moisture contents
We found that the land cover types and soil textures showed a close relationship with the dielectric constant measurements and simulations

Summary

Introduction

In microwave remote sensing backscattering models, the value of the soil dielectric constant is important for retrieving soil water contents. The emissivity and permittivity parts of the dielectric constant are determined using tool kit measurements or based on simulation models. For the tool kit measurement approach, usually soil samples are taken from the field, and the real and imaginary part of the dielectric constant are measured using a dielectric constant tool kit [1,2]. In an alternating electric field, permittivity varies depending on the applied frequency. Measurement of samples of the ε0 dielectric constant for each soil texture and computation of the dielectric constant for the water content (e.g., 20%), and repeating for the same soil texture. The dielectric constant of 36 soil samples was measured in a microwave remote sensing laboratory using a dielectric constant toolkit.

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