Remote Sensing (Nov 2023)

Sentinel-1 Imagery Used for Estimation of Soil Organic Carbon by Dual-Polarization SAR Vegetation Indices

  • Erli Pinto dos Santos,
  • Michel Castro Moreira,
  • Elpídio Inácio Fernandes-Filho,
  • José Alexandre M. Demattê,
  • Emily Ane Dionizio,
  • Demetrius David da Silva,
  • Renata Ranielly Pedroza Cruz,
  • Jean Michel Moura-Bueno,
  • Uemeson José dos Santos,
  • Marcos Heil Costa

DOI
https://doi.org/10.3390/rs15235464
Journal volume & issue
Vol. 15, no. 23
p. 5464

Abstract

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Despite optical remote sensing (and the spectral vegetation indices) contributions to digital soil-mapping studies of soil organic carbon (SOC), few studies have used active radar remote sensing mission data like that from synthetic aperture radar (SAR) sensors to predict SOC. Bearing in mind the importance of SOC mapping for agricultural, ecological, and climate interests and also the recently developed methods for vegetation monitoring using Sentinel-1 SAR data, in this work, we aimed to take advantage of the high operationality of Sentinel-1 imaging to test the accuracy of SOC prediction at different soil depths using machine learning systems. Using linear, nonlinear, and tree regression-based methods, it was possible to predict the SOC content of soils from western Bahia, Brazil, a region with predominantly sandy soils, using as explanatory variables the SAR vegetation indices. The models fed with SAR sensor polarizations and vegetation indices produced more accurate results for the topsoil layers (0–5 cm and 5–10 cm in depth). In these superficial layers, the models achieved an RMSE in the order of 5.0 g kg−1 and an R2 ranging from 0.16 to 0.24, therefore explaining about 20% of SOC variability using only Sentinel-1 predictors.

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