Prediction of soil properties immediately after fire using SAR backscatter data

Abstract

The physical sense of synthetic aperture radar (SAR) backscatter data is of particular interest for characterizing soil spatial variability in burned areas. The objective of this study was to evaluate the potential of SAR backscatter data in L-band (Advanced Land Observing Satellite-2; ALOS-2) for assessing fire effects on soil organic carbon, total nitrogen and available phosphorous immediately after wildfire in a burned landscape of the western Mediterranean Basin. ALOS-2 backscatter coefficients were used to estimate soil properties measured in the field in immediate post-fire situation through generalized linear models. The retrieval of soil properties from ALOS-2 L-band SAR backscatter data featured a high overall fit (R2 = 0.37-0.59) and low error (nRMSE = 12.7%-22.5%). ALOS-2 co-polarized channel showed the highest sensitivity to spatial variation in soil properties, and there were no noticeable under and overestimation effects. These results support the applicability of SAR sensors operating at long wavelengths for monitoring fire effects on soil properties, reducing data gathering costs within large burned landscapes.