Abstract
This paper aims to evaluate the ability of VNIR proximal soil spectroscopy to determine post-fire soil chemical properties and discriminate fire severity based on soil spectra. A total of 120 topsoil samples (0–3 cm) were taken from 6 ha of unburned (control (CON)) and burned areas (moderate fire severity (MS) and high fire severity (HS)) in Mediterranean Croatia within one year after the wildfire. Partial least squares regression (PLSR) and an artificial neural network (ANN) were used to build calibration models of soil pH, electrical conductivity (EC), CaCO3, plant-available phosphorus (P2O5) and potassium (K2O), soil organic carbon (SOC), exchangeable calcium (exCa), magnesium (exMg), potassium (exK), sodium (exNa), and cation exchange capacity (CEC), based on soil reflectance data. In terms of fire severity, CON samples exhibited higher average reflectance than MS and HS samples due to their lower SOC content. The PCA results pointed to the significance of the NIR part of the spectrum for extracting the variance in reflectance data and differentiation between the CON and burned area (MS and HS). DA generated 74.2% correctly classified soil spectral samples according to the fire severity. Both PLSR and ANN calibration techniques showed sensitivity to extract information from soil features based on hyperspectral reflectance, most successfully for the prediction of SOC, P2O5, exCa, exK, and CEC. This study confirms the usefulness of soil spectroscopy for fast screening and a better understanding of soil chemical properties in post-fire periods.
Highlights
Accepted: 4 January 2022Fire is a global phenomenon with positive and negative impacts on ecosystems [1]. fire can be beneficial to some ecosystems, high severity summer wildfires are responsible for land degradation [2] and socio-economic [3] and life losses [4]
Fire can be beneficial to some ecosystems, high severity summer wildfires are responsible for land degradation [2] and socio-economic [3] and life losses [4]
The skewness results imply that the distribution of soil properties varied from fairly negatively symmetrical to highly positive skewness
Summary
Fire can be beneficial to some ecosystems, high severity summer wildfires are responsible for land degradation [2] and socio-economic [3] and life losses [4]. Examples of this are the wildfire season in Portugal in 2017 (Pedrógão Grande), Greece in 2018 (Attica region), and Australia and California in 2020. Mediterranean environments are vulnerable to wildfire, which can have short or long impacts on soil properties depending on severity. High severity fires consume large amounts of organic matter [12,13], destroy soil structure [14,15], change aggregate stability and water repellence [16,17,18], and increase nutrient losses by volatilisation and sediment transport [19,20]
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