Wildfire effects on extractable elements in ash from a Pinus pinaster forest in Portugal

The aim of this work is to study the effects of a wildfire on water-extractable elements in ash from a Pinus pinaster forest located in Portugal. The pH, electrical conductivity (EC), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), sodium and potassium adsorption ratio (SPAR), aluminium (Al3+), manganese (Mn2+), iron (Fe2+), zinc (Zn2+), sulphur (S), silica (Si) and phosphorous (P) were analysed in ash sampled from a sloped area burned in a wildfire and from litter from a contiguous unburned area, with similar morphological conditions. The results showed that ash leachates had higher pH and EC, and were significantly richer in water-extractable Ca2+, Mg2+, Na+, K+, SPAR, S and Si and significantly poorer in water-extractable Al3+, Fe2+, Mn2+ and Zn2+ than litter solutions. No significant differences were observed in water-extractable P. The fire changed the ash solute chemistry compared with the unburned litter and increased the sample variability of nutrient distribution with potential implications for plant recovery.