Impact of fire and post-fire management techniques on soil chemical properties

Abstract The effects of fire (Control burned soil) and two emergency stabilisation techniques (grass Seeding and straw Mulching) on 20 chemical characteristics were evaluated on 0–5 cm top-soils sampled 1, 90, 180 and 365 days after an experimental fire in a steep shrubland of a temperate-humid region (NW Spain). Most part of pH (in H2O and KCl) variance was explained by the sampling date. No clear temporal trends were identifiable for total soil C and N content, likely due to the large SOM pool in these soils; however, changes on soil δ13C were explained by the deposition of 13C-depleted ashes, followed by its progressive erosion, while those on soil δ15N were a consequence of fire induced N outputs. After the fire, NH4+–N, P, Na, K, Mg, Ca, Mn, Cu, Zn and B concentrations increased, while those of NO3−–N, Al, Fe and Co did not vary significantly. Despite a significant decline with time, concentrations of Mg, Ca and Mn at the end of the study were still higher than in unburned soil, while those of K, Cu, Zn and B were similar to the pre-fire levels and those of NH4+–N, P and Na were below pre-fire values. Mulching and Seeding treatments for burned soil emergency stabilisation had significant effects on soil δ15N and extractable K, Mg and Ca, while data were inconclusive for their possible effects on the extractable Al, Fe and Co.