Effects of two emergency stabilization treatments on main soil properties four years after application in a severely burnt area

Abstract

In NW of the Iberian Peninsula, the incidence of anthropogenic fires is very high and, due to the climatologic and topographical conditions, burnt soils are prone to high erosion risks. In recent years several environmental management techniques (BAER: burnt area emergency response) have been applied after some wildfires, but there are still few field studies about their effects on soils (the foundations of terrestrial ecosystems) and most of them are short-term. Aiming to fill this gap of knowledge, sixteen properties useful as soil quality indices (pH, WHC, total N, δ15N, NH4+-N, NO3−-N, and NH4Ac-DTPA extractable Na, K, Ca, Mg, P, Al, Fe, Mn, Cu and Zn) were studied four years after BAER application in a severely burnt area in the 0–2 and 2–5 cm depth layers of unburnt soil (US), burnt soil untreated (BS), and burnt soil treated with two BAERs techniques: rye seeding (BSS) and straw mulching (BSM). The effects of fire on soil WHC, total N, Mg, Na, P, Zn, NO3−-N, Cu and K were mitigated in both BSS and BSM, but especially in the latter. The highest values for Ca and Mn were recorded in BSM. The BAER treatments affect NO3−-N, Cu and K only in the top layer, but no clear effects were found for soil pH, δ15N, NH4+-N, Al and Fe. Soil samples were quite similarly grouped by the hierarchical cluster and the principal component analyses (PCA): a) 0–2 cm layers of US plots; b) 0–2 cm layers of BSM plots; c) 2–5 cm layers of US plots; d) most of top layers of BS and BSS plots; and e) most of the 2–5 cm layers of BS, BSM and BSS plots. The distribution of soil samples in the PCA showed that straw mulching and, to a lesser extent, rye seeding reduced the distance between burnt and unburnt topsoil along Factor 1, but not along Factor 2 (explaining 56% and 29% of the variance, respectively). Consequently, these BAER treatments mitigated, but not wiped out, the effects of fire on soil quality after four years.