Water repellency of air-dried and sieved samples from limestone soils in central Portugal collected before and after prescribed fire

Abstract

Aims Soil water repellency (SWR) in Mediterranean sub-humid environments is poorly studied in soils derived from basic bedrock. This study addressed this gap by comparing SWR in soil samples collected before/ after a prescribed burning in a Mediterranean shrubland overlaying limestone. Methods Sampling was performed on two adjacent slopes (NE/SW) underneath Quercus coccifera, Pistacia lentiscus, Arbutus unedo shrubs, and on bare inter-patches, at two depths (0–2 and 2–5 cm). Samples were sieved at <0.25, 0.25–1, 1–2 and <2 mm and SWR was assessed through the Water Drop Penetration Time (WDPT) in each fraction. Samples were analysed for pH, AS, CaCO3 and SOM. Results SWR was present before fire, mainly in the <0.25 and 0.25–1 mm fractions at 0–2 cm, which could be explained by SOM (amount and chemical composition). Persistence varied between the two slopes (NE > SW) and the four patches (Arbutus unedo > Pistacia lentiscus ≈ Quercus coccifera > Bare). The low-severity fire slightly increased SWR but did not affect the above-mentioned prefire differences. Conclusions The wax and resins from different shrub species have implications for SWR persistence on the finer soil fractions. Prescribed fire increased the severity of SWR at surface but also its frequency at the subsurface layer.