Soils hydraulic conductivity tests in slopes affected by fire: an example on Pisani Mountains (Tuscany, Italy)

Forest fires are responsible for altering the hydrological dynamics and hydraulic properties of soils, including hydraulic conductivity. This affects several processes, including surface runoff, infiltration into the unsaturated zone, leaching and transport of soil chemical components into groundwater. In August 2021 a forest fire burnt 25 hectares of pine tree forest and olive groves in the southern part of the Pisani Mountains (Tuscany, Italy). The objective of the work is to provide a characterization of in-situ hydraulic conductivity values of the soils of a small catchment intersecting the burnt area. To perform rapid in-situ repeatable soil measurements, four replicas of the Di Prima (2015) automatic single ring infiltrometer were built. These infiltrometers are capable of performing autonomous infiltration test thanks to the automated data acquisition system and their water supply system, reducing disturbances of the tested material. The infiltrometric survey allowed for identification of statistically significant differences in soil hydraulic conductivity between vegetational types, and between burnt and unburnt areas. The soil hydraulic conductivity results lower in the burnt pine tree forest compared with the olive groves. The automatic infiltrometers proved to be a repeatable and rapid soil hydraulic properties survey devices also in a rough mountainous environment.