Post-fire evolution of soil properties and vegetation cover in a Mediterranean heathland after experimental burning: A 3-year study

Mediterranean soils under heathland are often shallow, with low capacity for water storage, and a high risk of erosion. In this context, recurrent wildfires can negatively affect their chemical and physical properties. Very little research has been carried out concerning the long-term variations on the ground surface after burning. The behaviour of plant communities and plant cover can regulate and control soil processes in the post-fire period, so that the evolution of vegetation communities must be taken into account when studying the evolution of soil processes after disturbance. In this study, the impact of fire on several physical and chemical soil properties has been investigated during 3 years after experimental burning in a Mediterranean heathland. On average, the soil organic matter content after the fire decreased strongly, and one year after the fire it did not vary substantially, although it increased slightly during the following two years until the end of experiments. Burning led to coarser texture immediately after fire, but clay content decreased strongly during the following 3 years due to post-fire erosion processes and selective detachment of fine particles. Soil pH and electrical conductivity increased ephemerally and returned to initial values just 1-year after the fire. Soil water repellency was partly destroyed by the scorching, but pre-fire proportion of water-repellent soil samples was observed just after 1 year. Water-repellent aggregates may have been removed by post-fire erosion, but water repellency also appears as a natural attribute of these soils. Reduction in organic matter content after the fire and changes in texture and water repellency contributed to a decreased stability of aggregates and an increased bulk density.

Research Highlights
► Recurrent wildfires in Mediterranean areas increase soil erosion risk.
► Fire-affected Mediterranean soils show a high resilience.
► The studied fire caused immediate changes in physical and chemical soil properties.
► Chemical properties and water repellency were rapidly re-established.
► Post-fire erosion led to unearthing of hydrophobic soil not affected by temperature.