Long-term evaluation of soil functionality in Mediterranean forests after a wildfire and post-fire hillslope stabilisation

Abstract

The effects of hillslope stabilisation techniques on soil properties and vegetation cover of Mediterranean forests affected by wildfires have been deeply explored in the short term, while the long-term evaluations are scarce. Following previous investigations carried out in a pine forest of Castilla-La Mancha (Spain) burned by a severe wildfire in 2012 and treated with log erosion barriers (LEBs) or contour felled log debris (CFD) as post-fire management actions, this study evaluates the changes in soil physico-chemical and biological properties, and vegetation cover eleven years after the fire and structure construction in unburned, burned and untreated (with north or south aspect), and burned and treated soils (with CFDs or LEBs). The results have shown that none of the physico-chemical and biological properties of soil as well as the ground cover significantly differs between sites treated with CFDs and LEBs. The latter structures appear to be more effective in storing organic matter and water in the soil, which is important for post-fire vegetation recovery. The aforementioned effectiveness of post-fire treatments in limiting the changes in soil and vegetation due to wildfire was particularly evident in the burned and untreated sites exposed to the south, which should be prioritised for treatment, since these areas show long-term reductions in soil water content and availability. This prioritisation helps to support a quicker restoration of vegetation cover, which may find water shortage as a limiting factor compared to sites with north aspect. Finally, since, in such a long term, the changes in several soil properties (e.g., most of the enzymatic activities and basal respiration) between unburned, and burned and treated sites disappeared, and vegetation cover was almost fully restored up to the unburned level, it can be confirmed that the analysed hillslope stabilisation techniques were successful in recovering the pre-fire conditions of soil and vegetation conditions that are typical of unburned sites.