Impacts of fire, fire-fighting chemicals and post-fire stabilisation techniques on the soil-plant system

Forest fires, as well as fire-fighting chemicals, greatly affect the soil-plant system causing vegetation loss, alterations of soil properties and nutrient losses through volatilization, leaching and erosion. Soil recovery after fires depends on the regeneration of the vegetation cover, which protects the soil and prevents erosion. Fire-fighting chemicals contain compounds potentially toxic for plants and soil organisms, and thus their use might hamper the regeneration of burnt ecosystems. In high severity fires and steep areas, natural revegetation can be delayed due to seed bank destruction and soil erosion, being paramount to adopt, as soon as possible, post-fire stabilization techniques. Straw mulching is very effective in reducing post-fire erosion, but it is necessary to optimize this technique because its costs and the availability of straw hinder its application on a regional scale. Moreover, even though it is well known that fires greatly affect the N cycle, there is not much information about the effects of straw mulching on gross N fluxes. The aims of this thesis are: 1) to assess how fire and three fire-fighting chemicals affect the soil-plant system in the long term (10 years); 2) to optimize the use of post-fire straw mulching, so it is economically viable, and to assess the effects of its application on the soil-plant system; 3) to evaluate the effects fire, fire severity and straw mulching on gross N fluxes