Soil bioengineering techniques for post-fire erosion control

Forest fires can increase the risk of soil erosion due to the decrease in vegetation cover or the changes in soil properties (i.e. infiltration capacity). This can lead also to economic, cultural, and ecological effects. Mediterranean areas due to multiple factors such as rainfall regime, physical-structural characteristics of the soil, land use, topography and the fire regime itself, are prone to erosive phenomena. Moreover, current climate change will accelerate soil erosion in burned areas. Soil bioengineering works are low impact mitigation measures which can be used to counteract post-fire erosion processes. This study aims at providing insights on the realization of a Soil Bioengineering pilot work in the forested area of Gravina in Puglia (an area of 1900 hectares, in which a fire of 1170 hectares was recorded on 12/08/2017) and analysing the restoration of the field development capacity of some selected species. The works were realized in two areas (area 1 and area 2) located along slopes with the same general conditions (slope, type of soil, fire severity) except for exposure. The intervention involved various strategies: the removal of weeds, the implementation of a wattle and a palisade and the planting of native shrubs and tree species. A monitoring plan, characterized by in field and remote activities was structured with the aim of evaluating the effects of the soil bioengineering works. The first field inspections revealed that the survival rate in both areas was approximately 82%. After the realization of the works, an increase in the average NDVI was detected in area 1. In area 2 instead, a decrease was highlighted due to the operation of the more dense weeds removal.