Effectiveness of community-based initiatives for mitigation of land degradation after wildfires

Local communities, informed about the main post-fire environmental threats, applied land restoration techniques after the 2017 Ponte Caldelas wildfire (Galicia, Spain). Volunteers crews, supervised by local researchers/technicians identified high-severity burned areas and applied: post-fire mulch by using corn mulch (chopped corn at a rate of 4 Mg ha⁻¹), corn strip mulch (chopped corn on 1-m wide contourline-strips at the bottom of plots, at 1 Mg ha⁻¹) and wheat mulch (wheat straw, at 2 Mg ha⁻¹), as well as acorn seeding with native oak (Quercus robur) acorns. Furthermore, the mulch effect on seed germination/root elongation was tested in the laboratory using direct topsoil samples and <0.45 microns-filtered soil solutions. Soil erosion during the first post-fire year was 27-11 Mg ha⁻¹ for the Parada-Laforet sites, respectively. Corn, corn strip, and wheat mulching were very effective at reducing soil erosion, leading to 95, 76% and 93% less erosion than in untreated plots. During post-fire year 2 mulching was still effective at reducing soil erosion in the case of corn (87%) and corn strip mulch (73%), but less effective with straw mulch (36%). For the third year no differences were observed. Acorn seedling establishment failed in 96% of the cases. Still, survival rate of the germinated acorns was significantly higher on the mulched (50%) than on the untreated spots (26%; p<0.05). The laboratory experiments also showed higher germination rates, shoot length and biomass in mulched than untreated soils. The results demonstrated that the mulching measures applied by the local volunteers were effective for preventing soil erosion after forest fires. The success of ecosystem restoration with acorn seeding was low due to the low germination and the high predation by rodents, and further research is needed to scale acorn seeding to natural recruitment rates.