Effects of straw mulching on initial post-fire vegetation recovery

Straw mulching is increasingly used after high severity wildfires for reducing post-fire runoff and erosion but can alter post-fire vegetation regeneration. However, information about the extent to which mulching affects the recovery of native vegetation is inconclusive. The soil seed bank plays an important role in the resilience of frequently disturbed shrubland communities but little is known about how it is affected by mulching treatments. In this study, we assessed the effects of straw mulching (2.0 Mg ha−1) on the recovery of vegetation after a wildfire in Galicia (NW Spain). For this purpose, we carried out a greenhouse and field-based study to evaluate the effects of mulching applied immediately after fire on the soil seed bank and recovery of vegetation cover in a shrubland area during the first year after wildfire. In the greenhouse, there were no differences in the total number of seedlings that emerged from the soil seed bank of mulched and untreated samples (634 seedlings m−2 vs 731 seedlings m−2). Species richness increased from 22 in untreated burned soils to 24 species in the mulched, burned soils. In the field, straw mulching favoured plant establishment and recovery of vegetation cover. At the end of the first post-fire year, plant cover was significantly higher (63%) in the mulching treatment compared to the untreated one (44%). Mulching did not affect species composition, and there was little evidence of the presence of non-native species. The results indicate that, in the present case, straw mulching immediately after the fire favoured recovery of plant cover in the first year after the fire by conserving the soil moisture.