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Background: Mediterranean Europe is witnessing an increase in extreme wildfire events, which has led to increasing socioeconomic and ecological impacts. Postfire restoration emerges as an important tool for impact mitigation and ecosystem recovery. However, there is a large knowledge gap on the ecological effects of such interventions. We used remote sensing to assess the impacts of postfire restoration on the recovery of deciduous oak forests in Portugal, based on a total of 3013 sampling points in areas with and without postfire intervention. We quantified the vegetation index NDVI as a proxy of oak forest recovery for a period of 4 years after the fire, for fire events that occurred in 2016 and 2017. Temporal changes in NDVI were modelled with a Generalized Additive Mixed Model (GAMM), as a function of postfire restoration, fire characteristics (burn severity, number of fires, and time since fire), topography (aspect, elevation, and slope) and postfire drought events (PDSI).Results: The fitted model accounted for 26.4% of NDVI variance. The model showed a significant positive effect of postfire restoration on NDVI recovery over time, although with a minor effect; it also showed a negative effect of severe drought and a positive effect of severe wetness on NDVI recovery. Regarding fire characteristics, low and high burn severities showed a positive effect on recovery, while moderate burn severity levels showed a null effect. Number of fires showed an increasingly negative effect on recovery, until a maximum of 6 fires.Conclusions: Oak forest recovery was positively affected by postfire restoration, although this effect was small and likely limited by lack of available data. On the contrary, oak forest recovery was negatively affected by increased drought severity but its relation with fire characteristics varied with thresholds of burn severity levels and number of fires. Our study highlights the importance of monitoring the effects of postfire restoration on forest recovery, in order to improve knowledge on postfire forest management and species adaptation. This becomes even more relevant under forecasted scenarios of increased wildfire frequency and severity interacting with other climate-driven disturbances, which will further impact the capacity of forest recovery in the future. |
