Assessing vegetation recovery in different fire-severity conditions in central Portugal

Abstract

Wildfire-induced landscape changes are a critical environmental issue in Southern Europe and are becoming increasingly relevant, especially in rural areas, where land use changes are leading to greater fuel availability, higher fire frequency, and wider affected areas. These factors are promoting scrubland-dominated landscapes and may contribute to biodiversity losses and impact vegetation dynamics. The aim of this study is to assess post-fire vegetation recovery in a mountainous region of central Portugal under different severity levels and environmental conditions, aiming to assess their influence on vegetation dynamics. Copernicus Sentinel-2 datasets were used to calculate different wildfire-relevant indices, such as the Normalized Difference Vegetation Index (NDVI), Relativized Burn Ratio (RBR) and Difference Relativized Burn Ratio (dNBR) and coupled with floristic and vegetation data collected from 15 field plots (100m² each). Results indicated that, although no relationship could be established between fire severity and vegetation recovery, post-fire vegetation attributes were clearly influenced by abiotic conditions and floristic composition, particularly the presence of sprouters. After 5,5 years, most sample plots displayed expected regrowth rates, considering the potential dynamics, as the predominant shrub species are well adapted to fire disturbance. However, plots with greater cover and height (high shrub stratum) were dominated by the invasive tree species Acacia dealbata, presenting a distinct pattern compared to the prevalent vegetation recovery conditions in the study areaWildfire-induced landscape changes are a critical environmental issue in Southern Europe and are becoming increasingly relevant, especially in rural areas, where land use changes are leading to greater fuel availability, higher fire frequency, and wider affected areas. These factors are promoting scrubland-dominated landscapes and may contribute to biodiversity losses and impact vegetation dynamics. The aim of this study is to assess post-fire vegetation recovery in a mountainous region of central Portugal under different severity levels and environmental conditions, aiming to assess their influence on vegetation dynamics. Copernicus Sentinel-2 datasets were used to calculate different wildfire-relevant indices, such as the Normalized Difference Vegetation Index (NDVI), Relativized Burn Ratio (RBR) and Difference Relativized Burn Ratio (dNBR) and coupled with floristic and vegetation data collected from 15 field plots (100m² each). Results indicated that, although no relationship could be established between fire severity and vegetation recovery, post-fire vegetation attributes were clearly influenced by abiotic conditions and floristic composition, particularly the presence of sprouters. After 5,5 years, most sample plots displayed expected regrowth rates, considering the potential dynamics, as the predominant shrub species are well adapted to fire disturbance. However, plots with greater cover and height (high shrub stratum) were dominated by the invasive tree species Acacia dealbata, presenting a distinct pattern compared to the prevalent vegetation recovery conditions in the study area.